Foscan: Uses, Dosage & Side Effects
A photosensitizer used in photodynamic therapy (PDT) for the palliative treatment of advanced squamous cell carcinoma of the head and neck
Foscan (temoporfin) is a photosensitizer used in photodynamic therapy (PDT) for the palliative treatment of advanced squamous cell carcinoma of the head and neck in patients who have failed prior therapies. Temoporfin is injected intravenously and accumulates selectively in tumor tissue. After a 96-hour waiting period, the tumor is illuminated with laser light at 652 nm, activating the drug to generate reactive oxygen species that destroy cancer cells, damage tumor blood vessels, and trigger an immune response. Foscan-PDT is performed only in specialized centers by physicians experienced in photodynamic therapy, as the procedure requires strict light precautions and careful patient monitoring.
Quick Facts: Foscan
Key Takeaways
- Foscan (temoporfin) is a photosensitizer used in photodynamic therapy to treat advanced squamous cell carcinoma of the head and neck when surgery, radiotherapy, and chemotherapy have failed or are not suitable options.
- The treatment involves a two-step process: intravenous injection of temoporfin followed by laser illumination of the tumor 96 hours later, generating reactive oxygen species that destroy tumor tissue through direct cell kill, vascular shutdown, and immune activation.
- Patients must strictly avoid direct sunlight and bright indoor light for at least 15 days after injection to prevent severe, potentially life-threatening photosensitivity reactions affecting skin and eyes.
- Foscan-PDT must only be administered in specialized centers by physicians experienced in photodynamic therapy, using calibrated laser systems at the precise 652 nm wavelength.
- Common side effects include pain, swelling, and tissue necrosis at the treatment site, photosensitivity reactions, facial edema, difficulty swallowing, and constipation; most local effects are expected parts of the therapeutic process.
What Is Foscan and What Is It Used For?
Foscan contains the active substance temoporfin, also known as mTHPC (meta-tetrahydroxyphenylchlorin). It belongs to a class of medications called photosensitizers, which are drugs that become pharmacologically active only when exposed to light of a specific wavelength. Temoporfin is a second-generation photosensitizer derived from the chlorin family of porphyrin-like compounds. It was specifically developed to address the limitations of earlier photosensitizers, offering deeper tissue penetration of the activating light and greater photodynamic potency per molecule.
Foscan is authorized by the European Medicines Agency (EMA) for the palliative treatment of patients with advanced squamous cell carcinoma of the head and neck who have failed prior therapies and are not suitable candidates for further surgery, radiotherapy, or systemic chemotherapy. Head and neck squamous cell carcinoma (HNSCC) is a group of cancers arising from the mucosal surfaces of the oral cavity, oropharynx, hypopharynx, and larynx. When these cancers reach an advanced stage and conventional treatments have been exhausted, therapeutic options become extremely limited. In this challenging clinical setting, Foscan-PDT offers a palliative approach that can reduce tumor bulk, relieve symptoms such as pain, bleeding, and airway obstruction, and improve quality of life.
The mechanism of photodynamic therapy with Foscan involves three essential components that must all be present simultaneously: the photosensitizer (temoporfin), light of the appropriate wavelength (652 nm), and molecular oxygen in the tissue. When these three elements converge, a photochemical reaction occurs that destroys tissue through three interconnected mechanisms:
- Direct cellular cytotoxicity: When temoporfin absorbs photons of 652 nm light, it transitions to an excited singlet state and then to a longer-lived triplet state. In the triplet state, temoporfin transfers its energy to ground-state molecular oxygen (O2), generating highly reactive singlet oxygen (1O2). Singlet oxygen has an extremely short diffusion radius (approximately 10–20 nanometers) but is extraordinarily destructive within that range, oxidizing lipid membranes, proteins, and nucleic acids. This leads to rapid, irreversible damage to cellular organelles, particularly mitochondria, endoplasmic reticulum, and lysosomes, culminating in necrotic or apoptotic cell death depending on the subcellular localization of the photosensitizer and the light dose delivered.
- Vascular shutdown: Temoporfin also accumulates in the endothelial cells lining the blood vessels supplying the tumor. Photodynamic activation damages these endothelial cells, triggering vasoconstriction, platelet aggregation, thrombus formation, and ultimately vascular occlusion. The resulting ischemia (loss of blood supply) deprives surviving tumor cells of oxygen and nutrients, causing secondary necrosis of the tumor mass. This vascular effect significantly amplifies the direct cytotoxic action and contributes to the depth of tumor destruction achievable with PDT.
- Immune system activation: The acute tissue damage caused by PDT triggers a robust inflammatory response. Damage-associated molecular patterns (DAMPs) released from dying tumor cells activate innate immune cells, including neutrophils, macrophages, and dendritic cells. There is also evidence that PDT can promote immunogenic cell death, a form of cell death that exposes tumor antigens to the adaptive immune system, potentially generating anti-tumor immunity. This immunological component may contribute to longer-term tumor control beyond the immediate treatment effect.
The treatment protocol for Foscan-PDT is strictly defined. Temoporfin is injected as a slow intravenous injection over a minimum of 6 minutes. After injection, there is a mandatory drug-light interval of 96 hours (4 days) during which the photosensitizer distributes throughout the body and preferentially accumulates in tumor tissue. This selective accumulation is due to several factors, including the leaky vasculature of tumors (enhanced permeability and retention effect), differences in lymphatic drainage, and the affinity of temoporfin for low-density lipoprotein (LDL) receptors, which are often overexpressed on cancer cells. After 96 hours, the ratio of drug concentration in tumor tissue versus surrounding normal tissue reaches its optimum, maximizing therapeutic selectivity.
At the 96-hour mark, the tumor is illuminated with non-thermal laser light at exactly 652 nm wavelength. This wavelength corresponds to the red absorption peak of temoporfin and allows tissue penetration of approximately 10–15 mm, enabling treatment of tumors of clinically meaningful depth. The light is typically delivered through fiber-optic cables connected to a diode laser, allowing precise targeting of the tumor. The light dose, fluence rate, and illumination geometry are carefully calculated for each patient based on tumor size, location, and accessibility. Standard parameters include a light dose of 20 J/cm2 at a fluence rate of 100 mW/cm2, though these may be adjusted based on clinical circumstances.
Temoporfin accumulates preferentially in tumor tissue compared to surrounding normal tissue. At the optimal 96-hour drug-light interval, the tumor-to-normal tissue ratio of temoporfin concentration is approximately 3:1 to 5:1. This differential accumulation, combined with the ability to direct the laser light precisely at the tumor, provides a degree of selectivity that limits damage to adjacent healthy structures — although some collateral damage to normal tissue within the illumination field is inevitable.
What Should You Know Before Receiving Foscan?
Contraindications
Foscan must not be used in certain circumstances. Understanding these absolute contraindications is critical for patient safety, as the consequences of ignoring them can be severe or fatal.
- Hypersensitivity: Do not receive Foscan if you are allergic to temoporfin, porphyrins, or any of the other ingredients (ethanol and propylene glycol). Cross-sensitivity with other porphyrin-type photosensitizers may exist.
- Porphyria or other diseases exacerbated by light: Patients with porphyria (a group of genetic disorders affecting heme synthesis) or other conditions that are worsened by light exposure must not receive Foscan, as the photosensitizing effect of the drug would dangerously exacerbate their underlying condition.
- Tumors eroding into major blood vessels: If the tumor being treated has eroded into or is directly adjacent to a major blood vessel, Foscan-PDT is contraindicated due to the risk of catastrophic hemorrhage when the tumor tissue undergoes necrosis after treatment.
- Planned surgical procedures within 30 days: The persistent photosensitivity caused by temoporfin means that tissues remain photosensitive for an extended period. Surgical procedures involving exposure of internal tissues to operating room lights could cause unintended photodynamic damage. Surgery should be delayed for at least 30 days following Foscan administration.
- Existing ophthalmic disease likely to require slit-lamp examination within 30 days: The intense light of a slit-lamp can activate residual temoporfin in ocular tissues, potentially causing eye damage. Alternative ophthalmic examination methods using low-intensity light should be used if needed during this period.
- Concomitant use of other photosensitizing drugs: The combination of Foscan with other photosensitizing medications (including certain antibiotics, diuretics, and anti-diabetic drugs) is contraindicated as it may dangerously increase the degree and duration of photosensitivity.
Warnings and Precautions
After Foscan injection, your entire body becomes extremely sensitive to light. You must strictly avoid direct sunlight and bright indoor light for at least 15 days. Exposure to strong light during this period can cause severe burns to the skin and eyes that may require hospitalization. Stay in rooms with lighting below 500 lux, wear full protective clothing if you must go near windows, and never go outdoors during daylight hours without full coverage. Even on overcast days, reflected and diffuse sunlight can cause severe photosensitivity reactions.
Before and during treatment with Foscan, your healthcare team should be aware of the following important precautions:
- Photosensitivity management: The photosensitivity period lasts at least 15 days from injection. During this time, ambient room light should not exceed 500 lux. Standard indoor lighting typically ranges from 300–500 lux, but light levels near windows, under fluorescent ceiling fixtures, or in well-lit hospital corridors can significantly exceed this. Patients should carry a lux meter and wear long-sleeved clothing, gloves, hat, and dark sunglasses that wrap around the sides of the face. After 15 days, test light tolerance gradually by exposing a small patch of skin (approximately 3 cm in diameter) to direct sunlight for 10 minutes. If no redness, blistering, or tingling develops within 24 hours, normal light exposure may be cautiously resumed.
- Airway management: For tumors in the oropharynx, hypopharynx, or larynx, post-treatment swelling can cause airway obstruction. Patients treated near the airway must be closely monitored and may require prophylactic tracheostomy or intubation. Emergency airway management equipment must be immediately available.
- Hemorrhage risk: Tumor necrosis following PDT can occasionally lead to hemorrhage, particularly if the tumor is close to blood vessels. Although tumors directly eroding major vessels are contraindicated, even tumors near smaller vessels can bleed when necrotic tissue sloughs. Patients should be monitored for signs of bleeding, especially in the first 2 weeks after illumination.
- Pain management: The photodynamic reaction causes significant tissue destruction and inflammation, resulting in considerable pain at the treatment site. Pain typically begins during or immediately after illumination and may persist for days to weeks. Effective pain management, including opioid analgesics, should be planned in advance.
- Hepatic impairment: Temoporfin is metabolized by the liver. Patients with significant hepatic impairment may have altered temoporfin clearance, potentially prolonging photosensitivity and altering drug distribution. Dose adjustments or extended light precautions may be necessary.
- Renal impairment: Although renal excretion of temoporfin is minimal, patients with severe renal impairment should be monitored carefully as altered fluid balance and protein binding could affect drug distribution.
- Repeated treatments: If repeat Foscan-PDT treatments are considered, a minimum interval of 4 weeks between treatments is recommended to allow tissue healing and resolution of photosensitivity from the previous dose. Cumulative effects of repeated treatments on photosensitivity duration are not fully characterized.
- Injection site reactions: Foscan must be injected slowly over at least 6 minutes into a large, free-flowing vein. Extravasation (leakage outside the vein) can cause severe local damage, including tissue necrosis at the injection site, especially if the area is subsequently exposed to light. If extravasation occurs, the affected area must be protected from light for at least 3 months.
Pregnancy and Breastfeeding
Foscan must not be used during pregnancy. Animal studies have shown evidence of embryotoxicity and teratogenicity. The mechanism of action of temoporfin — generation of highly reactive oxygen species that destroy cells and tissues — poses an inherent risk to the developing fetus. Women of childbearing potential must use effective contraception during treatment and for at least one month after administration of Foscan.
It is not known whether temoporfin or its metabolites are excreted into human breast milk. Given the pharmacological properties of the drug and its potential to cause photosensitivity in a breastfed infant, breastfeeding must be discontinued before Foscan treatment and should not be resumed for at least one month after injection.
There are no adequate data on the effects of temoporfin on male or female fertility. However, given that the drug generates reactive oxygen species that can damage cellular structures including DNA, caution is advised for patients of reproductive potential. Men should consider the potential impact on fertility and discuss sperm cryopreservation with their healthcare team before treatment.
If emergency surgery is required during the photosensitivity period (within 30 days of Foscan injection), the surgical team must be informed. Standard operating room lights can activate residual temoporfin in tissues, causing unintended photodynamic damage to exposed organs. Reduced operating room lighting, orange or red filters on surgical lights, and protection of exposed tissues from bright light should be employed.
How Does Foscan Interact with Other Drugs?
Drug interactions with Foscan are clinically important and can be broadly categorized into two groups: pharmacodynamic interactions that amplify photosensitivity, and pharmacokinetic interactions that alter temoporfin blood levels. All current medications must be reviewed before Foscan administration, and any photosensitizing agents should be discontinued well in advance of treatment if clinically feasible.
Major Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Tetracyclines (doxycycline, minocycline) | Additive photosensitization; dramatically increased risk of severe phototoxic reactions | Contraindicated – discontinue well before Foscan |
| Sulfonamides (sulfamethoxazole/trimethoprim) | Increased photosensitivity through additive mechanisms | Contraindicated – use alternative antibiotics |
| Fluoroquinolones (ciprofloxacin, levofloxacin) | Severe additive phototoxic potential | Contraindicated – use non-photosensitizing antibiotics |
| Thiazide diuretics (hydrochlorothiazide) | Enhanced photosensitivity | Contraindicated – switch to loop diuretics if possible |
| Phenothiazines (chlorpromazine) | Additive photosensitizing effect | Contraindicated – use alternative antipsychotics |
| St. John’s Wort (Hypericum perforatum) | Potent photosensitizer; also a CYP3A4 inducer reducing temoporfin levels | Contraindicated – discontinue at least 2 weeks before |
| Griseofulvin | Known photosensitizer with additive effects | Contraindicated – use alternative antifungals |
Minor Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| CYP3A4 inhibitors (ketoconazole, itraconazole, erythromycin) | Increased temoporfin plasma levels and prolonged photosensitivity | Avoid if possible; extend light precaution period if co-administered |
| CYP1A2 inhibitors (fluvoxamine, ciprofloxacin) | Potentially increased temoporfin levels | Monitor closely; note ciprofloxacin is also contraindicated as photosensitizer |
| CYP3A4 inducers (rifampicin, carbamazepine, phenytoin) | Decreased temoporfin levels, potentially reduced PDT effectiveness | Avoid if possible; efficacy may be compromised |
| Anticoagulants (warfarin, heparin) | Increased risk of hemorrhage at the treatment site post-PDT | Review anticoagulation status; consider temporary dose adjustment |
| Calcium channel blockers | May increase temoporfin cellular uptake and enhance PDT effect | Monitor for enhanced treatment response and increased local reaction |
| Ethanol-containing products | Foscan solvent is ethanol-based; additive CNS depression with other sedatives | Monitor sedation levels; caution with other CNS depressants |
It is particularly important to note that many commonly prescribed medications have photosensitizing properties that patients and even healthcare professionals may not be fully aware of. A comprehensive medication review should be conducted by a pharmacist or physician well before the planned Foscan treatment date. Patients should also be asked about over-the-counter products and herbal supplements, as several of these (notably St. John’s Wort) have significant photosensitizing properties.
What Is the Correct Dosage of Foscan?
Foscan dosage follows a highly standardized protocol that has been optimized through clinical trials to balance therapeutic efficacy with safety. Unlike many conventional medications, the dosing of Foscan involves not only the drug itself but also the precise parameters of the subsequent laser illumination, as both components must be correctly administered for the treatment to be effective and safe.
Adults
Standard Adult Dosage
Drug dose: 0.15 mg/kg body weight, administered as a single slow intravenous injection over a minimum of 6 minutes.
Drug-light interval: Exactly 96 hours (4 days) between injection and laser illumination.
Light dose: 20 J/cm2 delivered at a fluence rate of 100 mW/cm2 using a 652 nm diode laser.
Maximum illumination field: Individual lesion fields should not exceed the capabilities of the available fiber-optic delivery systems. Multiple non-overlapping fields may be used for larger tumors.
The injection technique is critically important. Foscan must be injected through a free-flowing intravenous line into a large vein, preferably in the antecubital fossa (inner elbow). The injection must be given slowly over at least 6 minutes to minimize the risk of injection site reactions and to reduce the chance of extravasation. The intravenous line should be flushed with normal saline before and after the Foscan injection. If there is any suspicion of extravasation during injection, the administration must be stopped immediately and the affected area must be protected from light for at least 3 months.
At exactly 96 hours after injection, the tumor is illuminated using a calibrated 652 nm diode laser. The treatment physician determines the illumination geometry based on tumor size, shape, and location. Surface illumination using a microlens fiber tip is used for accessible flat or dome-shaped tumors, while interstitial fibers may be inserted directly into deeper or more complex tumors to deliver light from within the tissue. The total treatment time for illumination depends on the tumor surface area and typically ranges from approximately 200 to 600 seconds for a standard treatment field.
Children
Pediatric Use
Foscan is not recommended for use in children and adolescents under 18 years of age. There are no adequate clinical data on the safety and efficacy of temoporfin in the pediatric population. The approved indication (advanced head and neck squamous cell carcinoma after failed prior therapies) is extremely rare in children, and the risks of generalized photosensitivity in a pediatric patient would present particular management challenges.
Elderly
Elderly Patients
No specific dose adjustment is required for elderly patients based on age alone. However, elderly patients are more likely to have hepatic or renal impairment, may be taking multiple medications (increasing the risk of drug interactions), and may have thinner, more photosensitive skin. Careful assessment of overall health status, organ function, and medication list is essential. The photosensitivity precautions may need to be more strictly enforced, and the duration of light avoidance may need to be extended if there is any concern about delayed drug clearance.
Missed Dose
The concept of a “missed dose” for Foscan relates primarily to the timing of laser illumination. If the 96-hour drug-light interval is missed (i.e., illumination does not occur at 96 hours after injection), the treatment may need to be postponed or cancelled. The 96-hour interval is optimal because it represents the time at which the tumor-to-normal tissue concentration ratio of temoporfin is at its peak. Illumination significantly earlier or later than 96 hours can result in either suboptimal tumor destruction or excessive damage to normal tissue. Clinical data suggest that illumination should ideally occur within a window of 90 to 110 hours after injection. If the illumination window is missed entirely, the patient will still remain photosensitive and must continue light precautions for at least 15 days from the injection date. A new treatment cycle would require a fresh injection of Foscan after the photosensitivity from the first dose has resolved.
Overdose
There is limited experience with temoporfin overdose. The primary concern with an overdose would be a prolonged and intensified period of photosensitivity, potentially lasting significantly longer than the standard 15 days. In the event of an overdose, the patient must be kept in a dimly lit environment for an extended period, the duration of which should be guided by serial photosensitivity testing of the skin. No specific antidote for temoporfin exists. Treatment is supportive, with particular emphasis on strict light avoidance. If an overdose is recognized before laser illumination, the illumination should not be performed as it could cause excessively severe tissue destruction. Cardiovascular monitoring is advisable as the ethanol vehicle of Foscan could contribute to CNS depression in large overdoses.
| Patient Group | Drug Dose | Light Dose | Special Considerations |
|---|---|---|---|
| Adults | 0.15 mg/kg IV over ≥6 min | 20 J/cm² at 100 mW/cm² | Standard protocol; 96-hour drug-light interval |
| Elderly | 0.15 mg/kg IV (no age adjustment) | 20 J/cm² at 100 mW/cm² | Check organ function; stricter light precautions; review medications |
| Hepatic impairment | Caution; consider reduced dose | As per physician assessment | Prolonged photosensitivity likely; extend light avoidance period |
| Children (<18 years) | Not recommended | Not recommended | No clinical data; indication extremely rare in pediatric patients |
What Are the Side Effects of Foscan?
Side effects of Foscan-PDT can be broadly classified into two categories: local effects at and around the treatment site (which are largely expected consequences of the therapeutic tissue destruction), and systemic effects related to the generalized photosensitivity caused by temoporfin distribution throughout the body. Understanding this distinction is important because many of the local effects, while uncomfortable, are signs that the treatment is working as intended.
The following side effects have been reported in clinical trials and post-marketing surveillance. Not all patients will experience all of these effects, and the severity can vary widely depending on tumor size, location, treatment parameters, and individual patient factors.
Very Common
Affects more than 1 in 10 patients
- Pain at the treatment site (often significant, requiring opioid analgesia)
- Photosensitivity reactions (skin redness, burning, blistering on sun-exposed areas)
- Edema and swelling at the illuminated site
- Tissue necrosis at the treatment site (expected therapeutic effect)
- Scarring and fibrosis at the treated area
- Facial edema (especially for tumors of the oral cavity or oropharynx)
- Dysphagia (difficulty swallowing, for pharyngeal/laryngeal tumors)
- Constipation
Common
Affects 1 in 10 to 1 in 100 patients
- Nausea and vomiting
- Skin burns from unprotected light exposure
- Headache
- Infection at the treatment site
- Bleeding (hemorrhage) at the treatment site as necrotic tissue sloughs
- Fever
- Anemia
- Ulceration at the treatment site
- Dysphonia (voice changes, for laryngeal tumors)
- Trismus (difficulty opening the mouth, for oral tumors)
Uncommon
Affects 1 in 100 to 1 in 1,000 patients
- Fistula formation (abnormal connections between body cavities)
- Abscess formation at the treatment site
- Airway obstruction (due to post-treatment swelling near the airway)
- Subcutaneous emphysema (air under the skin)
- Allergic or hypersensitivity reactions
- Injection site necrosis (if extravasation occurs)
Rare
Affects fewer than 1 in 1,000 patients
- Fatal hemorrhage (from tumors near major blood vessels)
- Severe anaphylactic reaction
- Third-degree photosensitivity burns requiring skin grafting
- Perforation of tissue planes adjacent to the tumor
- Stroke (reported in single case reports, causal relationship uncertain)
The local effects at the treatment site typically follow a predictable timeline. Pain begins during or immediately after laser illumination and peaks within the first 24–48 hours. Tissue swelling and edema develop within hours and peak at 2–4 days post-illumination. Tumor necrosis becomes apparent over the following 1–2 weeks as dead tissue sloughs, which may be accompanied by temporary worsening of symptoms, malodorous discharge, and minor bleeding. Healing and scar formation typically occur over 4–8 weeks, though this varies considerably based on the size and depth of tissue destruction.
Photosensitivity reactions are the most important systemic side effect and can range from mild erythema (redness) resembling a sunburn to severe blistering and deep tissue burns requiring hospitalization. These reactions can occur anywhere on the body that is exposed to light, including through window glass. The eyes are also at risk, and ocular photosensitivity can cause pain, tearing, and temporary visual disturbance. Strict adherence to the light avoidance protocol is the primary means of preventing photosensitivity reactions.
Contact your healthcare team immediately if you experience: difficulty breathing or swallowing that worsens suddenly (may indicate airway obstruction); significant bleeding from the treatment site; severe skin burns or blistering from light exposure; signs of infection such as high fever, increasing redness, warmth, or pus at the treatment site; or severe pain that is not controlled by your prescribed pain medication.
How Should You Store Foscan?
Foscan is a photosensitive medication that requires careful storage conditions to maintain its stability and therapeutic activity. Because temoporfin is activated by light, improper storage with light exposure could degrade the active substance and reduce treatment effectiveness.
- Temperature: Store in a refrigerator at 2–8°C. Do not freeze. If the solution has been frozen, it must not be used.
- Light protection: Keep the vials in the outer carton to protect from light. Ambient fluorescent or incandescent room lighting can degrade temoporfin over time. When the vial is removed from the carton for preparation, exposure to room light should be minimized.
- Preparation: Once drawn into a syringe for injection, Foscan should be administered immediately. If there is any delay, the syringe should be protected from light by wrapping in aluminum foil or using an opaque syringe cover.
- Shelf life: The shelf life is specified on the packaging. Do not use after the expiry date stated on the carton and vial label.
- Appearance: Foscan solution should be a clear, dark reddish-brown liquid. Do not use if the solution appears cloudy, contains particles, or has changed color significantly.
- Disposal: Any unused Foscan or waste material must be disposed of in accordance with local requirements for cytotoxic/photosensitizing pharmaceutical waste. Due to its photosensitizing nature, special precautions should be taken to avoid skin contact during handling and disposal.
As Foscan is exclusively a hospital-administered medication, patients do not need to store it at home. The hospital pharmacy is responsible for maintaining proper storage conditions and ensuring that the product is used within its shelf life. The treatment center should have established protocols for the safe handling and storage of photosensitizing agents.
What Does Foscan Contain?
Foscan is a relatively simple pharmaceutical formulation. The active substance, temoporfin, is a hydrophobic (water-insoluble) molecule that requires an organic solvent system for intravenous administration. The formulation details are as follows:
- Active substance: Temoporfin (meta-tetrahydroxyphenylchlorin, mTHPC) — 1 mg per milliliter of solution. Temoporfin is a synthetic chlorin-type photosensitizer with the molecular formula C44H32N4O4 and a molecular weight of approximately 680.7 g/mol. It is a dark reddish-brown crystalline powder that is practically insoluble in water but soluble in ethanol and propylene glycol.
- Ethanol (absolute): Serves as the primary solvent for temoporfin. The ethanol content per dose is clinically relevant, particularly for patients with liver disease, those taking disulfiram or metronidazole, patients with alcohol dependence, and in pediatric patients (though the drug is not indicated in children). Each vial contains a significant proportion of ethanol, and this should be considered in the context of the patient’s overall alcohol exposure.
- Propylene glycol: Acts as a co-solvent to maintain temoporfin in stable solution. Propylene glycol is generally well tolerated but can occasionally cause local irritation at the injection site. In very rare cases, propylene glycol can cause hyperosmolarity and lactic acidosis in susceptible patients, although the amount in a single Foscan dose is unlikely to cause such effects.
Foscan is available as a clear, dark reddish-brown solution in glass vials. Each vial contains either 1 ml (1 mg temoporfin), 3 ml (3 mg temoporfin), or 6 ml (6 mg temoporfin) of solution. The glass vials are amber-colored to provide additional light protection. The vials are closed with rubber stoppers and sealed with aluminum caps. The appropriate number of vials for a given patient is calculated based on the patient’s body weight using the standard dose of 0.15 mg/kg.
It is noteworthy that Foscan contains no preservatives, buffers, or complex excipients such as polysorbates or cyclodextrins that are found in many other injectable oncology products. The simplicity of the formulation reflects the good solubility of temoporfin in the ethanol/propylene glycol solvent system. However, this solvent system means that Foscan is not compatible with aqueous diluents and must not be mixed with saline or dextrose solutions. If dilution is ever required, it should be performed only with a compatible solvent as specified in the product information.
Frequently Asked Questions About Foscan
Photodynamic therapy (PDT) is a cancer treatment that uses a photosensitizing drug (such as Foscan) in combination with light to destroy tumor tissue. Unlike surgery, PDT does not require cutting and removes the tumor through a photochemical reaction. Unlike radiotherapy, PDT does not use ionizing radiation and does not have cumulative dose limits, so it can potentially be repeated. Unlike systemic chemotherapy, PDT primarily affects the illuminated area and has minimal systemic side effects apart from photosensitivity. PDT is particularly useful for tumors that are accessible to light delivery and where conventional treatments have failed or are not feasible.
The 96-hour (4-day) drug-light interval is critical for optimal treatment outcomes. After injection, temoporfin circulates throughout the body and gradually accumulates in tissues. Research has shown that at 96 hours, the concentration of temoporfin in tumor tissue is at its highest relative to surrounding normal tissue (a ratio of approximately 3:1 to 5:1). Illuminating too early means more drug in the blood vessels and normal tissue, leading to excessive vascular damage and collateral injury. Illuminating too late means the drug has begun to clear from the tumor, reducing effectiveness. The 96-hour interval represents the “sweet spot” for maximizing tumor destruction while preserving surrounding healthy tissue.
No, conventional sunscreens are not effective protection against Foscan-induced photosensitivity. Standard sunscreens are designed to block ultraviolet (UV) radiation, but temoporfin is activated by visible red light (652 nm wavelength), which sunscreens do not block. Physical barriers (thick clothing, gloves, wide-brimmed hats, dark wrap-around sunglasses) are essential. The only effective protection is to avoid exposure to bright light entirely. Stay in rooms with low ambient light levels (below 500 lux), keep curtains closed, and do not go outdoors during daylight hours for at least 15 days after injection.
The laser illumination phase of treatment can cause significant pain, which is a result of the photodynamic reaction destroying tumor tissue. Pain typically begins during illumination and peaks within the first 24–48 hours. The degree of pain depends on the tumor size, location, and depth of tissue destruction. Pain management is a critical part of Foscan-PDT and is planned in advance. Treatment may include local anesthesia during illumination, regular paracetamol and NSAIDs, opioid analgesics (morphine or oxycodone) for moderate to severe pain, and in some cases, patient-controlled analgesia (PCA) pumps. Pain usually improves significantly over the first 1–2 weeks as the acute inflammatory phase resolves.
Yes, one of the advantages of photodynamic therapy is that it can potentially be repeated. Unlike radiotherapy, which has cumulative dose limits, PDT does not have a maximum lifetime dose. If a tumor recurs or partially regrows after an initial Foscan-PDT treatment, a repeat treatment may be considered. A minimum interval of 4 weeks between treatments is recommended to allow tissue healing and resolution of photosensitivity from the previous dose. Each repeat treatment carries the same photosensitivity requirements (at least 15 days of strict light avoidance). The decision to repeat treatment should be made by the specialist team considering the response to previous treatment, the patient’s overall condition, and available alternatives.
All information is based on international medical guidelines and peer-reviewed research: EMA Summary of Product Characteristics for Foscan (current approved labeling), ESMO Clinical Practice Guidelines for Head and Neck Cancers (2024), peer-reviewed clinical trial data including the pivotal Phase III trials of Foscan-PDT in head and neck cancer (D’Cruz et al., Lancet Oncology; Copper et al., Archives of Otolaryngology), WHO guidelines for cancer treatment, and NICE technology appraisals on photodynamic therapy. All medical claims follow the GRADE evidence framework.
References
- European Medicines Agency (EMA). Foscan – Summary of Product Characteristics. Last updated 2024. Available from: EMA Product Information Database.
- D’Cruz AK, Robinson MH, Biel MA. mTHPC-mediated photodynamic therapy in patients with advanced, incurable head and neck cancer: a multicenter study. Lancet Oncology. 2004;5(10):627–632.
- Copper MP, Triesscheijn M, Tan IB,"; et al. Photodynamic therapy with temoporfin (Foscan) for squamous cell carcinoma of the oral cavity and oropharynx. Archives of Otolaryngology – Head and Neck Surgery. 2003;129(7):726–731.
- Agostinis P, Berg K, Cengel KA, et al. Photodynamic therapy of cancer: an update. CA: A Cancer Journal for Clinicians. 2011;61(4):250–281.
- European Society for Medical Oncology (ESMO). Clinical Practice Guidelines: Head and Neck Cancers. Updated 2024. ESMO Guidelines Committee.
- National Institute for Health and Care Excellence (NICE). Interventional procedures guidance: Photodynamic therapy for advanced head and neck tumours. 2023.
- Senge MO, Brandt JC. Temoporfin (Foscan) – a second generation photosensitizer. Photochemistry and Photobiology. 2011;87(6):1240–1296.
- Marchal S, Dolivet G, Lassalle HP, et al. Foscan and Foslip based photodynamic therapy in head and neck squamous cell carcinoma: outcome and mechanisms. Journal of Clinical Medicine. 2021;10(12):2657.
- World Health Organization (WHO). WHO Model List of Essential Medicines. 23rd List, 2023. Geneva: WHO.
- Hopper C, Kübler A, Lewis H, et al. mTHPC-mediated photodynamic therapy for early oral squamous cell carcinoma. International Journal of Cancer. 2004;111(1):138–146.
Editorial Team
Medical Writing
iMedic Medical Editorial Team – Specialists in oncology, head and neck surgery, and clinical pharmacology with documented clinical experience in photodynamic therapy
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iMedic Medical Review Board – Independent panel of medical experts who review all content according to EMA, WHO, and ESMO guidelines
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All content follows GRADE methodology for assessing quality of evidence and strength of recommendations
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