Photodynamic therapy (PDT) is a treatment with a long and successful clinical track record for oncology and non-malignancies. It is increasingly being used for aesthetic treatments, and in particular, for face rejuvenation. There are also basic and clinical studies in the field of antimicrobial PDT.
A cancer treatment protocol involves the introduction of a photosensitizing agent into the body, which can be administered intravenously, orally, or topically. Once the photosensitizer has preferentially accumulated in the tumor region, it is exposed to light of the appropriate wavelength and intensity. The photodynamic reaction produces an active form of oxygen that destroys nearby tumor cells and neovasculature. In addition, there are indications that this process may stimulate an immune response to attack tumor cells.
The FDA and regulatory agencies in other counties have approved a number of photosensitizers for use in PDT. A table below shows a list of photosensitizers that have been developed to date; the list is growing, as new photosensitizers are being developed to improve the effectiveness of PDT and to expand it to other conditions.
Photosensitizers for Photodynamic Therapy
| Sensitizer | Trade name | Indication | Wavelength | εmax(M−1cm−1) |
|---|---|---|---|---|
| Porfimer sodium | Photofrin® | Cervical, endobronchial, esophageal, lung, bladder and gastric cancers, and brain tumors | 410 nm 632 nm |
3,000 |
| Boronated protoporphyrin | BOPP | Brain tumors | 632 nm | |
| 5-ALA | Levulan® | Basal-cell carcinoma, head and neck, actinic keratosis and gynecological tumors | 635 nm | 5,000 |
| 5-ALA-methylesther | Metvix® | Basal-cell carcinoma | 635 nm | |
| 5-ALA benzylesther | Benzvix® | Gastrointestinal cancer | 635 nm | |
| m-THPC | Foscan® | Head, neck, prostate and pancreatic tumors | 652 nm | 35,000 |
| Tin ethil etiopurpurin (SnET2) | Purlytin® | Cutaneous metastatic breast cancer, basal-cell carcinoma, Kaposi’s sarcoma, prostate cancer | 664 nm | 30,000 |
| Taporfin sodium | Talaporfin® | Solid tumors of diverse origins | 664 nm | |
| N-aspartyl chlorin e6 (NPe6) | Laserphyrin® | Lung cancer | 664 nm | 40,000 |
| HPPH | Photochlor® | Basal-cell carcinoma, esophogeal cancer, lung cancer, Barrett’s esophagus | 665 nm | 47,000 |
| Silicon Phthalocyanine-4 | Pc 4 | Actinic keratosis, Bowen’s disease, skin cancer, mycosis fungoides | 675 nm | 200,000 |
| Aluminum phthalocyanine tetrasulfonate (AlPcS4) | Stomach, skin, lips, oral cavity, tongue, breast cancer | 676 nm | 200,000 | |
| Verteporfin (BPD-MA) | Visudyne® | Age-Related Macular Degeneration, Basal-cell carcinoma | 689 nm | 34,000 |
| Lutetium texaphyrin | Lutrin® Optrin® Antrin® | Cervical, prostate and brain tumors, breast cancer and malignant melanoma, peripheral arterial disease and coronary arterial disease, age-related macular degeneration | 732 nm | 42,000 |
| Palladium bacteriopheophorbide (WST11) | Tookad-Soluble® | Prostate cancer | 753-757 nm | 88,000 |
| Palladium bacteriopheophorbide (WST09) | Tookad® | Prostate cancer | 763 nm |
Each photosensitizer requires a specific wavelength and intensity of light for its activation. However, the penetration of light into a tissue is rather limited. A blue light will penetrate tissue to less than 1mm, while light with a wavelength from 650nm to 1350nm, can travel for more than 1cm in a human body. Therefore, the choice of wavelengths of light can influence the depth and volume of treatment. While blue light is often employed for epithelial cancer treatment and cutaneous procedures, it is not suitable for solid tumors. Red and infrared light, on the other hand, can be employed for bulky tumors. Therefore, there is no universal light source for every PDT protocol. Each photosensitizer requires a specific light source for optimal performance. An additional consideration is the uniformity of the laser light exposure within tumor tissue, as successful tumor ablation ultimately requires a precision amount of light energy to activate enough photosensitizer for lesion destruction.
Lasers are the most common sources of light for PDT. Diode lasers can be manufactured to output light with the wavelength corresponding to the absorption peak of the particular photosensitizer and with the required power.
At AKELA Lasers, we offer a wide range of multi-mode fiber coupled laser diode modules for PDT. They are available for every wavelength used in PDT with output power up to 10 watts. Our multi-wavelengths modules can be configured to work with multiple photosensitizers. We also offer a turn-key system that can deliver 4 different wavelengths. It is equipped with a sophisticated light delivery hardware, which provides unmatched uniformity of irradiation and exposure control. This innovation allows for a more uniform calculation of light dose for therapy, particularly for multicenter clinical trials where uniform treatment time was critical to assessing outcomes and morbidity.