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Photodynamic Therapy (PDT)

Photodynamic Therapy (PDT)

PHOTODYNAMIC THERAPY CANCER TREATMENT (PDT)

PDT is a non-surgical treatment used to treat a variety of medical conditions, including:

  • chronic pain and inflammatory joint disorders
  • skin conditions such as psoriasis, acne, and rosacea
  • pre-cancerous and cancerous lesions of the skin (actinic keratosis, small basal cell carcinomas, and other non-melanoma skin cancers)
  • solid tumors, leukemias, and lymphomas (investigational)

Photodynamic therapy is an effective treatment for tumours, such as Breast Cancer, Lymphoma, Prostate Cancer, Ovarian Cancer, Pancreatic Cancer, Hepatocellular Cancer, Sarcomas, Non-Muscle Invasive Bladder Cancer, Cervical Cancer, Head & Neck Cancer, Melanoma, etc).

Depending on your diagnosis, you may be a candidate for treatment with photodynamic therapy (PDT).
PDT is a non-toxic treatment that uses laser light to activate a light-sensitive compound in the presence of oxygen, which in turn causes tumor destruction by apoptosis (initiating cancer cell death), anti-vascular effects by tumor vessel destruction and the prevention of new tumor blood vessel formation, and stimulation of a T-cell tumor-specific immune response, thereby engaging the body’s own immune system to launch an attack against the cancer. The tumor-specific immune response is critical to address cancer stem cells to prevent distant metastases (spread of the cancer) and to prevent future cancer recurrence.

Treatment begins when you receive the compound intravenously (through an IV). The compound, called a photosensitizer, is absorbed by cells in your body within 24-48 hours, concentrating in cancer cells. Tumors are then exposed to a light of a specific wavelength, delivered through very thin, flexible fiber-optic cables. The laser light penetrates the cancerous tissue and activates the photosensitizer. Because the photosensitizer is inside the cancerous cells only, those cells are targeted for destruction, with little impact on healthy cells.

PDT has three main effects:

  • It kills cancer cells directly, by apoptosis and necrosis.
  • It destroys blood vessels feeding the tumor(s) and prevents neo-vascularization, also known as anti-angiogenesis, thereby slowing and preventing further growth and spread of cancer.
  • The action of PDT on cancer cells leads to the expression of certain proteins and chemokines (chemical messengers) that in turn recruit specific immune cells to the tumor to initiate destruction of the tumor and can alert other immune cells to destroy cancer cells throughout the body.

The photosensitizer causes no side effects other than sensitivity to light. Depending on the type of photosensitizer you receive, for several weeks after treatment, you will need to cover up, use sunscreen, and stay out of direct sunlight.

Photodynamic therapy can be applied externally without needle (on the skin overlying the area to be treated), interstitially (using a needle and often with ultrasound guidance to direct the placement of the fiber optic in the region of the tumor) and intravenously (using a needle catheter with fiber optic placed in the vein to irradiate blood).

PDT is widely recognized as an effective treatment for localized cancers. Presently offered at select private treatment centers, PDT for cancer treatment is being actively studied in several clinical trials across the globe. In most cases, PDT is not intended as a stand-alone treatment for cancer. It is novel, evidence-based and clinically useful therapy integrated with a multi-modal treatment approach for cancer that may include intravenous vitamin C therapy, intravenous DCA, local-regional hyperthermia, chemotherapy or targeted therapies or immune checkpoint inhibitors, and other therapies. Hyperbaric oxygen therapy (HBOT) enhances the effects of PDT by driving oxygen to the areas to be treated, amplifying the production of reactive oxygen species (ROS) and oxidative stress generated by photo-activation of the photosensitizer. As such, our protocols involve pre-treatment with HBOT. Several types of chemotherapy are sensitive to certain wavelengths of laser light. As a result, the anti-tumor effects of certain chemotherapy agents (such as Paclitaxel, Docetaxel, 5-Fluorouracil, Cisplatin, Carboplatin) can be augmented with the application of laser-light therapy.

Topical Treatment for Skin Conditions and Skin Cancer:

Photodynamic therapy for skin conditions (acne, actinic keratosis, etc.) involves three steps: a topical solution of a light-activated solution (photosensitizer) such as aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) also known as Levulan or Metvix, is applied to the area to be treated, the solution is left on the skin for about 60-90 minutes to incubate, and then a high-intensity light or laser source is applied to the skin to activate the Levulan or Metvix, causing destruction of the unhealthy cells, followed by a healing phase involving scaling, crusting, itching, redness and mild swelling.

Our physicians will recommend topical and supportive therapies to manage the immediate post-treatment effects and expedite healing. Our treatment not only resolves the specific dermatologic concern but also improves the overall tone, texture, and appearance of the skin, yielding a more youthful and rejuvenated visage. For 48 hours after treatment, you will need to avoid direct sunlight, wear protective clothing and SPF 50 (minimum). Treatments are usually performed 2-4 weeks apart, depending on the condition to be addressed. PDT is contraindicated in patients who are breastfeeding or pregnant. It is also contraindicated if you have lupus, porphyria or extreme photo-sensitivity (sun allergy). PDT may react with certain medications.

References
I-PDT A Focused Review 2017Advance in PS and Light Delivery for PDT
PDT for Pancreatic and Biliary Tract Carcinomas – 2005
Hypericin and PDT in Cancer
Perspective on PDT for Pancreatic Cancer – 2012
New PS agents in PDT – 2016
Nimotuzumab and PDT oral SCC (preclinical study) 2015