Medically reviewed by Prof. Shimon Slavin, MD. Updated: August 2026
Photodynamic therapy (PDT) is a cancer treatment method based on the use of a photosensitive agent and light of a specific wavelength to damage malignant cells.
At Biotherapy International, PDT may be included in an individualized cancer treatment protocol, most often in combination with oncolytic virus therapy. The goal of this approach is to use different mechanisms of action against the tumor and create more favorable conditions for a subsequent anti-cancer immune response.
What Is Photodynamic Therapy?
PDT includes two main components:
- A photosensitizer — a light-sensitive agent that is administered to the patient or applied locally.
- A controlled light source that activates the photosensitizer.
After light activation, reactive oxygen species are produced that can damage tumor cells and lead to their destruction.
The anti-cancer effects of PDT are associated not only with direct damage to malignant cells, but also with processes that may contribute to a subsequent immune response against the tumor.
How Does Photodynamic Therapy Work Against Cancer?
PDT can affect a tumor through several complementary mechanisms.
Direct Damage to Tumor Cells
After activation of the photosensitizer, reactive oxygen species are produced that damage cellular structures and may lead to cancer cell death.
Release of Tumor Antigens and Immune Response
When tumor cells are damaged and destroyed, tumor-associated antigens are released and may become more accessible to the immune system.
This effect is particularly important when PDT is used together with immunotherapy, as it may help immune cells recognize the tumor more effectively and support an anti-cancer immune response.
Effects on Tumor Blood Vessels
PDT may also damage abnormal blood vessels within the tumor, potentially interfering with its blood supply and providing an additional anti-cancer effect.
Why Combine PDT with Oncolytic Viruses?
At Biotherapy International, PDT is frequently used in combination with oncolytic virus therapy.
Our protocols use two types of oncolytic viruses known for their ability to preferentially infect malignant cells, replicate within them, and cause their destruction.
PDT affects tumor cells through a different mechanism, primarily through oxidative damage. Combining these approaches therefore makes it possible to target the tumor through different mechanisms:
- oncolytic viruses infect and destroy malignant cells;
- PDT provides an additional mechanism of tumor cell damage;
- destruction of tumor cells promotes the release of tumor-associated antigens;
- changes in the tumor microenvironment may create more favorable conditions for a subsequent immune response.
PDT is therefore considered one of the methods that can complement the effects of oncolytic virus therapy as part of a comprehensive treatment protocol.
Photodynamic Therapy and Immunotherapy
In our treatment strategy, PDT and oncolytic viruses may be used as a stage preceding subsequent immunotherapy.
The destruction of some tumor cells and the release of tumor-associated antigens may help the immune system recognize remaining malignant cells more effectively and may make the tumor more responsive to further immune-based treatment.
Subsequent treatment may include immune checkpoint inhibitors or Cytokine-Mediated Immunotherapy (CMI) to further strengthen the anti-cancer immune response.
How Is Photodynamic Therapy Performed?
The method of PDT administration depends on the location of the tumor, the photosensitizer used, and the individual clinical situation.
The photosensitizer may be administered intravenously or applied locally. After it has been distributed, light activation is performed. The physician determines the treatment parameters individually, including the wavelength, intensity, and duration of light exposure.
The method of light delivery also depends on the location of the tumor. For superficial tumors, light may be directed directly onto the affected area. For certain tumors located inside the body, light may be delivered to the treatment area using an optical fiber or endoscopic equipment.
The specific method of PDT administration is determined by the physician based on the type of tumor and the overall treatment protocol.
Photodynamic Therapy for Cancer in Germany
Biotherapy International may include PDT in individualized cancer treatment protocols carried out at our partner clinic in Germany.
In our programs, PDT is most often used as part of a combined approach together with oncolytic virus therapy and subsequent immunotherapy.
The protocol is developed individually after reviewing the patient’s diagnosis, previous treatments, current disease status, and medical records.
Individual Treatment Planning
There is no single PDT protocol suitable for every cancer patient.
Before treatment, the patient’s medical records are reviewed and an online consultation is conducted with Prof. Shimon Slavin, Medical & Scientific Director of Biotherapy International.
Based on the diagnosis, previous treatments, and current disease status, Prof. Slavin determines whether PDT, oncolytic viruses, and other immunotherapy approaches may be included in an individualized treatment protocol.
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