Photodynamic therapy (PDT) offers a targeted approach for treating mesothelioma, a rare and aggressive cancer affecting the lining of organs. This treatment involves a precise two-stage process. First, a light-sensitizing drug is introduced into the body. Then, after a specific period, a particular wavelength of non-thermal light is directed at the cancerous area. This combination aims to selectively destroy cancer cells while minimizing potential harm to surrounding healthy tissues.
The Mechanism of Photodynamic Therapy
Photodynamic therapy uses a specialized drug, a photosensitizer, which is administered to the patient. This drug circulates throughout the body and is absorbed by various cells, but it accumulates and remains longer within rapidly dividing cancer cells than in healthy ones. Porfimer sodium (Photofrin) is a common photosensitizer.
After a waiting period, typically 24 to 72 hours, non-thermal light of a precise wavelength, often 630 nanometers, is directed at the tumor. This light activates the photosensitizer within the cancer cells, triggering a chemical reaction. This reaction produces a highly reactive form of oxygen called a singlet oxygen. The singlet oxygen then kills nearby cancer cells directly through processes like apoptosis and necrosis, and can also disrupt the blood vessels supplying the tumor.
The Patient Treatment Journey
Photodynamic therapy for mesothelioma often integrates with surgical procedures. Treatment begins with the photosensitizer drug, commonly given intravenously as an outpatient procedure. For instance, porfimer sodium might be infused at a dosage of approximately 2 milligrams per kilogram of body weight. This allows the drug to distribute throughout the body.
After the drug administration and waiting period, the main light application procedure takes place. This is frequently performed during surgery, such as a pleurectomy/decortication, where visible tumor masses are surgically removed. After the surgeon resects the macroscopic disease, a specialized light source, often delivered via fiber optics, illuminates the chest cavity. This targets any remaining microscopic cancer cells not visible or fully removed. This multimodal approach, combining surgery with intraoperative photodynamic therapy, enhances local control of the disease.
Candidacy for Photodynamic Therapy
Determining a patient’s suitability for photodynamic therapy involves evaluating several specific factors. This treatment is primarily considered for individuals diagnosed with pleural mesothelioma, a form of the cancer affecting the lung lining. It demonstrates greater effectiveness in earlier stages of the disease, where the cancer is localized rather than widely spread throughout the body.
A significant consideration is the characteristics of the tumor itself. For the most common application of photodynamic therapy, particularly when combined with surgery, the tumor must be resectable, meaning it can be physically removed by a surgeon. Additionally, the patient’s overall health plays a role; they must be well enough to tolerate the associated surgical procedure, as PDT is often performed during or immediately following tumor removal. Prior treatments a patient has undergone might also influence their candidacy, as doctors assess the comprehensive medical history to determine the most appropriate course of action.
Side Effects and Recovery
Patients undergoing photodynamic therapy for mesothelioma can anticipate certain side effects, with photosensitivity being the primary concern. After receiving the photosensitizer drug, individuals become highly sensitive to both direct sunlight and bright indoor lights. This sensitivity typically lasts for several weeks, often between four to six weeks, as the drug gradually clears from the body. To manage this, patients receive specific instructions, including staying indoors, wearing protective clothing such as wide-brimmed hats, long sleeves, and gloves, and using sunglasses when outdoors, even on cloudy days.
Other potential side effects are generally related to the procedure itself and are often localized. These may include temporary pain, swelling, or inflammation in the treated area. Some patients might also experience mild fatigue as their body recovers from the treatment. Recovery time can vary, with hospital stays typically ranging from a few days to about a week, depending on the extent of the surgery performed alongside the PDT. Managing the light sensitivity is a distinctive aspect of recovery from photodynamic therapy compared to other cancer treatments.