Photodynamic therapy or PDT is a relatively new and non-invasive treatment for non melanomaskin cancer. It is mostly used in cases where the cancer is superficial and has not spread too deep. PDT is used mostly to treat Actinic Keratoses on the face and scalp, Basal cell carcinomas, Bowen’s disease, as well as other conditions such as head and neck, mouth, lung and gullet cancer.

How does it work?

This treatment involves the use of a drug known as photosensitize or a photosensitizing agent with a specific type of light. When the photosensitizing agents get exposed to a light of a specific wavelength, a form of oxygen is produced, which eliminates nearby cancer cells. Every photosensitizer gets activated by the special light. The wavelength of the light determines how much it can penetrate into the body.

Process of Photodynamic therapy

Skin cancer is cured by PDT in several steps. The first step involves the injection of a photosensitizer into the patient’s bloodstream. The blood cells absorb the agent all over the body, but in the cancer cells, it stays for a longer duration. Within 72 hours after the injection is given, the skin is exposed to light. The photosensitizer agent present in the cancer affected cells absorbs the light. An active oxygen form gets produced, which kills the cancer cells.

Other than killing the cancer cells directly, PDT uses two other ways to destroy cancerous tumors. The blood vessels in the tumor are affected, which leads to its death. The immune system also gets charged up and activated for fighting the cancer cells.

The light used for PDT is usually in the form of a laser. LEDs are also used to treat tumors present on the surface of the skin. The primary photosensitizing agent used in PDT is called porfimer sodium or Photofrin.

PDT can be undertaken in the outpatient department in a hospital. After taking the treatment, you have to keep the cancer affected area of the skin dry and covered for 36 hours. The area should be treated with care while showering. In case of thick skin lesions, repeat treatments are required within 4 weeks.

When is PDT used for skin cancer?

PDT can be undertaken instead of surgery for treating basal cell cancer, Bowen’s disease and actinic keratosis. PDT is used in cases where surgeries are required. It is used to treat large skin cancers, which are not very deep and in the case when several cancers develop in an area. For many skin conditions, PDT is a better remedy than undergoing a surgery.

Advantages of PDT

There are no long term side effects.
-The process is less invasive compared to surgery.
-A very short time is taken for this therapy to be undertaken.
-The process can be repeated several times in the same area.
-Very less scarring takes place in the affected area.
-The cost of this procedure is lesser than surgery.

Costly, time-consuming and painful, a biopsy in the country often leaves cancer patients exhausted much before treatment begins. In an attempt to simplify the process and alleviate the pain, IIT Ropar has come up with rough sketches of what promises to be, a low-cost mechanism to detect skin cancer.

The thermal imaging process to detect skin cancer is a mechanism that will make detection of skin cancer considerably cheaper and also ease the existing process, which involves a painful extraction of skin tissues for testing.

The research team, headed by professor Ramjee Repaka, proposes to cuts the process to a painless 20-minute hospital sitting. The technology uses highlysensitive infrared (IR) thermal cameras to videograph the surface of the skin.

The camera designed to capture an `image' of the thermal activity in the body, maps cellular-level temperature changes during the procedure to confirm presence of cancer cells. "It is a noninvasive and non-contact solution that we are working on," says Ramjee, explaining the procedure. In the first step, a patient is made to place a cold gel pack on the surface of their skin to cool the body temperature.

Following this, the skin is allowed to transition to room temperature, while the IR camera records the change in thermal state.
"If the human hand is tested, the healthy cells may return to say 37°C (average body temperature), while the cancerous cells will be 0.1°C higher, distinguishing themselves from the remaining cells.This is because cancer cells naturally release heat while speeding up metabolisis to metastasize (spread in the body).

This difference in temperature, which is picked up by sensitive IR cameras, shows on the screen as a gradient," explains Ramjee. This is especially useful for detecting early stage skin cancer, where tissue lesion only measure 0.2 millimetre, and don't show any symptoms.

The procedure is relevant since skin cancer is tricky, says the
professor. "Many are not aware of the symptoms.While it can be brushed off as a rash, it is only when the cancer metastasizes, noticeably dark pink hues appear. With a lower-cost procedure like this, skin cancer checkups -like other types of cancers -can be done without an exhaustive procedure," says Ramjee.

The challenge, says Ramjee, is the lower occurrence rate of this particular type of cancer in the country when com pared to the West, leading to testing being overlooked. "Breast and cervical cancer tests, for instance, are done more rigorously owing to larger occurrence rates, while this is often overlooked. But if testing can be made more accessible, people can stop neglecting symptoms that start out small," he said.