Is photodynamic therapy revolutionary enough to replace conventional treatments for cancer?

Photodynamic therapy uses light to selectively destroy cancer cells, minimizing damage to normal tissue and reducing side effects, and recent studies have proven its effectiveness and safety.

 

As of 2024, cancer is the number one cause of death in South Korea. Although attempts have been made to overcome cancer through various methods such as chemotherapy and radiation therapy, cancer has not been completely conquered and remains a major problem for mankind. Treating cancer means eliminating cancer cells. While complete eradication of cancer cells is important, it’s equally important to use a treatment that doesn’t destroy normal cells. Even if all the cancer cells in the body are removed, if other organs are damaged during the treatment process and the patient is unable to live a normal life, the treatment will be useless. That’s why most of the recent developments in cancer treatment are targeted therapies that attack and destroy only cancer cells. One of these targeted therapies is photodynamic therapy, which uses light to destroy cancer cells.
Photodynamic therapy, also known as photochemotherapy, consists of three main steps. These three steps work organically: the introduction of a photosensitizer, the projection of light, and the generation of oxygen. The photosensitizer reacts to light with a specific wavelength. The photosensitizers used in photodynamic therapy are harmless to the human body, and when they react to light, they produce free radicals. Free radicals are different from the oxygen we know as being present in the air. The oxygen in the air is in the form of a molecule with two oxygen atoms bonded together, so it is less reactive and does not react easily with surrounding substances. However, free radicals are highly reactive because they exist as a single oxygen atom that is not bonded to any other oxygen atom, so they can easily react with the surrounding substances. Therefore, when free radicals are produced in the body, the cells around them cannot function properly and are destroyed.
Therefore, it is important to make sure that the photosensitizer is attached to the tissue that contains the cancer cells in the body. If the photosensitizer is attached to normal tissue, the free radicals generated by the photosensitizer will destroy the normal tissue and the treatment will fail. This problem is solved by using antibodies. Cells and the substances that make up them have a specific structure that allows them to recognize each other. When a substance is found that was not originally in the body, the body makes antibodies that bind to the characteristic structure of the substance. The traditional function of this antibody is to help the body’s white blood cells recognize the antibody and remove the foreign substance, but in photodynamic therapy, the antibody helps the photosensitizer bind to the cancer cells. When the photosensitizer is attached to an antibody that is specific for cancer cells, the antibody binds to the cancer cells, causing the photosensitizer to cluster near where the cancer cells are located. When light of a specific wavelength is emitted to which the photosensitizer reacts, free radicals are generated in the vicinity of the cancer cells, and the free radicals destroy the cancer cells.
Photodynamic therapy, which has the function of targeted therapy, has recently gained attention as a treatment with fewer side effects and toxicity. This is because there are fewer side effects compared to radiation or drug treatment, and the photosensitizer in the body is discharged from the body over time after the procedure. However, limitations of photodynamic therapy include the fact that the patient cannot undergo the procedure until the photosensitizer has been absorbed into the cancer cells and all the remaining photosensitizer has been removed, and that cancer cells that are deeply embedded in the body cannot be removed with current technology due to the limitations of the depth at which light can penetrate.
However, photodynamic therapy is advancing every day. On September 5, 2022, the second-generation photosensitizer used in photodynamic therapy was designated as an orphan drug by the Ministry of Food and Drug Safety. Compared to the first generation of photosensitizers, the waiting time for treatment has been reduced from more than 48 hours to 3 hours and the depth of treatment from 4 mm to 12-15 mm. In addition, recent studies have confirmed that petosecond pulsed lasers can be used to effectively treat intractable cancers such as ocular melanoma. The technology uses high-energy light for a fraction of a second to destroy cancer cells with minimal damage to surrounding normal tissue.
Additionally, a new porphyrin dimer is being investigated as a potential drug for photodynamic therapy. The dimers exhibit higher photoreactivity than conventional monomers, which could significantly improve the efficiency and safety of the treatment. These steady advances in photodynamic therapy are opening up new possibilities for cancer treatment and are becoming an innovative way to treat a variety of cancers.
If the day comes when photodynamic therapy retains its advantages and overcomes its disadvantages, it will be the day when mankind conquers cancer.