Combining Radiation With Immunotherapy Shows Promise Against Melanoma

Combining radiation treatments with a new generation of immunotherapies is showing promise as a one-two-punch against melanoma, according to a study published in the Journal of Radiation Oncology.

When combined, the two therapies appear to have synergistic effects, according to James S. Welsh, MD, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, and colleagues.

On rare occasions, patients with melanoma can spontaneously go into remission. More common are partial spontaneous regressions of melanoma lesions. While scientists aren't certain what causes these effects, evidence points to the immune system mounting an attack on cancer cells.

A key observation that supports the role of the immune system in melanoma is the abscopal effect. This rare phenomenon occurs when a localised treatment such as radiation not only shrinks the targeted tumour but also stimulates the immune system to mount a systemic attack on cancer cells throughout the body.

Dr. Welsh saw the abscopal effect first-hand when he gave radiation treatment to a patient who had melanoma that had spread to his liver and bones. The radiation was intended to merely shrink the tumour in the patient's thigh bone, to relieve his pain, and reduce the risk of fracture. However, 3 months later, a computed tomography (CT) scan found no trace of cancer anywhere.

Many new immunotherapies for melanoma are being tried, some with notable results. One such example is a new generation of "checkpoint inhibitors." These are drugs that, in effect, remove the brakes that normally prevent the immune system from attacking cancer cells.

Radiation increasingly is being used alongside checkpoint inhibitors and other immunotherapies, with encouraging results, according to the authors.

Despite the recent successes of radiation and immunotherapy, not all patients are able to mount an effective immune system response to fight melanoma. So it is important to discover proteins or other biomarkers that can predict whether a patient will respond to immunotherapy, authors emphasised. Such biomarkers also could help quantify how well experimental therapies are working.