The treatment of malignant melanoma has undergone a revolution in the last ten years with the advent of highly effective immune therapy – so-called immune checkpoint inhibitors, which unleash the immune system against the cancer. Many patients have prolonged remissions after completing a course of therapy and going off treatment. Some have persistently positive PET scans, indicative of possible residual active cancer. What to do for such patients is unclear.
A very interesting study was recently published in the Journal of Immunotherapy. Several authors from the Dana Farber Cancer Institute at Harvard Medical School identified seven patients with persistently positive PET scans who had been on a prolonged course of immunotherapy but whose treatment had been discontinued at least six months before biopsy. These patients underwent biopsies of the persistently PET positive lesions, most of which were lymph nodes. So what was found?
Six of the seven patients had no tumor found at surgery. Many had extensive invasion of the biopsy site with activated immune cells. The seventh did have evidence of cancer. That patient underwent more extensive surgery as a result of that finding. All patients remain alive and free of disease.
Dr. Stark comments: “Persistent remission long after stopping therapy in patients with metastatic melanoma was unheard of until recently. This study provides reassurance that some patients with persistently positive PET scans can be observed safely without further treatment, and may indeed be cured.”