Ongoing Trial: The PET-Stop clinical trial is looking to improve the care of patients with advanced melanoma treated with immunotherapy

Immunotherapy has transformed the treatment landscape for patients with advanced melanoma that cannot be removed by surgery. Immunotherapy uses a person's own immune system to fight cancer, and a certain kind of immunotherapy—called immune checkpoint inhibitors such as anti-PD-1 drugs—are now standard treatment options for these patients. Research has shown that these therapies can be highly effective, even with short durations of treatment. However, the optimal duration of therapy has not yet been determined. Prior studies suggest that the cancer’s response to treatment as shown by imaging studies and biopsy may be key in identifying who can safely stop therapy early. Researchers are studying these approaches to improve patient outcomes by reducing risk of late side effects, costs of care, and the burden of frequent medical visits.

The PET-Stop study (EA6192) is investigating methods for determining when a patient has received the maximal benefit of immunotherapy, with no signs of residual tumor activity. The two primary methods include a PET scan to clarify if a stable or shrunken tumor site is still active and a biopsy to look for any residual cancer cells in patients with controlled/responding metastatic melanoma on anti-PD-1 therapy.

­­The primary goal of the study is to demonstrate that patients with no active disease by PET scan or biopsy can safely stop the anti-PD-1 therapy and will not see cancer growth or spread off treatment. Researchers are also studying the rate of late side effects. If this approach is successful, the researchers anticipate it will establish a new standard of care.

A second group of patients will also be evaluated on the study—those whose PET scan or biopsy shows residual active disease, but not growth or spread. Since these patients are not experiencing disease progression, the standard approach is to continue with anti-PD-1 therapy. In this group of patients, researchers will look to see if an additional year of anti-PD-1 therapy will clear their disease. If a large portion of patients experience disease progression, this will provide support for investigation of early intervention strategies in patients with a positive PET scan or biopsy on anti-PD-1 therapy.

Planned accrual for the study is up to 150 patients, and all participants will be monitored with scans every 3 months.

To be eligible for PET-Stop, patients must have advanced melanoma that cannot be removed by surgery and be actively receiving a standard anti-PD-1 therapy regimen (single drug or a combination of drugs). Their disease must be controlled or responding to treatment. They cannot be experiencing side effects that would prevent them from continuing their anti-PD-1 therapy, if needed.

Participants in the trial will be asked to contribute tumor and blood samples for future research. 

Learn more about EA6192/PET-Stop at ecog-acrin.org.