Pembrolizumab Effective Against Some Types of Sarcoma

An existing cancer immunotherapy drug reduces the size of tumors in some forms of rare connective tissue cancers, called sarcomas, report researchers at the University of Pittsburgh Cancer Institute (UPCI). Additional analyses of tumor biopsies and blood samples, which will help the researchers better understand which sarcoma subtypes will benefit most from the new treatment, are underway.

Interim results from the phase II clinical trial were presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago.

Sarcoma is a rare disease, encompassing less than 1 percent of adult cancers, and the available treatments are limited, so the need for new therapies is high, explained the current lead investigator for the Pittsburgh site, Melissa Burgess, M.D., assistant professor of medicine at UPCI.

“This is a pivotal trial for sarcoma, the first and largest trial to be conducted using this specific immunotherapeutic approach. What makes this trial special is that we collected biopsies and blood samples to really study how the treatment is working or not working in these patients. These immune monitoring studies will offer unique insights into the biology of immunotherapy in sarcoma,” Dr. Burgess said.

Pembrolizumab Efficacy

By using a patient’s own immune cells, immunotherapy works to target cancer cells. The new trial examined the safety and effect of pembrolizumab, which currently is approved for use in advanced melanoma and certain types of advanced lung cancer, on tumor size in four types of soft tissue sarcomas and three types of bone sarcomas.

“Unfortunately, these early results suggest that there is limited efficacy of pembrolizumab in the patient population as a whole. However, it’s promising that the drug seems to be beneficial in specific sarcoma subtypes. Our ongoing immune monitoring studies will allow us to better characterize the patients who will most benefit from this therapy for future clinical trials,” said Dr. Burgess.

About 20 percent of patients in the combined soft tissue sarcoma group showed a reduction in tumor size during at least one time point.

However, when the researchers looked at the sarcoma subtypes individually, they found one with especially promising results: 44 percent of patients with undifferentiated pleomorphic sarcoma experienced a reduction in tumor size. Encouraging improvements in tumor size also were found in two subtypes of bone sarcomas, osteosarcoma and chondrosarcoma, Dr. Burgess noted.

Image: National Center for Advancing Translational Sciences (NCATS), National Institutes of Health