An existing cancer immunotherapy drug reduces tumor size in some types 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 today at the 52nd annual American Society of Clinical Oncology (ASCO) annual meeting in Chicago by principal investigator Hussein Abdul-Hassan Tawbi, M.D., Ph.D., formerly of UPCI and current associate professor, University of Texas MD Anderson Cancer Center.
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.
Immunotherapies work by using a patient's own immune cells 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.
UPCI, the first of 12 sites to enroll subjects, contributed approximately one quarter of the 80 total patients. Patients received the drug every three weeks. Tumor assessments began at eight weeks and were conducted every 12 weeks thereafter. The trial enrolled on a rolling basis, and is still in progress, so in these results, not all patients have received the drug for the same amount of time.
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.
"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.
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