Immune-Cell Numbers Predict Response to Combination Immunotherapy in Melanoma

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Whether a melanoma patient will better respond to a single immunotherapy drug or two in combination depends on the abundance of certain white blood cells within their tumors, according to a new study conducted by UC San Francisco researchers joined by physicians from UCSF Health. The findings provide a novel predictive biomarker to identify patients who are most likely to respond well to a combination of immunotherapy drugs known as checkpoint inhibitors — and to protect those who won’t respond from potentially adverse side effects of combination treatment.

“Combination immunotherapy is super-expensive and very toxic,” said Adil Daud, MD, director of Melanoma Clinical Research at the UCSF Helen Diller Family Comprehensive Cancer Center and senior author of the new study. “You’re putting patients at a lot of extra risk if they don't need it, and you can adjust for that risk by knowing in advance who can benefit.”

The study, published online July 20, 2017 in Journal of Clinical Investigation Insight, describes an assay that measures the abundance of immune cells that infiltrate melanoma tumors. The findings revealed that patients who had lower levels of immune cells called T cells within their tumors benefitted most from two immunotherapy drugs in tandem. The measurements could provide clinicians with a means to predict patients who would most benefit from combination immunotherapy, the authors said.

“This is clinical research at its best,” said UCSF’s Katy Tsai, MD, a medical oncologist and lead author of the new report. “We have identified something as a predictive biomarker in melanoma, and we’re hoping to validate it in other tumor types as well.”

T cells are immune cells that patrol our body for signs of infection or other diseases, recognizing culprit cells via telltale proteins on their membranes. Our body’s normal cells carry certain proteins on their coats that act as “checkpoints,” making them invisible ...

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