Patients aged 62 and older are more likely to respond to immune checkpoint inhibitors for melanoma, such as pembrolizumab, according to findings from a study published in Clinical Cancer Research. A follow-up study showed that it may be because of age-related changes in the immune cells in melanoma tumors.
Researchers evaluated data from 538 people with metastatic melanoma who were treated with pembrolizumab at several cancer centers around the world. They found that 63% of patients aged 62 or older had tumor shrinkage or stable disease after treatment versus 51% of those younger than age 62. And for every additional decade of age, patients were 13% less likely to become resistant to pembrolizumab.
The findings are surprising because people’s immune system activity generally declines with age, the researchers explained. They conducted a follow-up study in mice to better understand the findings.
What they uncovered is that tumors in young mice contained more regulatory T cells and fewer cytotoxic T cells than tumors in older mice. Other studies have shown that tumors with fewer regulatory T cells than cytotoxic T cells respond better to immunotherapy treatments.
Researchers do not know exactly why older adults have fewer regulatory T cells in their melanoma tumors, but they hypothesized that the tumors are less able to recruit the cells as people age. Additionally, they noted that regulatory T cells differ by organ and that the findings may not apply to the types of T cells found in tumors in other areas of the body, such as the lung or stomach.