A recent study by researchers at the UCLA Health Jonsson Comprehensive Cancer Center has shown that a combination of the immune checkpoint inhibitor pembrolizumab and chemotherapy may improve survival outcomes for patients with small cell bladder cancer (SCBC) and small cell/neuroendocrine prostate cancer (NEPC). The research, published in Cell Reports Medicine, offers a promising new treatment method for these rare, but aggressive cancers.
Small cell cancers are known for their rapid growth and poor prognosis, with limited treatment options. Patients with advanced small cell bladder cancer typically survive between seven to 13 months, while people with small cell/NEPC have a median survival of only seven to nine months.
The research team, led by Arnold Chin, MD, PhD, a professor of urology at UCLA’s David Geffen School of Medicine, tested a regimen combining pembrolizumab with standard chemotherapy with encouraging results. The data show that 43% of patients saw either partial or complete regression of their disease. Significantly, 86% of those with small cell bladder cancer and 57% of those with small cell prostate cancer survived for two years, well beyond the typical survival rates for each of these forms of cancer.
“This combination of pembrolizumab and chemotherapy presents a promising new treatment approach for these challenging-to-treat, rare cancers and could be a major breakthrough for patient care,” said Chin, the study’s senior author.
The small trial include 15 people—seven with advanced or metastatic small cell bladder cancer and eight with small cell or neuroendocrine prostate cancer. All participants were those who would normally receive chemotherapy as part of their standard care.
The combination regimen was well-tolerated with no patients discontinuing therapy due to side effects and it showed favorable responses across both groups. In the bladder cancer cohort only one of the seven patients experienced disease progression during a median follow-up of almost three years. For the prostate cancer patients, the median survival was 27 months, far exceeding the seven to nine month survival typically expected for these patients.
“These results suggest that the combination therapy could provide a substantial survival benefit,” Chin noted.
In addition to the improved overall survival rates, the investigators also observed that the clonal expansion of CD8+ T cells in the blood, a type of immune cell, correlated with better progression-free survival. This suggests that blood tests could one day help predict which patients are more likely to benefit from this treatment.
While the findings are promising, the study’s authors caution that more research is needed due to the small number of patient involved and that these findings will need validation in larger clinical trials. Chin emphasized that the promising outcomes make the case for further studies to assess the potential for pembrolizumab and chemotherapy combinations in other forms of small cell cancer, as well as to explore how biomarkers might predict treatment response.
