A UCLA Health research team has found that combining pembrolizumab, an immunotherapy drug, with standard chemotherapy improves treatment outcomes for patients with small cell bladder cancer and small cell/neuroendocrine prostate cancer. The early-stage study, published in Cell Reports Medicine, demonstrates a promising new treatment approach for these rare and aggressive cancers.
Improved Survival Rates
The clinical trial involved 15 patients divided into two cohorts: seven with advanced or metastatic small cell bladder cancer and eight with primary small cell or neuroendocrine prostate cancer. The results showed that 43% of patients experienced a partial or complete regression of the disease. Notably, 86% of bladder cancer patients and 57% of prostate cancer patients were still alive after two years.
For the prostate cancer group, the median survival reached 27 months, significantly exceeding the historical average of 7 to 9 months. In the bladder cancer group, only one patient experienced disease progression after a median follow-up of nearly three years. These results suggest a substantial survival benefit from the combination therapy.
Mechanism and Biomarkers
The study also revealed that the clonal expansion of CD8+ T cells in the blood, a type of immune cell, correlated with better progression-free survival. This finding indicates that a blood test could potentially predict treatment response in future patients. According to Dr. Arnold Chin, professor of urology at the David Geffen School of Medicine at UCLA and senior author of the study, this could be a major breakthrough for patient care.
Study Design and Tolerability
The trial was designed for patients who would typically receive chemotherapy as part of their standard care. The combination treatment was well-tolerated, with no patients needing to discontinue therapy due to side effects. This favorable tolerability, combined with the encouraging survival rates, supports the need for larger clinical trials to confirm these findings.
Context and Future Directions
Small cell carcinomas, known for their rapid progression and high relapse rates, often lead to poor overall survival. The survival time for patients with advanced small cell bladder cancer is typically 7 to 13 months, while for small cell/neuroendocrine prostate cancer, it is only 7 to 9 months. Inspired by the success of immunotherapy in small cell lung cancer, researchers at UCLA hypothesized that a similar approach could benefit patients with urologic small cell cancers.
"These activities seen with this combination absolutely are promising," said Pedro Barata, a medical oncologist at University Hospitals who was not involved in the study. "If this data is proven in a large setting, [like] a larger data set, it could potentially become a new standard of care for these tumors."
The findings suggest that targeting cancers based on molecular similarities, rather than solely on the organ of origin, may be a promising strategy. Further research is underway to explore the potential of using pre-treatment blood tests to predict which patients are most likely to benefit from this combination therapy.
