What does this study add?
Our study introduces a novel multimodal therapeutic approach for patients with GG5 prostate cancer with a high-volume of intraprostatic disease defined as ≥30% of cores involved by integrating immune checkpoint inhibition (ICI) with standard androgen deprivation therapy (ADT) and radiation therapy. Specifically, the study demonstrates the feasibility of combining Nivolumab with standard-of-care treatment for very high-risk prostate cancer consisting of high-dose-rate brachytherapy, external beam radiation therapy, and ADT in men with high-volume Grade group 5 disease. In addition to establishing the safety of this regimen, our work provides early prospective evidence suggesting potential clinical activity in a patient population historically associated with poor outcomes after standard-of-care treatment. Importantly, the identification of the Decipher Immunosuppression Score as a potential predictive biomarker highlights an opportunity to better stratify patients who would benefit the most from this novel combination regimen and personalized treatment approaches.
Why are these findings important?
Patients with high-volume GG5 prostate cancer represent one of the most aggressive subsets of localized disease, with increased rates of recurrence, metastasis, and treatment resistance despite standard-of-care therapy. Current therapeutic paradigms primarily rely on prolonged ADT combined with radiotherapy or extensive surgery with additional salvage options, yet outcomes remain suboptimal for many patients. These findings are important because they demonstrate that immunotherapy can be safely incorporated into definitive localized therapy without compromising treatment feasibility.
It is important to note that several studies combining immunotherapy in patients with metastatic prostate cancer treated with ADT have shown minimal response rates. The lack of response to immunotherapy in prostate cancer has often been attributed to the poor immunogenicity of prostate tissue. On the other hand, there is growing evidence showing that radiotherapy can modulate the tumor to become an immuno-stimulatory milieu. Specifically, ablative-dose radiotherapy such as High-dose rate brachytherapy uniquely transforms the immunosuppressive tumor microenvironment by increasing CD8+ T-cell infiltration and reducing myeloid-derived suppressor cell levels. Importantly, this was observed only with ablative-dose radiotherapy and not with conventional radiotherapy. Ablative radiotherapy, with the advantage of delivering high doses of radiotherapy over a very short period of time to achieve localized and high dose distribution, could potentially enhance the immune-stimulatory effects of radiotherapy in the prostate while minimizing the off-target immune-suppressive effects on peripheral immune cells that occur with conventional radiotherapy.
The results from this study support the biological rationale that ablative radiotherapy may enhance antitumor immune responses, potentially sensitizing tumors to immune checkpoint blockade. Furthermore, the exploration of an immune-based biomarker provides a framework for identifying patients most likely to benefit from intensified or immune-directed treatment strategies.
How do these findings influence therapeutic strategies?
These results support a shift toward integrated multimodal treatment strategies that combine systemic immunomodulation with local ablative radiotherapy for high-volume GG5 prostate cancer. Our study provides a foundation for future randomized trials evaluating immune checkpoint inhibitors alongside radiotherapy and ADT in high-volume locally aggressive prostate cancer.
What are the next steps?
Future work is needed to establish that ablative radiotherapy approaches can enhance immune priming while minimizing lymphocyte exposure to radiotherapy, thereby improving synergy with ICIs. If validated in larger cohorts, this approach could expand the role of immunotherapy in the management of prostate cancer. Additionally, incorporation of biomarkers such as the Decipher Immunosuppression Score may facilitate more personalized therapeutic decision-making, enabling clinicians to tailor treatment intensity and identify patients who are most likely to derive benefit from immune-based combinations.
Written by: Purvish Trivedi, MPH, and Kosj Yamoah, MD, PhD
- H Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, USA