Moffitt Study Suggests Immunotherapy May Strengthen Treatment for Aggressive Prostate Cancer

Key Highlights

• The study examined whether adding the immunotherapy drug nivolumab to radiotherapy-based treatment regimen could improve outcomes in men with very high-risk prostate cancer. 

• After two years, about 90% of patients showed no signs of disease recurrence based on PSA blood tests.  

• The study also pointed to possible genomic indicators known as biomarkers that could assist doctors to determine which patients are most likely to benefit from immunotherapy. 

• The treatment was generally well tolerated, with no severe toxicities reported.  

TAMPA, Fla. — Researchers at Moffitt Cancer Center report encouraging early results from a phase 2 study examining whether immunotherapy can improve results when added to radiotherapy-based treatment regimen for men with aggressive prostate cancer. 

The work, led by Kosj Yamoah, MD, Ph.D., chair of the Radiation Oncology Department at Moffitt, was published in the Journal for ImmunoTherapy of Cancer.

Participants in the study were diagnosed with highly aggressive Grade Group 5 cancer, which is more likely to spread and become life-threatening. All 31 patients received an intensive combination of treatments: hormone therapy plus two forms of radiotherapy. One form, high-dose-rate brachytherapy, places radiotherapy directly into the prostate. The other, external beam radiotherapy, is delivered from outside the body. 

Patients also received nivolumab, a checkpoint inhibitor that helps the immune system attack cancer cells. Patients began nivolumab roughly a month before radiotherapy, and it was continued during therapy. The thinking was that activating the immune system earlier could improve results once radiotherapy treatment began.   

Given the single-arm design, study outcomes were evaluated in the context of previously reported results in a similar high-risk patient cohort. After two years, about 90% of patients showed no signs of disease recurrence based on PSA blood tests. These findings compare favorably with past outcomes for similar patients treated with standard therapy alone, though larger randomized studies will be needed to determine whether the addition of nivolumab truly improves outcomes. 

The combination treatment was generally well tolerated, with no severe toxicities reported. This is important given the intensity of combining immunotherapy with aggressive radiotherapy treatment.

The researchers also found that patients whose tumors had higher Decipher immunosuppression scores tended to do better in the study. Immunosuppression score is a genomic biomarker that looks for clues about how strongly the body’s immune system is fighting the tumor and whether the cancer may be blocking or weakening that immune response. The finding raises the possibility that doctors may one day be able to use markers such as Decipher Immunosuppression Score to identify patients most likely to benefit from the addition of immunotherapy.

Q&A with Kosj Yamoah, M.D., Ph.D., senior author and chair of the Department of Radiation Oncology at Moffitt 

What was the thinking behind adding nivolumab to treatment?

The goal was to see whether we could get the immune system more engaged early in treatment. Radiotherapy can cause tumor cells to break apart and release signals that may make them more visible to the immune system. The idea is that nivolumab might help the immune system respond more effectively to those signals and better target any remaining cancer cells. 

What stood out to you in the results?

One of the most encouraging findings was that most patients showed no biochemical evidence of disease recurrence at two years. In a group with this level of risk, that’s not something we typically see, although it’s still early and needs longer follow-up. 

Why is Grade Group 5 prostate cancer so difficult to treat?

These tumors can grow quickly and spread earlier than lower-grade disease, which limits how effective standard treatment alone tends to be over time. 

Can these results change treatment today?

Not yet. This is an early, single-arm study, so we can’t draw conclusions about superiority over standard treatment. What it does provide is a signal that deserves to be tested more rigorously. 

What needs to happen next?

The next step is larger, randomized studies. Those will help confirm whether the benefit holds up and whether certain patients are more likely to respond than others.  

Funding for this study was provided by Bristol Myers Squibb. This work was also supported by funding from the National Institute of Health (R37CA264518-01A1, P20‐CA233255, P30-CA076292) and Department of War (HT94252310651).   

About Moffitt Cancer Center  
Moffitt is dedicated to one lifesaving mission: to contribute to the prevention and cure of cancer. The Tampa-based facility is one of only 58 National Cancer Institute-designated Comprehensive Cancer Centers, a distinction that recognizes Moffitt’s scientific excellence, multidisciplinary research, and robust training and education. Moffitt’s expert nursing staff is recognized by the American Nurses Credentialing Center with Magnet® status, its highest distinction. For more information, call 1-888-MOFFITT (1-844-831-7061), visit MOFFITT.org, and follow the momentum on Facebook, X, Instagram and YouTube.  

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