Immunotherapy Shows Promise in Penile Cancer Subset

Immune checkpoint inhibitors may be a promising option for the treatment of penile squamous cell carcinoma, a rare form of cancer that forms in the penis, according to recent research published in the Journal of the National Cancer Institute.

The researchers analyzed immune checkpoint inhibitors, which are a type of immunotherapy drug that works by blocking proteins on cancer cells that help them to hide from the immune system, in 92 patients with locally advanced or metastatic penile cancer. Most patients received Keytruda (pembrolizumab), Opdivo (nivolumab) or Libtayo (cemiplimab), though some received a combination of Opdivo and Yervoy (ipilimumab).

Study findings showed that 13% of patients overall — including 35% who had metastatic disease that was limited to their lymph nodes — responded to immunotherapy. The average overall survival (time from treatment until death of any cause) was 9.8 months, and the average progression-free survival (time from treatment until disease worsens or death) was 3.2 months.

The average five-year survival for patients with penile cancer with distant metastases (the disease has spread to other parts of the body far away from the penis) is approximately 9%, according to data from the American Cancer Society that was collected between the years of 2012 and 2018. For those with regional disease, meaning that the cancer has spread out from the penis to nearby tissue or lymph nodes, the average five-year survival is approximately 51%.

“These findings provide encouraging evidence that immune checkpoint inhibitors can be effective in treating a subset of patients with penile squamous cell carcinoma," co-first author Dr. Amin H. Nassar, a member of Yale Cancer Center and a clinical fellow at Yale School of Medicine, said in a press release issued by Yale Cancer Center. "We believe that further translational studies and biomarker-based research are essential to identify patients most likely to benefit from this therapy and improve the outcomes for individuals with penile cancer."

According to the American Cancer Society, common treatment methods for patients with penile cancer include surgery, radiation, laser ablation, cryosurgery and chemotherapy.

Of note, visceral metastases (those in the lungs, adrenal glands, peritoneum, pleura, brain and dura) were associated with poorer outcomes, as was a higher ECOG status (meaning that patients were limited in their ability to perform daily tasks) and higher neutrophil/lymphocyte ratio were associated with worse survival.

Treatment-related side effects occurred in 29% of patients, with 9.8% experiencing side effects that were moderate to severe (grade 3 or higher).

“The study highlights the importance of high-quality, real-world research to advance therapeutic options for this rare cancer,” said co-first author Dr. Talal El Zarif, an oncology research fellow at the Dana-Farber Cancer Institute and a member of Yale Cancer Center. “We are hopeful that response and survival rates will continue to improve for patients fighting penile cancer.”

Looking ahead, the researchers mentioned that this study warrants further research on immunotherapy for this patient population.

“(Immune checkpoint inhibitors) are active in a subset of patients with (penile cancer),” the authors wrote in the study. “Future translational studies are warranted to identify patients more likely to derive clinical benefit from (immune checkpoint inhibitors).”

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