Pembro Combination Calls for irAE Monitoring in High-Risk Prostate Cancer

While the combination of pembrolizumab with standard-of-care (SOC) radiation, and androgen deprivation therapy with or without olaparib (Lynparza) was found generally feasible in high-risk localized prostate cancer, Zin W Myint, MD, advises vigilant clinical monitoring for immune-related adverse events (irAEs) associated with pembrolizumab.

Myint, who presented data from a trial (NCT05568550) of the experimental combinations in patients with high-risk localized prostate cancer, underscored the critical role of patient education in identifying early symptoms such as respiratory changes or vision disturbances to ensure prompt intervention and potential specialist referral.

Pembrolizumab Trial Design and Safety Outcomes

The study investigated the potential synergy between immune checkpoint inhibition, PARP inhibition, and radiation therapy in 17 patients with high- or very-high-risk localized prostate cancer. Participants were randomly assigned to receive either 1 year of pembrolizumab plus SOC, or the same regimen with the addition of olaparib at 200 mg twice daily. The median age of participants was 68 years (range, 53-84), and the majority (83%) met very-high-risk clinical criteria.

Findings indicated that the addition of olaparib did not significantly increase the frequency of high-grade toxicity. However, grade 1 to 2 renal and urinary adverse events were more common in the olaparib arm (86% vs 60%). Every patient in the study experienced some degree of fatigue and gastrointestinal upset. Grade 3 or higher events in the olaparib arm primarily included laboratory abnormalities (71%), followed by cardiac, infectious, and respiratory events (29% each). In the arm of patients who did not receive olaparib, grade 3 or higher events were most frequently laboratory-related (60%) and vascular disorders (50%).

Managing Immune-Related Adverse Events With Pembrolizumab Regimen

Serious irAEs were specifically linked to the pembrolizumab combination treatment. Reported irAEs included rash, fatigue, nausea, anorexia, and musculoskeletal pain, but more severe complications were also noted, such as grade 2 myositis, grade 3 colitis, grade 4 optic neuropathy, and grade 5 pneumonitis. One treatment-related death occurred due to immune-mediated pneumonitis.

Management of these toxicities required steroid intervention in 24% of patients, with 12% requiring additional immunosuppression beyond steroids. For oncology nurses and advanced practice providers, these results highlight the importance of routine laboratory assessments to detect anemia, lymphopenia, and creatinine elevations. Myint notes that because of the severity of potential reactions, early intervention and discontinuation of immunotherapy are critical when symptoms arise. Due to slow accrual, the trial has since been amended to a single-arm study focusing on the combination of pembrolizumab, olaparib, and radiation.

Transcript

Close monitoring is important. I would recommend monitoring the [complete blood count] and metabolic profile since we see more lymphopenia and anemia [in this group], but there were no increased infections. Still, it’s important to monitor those. We also see some elevations of creatinine [levels] in those patients receiving pembrolizumab, so I would recommend monitoring those.

Patient education and early intervention will be the key. Educate patients on when to report [symptoms such as] new cough, shorter breath, vision change, or other symptoms that could potentially be related to the immune-mediated adverse effects. When a symptom seems suspicious, early intervention with the steroid and discontinuation of immunotherapy are critical. Patients may need to be referred to specialists for immediate-mediated adverse effects.

This transcript has been edited for clarity and conciseness.

Reference

Myint Z, Yan D, Strup S. Interim safety analysis of a randomized phase II trial comparing pembrolizumab with radiation versus pembrolizumab, olaparib, and radiation in localized high risk prostate cancer. J Clin Oncol. 2026;44(suppl7):362. doi:10.1200/JCO.2026.44.7_suppl.362