Improved disease markers suggest dual response in a patient with metastatic castration resistant prostate cancer and chronic lymphocytic leukemia following active cellular immunotherapy.

Prostate cancer and chronic lymphocytic leukemia (CLL) are relatively common malignancies associated with advanced age. Although immunotherapy-based strategies are used to treat both, currently, there is no overlap in specific therapies. Sipuleucel-T is an active cellular immunotherapy that improves overall survival for patients with metastatic castration resistant prostate cancer (mCRPC) but is not typically associated with a decline in prostate-specific antigen (PSA) following administration. We report the case of a 78-year-old man with mCRPC and Rai stage 0 CLL who sustained a 12-month decline in both PSA and white blood cell (WBC) count following treatment with APC8015-2 (an investigational form of sipuleucel-T), as part of the phase II ProACT clinical trial. Two years later, the patient received commercial sipuleucel-T and again was noted to have a decline in PSA. Exploratory analysis did not clearly identify any peripheral immune markers associated with response. This case report suggests that treatment with sipuleucel-T can rarely lead to PSA decline, may have dual activity against both prostate cancer and CLL, and that these findings warrant further investigation.