The following is a summary of “Surgical Outcomes In Patients Receiving Neoadjuvant Vaccine Therapy (Prostvac) Prior To Radical Prostatectomy: A Phase Ii Experience,” published in the April 2023 issue of Urology by Blake et al.

The investigation of PROSTVAC, a cancer vaccine designed to activate T cells specific against prostate-specific antigen (PSA), in patients with localized prostate cancer (PCa) has shown promising results in immune modulation and safety profiles. This study delves into the safety and feasibility outcomes of neoadjuvant PROSTVAC therapy in a phase II trial (NCT02153918) involving patients with localized PCa scheduled for radical prostatectomy (RP).

In this open-label phase II trial, patients with histopathologically confirmed localized PCa, eligible for RP, received PROSTVAC vaccinations. The vaccination regimen included a priming vaccination with recombinant vaccinia (rV)-PSA(L155)-TRICOM followed by monthly boosts of recombinant fowlpox (rF)-PROSTVAC. The boosting schedule was amended midway to facilitate earlier surgeries. RP was performed after completing the vaccination series, around week 10, followed by a final safety assessment 12–15 months post-RP.

Between 2014-2016, 26 out of 27 enrolled patients underwent RP. On pre-RP biopsy, various Gleason grade groups were observed. 

There were notable changes in pathology findings between pre-RP biopsy and final pathology. Adverse features at RP were reported, with injection-site reactions being the most common adverse event associated with PROSTVAC. However, no serious PROSTVAC-related toxicities beyond grade 2 were recorded, although two patients experienced grade 3 serious adverse events (an infected lymphocele and a thromboembolic event) attributed to surgery rather than PROSTVAC.

The trial demonstrated that PROSTVAC was well-tolerated and feasible as a neoadjuvant vaccination strategy in localized PCa. Although the study observed encouraging safety profiles, further research is warranted to determine the efficacy of PROSTVAC in influencing both short and long-term oncological outcomes.

Source: auajournals.org/doi/10.1097/JU.0000000000003330.16