Long-term first-in-man Phase I/II study of an adjuvant dendritic cell vaccine in patients with high-risk prostate cancer after radical prostatectomy.

Patients with high-risk prostate cancer (PC) can experience biochemical relapse (BCR), despite surgery, and develop noncurative disease. The present study aimed to reduce the risk of BCR with a personalized dendritic cell (DC) vaccine, given as adjuvant therapy, after robot-assisted laparoscopic prostatectomy (RALP).

Twelve weeks after RALP, 20 patients with high-risk PC and undetectable PSA received DC vaccinations for 3 years or until BCR. The primary endpoint was the time to BCR. The immune response was assessed 7 weeks after surgery (baseline) and at one-time point during the vaccination period.

Among 20 patients, 11 were BCR-free over a median of 96 months (range: 84-99). The median time from the end of vaccinations to the last follow-up was 57 months (range: 45-60). Nine patients developed BCR, either during (n = 4) or after (n = 5) the vaccination period. Among five patients diagnosed with intraductal carcinoma, three experienced early BCR during the vaccination period. All patients that developed BCR remained in stable disease within a median of 99 months (range: 74-99). The baseline immune response was significantly associated with the immune response during the vaccination period (p = 0.015). For patients diagnosed with extraprostatic extension (EPE), time to BCR was longer in vaccine responders than in non-responders (p = 0.09). Among 12 patients with the International Society of Urological Pathology (ISUP) grade 5 PC, five achieved remission after 84 months, and all mounted immune responses.

Patients diagnosed with EPE and ISUP grade 5 PC were at particularly high risk of developing postsurgical BCR. In this subgroup, the vaccine response was related to a reduced BCR incidence. The vaccine was safe, without side effects. This adjuvant first-in-man Phase I/II DC vaccine study showed promising results. DC vaccines after curative surgery should be investigated further in a larger cohort of patients with high-risk PC.

The Prostate. 2021 Nov 11 [Epub ahead of print]

Anne M A Tryggestad, Karol Axcrona, Ulrika Axcrona, Iris Bigalke, Bjørn Brennhovd, Else M Inderberg, Turid K Hønnåshagen, Lisbeth J Skoge, Guri Solum, Stein Saebøe-Larssen, Dag Josefsen, Richard W Olaussen, Steinar Aamdal, Rolf I Skotheim, Tor Å Myklebust, Dolores J Schendel, Wolfgang Lilleby, Svein Dueland, Gunnar Kvalheim

Department of Oncology, Oslo University Hospital HF, Oslo, Norway., Department of Urology, Oslo University Hospital HF, Oslo, Norway., Department of Pathology, Oslo University Hospital HF, Oslo, Norway., Department for Clinical Research, Oslo University Hospital HF, Oslo, Norway., Department of Molecular Oncology, Oslo University Hospital HF, Oslo, Norway., Department of Registration, Cancer Registry Norway, Oslo, Norway., Medigene Immunotherapies GmbH, Munich, Germany.