Impact of human telomerase reverse transcriptase peptide vaccine combined with androgen deprivation therapy and radiotherapy in de novo metastatic prostate cancer: Long‐term clinical monitoring

Prostate cancer is considered as poorly immunogenic. In a phase I/II study on de novo metastatic prostate cancer we found that a human telomerase reverse transcriptase (hTERT) vaccine induced an early immune response in most of the patients. Here we present the results from the long‐term monitoring of the immune responses and clinical outcomes. Twenty‐two men with ISUP 4 to 5 and lymph node and/or bone metastases were treated with androgen deprivation therapy (ADT), radiotherapy and the hTERT vaccine UV1 between January 2013 and July 2014. Immune response was monitored before, during and after vaccination and continued every 6 months until PSA progression. All patients had magnetic resonance imaging (MRI) at baseline, and after 6 months, 1 and 2 years, and at progression. The clinical outcome was time to progression, overall survival and prostate cancer‐specific survival. The median follow‐up was 62 months (range: 19‐101). At the last observation, nine of the 22 patients were still alive. Six have no progression, two have castration‐resistant disease treated with second‐line ADT and one has castration‐refractory disease. Median time to PSA progression was 21 months, median overall survival was 62 months and median prostate cancer‐specific survival was 84 months. Lack of immune response was an independent marker of prostate cancer death. The long‐term monitoring showed that some patients had unanticipated subsequent high immune responses without developing recurrence. This association indicates that there might be a clinical benefit of hTERT vaccination in a subgroup of men with primary metastatic hormone‐sensitive prostate cancer treated with ADT and radiotherapy. What's new? Prostate cancer is considered poorly immunogenic. A human telomerase reverse transcriptase (hTERT) vaccine was previously reported to induce an early immune response in most patients with de novo metastatic prostate cancer in a phase I/II study. In this follow‐up study, about 40% of patients achieved long‐term treatment response to combined vaccination, radiotherapy and androgen deprivation therapy. Some patients presented a strong immune response several years after the initial treatment with no clinical relapse. The findings suggest the potential benefit of vaccination in a subgroup of men with primary metastatic hormone‐sensitive prostate cancer treated with androgen deprivation therapy and radiotherapy.