Long-term follow-up of prostate cancer patients treated with vaccine and definitive radiation therapy
Menée sur 36 patients atteints d'un cancer localisé de la prostate (durée médiane de suivi : 76, 79 ou 98 mois selon les groupes), cette étude évalue l'efficacité et la toxicité d'un traitement combinant une radiothérapie externe avec un vaccin à base de poxvirus et d'interleukine 2
Background : Vaccine therapy in combination with radiation therapy may improve distant and/or local control in prostate cancer. We present long-term follow-up data on the secondary and exploratory endpoints of safety and biochemical failure, respectively, from patients with clinically localized prostate cancer treated definitively with a poxviral vector-based therapeutic vaccine combined with external beam radiation therapy (EBRT). Methods : Thirty-six prostate cancer patients received definitive EBRT plus vaccine. A total of 18 patients were treated with adjuvant standard-dose interleukin-2 (S-IL-2) (4 MIU m–2) and 18 were treated with very low-dose IL-2 (M-IL-2) (0.6 MIU m–2). Seven patients were treated with EBRT alone. Twenty-six patients treated with EBRT plus vaccine returned for follow-up, and we reviewed the most recent labs and clinical notes of the remaining patients. Results : Median follow-up for the S-IL-2, M-IL-2 and EBRT-alone groups was 98, 76 and 79 months, respectively. Actuarial 5-year PSA failure-free probability was 78%, 82% and 86% (P=0.58 overall), respectively. There were no significant differences between the actuarial overall survival and the prostate cancer-specific survival between the two vaccine arms. Of the 26 patients who returned for follow-up, Radiation Therapy Oncology Group grade greater than or equal to2 genitourinary (GU) and gastrointestinal (GI) toxicity was seen in 19% and 8%, respectively, with no difference between the arms (P=1.00 and P=0.48 for grade greater than or equal to2 GU and GI toxicity, respectively). In all, 12 patients were evaluated for PSA-specific immune responses, and 1 demonstrated a response 66 months post-enrollment. Conclusions : We demonstrate that vaccine combined with EBRT does not appear to have significant differences with regard to PSA control or late-term toxicity compared with standard treatment. We also found limited evidence of long-term immune response following vaccine therapy.