Toward Maximizing Immunotherapy in Metastatic Castration-Resistant Prostate Cancer – Rationale for Combinatorial Approaches Using Chemotherapy

Prostate cancer is particularly suited for active immunotherapy because of the expression of a distinctive number of antigens which are overexpressed on prostate cancer cells and cell lines. There is evidence in this disease that tumors promote immune tolerance starting early in the disease course. As such, chemotherapy, by suppressing tumors and activating immune system homeostatic mechanisms, may help overcome this tumor-induced immune tolerance. Sipuleucel-T which has recently been approved in the US, is an autologous cellular product immunotherapy that induces immune activity likely through activation of dendritic cells. This was associated with a survival benefit in the absence of significant toxicity. However, a post hoc analysis of phase III trial participants found a substantial survival benefit to receiving docetaxel some months after sipuleucel-T. However, another phase III immunotherapy trial combining a prostate cancer therapeutic vaccine GVAX plus docetaxel versus standard docetaxel therapy in advanced prostate cancer, observed a lower overall survival with the vaccine regimen. These trials highlight major unresolved questions concerning the optimum choice, dosing, and timing of chemotherapy relative to active immunotherapy and the overall merits of considering this approach. The ideal treatment approach remains unclear; advances in biomarker validation and trial design may likely improve our ability to assess biologic benefit irrespective of the development of true antitumor immunity

Adjuvant and Salvage Radiotherapy After Prostatectomy: American Society of Clinical Oncology Clinical Practice Guideline Endorsement

PURPOSE: To endorse the American Urological Association (AUA)/American Society for Radiation Oncology (ASTRO) guideline on adjuvant and salvage radiotherapy after prostatectomy. The American Society of Clinical Oncology (ASCO) has a policy and set of procedures for endorsing clinical practice guidelines developed by other professional organizations. METHODS: The guideline on adjuvant and salvage radiotherapy after prostatectomy was reviewed for developmental rigor by methodologists. An ASCO endorsement panel then reviewed the content and recommendations. RESULTS: The panel determined that the guideline recommendations on adjuvant and salvage radiotherapy after prostatectomy, published in August 2013, are clear, thorough, and based on the most relevant scientific evidence. ASCO endorsed the guideline on adjuvant and salvage radiotherapy after prostatectomy, adding one qualifying statement that not all candidates for adjuvant or salvage radiotherapy have the same risk of recurrence or disease progression, and thus, risk-benefit ratios are not the same for all men. Those at the highest risk for recurrence after radical prostatectomy include men with seminal vesicle invasion, Gleason score 8 to 10, extensive positive margins, and detectable postoperative prostate-specific antigen (PSA). RECOMMENDATIONS: Physicians should discuss adjuvant radiotherapy with patients with adverse pathologic findings at prostatectomy (ie, seminal vesicle invasion, positive surgical margins, extraprostatic extension) and salvage radiotherapy with patients with PSA or local recurrence after prostatectomy. The discussion of radiotherapy should include possible short- and long-term adverse effects and potential benefits. The decision to administer radiotherapy should be made by the patient and multidisciplinary treatment team, keeping in mind that not all men are at equal risk of recurrence or clinically meaningful disease progression. Thus, the risk-benefit ratio will differ for each patient

Harnessing Naturally Occurring Tumor Immunity: A Clinical Vaccine Trial in Prostate Cancer

International audienceBACKGROUND:Studies of patients with paraneoplastic neurologic disorders (PND) have revealed that apoptotic tumor serves as a potential potent trigger for the initiation of naturally occurring tumor immunity. The purpose of this study was to assess the feasibility, safety, and immunogenicity of an apoptotic tumor-autologous dendritic cell (DC) vaccine.METHODS AND FINDINGS:We have modeled PND tumor immunity in a clinical trial in which apoptotic allogeneic prostate tumor cells were used to generate an apoptotic tumor-autologous dendritic cell vaccine. Twenty-four prostate cancer patients were immunized in a Phase I, randomized, single-blind, placebo-controlled study to assess the safety and immunogenicity of this vaccine. Vaccinations were safe and well tolerated. Importantly, we also found that the vaccine was immunogenic, inducing delayed type hypersensitivity (DTH) responses and CD4+ and CD8+ T cell proliferation, with no effect on FoxP3+ regulatory T cells. A statistically significant increase in T cell proliferation responses to prostate tumor cells in vitro (p = 0.002), decrease in prostate specific antigen (PSA) slope (p = 0.016), and a two-fold increase in PSA doubling time (p = 0.003) were identified when we compared data before and after vaccination.CONCLUSIONS:An apoptotic cancer cell vaccine modeled on naturally occurring tumor immune responses in PND patients provides a safe and immunogenic tumor vaccine