The impact of neoadjuvant weekly ixabepilone for high-risk prostate cancer: A phase I/II clinical trial.

158 Background: Potential benefits of neoadjuvant chemotherapy are tumor downstaging and treatment of micrometastatic disease. A prior study using docetaxel yielded no pathologic complete responses and concerns for increased operative morbidity. In Phase II studies, ixabepilone has promising activity in metastatic prostate cancer. Our study is a Phase I/II clinical trial evaluating neoadjuvant, weekly ixabepilone in men with high-risk prostate cancer opting for radical prostatectomy. Methods: Men with high risk prostate cancer defined as either Gleason 8-10, cT3 disease, high volume Gleason 4+3 and a palpable nodule or a PSA>20 ng/ml were eligible. Men received weekly ixabepilone 16-20/m2 for 12-16 weeks prior to surgery. Fifteen men underwent robotic prostatectomy; one patient who had an open prostatectomy. Initial PSA response, post-operative PSA values, pathology, and evaluation of adverse events were recorded. Results: We enrolled 16 men with a mean follow-up of 15.25 months at time of review. All had pretreatment Gleason scores of 4+3 or higher. With neoadjuvant treatment, PSA values decreased in 14/16 men (mean 46.8%); increased in 2/16 men. None reached an undetectable pre-operative PSA. Nine men experienced an adverse event requiring dose modification or cessation of chemotherapy (neuropathy or allergic reaction). Only 5/16 men completed planned treatment. Mean operative time, EBL, and hospital stay were 189 minutes, 184mL, and1.5 days, respectively; all consistent with institutional and national norms. Post surgery 15/16 (94%) had pT3 disease, 8/16 (50%) had a positive surgical margin and 2/16 (12.5%) had positive regional lymph nodes. There were no pathologic complete responses. Only 1/16 (6.25%) had a biochemical relapse. Conclusions: While a PSA response is achieved, there is substantial toxicity with neoadjuvant weekly ixabepilone. Men were able to undergo prostatectomy without increased morbidity after neoadjuvant therapy. Extracapsular extension and positive surgical margins remained common in this population with high-risk disease. Assessment of biochemical recurrence rates and time to treatment failure will require longer, planned follow-up.