Response to second-line chemotherapy in patients with hormone refractory prostate cancer (HRPC) receiving two sequences of mitoxantrone (M) and taxanes (T).

4616 Background: Treatment options for HRPC patients are limited. Trials show a survival benefit for initial T-based chemotherapy, but little data exist regarding the value of second-line chemotherapy.,We retrospectively identified all patients treated at one institution who received at least 2 chemotherapy regimens for HRPC: one M-based and one T-based. T-based regimens included docetaxel or paclitaxel, given weekly or q3 wks. Patients may have received concurrent steroids, estramustine, carboplatin, or investigational agents. Patients progressed after castration and were evaluable by PSA Working Group criteria. PR = PSA decline ≥50% from baseline. SD = PSA decline < 50% or rise ≤ 25%. PD = PSA rise > 25%.,68 patients were analyzed: M→T (n=33) and T→M (n=35). Median age: 66 and 58 yrs, respectively. Median PSA: 23 and 24 ng/ml, respectively. Median time from diagnosis to chemo: 78 and 56 wks, respectively. TABLE shows response to 1st and 2nd chemotherapy in each group. Response to T-based chemo was higher whether used 1st or 2nd (p<0.0001). No differences were seen between groups in Gleason score, TNM stage, or local therapy. Progression-free survival (PFS) was longer with T-based chemo compared with M, whether used 1st or 2nd. However, total PFS from start of 1st regimen to progression on 2nd regimen was 39.9 and 38.7 wks, respectively (p=.67). Overall survival (OS) was 15.2 and 17.1 mos, respectively (p=.96). Multivariable analysis indicated that age and time from diagnosis to chemo did not influence differences in PFS.,T-based chemotherapy is active whether used before or after M. Though PFS is longer with T-based chemo, total PFS and OS after either M→T or T→M was equivalent. This suggests that T-based chemo remains active even if delayed. Though PRs and SD were seen with M after T-based chemotherapy, PFS is short and new agents are needed in patients who progress after taxanes. [Figure: see text] [Table: see text].