123 Background: Recent developments in the treatment of metastatic castration resistant prostate cancer (mCRPC) lead to a revival of platinum-based chemotherapy demonstrating increased activity in patients with aggressive variants of disease. Here, we report on the results of a combinational salvage therapy with cisplatin, ifosfamide and paclitaxel (TIP) in mCRPC. Methods: We retrospectively analyzed patients with mCRPC treated with TIP at the University Hospital Hamburg-Eppendorf between November 2013 and September 2020. Accompanying in vitro analyses were performed using human prostate carcinoma cell lines harboring different levels of drug resistance including the docetaxel-resistant sublines PC3-DR and DU45-DR. Results: In total, 17 mCRPC patients treated with TIP were eligible for efficacy analyses with a median age of 65 yrs. At baseline, liver metastases were present in 88%, metastases of other visceral sides (lung, adrenal gland, brain) in 47% and bone metastases in 76% of the patients. Median hemoglobin was 9.8mg/dl, LDH 903 U/l and AP 205 U/l. Median PSA value was 77 ng/ml covering a wide range including three patients with a PSA-value below 1ng/ml. NSE was evaluated in 83% of the patients (median 38,5 U/l). Patients were extensively pretreated with a median of three treatment lines before TIP (100% docetaxel, 82% abirateron and/or enzalutamide, 47% cabazitaxel, 41% others). A median of 3,5 cycles of TIP were applied with 29% of the patients receiving the maximum of 6 cycles. Four patients discontinued treatment due to side effects (PNP, infection, ifosfamide induced psychosis). At interim analyses, 59 % of the patients showed a radiological response or stable disease with only one patient progressing till the end of treatment. Median PFS was 2.5 months, median OS 6 months. A decrease of PSA > 30% and LDH > 50% was observed in 41% and 35% of the patients, respectively. In vitro experiments revealed additive effects of TIP in 22Rv1, LNCaP and DU45 cells and synergistic effects in neuroendocrine LASCPC-01 cells. In PC3 cells, TIP induced antagonistic effects at lower doses, whereas dose-independent additive effects were observed in docetaxel-resistant PC3-DR. Surprisingly, preliminary data of combined therapies with different drug pairs suggest an antagonistic effect of paclitaxel in the combination with both, cisplatin and ifosfamide. Conclusions: Combinational therapy with cisplatin, ifosfamide and paclitaxel showed promising activity in some patients with aggressive mCRPC. Preclinical data suggest that the drug combination of cisplatin and ifosfamide rule the efficacy of TIP in mCRPC.
Neuroendocrine and Aggressive-Variant Prostate Cancer
