ASCO 2017: Cabazitaxel in patients with locally advanced or metastatic transitional cell carcinoma who developed disease progression within 12 months of platinum based chemotherapy: Results of a phase II trial—CAB-B1.

Chicago, IL (UroToday.com) In the past 1 year, five different immune checkpoint inhibitors have been approved by the FDA approved for the treatment of metastatic or advanced urothelial carcinoma (UC): atezolizumab, durvalumab, nivolumab, pembrolizumab and most recently avelumab. However, while the initial enthusiasm for this new class of therapies appears warranted, further long-term studies and confirmatory studies are required. Importantly though, each of these drugs has an objective response rate of approximately 20%, indicating that 80% of patients do not have a strong response. So, while studies on ICI’s should continue, additional treatment options for this patient population are needed.

As second-line chemotherapy options are currently limited, further research into newer agents may provide better salvage treatment options. Cabazitaxel is the fourth taxane to be approved for cancer therapy, and is a microtubule inhibitor like the others. It has had demonstrated success in the management of castration-resistant prostate cancer, and is currently an approved option for CRPC patients who have failed docetaxol chemotherapy.

In this study, however, the United Kingdom group assesses cabazitaxel efficacy in patients with metastatic or advanced urothelial carcinoma (mUC) who have failed platinum-based chemotherapy (CT), based on positive in-vivo studies in resistant UC cell lines.

Study Design:
This a single-center phase II trial in patients with advanced or metastatic UC who have been treated with platinum-based CT, but who have recurred within 12 months of CT completion. Treatment arms were best supportive care (BSC) or Cabazitaxel (CAB; 25mg/m2 q3 weeks for 6 cycles). Primary outcome was overall response rate (ORR) using RESIST. Secondary outcomes were Progression Free Survival (PFS), Overall Survival (OS), Quality of Life assessment, safety and tolerability. As a two-stage design was generated, this first stage required only 20 patients.

Results:
In a 3-year period, 20 patients were randomized (10 to each arm) – the cohort was primarily male, median age 68, and most had recurred within 6 months of the last CT cycle. For the BSC arm, 9 patients received paclitaxel and 1 received radiotherapy.

Only 8 of the 19 patients undergoing chemotherapy completed the chemotherapy course – 3 in the CAB arm, 5 in the BSC arm. Main reason for discontinuation of cabazitaxel was adverse events, and 5 cycles that were administered were dose reduced. There were 10 serious adverse events due to toxicities that resulted in hospitalization were experienced by 6 patients on the cabazitaxel arm.

Since 6 patients in each arm had completed 2/3 of the CT cycles, these patients were compared for response – 2 CAB patients had evidence of objective response, while only 1 in the BSC arm.

In the time frame, 14 patients (70%) died of disease – 8 in the CAB arm, 6 in the BSC arm.

Median OS was 5.6 months for CAB pts and 8.2 months for BSC pts. Median PFS was 4.4 months for CAB pts and 4.1 months for BSC pts.

It is important to note, the authors had significant trouble recruiting even the 20 patients needed for the first phase. They will need an additional 76 patients to detect difference in ORR between 5-30%. This will likely be difficult to achieve due to poor clinical status of many of these patients.

Based on preliminary results, the authors conclude that CAB has promise as a second-line option in patients who have early failures of platinum-based chemotherapy for metastatic or advanced UC. However, it should be noted that there was significant drug cessation due to adverse events.

Presented By: Anjali Zarkar

Co-Authors: Andre Machado, Ricardo Waksman, Guilherme Garcia, Paulo Esteves, Sanarelly Adonias, Luis Botelho, Mauricio Cordeiro, Claudio Murta, Leopoldo Ribeiro-Filho, Alvaro Sarkis, Diogo Assed Bastos, Carlos Dzik, Miguel Srougi, William Carlos Nahas

Institution(s): University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom; Warwick Clinical Trials Unit, Coventry, United Kingdom; University Hospital of Birmingham, Birmingham, United Kingdom; Queen Elizabeth Hospital, Coventry, United Kingdom

Written By: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Princess Margaret Cancer Centre
Twitter: @tchandra_uromd

at the 2017 ASCO Annual Meeting - June 2 - 6, 2017 – Chicago, Illinois, USA
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