A recent randomized phase II study on pancreatic cancer treatment has shown that a dose-reduction strategy for a commonly used first-line combination of nab-paclitaxel (Abraxane) and gemcitabine can lead to similar survival outcomes but with improved tolerability. The ALPACA trial, conducted from 2016 to 2021, included 325 patients with metastatic pancreatic ductal adenocarcinoma, out of which 319 began induction treatment with nab-paclitaxel-gemcitabine. After three induction cycles, 174 patients with stable disease were eligible for randomization, with 167 starting randomized treatment. The trial compared patients who continued on the combination therapy against those who switched to alternating cycles of the combination and gemcitabine alone, and the results showed no significant difference in overall survival between the two groups.
Response rates, disease control rates, and median progression-free survival were similar between the continuous and alternating treatment groups. However, the standard approach was associated with higher rates of treatment-emergent serious adverse events (50% vs 33%) and grade ≥3 AEs (71% vs 59%) compared to the alternating approach. The researchers, led by Frank Kullmann, MD, concluded that applying alternating cycles of nab-paclitaxel-gemcitabine and gemcitabine alone after three induction cycles could be a promising dose-reduction strategy to improve tolerability without compromising efficacy in patients with metastatic pancreatic cancer.
While the results of the ALPACA trial are encouraging, some limitations were noted by editorialists Paula Ghaneh, MD, and Daniel Palmer, MD, PhD, from the University of Liverpool in England. They pointed out that the trial was underpowered to determine meaningful group differences in overall survival and that there were imbalances in some important prognostic variables between the study groups. The editorialists also highlighted that the trial lacked a formal hypothesis on whether the alternating approach would be superior or non-inferior to the standard approach. Therefore, the equivalence in efficacy is still unproven.
Despite the limitations, the ALPACA trial provides important data and lessons for the design of future prospective studies on dose-reduction approaches in pancreatic cancer treatment. The researchers suggested that sample size calculations should account for dropout rates to provide adequate statistical power to show non-inferiority for clinical outcomes. The study’s primary endpoint of overall survival could not be estimated with prespecified precision due to the limited number of overall survival events. However, the authors highlighted the clinical relevance of better tolerability and reduced toxicity endpoints with the alternating treatment schedule.
The ALPACA trial shows that proactive dose management of nab-paclitaxel in combination with gemcitabine can lead to improved tolerability in patients with metastatic pancreatic cancer. While further studies are needed to confirm the efficacy of dose-reduction strategies, the results of this trial are promising and provide valuable insights for the future of pancreatic cancer treatment.
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