In his discussion of the presentation, Daniel V.T. Catenacci, MD, Assistant Professor of Medicine at the University of Chicago, said that conclusions cannot be drawn from the results of NEOSCOPE, which is underpowered to show differences. “On the surface, we see an improvement in the CarPacRT [chemoradiotherapy with carboplatin/paclitaxel] arm, but there are limitations to the study, including its small size,” he pointed out.
He also noted that the R0 resection rate is “relatively low” in both arms (72%, 80%). In addition, there was an imbalance between the arms in that the chemoradiotherapy with carboplatin/paclitaxel cohort included 10% fewer patients with advanced disease (lymph node–positive) and 10% fewer with proximal disease. It is more difficult to achieve R0 resection in these groups, he said. In such a small study, this imbalance is important, Dr. Catenacci suggested. “The imbalance in poor-prognosis factors disfavors the oxaliplatin/paclitaxel arm, but the numbers are small,” he added.
Clinical trials of neoadjuvant oxaliplatin-containing regimens have reported pathologic complete response rates ranging widely, from about 13% to 50%, and a broad range of R0 resection rates as well. “It is challenging to put NEOSCOPE into context with other trials,” he said.
More Definitive Answers Needed
Among the “layers of heterogeneity” in this area, he added, is the observation that pathologic complete response also varies by tumor histology. “From a global context, we can say both pathologic complete response and R0 resection correspond to outcome, but studies need to be more uniform,” he said.
More definitive answers are expected to come from CALGB 80803, “a larger trial that incorporates better controls and is assessing the role of PET [positron-emission tomography]–directed therapy by continuing the chemotherapy regimen that appears active during the induction phase with the radiation (PET response) while moving to the alternate regimen with radiation when induction is not active (PET nonresponse),” he said. “This trial has the potential to elucidate the efficacy in responders and nonresponders and assess toxicity with larger numbers.” ■
Disclosure: Dr. Catenacci reported no potential conflicts of interest.