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Comment & Response
June 25, 2020

Risk-Benefit Comparisons Between Shorter and Longer Durations of Adjuvant Chemotherapy in High-Risk Stage II Colorectal Cancer

Author Affiliations
  • 1Google, Mountain View, California
  • 2Institute for Aging Research, Hebrew SeniorLife, Boston, Massachusetts
  • 3Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
JAMA Oncol. 2020;6(8):1301-1302. doi:10.1001/jamaoncol.2020.2256

To the Editor Petrelli and colleagues1 assessed the noninferiority of 3-month vs 6-month adjuvant chemotherapy for relapse-free survival (RFS). The hazard ratio (shorter vs longer) was 1.41. Because the CI upper bound of 1.89 exceeded the prespecified noninferiority margin of 1.2, there was insufficient evidence to claim that short-term therapy was noninferior to long-term therapy. However, the greater than 41% increase in hazard is difficult to interpret. Using reconstructed RFS data, with 8 years of follow-up, the mean RFS times were 6.86 and 7.19 years for shorter and longer therapies. The difference of 4.0 months (95% CI, 0.9-7.0; P = .01) was only 4% of the 96 months of follow-up. On the other hand, the rates of severe toxic effects were substantially higher in the 6-month arm. For example, 8.4% of patients in the 6-month arm experienced grade 3 to 4 neuropathy compared with only 1.3% of patients in the 3-month arm. Similar trends were observed for the other adverse events. It is challenging to make an overall risk-benefit assessment based on these separate summaries, one for efficacy and the other for toxicity. Moreover, it is unclear whether the efficacy and toxicity outcomes occurred together in the same patients. This difficulty is reflected in the authors’ vague conclusions that either short-term or long-term therapy can be used for stage II colorectal cancer.1

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