Evaluating longitudinal toxicity of cetuximab in patients with metastatic colorectal cancer (mCRC): A pooled analysis from 1,302 patients in the ARCAD database.
Authors: Lopes Guilherme , So Jane Yeojeong , Sjoquist Katrin Marie , Olswold Curtis L. , Van Cutsem Eric , Bokemeyer Carsten , Adams Richard , Chibaudel Benoist , Grothey Axel , Yoshino Takayuki , De Gramont Aimery , Shi Qian , Tournigand Christophe , Zalcberg John Raymond 
Published: June 2021

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Background: Chronic lower grade adverse events (AE) can negatively affect a patient’s quality of life but it is difficult to capture using a traditional toxicity reporting approach. A novel AE reporting method was recently developed to describe, summarize, and present longitudinal AE profiles(Lopes et al, 2021). We leveraged this method to describe and compare the AE profiles of doublet chemotherapy (DC) + Cetuximab and DC alone in mCRC patients. Methods: This AE reporting method utilizes two additional AE metrics to complement the maximum (max) toxicity grade usually reported in clinical trials. Onset time indicates the time period in which max grade for an AE occurred for the first time, defined here as “early” (i.e. within first 42 days) and “late” (i.e. after the 42nd day). AE Load (AEL) indicates the overall severity of an AE in the entire treatment. AEL varies from 0 to 1. Higher AEL indicates a worse overall severity of that AE over time. AEL is the key metric for describing chronic AE. We included patients receiving DC + cetuximab (n = 738) and DC alone (n = 564 [ref group]) from two randomized first-line trials in the ARCAD database. Diarrhea, rash, hand-foot syndrome (HFS), fatigue, anorexia, and mucositis were examined and adjusted for backbone (FOLFOX vs. FOLFIRI), ECOG PS, sex, site location, dose reduction, and treatment length. Results: For rash, DC + cetuximab had a higher risk of G3+ (21% vs. 0.5%; odds ratio {OR} [95% confidence interval {CI}] = 50 [16,157], p < 0.001), increased overall severity over the entire treatment (AEL = 0.257 vs. 0.069; Adjusted difference in means–Mdiff [95% CI] = 0.22 [0.21,0.23], p < 0.001), and increased risk of early onset (67% vs. 33%; OR [95% CI] = 4.3 [2.7,6.7], p < 0.001). DC + cetuximab also had higher AEL for rash across max grades (p < 0.001 within G1, G2, and G3+). For HFS, DC + cetuximab had a higher risk of G3+ (OR [95% CI] = 6.0 [2.5,14], p < 0.001), increased overall severity (AEL = 0.139 vs. 0.087; Mdiff [95% CI] = 0.03 [0.03,0.04], p < 0.001), and slightly earlier onset (12.4 vs. 13.9 weeks; Mdiff, weeks [95% CI] = -4.9 [-0.80,-9.0], p = 0.021). Within each max grade, DC + cetuximab did not have higher AEL of HFS. No associations were found for diarrhea, fatigue, anorexia, or mucositis. Conclusions: The addition of cetuximab is associated with higher grade, more persistent, and more immediate rash. The higher severity in HFS with the addition of cetuximab appears to be related to higher grade but not chronic HFS. This method may be useful to describe different strategies, e.g. intermittent cetuximab. It provided a comprehensive view of acute and chronic toxicity profiles supporting its potential interest as new metrics in clinical trials. Lopes GS, Tournigand C, Olswold CL, et al. Adverse event load, onset, and maximum grade: A novel method of reporting adverse events in cancer clinical trials. Clinical Trials. 2021;18(1):51-60