PURPOSE:The time spent in pursuing treatments for advanced cancer can be substantial. We have previously proposed a pragmatic and patient-centered metric of these time costs—which we term time toxicity—as any day with physical health care system contact. This includes outpatient visits (eg, bloodwork, scans, etc), emergency department visits, and overnight stays in a health care facility. Herein, we sought to assess time toxicity in a completed randomized controlled trial (RCT).METHODS:We conducted a secondary analysis of the Canadian Cancer Trials Group CO.17 RCT that evaluated weekly cetuximab infusions versus supportive care alone in 572 patients with advanced colorectal cancer. Initial results reported a 6-week improvement in median overall survival (OS) with cetuximab (6.1v4.6 months). Subsequent analyses reported that benefit was restricted to patients withK-raswild-type tumors. We calculated patient-level time toxicity by analyzing trial forms. We considered days without health care contact as home days. We compared medians of time measures across arms and stratified results byK-rasstatus.RESULTS:In the overall population, median time toxic days were higher in the cetuximab arm (28v10,P< .001) although median home days were not statistically different between arms (140v121,P= .09). In patients withK-ras–mutated tumors, cetuximab was associated with almost numerically equal home days (114 daysv112 days,P= .571) and higher time toxicity (23 daysv11 days,P< .001). In patients withK-raswild-type tumors, cetuximab was associated with more home days (186v132,P< .001).CONCLUSION:This proof-of-concept feasibility study demonstrates that measures of time toxicity can be extracted through secondary analyses of RCTs. In CO.17, despite an overall OS benefit with cetuximab, home days were statistically similar across arms. Such data can supplement traditional survival end points in RCTs. Further work should refine and validate the measure prospectively.