The real-world outcomes from late-line chemotherapy for advanced colorectal cancer: A population-based analysis of attrition rates, outcomes, and health care contact in a single-payer health system.

Abstract

e23443 Background: Few population-level real-world studies have evaluated the uptake, health care contact time, and efficacy of later-line treatments for metastatic colorectal cancer (mCRC). We evaluated treatment patterns, attrition rates, survival outcomes, and health care contact time across multiple lines of therapy for patients with mCRC in Ontario, Canada. Methods: We performed a population-based retrospective cohort study of adults with mCRC in Ontario (population 16 million; single-payer public health system) diagnosed between Jan 2010 and December 2019 and receiving at least one line of palliative chemotherapy. Patients were linked across multiple administrative datasets using a unique patient identifier to determine demographics, chemotherapy prescription, outcomes and health care contact time. Health care contact time was calculated as the percentage of contact days per month, accounting for both inpatient and outpatient contact. Overall survival was estimated using Kaplan-Meier methods. Cox proportional hazards regression was used to examine factors associated with survival, and logistic regression for factors association with the receipt of more than one line of therapy. Results: We included 4,541 patients in our study. Excluding patients undergoing metastectomy within 12 months of first chemo (n = 167), median overall survival was 16 months (95% CI 15.6 – 17.04). Approximately 45% (n = 1988) received only 1 line of therapy, 28% (n = 1,221) received only 2 lines of therapy, 19% (n = 819) received only 3 lines of therapy, and 8% (n = 346) received 4 or more lines of therapy. Younger age, fewer comorbidities and higher socioeconomic status were associated with receiving more than one line of therapy, while geographic location and sex showed no clear association. The average proportion of monthly contact time was similar across lines of therapy (11.8% during 1st, 12.6% during 2 nd line, 12.8% during 3 rd line, 12.4% during 4 th line and beyond). Monthly contact days were also similar among the commonly used intravenous first line regimens but were slightly lower among those receiving capecitabine. Most contacts days were outpatient contact days. Conclusions: Median overall survival in this real-world cohort of patients receiving at least one line of palliative chemotherapy is shorter than typically seen in first line clinical trials. Just over half of patients who receive first line chemotherapy for mCRC in Ontario receive a 2 nd line of treatment, illustrating high attrition rates in real world practice. Patients with mCRC treated within the Ontario cancer system should expect to spend approximately 10-13% of their time each month in contact with the health care system, regardless of line of therapy or type of systemic treatment.