PATTERNS OF CARE IN PATIENTS WITH ASYMPTOMATIC STAGE IV COLON CANCER: A POPULATION-BASED ANALYSIS
Catherine Tran*1, Paolo Goffredo2, Amanda Kahl3, Jeremy Chang1, Aditi Mishra1, Dakota T. Thompson1, Mary Charlton3, Imran Hassan1
1Department of Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA; 2University of Minnesota Academic Health Center, Minneapolis, MN; 3University of Iowa, Iowa City, IA Background
Based on National Comprehensive Cancer Network guidelines, the treatment of asymptomatic, unresectable stage IV colon cancer is systemic chemotherapy (CTX) with or without biologic agents (BA), while primary tumor resection (PTR) is considered only in patients with symptomatic tumors or resectable metastases. To date, there is a scarcity of data on the overall management trends of metastatic colon cancer patients with an asymptomatic primary tumor across the US. The Surveillance, Epidemiology, and End Results Patterns of Care (SEER-POC) is a targeted data base collecting additional variables in a sample of patients from SEER registries and provides a unique opportunity to study real-world approaches and outcomes of asymptomatic stage IV colon cancer at a population level.
Methods
Adults diagnosed with stage IV colon cancer without perforation or obstruction were identified in the 2014 SEER-POC study and categorized into 6 groups: CTX ± BA, CTX ± BA with PTR and metastasectomy, CTX ± BA and PTR, PTR only, no treatment, or other treatments. Multinomial logistic regression models were used to determine factors associated with each management modality compared to CTX ± BA. Cox proportional hazard modeling assessed relationships between treatment modalities and risk of all-cause mortality.
Results
Among 1,717 weighted cases, 28% received CTX ± BA, 12% CTX ± BA with PTR and metastatectomy, 23% CTX ± BA and PTR, 12% PTR only, 23% had no treatment, and 2% other treatments. Younger patients were significantly more likely to undergo CTX ± BA with PTR and metastasectomy than medical management alone (OR 3.32, 95% CI 1.3-8.6) and had decreased odds of receiving no treatment (OR 0.05, 95% CI 0.02-0.17) compared to the elderly. Race, insurance status, and laterality did not impact the type of treatment administered. Also, patients with M1b disease (metastases involving > 1 organ) were more commonly treated with CTX ± BA than surgery. Median follow-up for the entire cohort was 14 months [IQR: 4-32]. Median survival months by groups are summarized in Table 1 with patients undergoing CTX ± BA and PTR with metastatectomy having the longest median overall survival (OS = 61 mos), and those having no treatment the worst (1 mo). Median OS for CTX ± BA was 14 mos.
Discussion
In this population-based analysis, of patients with asymptomatic stage IV colon cancer, almost one-quarter do not receive any treatment with the main factors associated being age and disease burden. Patients receiving guideline concordant treatment had OS comparable to survival reported in clinical trials in patients with stage IV disease treated with palliative intent. A small proportion (12%) of patients undergoing multimodality curative treatment had a median OS of 5 years, confirming the optimal outcomes of this approach in appropriately selected patients.
Table 1. Overall survival and multivariable Cox proportional hazards by treatment category
Figure 2. Kaplan Meier curve demonstrating survival of patients with asymptomatic stage IV colon cancer stratified by treatment modality
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