Impact of smoking on patients with stage iii colon cancer: Results from cancer and leukemia group B 89803

BACKGROUND: Cigarette smoking has been shown to increase the risk of developing colorectal cancer, particularly smoking early in life. Little is known about the impact of tobacco use on colon cancer recurrence among colon cancer survivors. METHODS: The authors prospectively collected lifetime smoking history from stage III colon cancer patients enrolled in a phase 3 trial via self-report questionnaires during and 6 months after completion of adjuvant chemotherapy. Smoking status was defined as never, current, or past. Lifetime pack-years were defined as number of lifetime packs of cigarettes. Patients were followed for recurrence or death. RESULTS: Data on smoking history were captured on 1045 patients with stage III colon cancer receiving adjuvant therapy (46% never smokers; 44% past; 10% current). The adjusted hazard ratio (HR) for disease-free survival (DFS) was 0.99 (95% confidence interval [CI], 0.70-1.41), 1.17 (95% CI 0.89-1.55), and 1.22 (95% CI 0.92-1.61) for lifetime pack-years 0-10, 10-20, and 20+, respectively, compared with never smoking (P = .16). In a preplanned exploratory analysis of smoking intensity early in life, the adjusted HR for 12+ pack-years before age 30 years for DFS was 1.37 (95% CI, 1.02-1.84) compared with never smoking (P = .04). The adjusted HR for DFS was 1.18 (95% CI, 0.92-1.50) for past smokers and 1.10 (95% CI, 0.73-1.64) for current smokers, compared with never smokers. CONCLUSIONS: Total tobacco usage early in life may be an important, independent prognostic factor of cancer recurrences and mortality in patients with stage III colon cancer.