Population-based study of prognostic factors in stage II colonic cancer

Background: Adjuvant chemotherapy in stage II colorectal cancer may be considered for patients whose tumours have poor prognostic features. The aim of this study was to evaluate the prognostic significance of commonly reported clinical and pathological features of stage II colonic cancer. Methods: A population-based observational study of all patients with stage II colonic cancer diagnosed in the state of Western Australia from 1993 to 2003 was performed. A total of 1306 patients treated by surgery alone were identified, with a median follow-up of 59 (range 0-145) months. Results: Multivariable analysis revealed that the only independent prognostic factors for disease-specific survival were stage T4 (hazard ratio (HR) 1.75 (95 percent confidence interval (c.i.) 1.32 to 2.32); P < 0.001) and vascular invasion (HR 1.63 (95 per cent c.i. 1.15 to 2.30); P < 0.001). In younger patients (aged 75 years or less), who are more likely to be considered for chemotherapy, these two features showed independent prognostic significance but with higher HR values (1.96 for stage T4 and 2.73 for vascular invasion). Stage T4 and/or the presence of vascular invasion identified a 'poor' prognostic group, comprising 26.6 per cent of younger patients and with a 5-year survival rate of 71.2 per cent. The remaining 'good' prognostic group had a survival rate of 84.3 per cent at 5 years' follow-up. Conclusion: This study highlights the importance of accurate pathological assessment of tumour stage and vascular invasion for the prognostic stratification of patients with stage II colonic cancer. The results provide clarification of guidelines for the management of stage II disease in relation to recommendations for chemotherapy.