Examining the characteristics of unstaged colon and rectal cancer cases

Background: There are only three published studies that have examined unstaged cancers, including breast, prostate and colorectal cancer, but none have specifically examined which aspects of tumor staging were missing. The objective of the study was to identify which stage components were missing, to characterize and to identify predictors of unstaged cancer, and to evaluate prognosis of unstaged in colon and rectal cancer patients. Methods: Data on all colon and rectal cancer cases diagnosed during 1991 to 2002 were identified from the Surveillance, Epidemiology and End Results (SEER) database. Information included in the analysis encompassed socio-demographics; tumor size (T); number of lymph nodes (N); metastases (M); SEER summary stage; SEER sites; cancer treatment; month and year of diagnosis; and last date known alive. Results: The study included 128,418 colon and 44,616 rectal cancer patients. Overall, 5.1% of colon and 7.8% of rectal cancer patients were unstaged. Compared to staged cases, both unstaged colon and rectal cancer cases were more likely to be older, African American, female, diagnosed in the Northeast and South, and have unknown treatment (all p < 0.001). The stage component of M was found to be the factor missing most frequently which attributed most to being unstaged. Survival was significantly higher in unstaged and the overall cohort compared to distant staged colon and rectal cancer patients (both p < 0.001) except for patients ≥ 65 years old (p > 0.99). Conclusions: Given that unstaged cases differ from staged, the findings have methodological implications in accounting for unstaged cases in epidemiological and health services research.