Practical application of a calculator for conditional survival in colon cancer

Conditional survival (CS) estimates provide important prognostic information for clinicians and patients who have survived a period after diagnosis. In this study we performed a contemporary evaluation of conditional survival among colon cancer patients and created a browser-based tool for real-time determination of conditional survival expectancies.

Patients with colon adenocarcinoma diagnosed between 1988 and 2000 were identified from the Surveillance Epidemiology End Results (SEER) registry. Conditional survival estimates were calculated by using the multiplicative law of probability after adjustment for age; sex; ethnicity; grade; and American Joint Commission on Cancer, sixth edition stage. A browser-based calculator was constructed.

A total of 83,419 patients were analyzed. As the time alive after initial treatment increased from 0 to 5 years, significant improvements in CS were observed for patients in all stages except stage I, which was associated with good CS even at diagnosis and which reflected the high likelihood of cure. Notably, adjusted 5-year CS rates improved from 42% to 80% for stage IIIC cancers and from 5% to 48% for stage IV cancers during the first 5 years. Differences in cancer-related CS at diagnosis were identified on the basis of age, ethnicity, and grade, but these differences decreased over time. A browser-based CS calculator was implemented by using the multivariate survival model (concordance index, 0.81).

For patients with colon cancer who survive over time, 5-year, cancer-specific CS improved dramatically, and the greatest improvements were among patients with poorer initial prognoses. These prognostic data are critical to inform patients for non-treatment-related life decisions and to inform treating physicians for planning of follow-up and surveillance strategies.