Practical application of a calculator for conditional survival in colon cancer

Abstract

Purpose: 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 and methods: 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.

Results: 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).

Conclusion: 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.

Fig 1.

Unadjusted American Joint Commission on Cancer disease-specific survival for patients with colon cancer who were diagnosed between 1988 and 2000.

Fig 2.

Overfitting-corrected calibration plot with Efron's bootstrap and with 200 resamples and at least 10,000 patients per interval. Solid gold line represents bias-corrected calibration. Dashed blue line represents the perfect calibration in which predicted outcome corresponds perfectly with actual ones.

Fig 3.

(A) Crude and (B) adjusted 5-year, conditional, disease-specific survival by American Joint Commission on Cancer stage adjusted for age, sex, ethnicity, and tumor grade. Bars represent the 95% CIs. The x-axis represents patients who have already survived 0 to 5 years.

Fig 4.

Adjusted 5-year, conditional, disease-specific survival by (A) age, (B) sex, (C) ethnicity, and (D) grade. Bars represent the 95% CIs. The x-axis represents patients who have already survived 0 to 5 years.