Conditional Survival and the Choice of Conditioning Set for Patients With Colon Cancer: An Analysis of NSABP Trials C-03 Through C-07

Abstract

A B S T R A C T PurposeColon cancer overall survival (OS) is usually computed from the time of diagnosis. Survival gives the initial prognosis but does not reflect how prognosis changes with changing hazard rates over time. Conditional survival (probability of surviving y additional years given they have survived x years [CS or OS͉OS]) is an alternative measure that accounts for elapsed time since diagnosis, providing more relevant prognostic information. We extend the concept of CS to condition on the set of patients alive, recurrence-free, and second primary cancer-free (disease-free survival [OS͉DFS]). Patients and MethodsUsing data from National Surgical Adjuvant Breast and Bowel Project trials C-03 through C-07, 5-year OS͉DFS was calculated on patients who were disease free up to 5 years after diagnosis, stratified by age, stage, nodal status, and performance status (PS). ResultsFor stage II, OS͉DFS improved from 87% to 92% at 5 years. For stage III, OS͉DFS improved from 69% to 88%. Patients younger than 50 years showed OS͉DFS improvement from 79% to 95%; those older than 70 years showed no sustained increase in OS͉DFS. Node-negative patients with Ն 12 nodes resected showed little change (89% to 94%); those with more than four positive nodes showed an improvement (57% to 86%). Patients with a PS of 0 or 1 demonstrated a small improvement; those with a PS of 2 did not (64% to 58%). ConclusionPrognosis improves over time for almost all groups of patients with colon cancer, especially those with positive nodes. OS͉DFS is a more relevant measure of prognosis for those who have already survived disease free a period of time after diagnosis.

Conditional Survival: A Useful Concept to Provide Information on How Prognosis Evolves over Time

“…Alternatively, one could determine CS, given that the patient is alive and progression/recurrence free at s. This approach is used for example by Zamboni and colleagues (2) when determining CS for patients with colon cancer. In general, by using a patient's "history"-from diagnosis to prediction time s-we can refine CS toward a more specifically determined prognosis.…”

Conditional net survival: Relevant prognostic information for colorectal cancer survivors. A French population-based study

“…Several studies have previously published results on conditional survival from colorectal cancer [6][7][8][9][10][11][12][13][14][15][16]. Few of them include detailed data of patients and his tumour (stage at diagnosis, location) and none have a 33-year period study.…”

Multiple primary cancers among colorectal cancer survivors in Queensland, Australia, 1996–2007

“…[3] One of the challenges faced by the growing number of survivors is the possibility of being diagnosed with a subsequent tumor, [4] with its associated implications in terms of poorer quality of life [5] and decreased long-term survival. [6] Several Australian and international studies in recent years have examined the risk of developing new primary cancers following an initial CRC diagnosis [7][8][9][10][11][12]. The focus of most of these studies has been on identifying which cancer types were more likely to occur after the initial CRC, with inconsistent results.…”