Purpose To provide an analysis of conditional survival (CS) in rectal cancer patients. Cancer survival is typically reported in terms of survival from time of diagnosis. CS can provide improved prognostic information for patients surviving a given period after diagnosis. Methods Data from 36,321 rectal cancer patients diagnosed between 1988 and 1998 were analyzed using the Surveillance, Epidemiology, and End Results (SEER 17) database. Observed 5-year CS rates according to disease stage, age, sex, and race were calculated using the life-table method. Results As survival from diagnosis increased from 0 to 5 years, the 5-year observed CS changed from 73% to 74% for stage I disease, 56% to 66% for stage II, 47% to 65% for stage III, and 6% to 48% for stage IV. Patients aged 65 years and over at diagnosis had lower CS than those under 65 years, both at diagnosis (45% vs. 61%) and at 5 years from diagnosis (59% vs. 81%). Men had slightly lower 5-year survival than women, both at diagnosis (50% vs. 53%) and after 5 years (68% vs. 71%). Black patients had slightly lower survival than white patients for nearly all time points and stages. Conclusion For rectal cancer patients who survive a given period of time after diagnosis, the largest increases in CS are in patients with advanced stage disease and for those under 65 years of age. CS can provide more accurate prognostic information for rectal cancer patients who survive a given period after diagnosis. Survival estimates for cancer patients are most commonly reported as survival from the time of diagnosis. Survival probability changes, however, for patients who survive a given period of time after diagnosis, and their prognosis is more accurately described using conditional survival (CS). CS, which is based on the concept of conditional probability, accounts for the fact that hazard rates can change over time. For many cancer types, hazard rates decline at some point (eg, after the first few years) after diagnosis. For patients surviving past a given duration from diagnosis, subsequent prognosis can be quite different from prognosis at the time of diagnosis. CS can therefore be a more accurate measure of survival probability for many surviving cancer patients. Conditional survival is of practical value to patients, providers, and researchers. 1 , 2 Cancer patients who are followed for several years after their diagnosis may wish to know how their prognosis is changing over time. Indeed, if a cancer patient’s CS has risen to the extent that it is comparable to expected survival among the general population, it provides a more objective basis upon which to deem a patient “cured” of their disease. Providers can make use of CS information to more objectively determine appropriate frequency of follow-up visits and level of aggressiveness of surveillance testing. When designing clinical trials, clinical researchers may find CS useful in helping to determine sufficient follow-up times for trial end points. Although CS provides a more accurate quantification of prognosis for long-term survivors, it is important that this measure be used in combination with other estimates of mortality risk (eg, overall 5-year survival), since CS still provides only an estimate at a single point in time. Several authors have reported studies on CS for various disease sites, including breast, 3 colon, 4 central nervous system, 5 , 6 lung, 7 , 8 and other advanced carcinomas. 9 We have also reported CS analyses for various disease sites. 10 – 24 To our knowledge, however, no published data exist on CS patterns in rectal carcinoma. The specific aim of this project was to investigate the CS of rectal cancer patients in the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER 17) dataset. 25
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