Excess risk of dying of other causes of cured cancer patients

Abstract

Background:

The proportion of patients cured of cancer is usually estimated with cure models assuming they have the same death risk as the general population. These patients, even when cured, often maintain an extra death risk compared to the overall population. Our aims were to estimate this extra risk, and to take it into account in estimating cure proportions and relative survival (RS).

Methods:

We used RS mixture model with an additional parameter expressing the extra noncancer death risk of patients, assumed constant with age. We applied the model to the SEER registries survival data (1990–1994 diagnosed patients) with colorectal, breast, and lung cancers, and followed up to 2013.

Results:

The estimated relative risk of death for cured patients versus the general population was 1.11 for colorectal, 1.16 for breast, and 2.17 and 2.12, respectively, for female and male lung cancers. Taking this extra risk into account leads, for all cancers, to a higher estimated proportion of cured and a lower RS of uncured patients. In addition, it leads to a higher estimated RS for all patients aged >70 years, and for lung cancer patients aged >50 years, at diagnosis.

Conclusions:

Mortality of survivors not directly due to the diagnosed cancer was significantly higher than in the general population. It affected the estimates of cure proportions for all age classes and RS in the elderly.