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Comment & Response
November 11, 2021

Association of Adiposity With Mortality Among Black Patients With Breast Cancer—Reply

Author Affiliations
  • 1Rutgers Cancer Institute of New Jersey, New Brunswick
  • 2Roswell Park Cancer Institute, Buffalo, New York
JAMA Oncol. 2022;8(1):170-171. doi:10.1001/jamaoncol.2021.5762

In Reply Guo et al expressed concerns about potential immortal time bias in our prospective population-based cohort study1 because entry into the cohort occurred on average 10 months after cancer diagnosis, as this was a cohort study of breast cancer survivors. This led to some patients dying prior to being contacted about the study, who might represent those with the most advanced cancers who might have cachexia. The concern of Guo et al is that excluding individuals with lower levels of adiposity and following participants from the time of diagnosis may potentially inflate the benefits of low adiposity. Immortal time bias in our study, however, is unlikely for several reasons. First, because we enrolled patients from the New Jersey State Cancer Registry using rapid ascertainment protocols, we know that only 2.8% of all eligible cases died before they could be approached.2 Second, if the women who died were indeed cachexic, measures of low adiposity would be associated with increased mortality outcomes and attenuate, rather than inflate, the benefits of low adiposity. Furthermore, cachexia is uncommon in breast cancer, particularly among Black breast cancer survivors, with more than 80% being overweight or obese.1 As described in the article,1 we excluded underweight women, which represented less than 0.5% of the study population. We also conducted sensitivity analyses excluding women with stage IV disease (2% of the cohort) and women who lost more than 5% body weight, as weight loss is a predictor of poor prognosis,3 with essentially no change in risk estimates.

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