1. ¹Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, PO Box 19024,MP 474, Seattle, Washington, WA 98109-1024, USA
2. ²The Station for Prevention and Treatment of Cancer of the Shanghai Textile Industry Bureau, 1474 Yan An Xi Road, Shanghai 200052, Peoples Republic of China

Correspondence: D B Thomas, E-mail: dbthomas@fhcrc.org

Received 24 June 2002; Revised 28 August 2002; Accepted 30 August 2002.

Abstract

The possible influence of induced abortion on breast cancer risk was assessed in a cohort of 267 040 women enrolled in a randomised trial of breast self-examination in Shanghai, China. Based on answers to a baseline questionnaire, subsequent breast cancer risk was not significantly associated with ever having an induced abortion. After adjustment for potential confounders, the relative risk estimate was 1.06 (95% C.I.: 0.91, 1.25), and there was no trend in risk with number of abortions. Analysis of data from more detailed interviews of 652 cases and 694 controls from the cohort yielded similar results. There was also no overall increase in risk in women with induced abortion after first birth. Few women had undergone an abortion after 13 weeks gestation or before their first child. Although increases in risk were observed in such women, they were not statistically significant and could have been due to recall bias. Abortions as they have been performed in China are not an important cause of breast cancer.