| Abstract: | It has been proposed that breast cancers may differ in their pathogenesis and etiology according to their estrogen receptor (ER) and progesterone receptor (PR) status. This hospital-based case-control study in Japan assessed the relationship between known and suspected breast-cancer risk factors and ER and PR status. Information on risk factors was collected from histologically confirmed breast-cancer cases (n=519) and from cancer-free controls (n=9,506). Of 160 cases with known ER status, 58 percent were ER-positive; 38 percent of 157 cases with known PR status were PR-positive. No statistically significant differences were found between ER-positive cf ER-negative cases. However, statistically significant differences between PR-positive cf PR-negative cases were observed for number of full-term pregnancies (P=0.01), menstrual regularity as a teenager (P=0.024), and occupation as housewife (P=0.036). Borderline differences were observed for age at menopause (P=0.074), and age at menarche (P=0.083). This study provides some evidence that etiologic distinctions may be greater between PR-positive and PR-negative breast cancers than between ER-positive and ER-negative breast cancers.Dr Yoo is with the Seoul National University College of Medicine, Korea. Drs Tajima, Miura, Yoshida, Murai, and Kuroishi are with the Aichi Cancer Center, Nagoya, Japan. Dr Lee is with the College of Natural Science, Hallym University, Chuncheon, Korea. Drs Risch and Dubrow are with Yale University School of Medicine, New Haven, CT, USA. Address correspondence to Dr Yoo, Department of Preventive Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongo-gu, Seoul 110-460, Korea. Keun-Young Yoo was a recipient of a grant from the Exchange Scientist Program of the US National Institutes of Health (G-5-0111). Robert Dubrow received support from a US National Cancer Institute Preventive Oncology Academic Award (K07-CA01463). |
