Smoking associated with hormone receptor negative breast cancer

Women who smoke have less favourable prognosis following breast-cancer diagnosis. Some studies suggest that this is due to a more advanced stage at diagnosis, on average. Our present aim was to assess whether smoking is associated with other prognostic markers as well, e.g., hormone receptor status, histopathology and tumour differentiation. The evaluation was based on 268 incident cases in a cohort of 10,902 women (35% smokers) followed for an average of 12.4 years. An immunohistochemical method on recuts of tumour tissue was used to assess hormone receptor status. One pathologist classified all tumours according to the WHO system, Nottingham grade and Nottingham Prognostic Index. The relative risk (RR) of oestrogen receptor-negative tumours was, for current smokers, 2.21 [95% confidence interval (CI) 1.23-3.96] and, for ex-smokers, 2.67 (95% CI 1.41-5.06) compared to never-smokers. Ex-smokers had an increased risk of progesterone receptor-negative tumours (RR = 1.61, 95% CI 1.07-2.41), but there were no other significant associations between smoking habits and oestrogen receptor-positive or progesterone receptor-positive or -negative tumours. The incidence of Nottingham grade III tumours was higher in ex-smokers than in never-smokers (RR = 2.03, 95% CI 1.17-3.54). In terms of histopathological type or Nottingham Prognostic Index, there were no significant differences between smoking groups. We conclude that smoking is associated with an increased occurrence of hormone receptor-negative tumours.