Cigarette smoking and breast cancer risk: A long latency period?

Abstract

The association between cigarette smoking and breast cancer risk remains unclear. Few studies have examined cigarette smoking of very long duration as there may not have been a sufficient number of long-term smokers in studies conducted before the 1980s. Therefore, we examined the association between smoking and breast cancer risk using data from participants in a randomized controlled trial of screening for breast cancer involving 89,835 women aged 40 -59 years at recruitment and with up to 40 years of smoking duration at that time. Women with breast cancer diagnosed through 31 December 1993 were identified by linkage to the Canadian Cancer Database. Cox proportional hazards models were used to estimate rate ratios (RRs) and 95% confidence intervals (CIs). During an average of 10.6 years of follow-up, we observed 2,552 incident cases of breast cancer. We found a positive association between cigarette smoking and breast cancer risk, driven mainly by women who had smoked for several decades and who, therefore, had commenced smoking many years earlier. Relative to never-smokers, women who had smoked 40 years or more and 20 cigarettes/day or more were at the highest risk (RR ‫؍‬ 1.83, 95% CI 1.29 -2.61); for women who had commenced smoking 40 years or more before assessment (a measure of smoking latency rather than duration and intensity), the RR was 1.22 (95% CI 0.99 -1.59). Our findings suggest that smoking of very long duration and high intensity may be associated with increased risk of breast cancer.

Reply to the letter to the editor Lissowska J, Brinton LA, Zatonski W, Blair A, Bardin‐Mikolajczak A, Peplonska B, Sherman ME, Szeszenia‐Dabrowska N, Chanock S, García‐Closas M. Tobacco smoking, NAT2 acetylation genotype and breast cancer risk. Lissowska et al. (Int J Cancer 2006; 119:1961–69). More evidence for passive and active smoking and breast cancer risk among younger women

“…1 The report adds to the mounting evidence that active smoking is associated with increased breast cancer risk in younger/premenopausal women, 2 ( Table 6 in that review) as well as a more general trend toward studies observing increased breast cancer risk associated with smoking including 3 large American cohort studies, [3][4][5] a large Canadian cohort study, 6 two European cohorts 7,8 and studies that have controlled for passive smoking. 9 Although the authors conclude that the ''data indicate that passive smoking is not associated with breast cancer risk", they present passive smoking breast cancer risk estimates of 1.28 (95% confidence interval (CI) 0.52-3.11) and 1.27 (95% CI 0.76-2.11) for women aged less than 45 and 45-55, respectively.…”

The Surgeon General Report on Smoking and Health 50 Years Later: Breast Cancer and the Cost of Increasing Caution

“…(11)(12)(13)(14)(15)(16)(17)], examined risks for women with in higher exposure categories: early age of smoking initiation, smoking before first pregnancy, highest total years of smoking and total pack-years (11,13,(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29), and the effect on risk estimates for active smoking of controlling for passive smoking (30).…”

“…9, p. 7-78). Six prospective cohort studies published between 2002 and 2005 (22,26,28,29,31,32) found statistically significant elevated breast cancer risk associated with active smoking for at least some of the metrics of exposure (ref. 9, p. 7-78).…”

Factores De Riesgo Convencionales Y Emergentes en Cáncer De Mama: Un Estudio en Pacientes Posmenopáusicas

“…El ejercicio físico ocasiona la pérdida de masa adiposa y el aumento de la masa muscular, disminuyendo los niveles de estrógenos, insulina y factores de crecimiento circulantes (21,22). Entre otros hábitos socioculturales se acepta que el consumo de grasas y alcohol, así como también el hábito tabáquico podrían aumentar el riesgo de desarrollar CM (23)(24)(25).…”