RESUMO
BACKGROUND: The association of reproductive factors with hormone receptor (HR)-negative breast tumors remains uncertain. METHODS: Within the EPIC cohort, Cox proportional hazards models were used to describe the relationships of reproductive factors (menarcheal age, time between menarche and first pregnancy, parity, number of children, age at first and last pregnancies, time since last full-term childbirth, breastfeeding, age at menopause, ever having an abortion and use of oral contraceptives [OC]) with risk of ER-PR- (n = 998) and ER+PR+ (n = 3,567) breast tumors. RESULTS: A later first full-term childbirth was associated with increased risk of ER+PR+ tumors but not with risk of ER-PR- tumors (≥35 vs. ≤19 years HR: 1.47 [95% CI 1.15-1.88] p(trend) < 0.001 for ER+PR+ tumors; ≥35 vs. ≤19 years HR: 0.93 [95% CI 0.53-1.65] p(trend) = 0.96 for ER-PR- tumors; P(het) = 0.03). The risk associations of menarcheal age, and time period between menarche and first full-term childbirth with ER-PR-tumors were in the similar direction with risk of ER+PR+ tumors (p(het) = 0.50), although weaker in magnitude and statistically only borderline significant. Other parity related factors such as ever a full-term birth, number of births, age- and time since last birth were associated only with ER+PR+ malignancies, however no statistical heterogeneity between breast cancer subtypes was observed. Breastfeeding and OC use were generally not associated with breast cancer subtype risk. CONCLUSION: Our study provides possible evidence that age at menarche, and time between menarche and first full-term childbirth may be associated with the etiology of both HR-negative and HR-positive malignancies, although the associations with HR-negative breast cancer were only borderline significant.
Assuntos
Neoplasias da Mama/metabolismo , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Aleitamento Materno , Neoplasias da Mama/epidemiologia , Neoplasias da Mama/etiologia , Anticoncepcionais Orais Hormonais/efeitos adversos , Feminino , Número de Gestações , Humanos , Idade Materna , Menarca , Menopausa , Pessoa de Meia-Idade , Paridade , Gravidez , Modelos de Riscos Proporcionais , Estudos Prospectivos , Fatores de Risco , Adulto JovemRESUMO
BACKGROUND & AIMS: There has been consistent evidence for a relationship between smoking and colorectal cancer (CRC), although it is not clear whether the colon or rectum is more sensitive to the effects of smoking. We investigated the relationships between cigarette smoking and risk of CRC and tumor location. METHODS: We analyzed data from 465,879 participants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study; 2741 developed CRC during the follow-up period (mean, 8.7 years). Cox proportional hazard regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS: The risk of colon carcinoma was increased among ever smokers (HR, 1.18; 95% CI, 1.06-1.32) and former cigarette smokers (HR, 1.21; 95% CI, 1.08-1.36), compared with never smokers; the increased risk for current smokers was of borderline significance (HR, 1.13; 95% CI, 0.98-1.31). When stratified for tumor location, the risk of proximal colon cancer was increased for former (HR, 1.25; 95% CI, 1.04-1.50) and current smokers (HR, 1.31; 95% CI, 1.06-1.64), but the risks for cancers in the distal colon or rectum were not. Subsite analyses showed a nonsignificant difference between the proximal and distal colon (P = .45) for former smokers and a significant difference for current smokers (P = .02). For smokers who had stopped smoking for at least 20 years, the risk of developing colon cancer was similar to that of never smokers. CONCLUSIONS: Ever smokers have an increased risk of colon cancer, which appeared to be more pronounced in the proximal than the distal colon location.