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Breast Cancer Risk After Recent Childbirth: A Pooled Analysis of 15 Prospective Studies.

ABSTRACT: Background:Parity is widely recognized as protective for breast cancer, but breast cancer risk may be increased shortly after childbirth. Whether this risk varies with breastfeeding, family history of breast cancer, or specific tumor subtype has rarely been evaluated. Objective:To characterize breast cancer risk in relation to recent childbirth. Design:Pooled analysis of individual-level data from 15 prospective cohort studies. Setting:The international Premenopausal Breast Cancer Collaborative Group. Participants:Women younger than 55 years. Measurements:During 9.6 million person-years of follow-up, 18 826 incident cases of breast cancer were diagnosed. Hazard ratios (HRs) and 95% CIs for breast cancer were calculated using Cox proportional hazards regression. Results:Compared with nulliparous women, parous women had an HR for breast cancer that peaked about 5 years after birth (HR, 1.80 [95% CI, 1.63 to 1.99]) before decreasing to 0.77 (CI, 0.67 to 0.88) after 34 years. The association crossed over from positive to negative about 24 years after birth. The overall pattern was driven by estrogen receptor (ER)-positive breast cancer; no crossover was seen for ER-negative cancer. Increases in breast cancer risk after childbirth were pronounced when combined with a family history of breast cancer and were greater for women who were older at first birth or who had more births. Breastfeeding did not modify overall risk patterns. Limitations:Breast cancer diagnoses during pregnancy were not uniformly distinguishable from early postpartum diagnoses. Data on human epidermal growth factor receptor 2 (HER2) oncogene overexpression were limited. Conclusion:Compared with nulliparous women, parous women have an increased risk for breast cancer for more than 20 years after childbirth. Health care providers should consider recent childbirth a risk factor for breast cancer in young women. Primary Funding Source:The Avon Foundation, the National Institute of Environmental Health Sciences, Breast Cancer Now and the UK National Health Service, and the Institute of Cancer Research.

SUBMITTER: Nichols HB

PROVIDER: S-EPMC6760671 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Breast Cancer Risk After Recent Childbirth: A Pooled Analysis of 15 Prospective Studies.

Nichols Hazel B HB Schoemaker Minouk J MJ Cai Jianwen J Xu Jiawei J Wright Lauren B LB Brook Mark N MN Jones Michael E ME Adami Hans-Olov HO Baglietto Laura L Bertrand Kimberly A KA Blot William J WJ Boutron-Ruault Marie-Christine MC Dorronsoro Miren M Dossus Laure L Eliassen A Heather AH Giles Graham G GG Gram Inger T IT Hankinson Susan E SE Hoffman-Bolton Judy J Kaaks Rudolf R Key Timothy J TJ Kitahara Cari M CM Larsson Susanna C SC Linet Martha M Merritt Melissa A MA Milne Roger L RL Pala Valeria V Palmer Julie R JR Peeters Petra H PH Riboli Elio E Sund Malin M Tamimi Rulla M RM Tjønneland Anne A Trichopoulou Antonia A Ursin Giske G Vatten Lars L Visvanathan Kala K Weiderpass Elisabete E Wolk Alicja A Zheng Wei W Weinberg Clarice R CR Swerdlow Anthony J AJ Sandler Dale P DP

Annals of internal medicine 20181211 1

<h4>Background</h4>Parity is widely recognized as protective for breast cancer, but breast cancer risk may be increased shortly after childbirth. Whether this risk varies with breastfeeding, family history of breast cancer, or specific tumor subtype has rarely been evaluated.<h4>Objective</h4>To characterize breast cancer risk in relation to recent childbirth.<h4>Design</h4>Pooled analysis of individual-level data from 15 prospective cohort studies.<h4>Setting</h4>The international Premenopausal ...[more]

PMID: 30534999

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Project description:BackgroundCarotenoids, micronutrients in fruits and vegetables, may reduce breast cancer risk. Most, but not all, past studies of circulating carotenoids and breast cancer have found an inverse association with at least one carotenoid, although the specific carotenoid has varied across studies.MethodsWe conducted a pooled analysis of eight cohort studies comprising more than 80% of the world's published prospective data on plasma or serum carotenoids and breast cancer, including 3055 case subjects and 3956 matched control subjects. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels to a common standard by reassaying 20 plasma or serum samples from each cohort together at the same laboratory. Using conditional logistic regression, adjusting for several breast cancer risk factors, we calculated relative risks (RRs) and 95% confidence intervals (CIs) using quintiles defined among the control subjects from all studies. All P values are two-sided.ResultsStatistically significant inverse associations with breast cancer were observed for α-carotene (top vs bottom quintile RR = 0.87, 95% CI = 0.71 to 1.05, P(trend) = .04), β-carotene (RR = 0.83, 95% CI = 0.70 to 0.98, P(trend) = .02), lutein+zeaxanthin (RR = 0.84, 95% CI = 0.70 to 1.01, P(trend) = .05), lycopene (RR = 0.78, 95% CI = 0.62 to 0.99, P(trend) = .02), and total carotenoids (RR = 0.81, 95% CI = 0.68 to 0.96, P(trend) = .01). β-Cryptoxanthin was not statistically significantly associated with risk. Tests for heterogeneity across studies were not statistically significant. For several carotenoids, associations appeared stronger for estrogen receptor negative (ER(-)) than for ER(+) tumors (eg, β-carotene: ER(-): top vs bottom quintile RR = 0.52, 95% CI = 0.36 to 0.77, P(trend) = .001; ER(+): RR = 0.83, 95% CI = 0.66 to 1.04, P(trend) = .06; P(heterogeneity) = .01).ConclusionsThis comprehensive prospective analysis suggests women with higher circulating levels of α-carotene, β-carotene, lutein+zeaxanthin, lycopene, and total carotenoids may be at reduced risk of breast cancer.

Project description:BackgroundGreater height and body mass index (BMI) have been associated with an increased risk of thyroid cancer, particularly papillary carcinoma, the most common and least aggressive subtype. Few studies have evaluated these associations in relation to other, more aggressive histologic types or thyroid cancer-specific mortality.MethodsThis large pooled analysis of 22 prospective studies (833,176 men and 1,260,871 women) investigated thyroid cancer incidence associated with greater height, BMI at baseline and young adulthood, and adulthood BMI gain (difference between young-adult and baseline BMI), overall and separately by sex and histological subtype using multivariable Cox proportional hazards regression models. Associations with thyroid cancer mortality were investigated in a subset of cohorts (578,922 men and 774,373 women) that contributed cause of death information.ResultsDuring follow-up, 2996 incident thyroid cancers and 104 thyroid cancer deaths were identified. All anthropometric factors were positively associated with thyroid cancer incidence: hazard ratios (HR) [confidence intervals (CIs)] for height (per 5 cm) = 1.07 [1.04-1.10], BMI (per 5 kg/m2) = 1.06 [1.02-1.10], waist circumference (per 5 cm) = 1.03 [1.01-1.05], young-adult BMI (per 5 kg/m2) = 1.13 [1.02-1.25], and adulthood BMI gain (per 5 kg/m2) = 1.07 [1.00-1.15]. Associations for baseline BMI and waist circumference were attenuated after mutual adjustment. Baseline BMI was more strongly associated with risk in men compared with women (p = 0.04). Positive associations were observed for papillary, follicular, and anaplastic, but not medullary, thyroid carcinomas. Similar, but stronger, associations were observed for thyroid cancer mortality.ConclusionThe results suggest that greater height and excess adiposity throughout adulthood are associated with higher incidence of most major types of thyroid cancer, including the least common but most aggressive form, anaplastic carcinoma, and higher thyroid cancer mortality. Potential underlying biological mechanisms should be explored in future studies.

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Breast Cancer Risk After Recent Childbirth: A Pooled Analysis of 15 Prospective Studies.

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Breast Cancer Risk After Recent Childbirth: A Pooled Analysis of 15 Prospective Studies.

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