Body mass index, age at breast cancer diagnosis, and breast cancer subtype: a cross-sectional study

Association of body mass index with clinicopathological features and survival in patients with primary invasive lobular breast cancer

PURPOSE

Invasive lobular carcinoma (ILC) represents up to 15% of all breast carcinomas. While the proportion of women with overweight and obesity increases globally, the impact of body mass index (BMI) at primary diagnosis on clinicopathological features of ILC and the prognosis of the patients has not been investigated yet.

PATIENTS AND METHODS

We performed a multicentric retrospective study including patients diagnosed with non-metastatic pure ILC. The association of BMI at diagnosis with clinicopathological variables was assessed using linear or multinomial logistic regression. Univariable and multivariable survival analyses were performed to evaluate the association of BMI with disease-free survival (DFS), distant recurrence-free survival (DRFS), and overall survival (OS).

RESULTS

The data of 2856 patients with ILC and available BMI at diagnosis were collected, of which 2570/2856 (90.0%) had oestrogen receptor (ER)-positive and human epidermal growth factor receptor (HER2) not amplified/overexpressed (ER+/HER2-) ILC. Of these 2570 patients, 80 were underweight (3.1%), 1410 were lean (54.9%), 712 were overweight (27.7%), and 368 were obese (14.3%). Older age at diagnosis, a higher tumour grade, a larger tumour size, a nodal involvement, and multifocality were associated with a higher BMI. In univariable models, higher BMI was associated with worse outcomes for all end-points (DFS: hazard ratio (HR) 1.21, 95CI 1.12-1.31, p value<0.01; DRFS: HR 1.25, 95CI 1.12-1.40, p value<0.01; OS: HR 1.25, 95CI 1.13-1.37, p value<0.01). This association was not statistically significant in multivariable analyses (DFS: HR 1.09, 95CI 0.99-1.20, p value 0.08; DRFS: HR 1.03, 95CI 0.89-1.20, p value 0.67; OS: HR 1.11, 95CI 0.99-1.24, p value 0.08), whereas grade, tumour size, and nodal involvement were still prognostic for all end-points.

CONCLUSION

Worse prognostic factors such as higher grade, larger tumour size, and nodal involvement are associated with higher BMI in ER+/HER2- ILC, while there was no statistical evidence for an independent prognostic role for BMI. Therefore, we hypothesise that the effect of BMI on survival could be mediated through its association with these clinicopathological variables.

Association between Obesity, Race or Ethnicity, and Luminal Subtypes of Breast Cancer

Luminal breast cancers are the most common genomic subtype of breast cancers where Luminal A cancers have a better prognosis than Luminal B. Exposure to sex steroids and inflammatory status due to obesity are key contributors of Luminal tumor development. In this study, 1928 patients with Luminal A breast cancer and 1610 patients with Luminal B breast cancer were compared based on body mass index (BMI), age, race, menopausal status, and expressed receptors (i.e., estrogen (ER), progesterone (PR), and human epidermal growth factor receptor 2 (HER2)). Patients with Luminal B tumors had a significantly higher mean BMI (Δ = 0.69 kgm−2 [0.17, 1.21], p = 0.010) versus Luminal A. Interestingly, the risks of Luminal B tumors were higher among Black/African American patients versus White and Hispanic patients (p < 0.001 and p = 0.001, respectively). When controlled for each other, Black/African American race (p < 0.001) and increased BMI (p = 0.008) were associated with increased risks of Luminal B carcinoma, while postmenopausal status was associated with a decreased risk (p = 0.028). Increased BMI partially mediated the strong association between Black/African American race and the risk of Luminal B carcinoma. Thus, Black/African American race along with obesity seem to be associated with an increased risk of more aggressive Luminal B breast carcinomas.

Rat Mammary carcinoma susceptibility 3 (Mcs3) pleiotropy, socioenvironmental interaction, and comparative genomics with orthologous human 15q25.1-25.2

Genome-wide association studies of breast cancer susceptibility have revealed risk-associated genetic variants and nominated candidate genes; however, the identification of causal variants and genes is often undetermined by genome-wide association studies. Comparative genomics, utilizing Rattus norvegicus strains differing in susceptibility to mammary tumor development, is a complimentary approach to identify breast cancer susceptibility genes. Mammary carcinoma susceptibility 3 (Mcs3) is a Copenhagen (COP/NHsd) allele that confers resistance to mammary carcinomas when introgressed into a mammary carcinoma susceptible Wistar Furth (WF/NHsd) genome. Here, Mcs3 was positionally mapped to a 7.2-Mb region of RNO1 spanning rs8149408 to rs107402736 (chr1:143700228-150929594, build 6.0/rn6) using WF.COP congenic strains and 7,12-dimethylbenz(a)anthracene-induced mammary carcinogenesis. Male and female WF.COP-Mcs3 rats had significantly lower body mass compared to the Wistar Furth strain. The effect on female body mass was observed only when females were raised in the absence of males indicating a socioenvironmental interaction. Furthermore, female WF.COP-Mcs3 rats, raised in the absence of males, did not develop enhanced lobuloalveolar morphologies compared to those observed in the Wistar Furth strain. Human 15q25.1-25.2 was determined to be orthologous to rat Mcs3 (chr15:80005820-82285404 and chr15:83134545-84130720, build GRCh38/hg38). A public database search of 15q25.1-25.2 revealed genome-wide significant and nominally significant associations for body mass traits and breast cancer risk. These results support the existence of a breast cancer risk-associated allele at human 15q25.1-25.2 and warrant ultrafine mapping of rat Mcs3 and human 15q25.1-25.2 to discover novel causal genes and variants.

Dietary effects on breast cancer molecular subtypes, a 1:2 paired case-control study

To explore the associations between dietary factors and breast cancer (BC) molecular subtypes. The retrospective cases were confirmed by pathological diagnosis with breast cancer were gathered in two major hospitals in Xuzhou city, China, from 2015 to 2016. These cases were classified by the meeting standard of 13th St Gallen: luminal A, luminal B, Her-2 overexpression, and triple-negative breast cancer (TNBC) subtypes. A 1:2 paired retrospective case-control study with 210 cases and 420 controls was conducted to evaluate individual dietary intake, by food frequency questionnaire (FFQ) and estimate odds ratios (ORs), by the Cox regression model. For overall breast cancer patients, the more frequency of red meat (OR = 1.002, 95% CI = 1.001-1.004) and salted food (OR = 1.003, 95% CI = 1.001-1.005) were statistically significantly associated with a greater risk of breast cancer. Beans (OR = 0.997, 95% CI = 0.995-0.999), white meat (OR = 0.993, 95% CI = 0.989-0.997), aquatic products (OR = 0.990, 95% CI = 0.984-0.996), vegetables (OR = 0.999, 95% CI = 0.999-0.999), fruit (OR = 0.998, 95% CI = 0.997-0.999), and green tea (OR = 0.997, 95% CI = 0.994-0.999) were significantly associated with a lower risk of breast cancer. For luminal breast cancer patients, beans (OR = 0.997, 95% CI = 0.994-0.999), white meat (OR = 0.992, 95% CI = 0.987-0.997), green tea (OR = 0.995, 95% CI = 0.991-0.999), and milk (OR = 0.998, 95% CI = 0.996-0.999) were protective factors. While for nonluminal breast cancer, red meat was not included in the equation, and beans (OR = 0.989, 95% CI = 0.981-0.997), white meat (OR = 0.989, 95% CI = 0.981-0.998), vegetables (OR = 0.998, 95% CI = 0.997-0.999), and milk (OR = 0.994, 95% CI = 0.989-0.999) still showed a significantly reduced risk of nonluminal breast cancer. Different dietary factors revealed different effects on the etiology of breast cancer. Red meat may be a specific risk factor for luminal-type breast cancer.

Comparison of breast cancer risk factors among molecular subtypes: A case-only study

Epidemiological studies have a clear definition of the risk factors for breast cancer. However, it is unknown whether the distribution of these factors differs among breast cancer subtypes. We conducted a hospital‐based case‐only study consisting of 8067 breast cancer patients basing on the Tianjin Cohort of Breast Cancer Cases. Major breast cancer subtypes including luminal A, luminal B, human epidermal growth factor receptor 2 (HER2)‐enriched and basal‐like were defined by estrogen receptor, progesterone receptor, HER2, and Ki‐67 status. Variables including demographic characteristics, reproductive factors, lifestyle habits, imaging examination, and clinicopathologic data were collected for patients. Chi‐square test and one‐way analysis of variance were used to compare the distributions of variables among the four breast cancer subtypes. Multivariate logistic regression was used to estimate the odds ratios and associated 95% confidence intervals where luminal A patients served as the reference group. Overall, more commonality rather than heterogeneity on the distributions of factors was found between the four molecular subtypes of breast cancer. The proportion of overweight and obesity were lower in HER2‐enriched subtype. Women with age at menarche ≤13 years were more likely to be found in basal‐like subtype. Postmenopausal women were more frequent in HER2‐enriched and basal‐like subtypes. Women with benign breast disease and higher breast density were more common in HER2‐enriched subtype. Risk factor scoring showed that total risk scores were similar among the four subtypes. HER2‐enriched and basal‐like subtypes were more frequently diagnosed with large tumors. Calcification was more likely to be found in luminal B and HER2‐enriched subtypes, whereas less distributed in basal‐like subtype. Most of the breast cancer risk factors were similarly distributed among the four major breast cancer subtypes; commonality is predominant.

Pregnancy complications and subsequent breast cancer risk in the mother: a Nordic population-based case-control study

Certain features of pregnancy are important risk factors for breast cancer, such as protection afforded by young age at first birth. Preeclampsia, a pregnancy complication, is associated with reduced maternal breast cancer risk. However, questions remain regarding causality, biological mechanisms and the relation of other hypertensive conditions to risk. We conducted a population-based case-control study of breast cancer cases (n = 116,196) in parous women identified through linkage of birth and cancer registries in Denmark, Finland, Norway and Sweden (1967-2013), including up to 10 matched controls per case (n = 1,147,192) sampled from the birth registries (complete data were not available on all variables). Odds ratios (ORs) with 95% confidence intervals (CIs) were derived from unconditional logistic regression models including matching factors (country, maternal birth year) and parity. Hypertension diagnosed before pregnancy (OR 0.87; 95% CI 0.78-0.97), gestational hypertension (OR 0.90; 95% CI 0.86-0.93) and preeclampsia (OR 0.91; 95% CI 0.88-0.95) were associated with reduced breast cancer risk. Results remained similar after adjustment for smoking and maternal body mass index before first pregnancy, and were generally similar stratified by parity, age at breast cancer diagnosis, time since first and last birth, sex of the offspring and calendar time. Except for retained placenta (OR 1.14; 95% CI 0.98-1.32), no other pregnancy complication appeared associated with breast cancer risk. The mechanisms mediating the modest risk reductions for history of preeclampsia or hypertension preceding or arising during pregnancy, and possible increased risk with history of retained placenta are unknown and warrant further laboratory, clinical and epidemiological investigation.