Bilateral breast cancer and the influence of body mass index in clinicopathological features and overall survival.

Background: Breast cancer (BC) and obesity are two closely associated pathologies with increasing incidence and mortality rates. Bilateral Breast Cancer (BBC) displays a low incidence rate within BC and obesity represents a major risk factor.

Objective: The aim of this study is to analyzed BBC clinicopathological features distribution and determine the potential influence of obesity in BBC in these same features and overall survival.

Methods: Clinicopathological information was obtained from 42 cases of women with BBC diagnosed in IPO-Porto. To evaluate the frequency distribution of the clinicopathological data, a chi-square goodness of fit test was performed for BBC cases. A chi-square test of independence was applied for BMI stratification. Cox regression was performed for overall survival. Statistical significance was set at p-value < 0.05.

Results: Distribution of BBC clinicopathological features was found to be statistically significant in family history (p-value < 0.001), BBC type (p-value < 0.001), stage (p-value = 0.005), differentiation grade (p-value < 0.001), receptor expression (p-value < 0.001) and histological type (p-value = 0.031). In comparison to the statistical expected results, we observed an increased cases of absence of family history and less cases of metachronous BBC. Histological types between tumours of BBC were mostly concordant. All cases presented concordant receptor expression. Analysis stratified by BMI revealed that obese women were diagnosed later, although without statistical significance. All obese women presented poor differentiation grade (n = 6). Overweight patients display a tendency to a better overall survival with lower tumour stages and lower differentiation grades.

Conclusions: Our results reveal the same receptor expression between contralateral tumours. Also, most tumours share the same histological type. When stratified by BMI, we observed a tendency for overweight women to have improved overall survival.