Incidence of other cancer diagnoses in women with breast cancer: a retrospective cohort study with 42,248 women.

purposeThe aim of the present study was to determine whether women diagnosed with breast cancer (BC) have an increased incidence of other cancers, e.g., gastric cancer, lung cancer, skin cancer, and so on, compared to healthy women without a breast cancer diagnosis.

methodsThis retrospective cohort study was based on data from the Disease Analyzer database (IQVIA) and included adult women with an initial diagnosis of BC documented in one of 1,274 general practices in Germany between January 2000 and December 2018. Women with BC were matched to women without cancer by age, index year, yearly consultation frequency, and co-diagnoses. Univariate Cox regression models were used to study the association between BC and the incidence of other cancer diagnoses.

results21,124 women with BC and 21,124 women (mean age: 63 years) without cancer were included. Within 10 years of the index date, 14.3% of women with BC and 10.0% of women without cancer were diagnosed with cancer (p < 0.001). BC was significantly associated with the incidence of other cancer diagnoses (HR: 1.42, p < 0.001). The strongest association was observed for respiratory organ cancer (HR = 1.69, p < 0.001), followed by female genital organ cancer (HR = 1.61, p < 0.001) and cancer of lymphoid and hematopoietic tissue (HR: 1.59, p < 0.001).

conclusionThe results of this study show that women with BC have an increased incidence of another cancer compared to women without cancer. Therefore, it is important to pay particular attention to the development of other malignancies during follow-up in patients with BC. This should be considered especially in patients with a proven genetic mutation.