Gynecologic tumors in Thai women with breast cancer: a cross-sectional surveillance and ten-year cohort study

BACKGROUND: Breast cancer and gynecologic tumors share common hormonal and genetic risk factors. Previous studies mainly focused on the risk of endometrial pathology in women receiving tamoxifen, while the data on the overall prevalence of concurrent and subsequent gynecologic tumors in patients with breast cancer, especially in Asian populations, remain limited. Clarifying this association is important to survey the prevalence of concurrent gynecologic tumors and the incidence of de novo tumors in Thai women with breast cancer. This study aimed to determine the prevalence of concurrent gynecologic tumors and the incidence of de novo gynecologic tumors in Thai women with breast cancer. METHODS: An initial cross-sectional study was conducted at the Faculty of Medicine Siriraj Hospital, Mahidol University. Participants were women scheduled for breast cancer surgery between September 2007 and January 2009. They were investigated for gynecologic tumors using clinical examination, cervical cytology testing, and pelvic ultrasonography; additional procedures were as indicated. In 2019, data from this cohort were reviewed for the de novo gynecologic tumors arising during the previous 10 years. RESULTS: Concurrent gynecologic tumors were identified in 114 of 281 women (40.6%) with newly diagnosed breast cancer; most tumors were benign, including leiomyoma, adenomyosis, endometrial polyp, and ovarian tumor. Synchronous genital cancers were found in two cases, giving a prevalence of 0.7% [95% confidence interval (CI): 0.3-1.7]. During the 10-year follow-up period, de novo gynecologic tumors were found at an incidence of 3.1 per 100 person-years (95% CI: 2.1-4.4). Metachronous genital cancers were found in three cases, giving an incidence of 1.4 per 100 person-years (95% CI: 0.3-4.2). The risk of having either concurrent or de novo gynecologic tumors was associated with earlier age at menarche. CONCLUSIONS: Gynecologic tumors are prevalent in Thai women with breast cancer. The second primary genital cancers, both synchronous and metachronous, are not uncommon. Therefore, surveillance for the concurrent gynecologic tumors and further follow-up for the de novo ones should be considered in these patients.