baseline characteristics

The baseline patient characteristics according to BRCA1/2 mutation are shown in Table 1. All patients were Korean. BRCA1/2 mutation carriers were significantly younger (mean age 45.5 ± 11.0 vs. 50.1 ± 10.8) and premenopausal (63.1% vs. 47.3%) at the time of diagnosis compared to non-carriers (P = 0.002 and P = 0.0011, respectively). Also, BRCA1/2 mutation carriers were more likely to have a family history of breast cancer and/or ovarian cancer (40.2% vs. 9.4%, P < 0.0001), personal history of ovarian cancer (9.0% vs. 0.5%, P < 0.0001), bilateral breast cancer (4.9% vs. 1.2%, P = 0.0105), and a higher nuclear grade (86.0% vs. 73.4%, P = 0.0140). Pathologic stage, lympho-vascular invasion, multiplicity, and proportion of mastectomy were not significantly different in those with or without BRCA1/2 mutation. Although differences in the proportion of adjuvant chemotherapy (81.2% vs. 70.2%, P = 0.0120) and neo-adjuvant chemotherapy (13.1% vs. 21.8%, P = 0.0273) were observed, the total proportion of chemotherapy treatment was comparable between the two groups (94.3% vs. 89.4%, P = 0.1314).

In our previous study, with a median follow-up period of 53.6 months, we demonstrated the high prevalence of BRCA1/2 mutation in unselected Korean TNBC patients and the higher incidence rate of CBC in BRCA1/2 mutation carriers compared to non-carriers16. With a median follow-up duration of 80.9 months, this long-term follow-up study showed a consistently increased CBC incidence rate in BRCA1/2 mutation carriers compared to non-carriers. There were no significant differences in disease-free survival (DFS), OS, BCSS, and DMFS between the two groups. Additionally, BRCA1/2 mutation was a significant risk factor for CBC occurrence with an HR of 6.242. Among patients with CBC recurrence, ~80% had TNBC-type as recurred CBC, and over 60% resumed chemotherapy.