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Multigene Germline Testing in Patients with DCIS vs Invasive Breast Cancer in a Large, Integrated Health Care System
Jessica M Dzubnar1, Laurel A Habel2, Sheng-Fang Jiang2
1University of California San Francisco, East Bay, Oakland, CA, USA.
Background:
Identification of germline pathogenic (PV) and likely pathogenic variants (LPV) can inform patients of their risk for breast cancer, empowering them to utilize risk-reducing strategies. National guidelines for germline testing are the same for invasive breast cancer (IBC) and ductal carcinoma in situ (DCIS); however, data on how testing and results compare for patients with DCIS versus IBC are limited.
Methods:
This retrospective cohort study of multigene panel germline testing compared women with DCIS versus stage I-III IBC diagnosed between September 2019 through September 2022 at Kaiser Permanente Northern California.
Results:
Of the 1490 patients with DCIS and 8474 patients with IBC, the percentage of patients who underwent genetic testing was higher in those with IBC (38%, n = 3223) than in those with DCIS (28.5%, n = 424) (p < 0.00001). Among tested patients, the prevalence of PV/LPV in any breast cancer-related (BCR) gene was higher for IBC (9.1%) than for DCIS (6.1%) (p=0.041). The prevalence of PV/LPV in moderate-risk genes was similar (3.4% in IBC and 3.3% in DCIS; p=0.8798), whereas the prevalence in high-risk genes was higher for patients with IBC (5.8%) than for those with DCIS (3.1%) (p =0.0189).
Conclusions:
Although the prevalence of PV/LPV in high-risk BCR genes was lower in DCIS than in IBC, the prevalence of PV/LPV was similar in moderate-risk BCR genes. Our study supports continuing the same genetic testing guidelines for DCIS and IBC since carrying a PV/LPV in a moderate-risk BCR gene will affect treatment and surveillance decisions.
