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Abstract P3-03-21: Contralateral breast cancers detected by pre-operative MRI in patients diagnosed with DCIS: Whart do they mean?


 Background: For patients with ductal carcinoma in situ (DCIS), data about contralateral breast cancers detected by MRI at primary diagnosis and the impact of MRI use on the incidence and stage of contralateral breast cancers during follow-up are scarce. Methods: We selected all women diagnosed with a primary DCIS in the Netherlands in 2011-2015 from the Netherlands Cancer Registry. The synchronous and metachronous detection of contralateral DCIS and contralateral invasive breast cancer was assessed for patients who did receive an MRI upon primary diagnosis (MRI group) and for an age-matched control group without MRI. Incidence of contralateral disease during follow-up was calculated using competing risk methods.Results: Of the 8486 patients diagnosed with primary DCIS, 1571 (19%) received an MRI. In the MRI group, 0.8% of patients were diagnosed with a synchronous contralateral DCIS and 1.3% with synchronous contralateral invasive breast cancer. Median follow-up time was 6.4 years (IQR: 5.1-7.6). The estimated five-year cumulative incidence of synchronous plus metachronous contralateral DCIS was 2.0% (95% CI: 1.4%-2.8%)) for the MRI group and 0.9% (95% CI: 0.5%-1.5%) for the age-matched control group. The five-year cumulative incidence of contralateral invasive breast cancer was 3.5% (95% CI: 2.7%-4.5%) for the MRI group and 2.3% (95% CI: 1.6%-3.1%) for the age-matched control group. In patients aged <50 years, the cumulative incidence of metachronous contralateral DCIS was statistically significantly higher in the MRI group than in the age-matched controls (sHR= 4.22 (95%CI: 1.19-14.99), P=0.03). This was not the case in patients aged 50-74 years (sHR=0.89 (95%CI: 0.41-1.93), P=0.77). Conclusions: MRI led to more frequent detection of synchronous contralateral invasive breast cancers without lowering the number of metachronous contralateral invasive breast cancers. In patients aged below 50 years, MRI added to conventional imaging led to a persisting higher rate of DCIS diagnosed in the opposite breast, also without influencing the occurrence of invasive breast cancers being detected during the first five years of follow-up. Footnotes
 Citation Format: Kristien Keymeulen, Sandra Geurts, Loes Kooreman, Lucien Duijm, Sanne Engelen, Sigrid Vanwetswinkel, Ernest Luiten, Sabine Siesling, Adri Voogd, Vivianne Tjan-Heijnen. Contralateral breast cancers detected by pre-operative MRI in patients diagnosed with DCIS: Whart do they mean? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-03-21.