Long-term follow-up of high-risk breast lesions at vacuum-assisted biopsy without subsequent surgical resection

Purpose: B3-lesions of the breast are a heterogeneous group of neoplasms, associated with a higher risk of breast cancer. Recent studies show a low upgrade rate into malignancy after subsequent open surgical excision (OE) of most B3-lesions when proven by vacuum-assisted biopsy (VAB). However, there is a lack of long-term follow-up data after VAB of high-risk lesions. The primary aim of this study was to demonstrate whether follow-up of B3 lesions is a beneficial and reliable alternative to OE in terms of long-term outcome. The secondary aim was to identify patient and lesion characteristics of B3 lesions for which OE is still necessary. Methods: This retrospective multi-center study was conducted at 8 Swiss breast centers between 2010 - 2019. A total of 278 women (mean age 53.5 +/- 10.7 years) with 286 B3-lesions who had observation only and who had at least 24 months of follow-up were included. Any event during follow-up (DCIS, invasive cancer, new B3-lesion) was systematically recorded. Data from women who had an event during follow-up were compared with those who did not. The results for the different B3 lesions were analyzed using the t-test and Fisher's exact test. A p-value of < 0.05 was considered statistically significant. Results: The median follow-up interval was 59 months (range 24-143 months) with 52% (148 /286) having a follow-up of more than 5 years. During follow-up, in 42 women 44 suspicious lesions occurred during follow up, with 36.4% (16/44) invasive cancer and 6.8% (3/44) DCIS. Thus, 6.6% (19/286) of all women developed malignancy during follow-up after a median follow-up interval of 6.5 years (range 31-119 months). The initial histology of the B3 lesion influenced the subsequent occurrence of a malignant lesion during follow-up (p<0.038). The highest malignancy-developing rate was observed in ADH (24%, 19/79), while all other B3-lesions had malignant findings ipsi- and contralateral between 0%6%. The results were not influenced by the VAB-method (Mx-, US-, MRI-guided), the radiological characteristics of the lesion, or the age or menopausal status of the patient (p>0.12). Conclusion: With a low risk of <6% of developing malignancy, VAB followed by long-term follow-up is a save alternative to OE for most B3-lesions. A higher malignancy-rate only occurred in ADH (24%). Based on our results, radiological follow-up should be bilateral, preferable using the technique of initial diagnosis. As we observed a late peak (6-7 years) of breast malignancies after B3-lesions, follow-up should be continued for a longer period (>10 years). Knowledge of these long-term outcome results will be helpful in making treatment decisions and determining the optimal radiological follow-up interval.