Implications of short-term follow-up tomosynthesis mammography on downstream workup after breast conservation therapy.

Abstract

311 Background: We previously reported that premature (less than 6 months) follow-up screening mammography after radiotherapy in breast conservation therapy was associated with an increased rate of unnecessary downstream workup. We now present the results of a similar study conducted with follow-up tomosynthesis mammogram (TS). Methods: Between the years 2015-2017, 143 consecutive breast cancer patients between ages 33 – 82 were treated with lumpectomy and adjuvant radiotherapy with follow-up TS and reviewed in this IRB-approved study. Cases were stratified by time interval until the first post-radiation TS, and secondarily by radiation technique: conventional fractionation (n = 84), hypofractionation (n = 59), boost (n = 116), no boost (n = 27), and accelerated partial breast irradiation (n = 10). The primary endpoint was the rate of further imaging/workup following TS, correlated with clinical, treatment, and post-treatment timing related variables using multivariable binomial regression analysis. Results: The patient cohort included the following clinical characteristics: 6 patients with ductal carcinoma in-situ (the remaining demonstrated either invasive ductal or invasive lobular histology), Ninety-seven patients had stage T1 lesions, 34 had T2, and 4 had T3/T4 lesions. Eighteen patients were node+, 95 ER+/ Her2-, 13 were triple negative, and 13 triple positive. No patients had clinical suspicion of recurrence before their first follow-up TS. Conclusions: Unlike with post-treatment screening two-dimensional mammography, there was no association with post-treatment tomosynthesis timing and downstream workup. Further study should be considered to confirm these preliminary findings.