Followup mammography after breast conservation therapy: Is 3D Tomosynthesis(3DT) worth it?

Abstract

6628 Background: Screening three-dimensional tomosynthesis mammography (3DT) is more cost-effective than two-dimensional mammography (2DM) for detecting breast cancer, however cost-effectiveness as a follow-up for treated breast cancer is unknown. We retrospectively analyzed the downstream workup and costs associated with 3DT compared to 2DM when employed as initial follow-up imaging in breast conservation therapy (BCT). Methods: Between the years 2015-2017, 450 consecutive BCT patients ages 32 – 89 with a follow-up 3DT (n = 162) or 2DM (n = 288) were reviewed in this IRB-approved study. The primary endpoint was further workup after follow-up mammogram and associated healthcare costs at 1 year. Downstream workup was secondarily tested for correlation with clinical and treatment-related variables. A single 3DT cost an estimated $149 compared to $111 for a 2DM, based on Centers for Medicare claims data Oncology Care Model. Results: Patient clinical characteristics were : 6% DCIS, 10% T1a, 29% T1b, 35% T1c, 19% T2, 88% N0, 9% N1, 3% N2, 76% ER+/PR+/HerNeu2-, 12% TNBC, and 14% Her2Neu+. Whole breast radiation was given with conventional (59%) and hypo (39%) fractionation (81% with a boost), and 10% received accelerated partial breast irradiation. First post-treatment mammogram was received within 3 months (20%), 3-6 months (32%), and after 6 months (48%) following RT. There were no differences in breast density, patient age, T/N stage, receptor status, type of RT, or mammogram timing between those in the 2DM and 3DT groups. The following downstream workup ensued for 3DT compared to 2D imaging: 18% vs 29% short-interval (6-month) mammogram (OR = 1.83, P = 0.01), 6% vs 11% breast MRI (OR = 1.90, P = 0.08), 4% ultrasound for each, and 3% biopsy for each (1 positive in the 2D group). Including downstream workup, the estimated cost per patient in the 3DT group = $249.00 compared to $253.64 in the 2D group. With multivariable analysis the independent predictors for reduced downstream workup was the use of 3DT and follow-up mammogram at least 6 months after radiation (P < 0.05). Conclusions: Excess workup was reduced with 3DT compared to 2DM in the post-treatment setting. A single 3DT costs approximately 34% more than 2DM, however in this study the associated reduction in downstream workup with 3DT actually made it more cost-effective.