ESTRO 2024 - Abstract Book

S559

Clinical - Breast

ESTRO 2024

(range: 2600 – 5000 cGy) in 5 to 25 fractions (mode=15). Sixteen of 28 patients (59%) received a sequential lumpectomy bed boost. Most patients (64%) had WB radiation, 24% (n=7) had additional axillary radiation or comprehensive nodal irradiation. Mean of the V90% 1560 cc (274 cc to 4949 cc), V95% 1353 cc (235 cc to 4145 cc), V100% 983 cc (161 cc to 2646 cc) were calculated. Compared with WB, WB+Ax (RR=1.3, 95% CI [0.65, 2.8] and WB+CNI (RR=1.8, 95% CI [1.1, 2.8]) were positively associated with BLE. The V90%, V95% and V100% were all highly correlated and positively associated with extent of BLE: for example, Figure 1 plots dermal thickness difference values within tertiles of V95%. Comparing the top and bottom tertiles of V95%, the mean dermal thickness difference increased by 1.7mm (95% CI: 0.35, 3.1).

Conclusion:

Patients who received radiation therapy to the WB+Ax and WB+CNI are at higher risk of developing BLE. Thus, the extent of the radiation field may be used as a factor to evaluate BLE in patients who underwent breast conservation therapy. High dose volume of the irradiated breast also shows strong association with severity of BLE as measured by difference in dermal thickness. Future studies with a larger patient cohort and longitudinal follow-up should be done to further study this relationship.

Keywords: lymphedema, ultrasound, radiation

1543

Mini-Oral

Stereotactic radiotherapy in metastatic breast cancer patients - a multicenter cohort study