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Clinical Outcomes and Setup Reproducibility in Patients Receiving Synchronous Bilateral Breast Radiation in the Prone
Aishwarya Shah1, Paulina Galavis1, Sarah Morris1
1Department of Radiation Oncology, New York University Langone Health and Perlmutter Cancer Center, New York, New York.
Purpose:
Radiation therapy (RT) positioning and planning are vital to minimizing toxicity in patients with synchronous bilateral breast cancer (SBBC). We studied clinical outcomes and setup reproducibility in SBBC patients treated in the prone position.
Methods And Materials:
This retrospective study analyzed SBBC patients treated prone between 2012 and 2022. Demographics, clinical RT dose/field, dosimetry, on-treatment imaging, toxicity, and outcomes data were collected. RT delivery was standardized, with the left breast treated first. After 2014, radiochromic (GaF) films were placed for fractions 1 to 5 to evaluate field overlap, prompting resimulation or replanning if consistent overlap was detected. Positional shifts during setup were collected for bilateral whole breast irradiation (WBI) and partial breast irradiation (PBI).
Results:
Forty-five patients were included. Median age was 67 years, and median follow-up was 64 months. Thirty-five, 5, and 5 patients received bilateral WBI (1 with low axilla), bilateral PBI, and a combination of WBI and PBI, respectively. The most common WBI dose was 40.5 Gy, with a simultaneous tumor bed boost to 48 Gy. PBI patients received 30 Gy in 5 fractions (n = 4) or 40.05 Gy in 15 fractions (n = 1). All patients who developed grade 2 (17.7%) and grade 3 (2%) dermatitis received bilateral WBI except for 1. Six patients had acute dermatitis in the sternal area, with overlap on GaF seen in 2 patients. Of 20 patients with late toxicity follow-up, 25% had late grade 1 to 2 dermatitis (20% received WBI). One patient recurred locally and distantly. Mean positional shifts were mostly subcentimeter or subdegree. Only 10% of patients had field overlap on GaF.
Conclusions:
To our knowledge, this is the first study examining patients treated for SBBC in the prone position. Prone bilateral RT is feasible with minimal shifts and overlap. However, higher rates of acute dermatitis occurred in bilateral WBI patients (vs PBI), and overlap was not seen on GaF in all patients who developed midline dermatitis.
