2310 - Should We Evaluate Liver as an Organ at Risk for Radiotherapy Right Breast Cancer Treatment?

S. Huerta Vega¹, M. D. De La Mata², L. M. C. T. Tenorio³, and A. S. Ramirez Estudillo⁴; ¹Centro Medico ABC, Mexico City, EM, Mexico, ²Centro Medico ABC, MEXICO CITY, Mexico, ³ABC Medical Center, MEXICO CITY, Mexico, ⁴Centro Medico ABC, Mexico City, DF, Mexico

Purpose/Objective(s): During breast cancer radiotherapy (RT) planning we are familiarized with the evaluation of different organs at risk (OAR) and the impact in short and long term. But liver as OAR hasn’t been evaluated and neither the potential consequences for it. The purpose of the present work is to analyze the liver dose for right breast cancer patients. Materials/

Methods: This study was conducted at our institution between January 2020 and August 2023. A total of 209 patients (p.) diagnosed with right breast cancer suitable to radiation therapy to the right breast and/or right supraclavicular and axillary lymph nodes were treated with three-dimensional conformal radiation therapy (3D-CRT) or intensity modulated radiation therapy (IMRT/VMAT), with the following schedules: 50Gy/25Fx, 42.56Gy/16Fx, 45Gy/15Fx and 26.5Gy/5Fx. Database including information about each p. treatment and anatomy was generated and analyzed by Spearman´s rank correlation coefficient.
Results: Mean age among 209 p. was 57 years old (range 25-91), 144 p. received 3D-CRT and 65p. IMRT. P. were stratified by age without significant difference for liver size, of 1434 cc (r= -0.001 ?=NS). Also, there was no significant relationship between the right lung size and the liver size (r=-0.2 ?=NS). However, a very strong relationship was found between the right lung size and the mean dose to the liver (r=0.84 ?=0.0003), where if the volume of the lung is increased, the mean dose to the liver decreases. If we compare techniques, the mean dose to the liver was significantly lower, 3.6Gy with 3D-CRT vs. 7.1Gy with IMRT. While there was not any relationship found between the mean dose to the liver and the size of it (r=0.08 ?=NS).
Conclusion: For right breast cancer radiotherapy treatment, liver should be taken into account as an OAR. Results show liver mean dose is greatly diminished when the size of the right lung is increased, which suggests a big benefit for using deep inspiration breath hold in right breast cancer patients. However, results show the age of the patient and the size of the right lung, don’t seem to have any impact on the liver size. As for the planning technique, the mean dose for the liver is lower for the 3D-CRT cases, so a suggestion for pushing constraints harder on the optimization for IMRT cases is suggested. Following studies should be taken into consideration to keep on studying consequences short and long term on liver as OAR in right breast radiotherapy cancer treatments.