Parotid gland as an organ at risk in whole-brain radiation therapy: A retrospective comparison of 3D-CRT and IMRT techniques from a tertiary cancer center

Background: Regardless of primary malignancy, whole-brain radiation therapy (WBRT) is the preferred treatment for brain metastases. However, WBRT exposes the parotid glands to significant radiation. Advances in systemic therapy and early detection have improved survival in these patients, making the reduction of radiation-induced toxicity increasingly important. Objectives: Our primary objective was to determine parotid gland doses during WBRT in Indian setting. The secondary objective was to compare doses between 3-dimensional conformal radiation therapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT). Materials and Methods: This retrospective study was conducted in the Department of Radiation Oncology at Kidwai Memorial Institute of Oncology between January 2023 and April 2023. We analyzed computed tomography (CT) scans of patients who received WBRT using 3D-CRT. Bilateral parotid glands were contoured, and doses were documented. A new IMRT plan was then generated for the same CT scans, delivering 30 Gy in 10 fractions while maintaining the existing planning target volume (PTV). Parotid doses were compared between 3D-CRT and IMRT using a paired t -test. Results: We included 54 patients. The mean dose to the right parotid gland was 17.01 ± 3.28 Gy with 3D-CRT versus 9.44 ± 1.32 Gy with IMRT, while the left parotid received 18.69 ± 2.86 Gy with 3D-CRT versus 9.44 ± 1.71 Gy with IMRT. IMRT significantly reduced parotid dose ( P < 0.05) compared to 3D-CRT. Conclusion: IMRT significantly lowers the mean parotid dose without sacrificing WBRT goals. While outcomes remain similar, IMRT can improve quality of life and should be considered when delivering WBRT for brain metastases.