Comparison of the Dosimetric Benefits of Two Different Three-dimensional Conformal Radiotherapy Treatment Approaches for Postmastectomy Radiotherapy

Abstract

Introduction: Breast cancer is the most common cancer among women in urban areas in India, which is treated with external beam radiotherapy as a part of a multimodality treatment approach. Delivering external beam radiation therapy to the chest wall and nodal basins is challenging because of the anatomical morphology of the chest wall as well as the near proximity of critical structures. In the current study, we aim to compare the dose volumetric histograms of different organs at risk (OAR) and target volume in carcinoma breast patients whose supraclavicular field is included for radiation therapy using two different three-dimensional conformal radiotherapy (3D-CRT) techniques. Materials and Methods: All patients received a prescribed dose of 50 Gy to the postmastectomy chest wall and nodal basins in 25 fractions. Patients underwent standard computed tomography simulation at 3.5 mm slice spacing, in the supine position. Then, patient clinical target volume (CTV) was created using GEC-ESTRO guidelines, and planning target volume was created with an institution-specific margin around CTV. OAR parameters assessed using dose-volume histograms obtained using treatment planning techniques are compared in terms of the ipsilateral lung (V 5, V 10, V 20, V 30, and mean dose), contralateral lung (V 5, V 10, V 20, V 30, and mean dose), heart (V 5, V 25, max, mean, and minimum dose), esophagus (V 35, V 50, and mean dose), contralateral breast (V 5, D 5, minimum, maximum, and mean dose), and spinal cord doses (maximum dose). Results: Technique 1 and Technique 2 3D-CRT treatment plans were clinically comparable for postmastectomy radiotherapy (PMRT). Technique 1 plans showed significantly better dose coverage and minimum dose to the spinal cord. On the other hand, Technique 2 plans showed significantly better sparing of normal tissues. Conclusion: The choice of radiotherapy technique in PMRT is a very important factor in the protection of neighboring normal structures and the identification of associated risks. Technique 1 can provide significantly superior dose coverage and minimum dose to the spinal cord, whereas Technique 2 offers better sparing of normal tissues.

Keywords

• postmastectomy radiotherapy
• three-dimensional conformal radiotherapy
• treatment technique