Search

Introduction: 3D-Conformal Radiation Therapy(3D-CRT) is the standard of care for Carcinoma of esophagus cases. This treatment modality involves initial AP-PA field arrangement followed by 3-field technique (AP-RPO-LPO) for the boost volume. In this technique, PTV coverage is generally sub-optimal owing to the requirement of maintaining the spinal cord dose to its tolerance level. Intensity Modulated Radiation Therapy (IMRT) improves the coverage and reduces the Organ at Risk doses. With the continued advancement in Radiotherapy, Volume Modulated Arc Therapy (VMAT) came into existence. While both IMRT and VMAT tend to deliver large volume of low dose regions, VMAT has the advantage of delivering the plan with lesser MU as compared to IMRT. In order to have balance between various aspects of Dose Volume considerations, we intend to introduce Hybrid technique (combination of 3D-CRT and VMAT) and compare the results with other treatment techniques, such as 3D-CRT and VMAT. Objective: The purpose of this study is to carry out planning study on the potential benefit of Hybrid technique (3D CRT combined with VMAT concurrently) against full course of 3D-CRT & VMAT technique in the treatment of mid thoracic esophageal cancer patient. Materials and Methods In this planning study, 10 patients was planned for these three techniques. Mean target volume was 220cc (range 109-301 cc). Patients were simulated with appropriate immobilization devices. CT image of 2.5 mm acquired. All treatment plans were generated in TPS (Eclipse; v11.1; Varian Medical Systems, USA), to a prescribed dose of 5040 cGy in 28 fractions with 5 fractions/week. The calculation algorithm used for calculation for all the technique is Anisotropic Analytic Algorithm(AAA). In 3D-CRT plan, the first phase contained AP-PA (3600cGy in 20 fr) followed by boost (1440cGy in 8 fr) through 3-field technique. In VMAT plan, full dose was planned using single arc. In HYBRID plan, the dose is concurrently split as AP-PA (55% of the dose) and VMAT (45% of the dose). Quantitative and qualitative analysis were carried out using various dosimetric parameters for both target volume and OARs. Result & Discussion The Conformity Indices (CI) & Homogeneity Indices (HI) for Hybrid plan are comparable to VMAT plan and better than 3D-CRT plan. Total lung dose (V5%, V10% and V20%) in Hybrid plan is less as compared to both VMAT and 3D-CRT plans. The max. dose of spinal cord in Hybrid plan was higher than VMAT plan and smaller than 3D-CRT plan. For region of heart, the dose evaluation (V40%) for hybrid plan, are comparable to VMAT plan and better than 3D CRT plan. VMAT alone plan results in higher integral dose since this technique has larger beam entry and exit points for the full therapeutic dose as compared to 3D-CRT and Hybrid techniques. Conclusion Given the clear dosimetric advantages, Hybrid technique can improve the target coverage while reducing the volume of the lung and healthy tissue during radiotherapy of mid thoracic esophageal cancer. Hence Hybrid Technique could be a treatment of choice in ultra modern radiotherapy. Conflict of Interest: NIL. [ABSTRACT FROM AUTHOR]