DOSIMETRIC COMPARISON BETWEEN 3-DIMENSIONAL CONFORMAL RADIATION THERAPY AND INTENSITY MODULATED RADIOTHERAPY IN CARCINOMA ESOPHAGUS

Dr. Khaleel M. Ali Khan, Dr. Divyashree N.*, Dr. Geeta S. Narayanan and Dr. Bhanumathy G.

ABSTRACT

Background: The management of loco regional or locally advanced esophageal or gastro esophageal junction cancer has shifted from surgery or radiation single modality approaches to tri modality approach with the addition of chemotherapy.[1] This Multimodality approach can cause various treatment-related complications.[2-4] Despite improved local, regional, and distant control and increased survival, roughly 50% of patients treated with chemoradiation will have persistent local disease or recurrence.[5] Hence better local treatment through radiotherapy may be needed to improve the overall treatment outcome. Aims and objectives  To compare Planning Target Volume (PTV) coverage and doses to normal structures between 3DCRT and IMRT plans for esophageal carcinoma patients.  To evaluate if Dose Escalation is possible by using IMRT. Methods: A total of 30 patients presenting to department of Radiation Oncology with non-metastatic Carcinoma Esophagus of any subsite with less than or equal to 10 cms were enrolled to the study. Patients were treated with 3DCRT to a dose of 5040cGy in 28 fractions. Three IMRT plans were generated on the same CT images. First plan of dose 5040cGy was compared with 3DCRT plan for PTV coverage and doses to organs at risk using DVH. Two more plans were generated to check feasibility of dose escalation to 6040cGy and 7040cGy with respect to organs at risk. Results: In our study IMRT had a better PTV coverage and Conformality Index (CI) when compared with 3DCRT. Doses to normal structures like Spinal cord and Heart were significantly spared with IMRT (p < 0.001) while Lung doses were higher in IMRT. Dose escalation to 6040cGy and 7040cGy was feasible with IMRT as the organs at risk did not exceed tolerable limits. Interpretation & Conclusion: IMRT offers the opportunity to sculpture radiation dose by improving target homogeneity while sparing normal organs by taking advantage of a sharp dose gradient except lung. Hence Hybrid technique of combining 3DCRT and IMRT is recommended to take advantage of both the techniques.

Keywords: 3DCRT, IMRT, Carcinoma Esophagus.