Abstract Aim: To analyse and correct interfractional set up error in cervical carcinoma patients with intact cervix, treated with VMAT technique through daily online kilo voltage cone beam CT.
Materials and Methods: The present study was conducted in for 2 years to assess interfractional setup error by online CBCT in VMAT technique in patients of intact carcinoma cervix. A total of 30 patients, as per inclusion and exclusion criteria who opted for VMAT are included in our study. They were planned as per guidelines.
Results: 63.33% of patients included in our study were in the age group of 4160 years of age. 43.33% of patients were Stage IIB was the most common stage of presentation in our study. Squamous cell carcinoma was the most common type of histopathology in our study. Systematic error in XAxis was 0.19cm, in YAxis was 0.17cm, and in ZAxis was 0.15cm and the average systematic error in all three directions was 0.17cm. Random error in XAxis was 0.40cm, in YAxis was 0.44cm and in ZAxis was 0.36cm and average random error in all three directions was 0.40cm. P value was >0.05 in X and Z directions, setup error wasnot significant in these directions. On YAxis, P value was <0.05 and setup error was significant in Y direction. In XAxis (MedialLateral direction) CTVPTV margin was 0.75cm, in Yaxis(SuperiorInferior direction) CTVPTV margin was 0.73cm and in ZAxis (AnteriorPosterior direction) CTVPTV margin was 0.63cm. Bladder average D35 dose was 49.41Gy with standard deviation of 2.37; average D50 dose was 47.33Gy with standard deviation of 2.96. In VMAT due to minimum CTVPTV margin, dose to Organ at Risk (OAR) was less.
Conclusion: use of daily online cone beam CT in cervical carcinoma patients treated with VMAT, we can achieve a lesser CTVPTV margin, which can thus minimise the dose to organs at risk.
Keywords: Cone Beam Computed Tomography, (CBCT); Volumetric Modulated ARC Therapy
(VMAT); Cervical Carcinoma.