Biomed Phys Eng Express. 2021 Apr 16. doi: 10.1088/2057-1976/abf90a. Online ahead of print.
ABSTRACT
INTRODUCTION: The present study aims to investigate the dosimetric and radiobiological impact of patient setup errors (PSE) on the target and organs at risk (OAR) of the cervix carcinoma stage IIB patients treated with volumetric-modulated arc therapy (VMAT) delivery technique using plan uncertainty parameters module of Varian Eclipse treatment planning system and in-house developed DVH Analyzer program.
MATERIALS AND METHODS: A total of 976 VMAT plans were generated to simulate the PSE in the base plan that varies from -10 mm to 10 mm in a step size of 1 mm in x- (lateral), y- (craniocaudal), and z- (anteroposterior) directions. The different OAR and tumor volumes were delineated in each case. The various plan quality metric parameters, NTCP and TCP were calculated from the DVH bands generated from the cohort of treatment plans associated with each patient case, using an in-house developed “DVH Analyzer” program. The extracted parameters were statistically analyzed and compared with the base plan’s dosimetric parameters having no PSE.
RESULTS: The maximum variation of (i) 2.4%, 21.5%, 0.8%, 2.5% in D2cc of bladder, rectum, small bowel and sigmoid colon respectively; (ii) 19.3% and 18.9% in Dmax of the left and right femoral heads (iii) 16.9% in D95% of PTV (iv) 12.1% in NTCP of sigmoid colon were observed with change of PSE in all directions. TCP of PTV was found to be drastically changed beyond 0.4 cm in x+, y+, z+ directions and 0.7 cm in x-, y- and z- directions respectively.
CONCLUSION: This study presents the effect of PSE on TCP of PTV and NTCP of the OAR for the cervix carcinoma cases treated with VMAT technique and also recommends daily image guidance to mitigate the effects of PSE. Advances in knowledge: Dosimetric analysis of PSE helps in evaluation of robustness of the radiotherapy treatment plans.
PMID:33862601 | DOI:10.1088/2057-1976/abf90a
