Inter-Fraction Variations Of Dose To Point A, Bladder And Rectal Points In Locally Advanced Carcinoma Cervix Patients Treated With Hdr Brachytherapy Fletcher Suite Applicator.

Purpose - Quantification of inter-fraction dose variations to point A, bladder and rectal points using Fletcher suite applicator. Background - It is a well established fact that planning prior to each ICBT fraction is an accurate method of dose delivery keeping in mind the change in applicator position, tumour volume shrinkage and change in anatomy. But in a busy institute with a huge patient load, how feasible is application of data from the plan of first fraction to subsequent fractions. Methods - A total of 46 patients of locally advanced carcinoma cervix from November 2016 to June 2017 received External Beam Radiotherapy (Bhabatron II Co60) followed by 3# of HDR-Intra-cavitary Brachytherapy (Nucletron - Ir192) with Fletcher Suite applicator, final EQD2 of 80-90Gy . For each of 3 ICBT applications same applicator and similar vaginal gauze packing was done, a pelvic CT scan was performed and dose at point A, bladder and rectal points were defined according to ICRU 38, by same physicist. Planning was done on Oncentra Brachy Treatment Planning. Variation of dose at Point A, bladder and rectal points for 1st fraction ICBT was compared with 2nd and 3rd fractions, using paired-t test. Data was analysed using SPSS Version 24. Results- 42 patients completed 3 fraction of HDR ICBT, 4 patients after completing 2nd fraction, dropped out of 3rd fraction. Difference between 1st vs 2nd fraction mean doses of: • Point A 7.13 cGY (n=46, p=0.632) • Bladder point 28.06 cGY (n=46, p=0.188) • Rectal Point 21.06 cGY (n=46, p=0.176) Difference between 1st vs 3rd fraction mean doses of: • Point A 6.22 cGy (n=42, p=0.625) • Bladder point 0.81 cGy (n42, p=0.976) • Rectal Point 21.18 cGy (n42, p=0.211) Conclusions - First fraction TPS planning and its use for subsequent fractions is justified as the inter-fraction differences of dose to Point A, Bladder and rectal points are statistically not significant, ensuring correct instrument placement and similar vaginal gauze packing. We also found out that the major variation was in the Bladder point dose, with minimum difference of 0.5cGy(1st vs 2nd ) maximum difference of 314.80(1st vs 3rd). Variations in Rectal dose was much lesser, minimum difference of 6.82cGY(1st vs 2nd ) and maximum difference of 199.50 cGY (1st vs 3rd) We conclude that a single plan created at the time of first fraction can be used for a single patient for three fractions, without significant variation of dose to cervix, bladder and rectum. Thus saving valuable brachytherapy OT time which can be utilised to treat other patients, specially in a country like India where Brachytherapy machines are scarce and patient load is mammoth. [ABSTRACT FROM AUTHOR]