Body mass index versus bladder and rectal doses using 2D planning for patients with carcinoma of the cervix undergoing HDR brachytherapy
Purpose: To assess bladder and rectum doses in relation to body mass index of patients undergoing high dose rate brachytherapy for the treatment of carcinoma of the cervix.
Methods: The cohort consists of fifty subjects with carcinoma of the uterine cervix presented with grade II and III. Patient’s height and weight was measured before the insertion of applicator in situ. Body mass index (BMI) of the patient was calculated in accordance to World Health Organization definition (weight in Kg/ height in m2). Adequacy of position and orientation of the applicator was confirmed with the help of orthogonal X-ray images and the same were transferred to the treatment planning system (TPS) to generate treatment plan. Prescription doses were optimized to Point A and to reference lines placed at 0.5 cm apart from the surface of ovoids. The following dose reference points were identified on orthogonal x-ray images for analysis using the rectal marker and Foleys bulb inflated with radio opaque dye Rectal points at the level of femoral heads (RL) and pubis symphysis (RLP), Anorectum Junction (AR Jn) point and Rectosigmoid (RS) point and Bladder point (BL). Pearson regression analysis was used to analyze data from TPS.
Results: The mean BMI was 22.7 kg/m2 and average age was 49.9 years. Analysis showed that RL point dose and BMI were inversely correlated with a coefficient -0.45 (p = 0.001). The trend continued along the rectal tube in cranio-caudal direction, as RLP and AR Jn points showed inversion co-efficiency with increase in BMI,-0.48 (p < 0.01) and -0.51 (p < 0.01) respectively. Bladder point showed weak positive correlation to BMI, 0.12 (p = 0.38).
Conclusion: Significant rectal dose reduction is observed with increase in BMI. Bladder dose did not show statistically significant correlation with BMI. Based on the findings, BMI constitutes a confounding factor in the treatment of carcinoma of cervix.
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