Significance of ovoid separation with various applications of high-dose-rate-intracavitary radiotherapy in carcinoma of uterine cervix: a study from rural centre of Maharashtra, India.

Aims: To analyze the differences in dose distribution, with ovoid separation in various applications, by different radiotherapists in the same patient of carcinoma of the uterine cervix treated by multiple fractions of high-dose-rate (HDR) intracavitary Radio therapy (ICRT).

Settings: Pravara Rural Hospital and Rural Medical College.

Design: Retrospective study.

Materials And Methods: Retrospective analysis of six cases of carcinoma uterine cervix, randomly chosen in the period from January 2004 and December 2007. Three selected radiotherapists performed the applicator placement for ICRT on the aforementioned patients in a consistent pattern-three consecutive ICRT treatments separated by weekly intervals. Ovoid separation was categorized into three groups: < 25 mm, 26-35 mm and > 36 mm. Prescribed point 'A' isodose lines with maximum separation laterally in right and left parametrium and antero-posteriorly in lateral plane was calculated for all 36 isodose charts for the 18 ICRT applications.

Results: In this study, there proves to be a significant difference in the ovoid separation between the applications of the different radiotherapists in the same patient with multiple fractions of HDR-ICRT. The applications done by 'A' radiotherapist resulted in an ovoid separation of < 25 mm more often, 'B' radiotherapist of > 36 mm while, 'C' radiotherapist fell in between the two.

Discussion And Conclusion: With more ovoid separation, lateral dose to parametrium was improved; however, antero-posterior dose was not significantly affected. In order to determine the best dose distribution, as evident in the dose charts of 'C' radiotherapist, it is recommended to choose the optimum ovoid separation in accordance to the patient's anatomy.