Dosimetric comparison of tandem and ovoids with tandem and ring for intracavitary brachytherapy for carcinoma cervix.

Carcinoma Cervix is the most common gynecological malignancy in India. Treatment of Cervical cancer includes a combination of external beam radiotherapy (EBRT) with intracavitary brachytherapy(ICBT) with or without concurrent chemotherapy. ICBT helps to boost radiation dose to primary disease. Most commonly used applicators for ICBT are Tandem & Ovoid (TO) and Tandem & Ring (TR) applicators. With this study we want to do a dosimetric comparison between TR and TO applicators. Materials & Methods : Dosimetric details of 60 ICBT applications done in 20 patients during the period from 01/01/2018 to 31/12/2018 were retrospectively analysed. Among that 30 were icbt with TO applicator and rest 30 with TR applicator.All patients received EBRT dose of 50.4 Gy in 28 fractions. All patients had ICBT, three sessions with 7 Gy prescribed to point A.Dosimetric data including dose to right and left point A and dose to OARs were recorded from Oncentra Planning System. Results: Mean dose to Right and left Point A with TO applicator was 6.83 Gy and 6.97Gy and with TR applicator was 6.90 Gy and 6.93 Gy respectively without statistically significant difference. Mean Rectal doses D2cc,D1cc and D0.1cc with TO applicator was 3.90Gy,4.37Gy,5.47Gy and with TR applicator was 3.30Gy,3.73Gy and 4.83Gy respectively without statistical significance. Mean Bladder doses D2cc,D1cc and D0.1cc with TO applicator was 5.37Gy,5.97Gy,7.47Gy and with TR applicator was 5.53Gy,6.07Gy and 7.73Gy respectively without statistical significance.Mean Sigmoid doses D2cc,D1cc and D0.1cc with TO applicator was 4.47Gy,5.07Gy,6.37Gy and with TR applicator was 4.87Gy,5.47Gy and 6.97Gy respectively without statistical significance .Mean Small bowel doses D2cc,D1cc and D0.1cc with TO applicator was 3.27Gy,3.70Gy,4.67Gy and with TR applicator was 3.10Gy,3.60Gy and 4.30Gy respectively without statistical significance. Volumes treated with different isodose lines like V95, V85, V50, V20 with TO applicator was 89.37cc, 105.43cc, 230.60cc, 856.45cc and with TR applicator was 83.03cc,97.73cc,211.10cc,826.56cc respectively without statitistical significance. Conclusion: TO and TR applicators delivered the same prescription dose to points A, with no statistically significant difference between both applicators in terms of OAR doses. Compared to TO, TR applicators treated smaller volumes but was not statistically siginificant. Since point A , OAR doses and treated volumes were not significantly different for TR and TO applicators and these findings suggest a dosimetric equivalence of both applicators. Based on the result of our study we would suggest that both applicators can be used interchangeably. However further studies with larger sample size is needed to validate our study finding.