Feasibility of vaginal dose points reporting in cancer cervix patients treated by external beam radiotherapy and brachytherapy

Abstract

Background: Cervical cancer is the second most common malignancy among women in India. The standard of treatment for locally advanced lesions is Concurrent Chemoradiation with External Beam Radiotherapy followed by Intracavitary Brachytherapy (GEC-ESTRO). The dose received by the entire vagina cannot be accurately measured by a vaginal dose point assessment at the level of the ovoids alone.

Aims and Objectives: Our study aims to see the feasibility of measuring vaginal dose at various levels and define the dose points that can be practiced in 2D and 3D external radiation and brachytherapy (BT).

Materials and Methods: Radiotherapy plans of 29 patients with stages IIA to IVA cancer cervix treated with concurrent chemoradiation from January 2020 to December 2020 were retrospectively reviewed for the feasibility of measuring the vaginal dose points throughout the vagina. Every patient underwent cisplatin-based weekly chemotherapy along with BT and external beam radiotherapy. We have assessed the vaginal dose locations 2 cm above and below the point of the posteroinferior border of the pubic symphysis (PIBS). The superior surface of the ovoid to the PIBS point constitutes the vaginal reference length (VRL).

Results: The mean and median doses from external beam radiation therapy (EBRT) were 50Gy and 51 Gy at PIBS, 52 Gy and 53.5 Gy at +2 cm, and 18Gy and 28 Gy at -2 cm, respectively. The combined mean and median EQD2 doses from EBRT and BT at PIBS, PIBS+2, and at PIBS-2 were 56 and 57 Gy, 65 and 66 Gy, and 35 and 31 Gy, respectively. The mean VRL was 5.25 cm before EBRT and 4.75 cm before BT.

Conclusion: Our study found that it is feasible to measure the dose received by the vagina using the PIBS system and large dose variations throughout the vagina were observed.