Transabdominal Ultrasonography Based High Dose Rate Conformal Intracavitary Brachytherapy In Cervical Carcinoma

Magnetic Resonance Imaging (MRI) based planning has been recently recommended to be the gold standard in intracavitary brachytherapy (ICBT) planning. In developing countries, where the disease burden of cervical carcinoma is high, MR based planning is neither cost effective nor universally available. Trans-abdominal ultrasonography (TAUSG) has been used in verifying the intra cavitary application as well as conformally planning intracavitary treatment. This study aimed at determining the feasibility of TAUSG based conformal brachytherapy in cervical cancer patients as well as reporting their clinical outcomes Patients of Stage IB-IVA cervical cancer who were referred for curative intent radiotherapy from December 2014- 2015 were analyzed. All patients received external beam radiotherapy (EBRT) with concurrent chemotherapy and sequential high-dose rate brachytherapy. EBRT was planned using conventional technique and fractionation to a dose of 46 Gy-50 Gy. ICBT was planned and verified using serial USG imaging followed by orthogonal imaging for applicator reconstruction. ICBT doses used were 7 Gy in 3- 4 fractions weekly so as to achieve a dose of 85-90Gy10EQD2 to the HRCTV. The HRCTV assessed using USG included residual disease after EBRT, the cervix and the uterus. USG was used to position the tandem centrally in the uterus to allow uniform coverage of the uterus .Mid sagital USG image with complete depiction of the central tandem and trans-axial image at the level of external cervical os was acquired. Tandem to uterine surface measurements at 2cm intervals were taken using the mid sagital image. The trans axial image was used to measure the parametrial extent of the disease at the external os with respect to the tandem. These measurements were extrapolated on to X ray images. Dwell weights and positions were manipulated to cover the uterine and cervical dimensions depicted on the USG images. Patients were treated using this plan. CT based planning was done retrospectively to identify the doses to the organs at risk. Sixty patients were available for analyses. One patient was lost to follwup.With a median follow up of 22 months (8-28months), 2 year local control, failure free survival and overall survival were 91.5%, 78% and 83% respectively. Mean combined EBRT and ICBT point A doses, equivalent to doses in 2 Gy fractions were 82.7 Gy10 (66.5-120Gy). There was a statistically significant difference between standard point A plan and USG based plans—having consistent (p < 0.001) respectively for Point A, bladder, rectum and sigmoid 2cc doses. 2 patients developed Grade II CTCAE rectal toxicity. No bladder/GI toxicities were observed. TAUSG offers an accurate, quick, accessible, and cost-effective method of conformal brachytherapy planning which is comparable to X ray as well as MRI based planning.