Dosimetric data of 35 patients with histopathologically proven locally advanced carcinoma cervix who had undergone HDR-ICBT from May 2018 to August 2018 at our centre were retrospectively analysed. All patients who had received EBRT of 46 Gy in 23 fractions using the 3-dimensional conformal radiotherapy (3DCRT) technique over four and a half weeks with concurrent chemotherapy (cisplatin 40 mg/m2) followed by HDR-ICBT of 9 Gy per session for 2 sessions (each application done at weekly intervals) as per the departmental protocol were included for analysis. The choice of the sedation technique was based on the local anatomy and the anticipated ease of application.
Procedure under GA
After pre-anaesthesia clearance and routine preparation, patients who were taken up for ICBT in major OT under GA were asked to lie down in lithotomy position. After adequate cleaning and draping, Foley’s catheter was inserted, and the balloon was inflated with 7 cc of normal saline. Size and extent of disease and local anatomy were assessed by EUA which included per-speculum, per-vaginal, and per-rectal examinations. After assessment of uterine length and angle, and adequate dilation of the cervical os, the most suitable central tandem was inserted into the uterus. The ovoids were placed in the right and left vaginal fornices equidistant from the central tandem. The vagina was packed with roller gauze to displace the bladder further anteriorly and the rectum posteriorly to minimize the dose to these organs and to immobilize the applicators.
Procedural sedation
The same pre-procedural protocol was followed for patients taken up for ICBT in day care minor OT setup under PS. Intravenous pentazocine (30 mg) and intravenous promethazine (25 mg) intravenously were given for PS.
Post application procedure
Post application, patients were taken up for planning computerized tomography (CT) scan in the dedicated departmental CT scan machine (GE Healthcare Technologies, Wankesha, WI, USA). Subsequently, the patients’ bladder was filled with 2 ml of iohexol diluted with 18 ml of normal saline, and planning CT images were acquired with the patient in supine position and applicator in situ using multi-slice CT scanner with slice thickness of 2.5 mm. The images were then transferred to Eclipse treatment planning system (v.8.6, Varian Associates, Palo, Alto, CA, USA); organs at risk (OARs), i.e. bladder, rectum and sigmoid, were contoured according to the Groupe Européan de Curiethérapie - European Society for Radiotherapy & Oncology (GEC-ESTRO) guidelines. A dose of 9 Gy HDR was prescribed to point A as per departmental protocol (dwell positions for both ovoids are 3,4,5,6 while central tandem positions are 1,3,5,7,9,12,15,18), and the plan was evaluated. The optimisation was done when required with the aim of delivering a minimum dose of 100% to the HRCTV (high-risk clinical target volume).
Dosimetry
Generated dose volume histograms (DVH) were analysed, and EQD2 (dose equivalent of 2 Gy) doses received by 0.1 cc and 2 cc of organs at risk (OARs), i.e. bladder, rectum and sigmoid colon, were evaluated (Fig. 1). EQD2 dosage was calculated by combining both EBRT dose and dosage received during HDR-ICBT.
Statistical analysis
SPSS 22.0 (SPSS Inc., Chicago, IL) software was used for data analysis. Standard methods of descriptive statistics (arithmetic mean with the standard deviation and the numerical range from minimum to maximum value) were used for 0.1 cc and 2 cc dosage, respectively (Tables 2 and 3). Statistical significance of differences amongst the examined groups (GA and PS) was tested using two sample independent t-test at 5% level of significance. p value < 0.05 was considered as significant.