Dosimetric implications of omitting vaginal loading in hybrid brachytherapy for carcinoma cervix without vaginal infiltration.

Purpose: To compare the dosimetric parameters in hybrid brachytherapy with and without using the vaginal component for carcinoma cervix patients that do not have disease extending to the vagina.

Materials and methods: Patients without vaginal involvement who received chemoradiation and hybrid brachytherapy were prospectively included for analysis. Two plans were created for each patient. The first plan (Plan 1) was created by loading the interstitial component to 10-20% of the tandem loading and reducing the vaginal loading to 30%. The second plan (Plan 2) was created by loading the tandem and interstitial component only and eliminating the vaginal loading (ovoid's). The dose delivered with brachytherapy was 21 Gy in 3 fractions. The dosimetric parameters compared between the two plans were D90 HRCTV, D98 IRCTV, TRAK, D2cc to bladder, rectum, sigmoid, and dose to the ICRU 89 RV point.

Results: Thirty patients were included for analysis. The mean HRCTV volume was 30 cc. The mean D90 HRCTV was 88.1 Gy EQD2 for Plan 1 vs 87.8 Gy EQD2 for Plan 2, respectively (P = 0.113). On statistical analysis, there was a significant difference between Rectum D2cc (72.4 Gy vs 67.3 Gy) and ICRU 89 RV point dose (71.3 Gy vs 61.2 Gy) between the two plans (P = 0.0001). The mean D2cc to bladder and sigmoid was similar between the two plans.

Conclusion: In carcinoma cervix patients without vaginal involvement, omission of vaginal loading in tandem and ovoid hybrid brachytherapy reduces rectum and RV point doses while maintaining target coverage.