Dosimetric feasibility and clinical outcome of image guided interstitial brachytherapy using two different fractionation schedule in carcinoma cervix

Abstract

Background: In advanced cervical cancer, external beam radiotherapy along with concurrent chemotherapy followed by brachytherapy is the treatment of choice. There are various dose fractionation regimes for template-based high dose rate (HDR) interstitial brachytherapy (ISBT) following external beam radiotherapy (EBRT) for cancer cervix with consideration of the normal-tissue EQD2 3Gy dose limits and recommended D90 goal between 85 and 95 Gy EQD2 10Gy for the high risk clinical target volume (HR-CTV). Materials and methods: 60 patients were accrued between 2014–2017 and treated with ISBT using Syed–Neblett Template by iridium 192 with Gamma Med plus HDR after loader unit. They were allotted in 2 arms (n = 30) and received 9 Gy ×2# and 7 Gy ×3 #, respectively. All patients received 50 Gy/25# whole pelvis EBRT by Theratron 780C. Coverage index (CI), dose homogeneity index (DHI), overdose index (OI), dose non-uniformity ratio (DNR), D90 Target and 2 cc EQD2 of OARs were calculated and correlated with toxicity, locoregional control and survival. Unpaired t-test and χ 2 test were used. Progression-free survival (PFS) and overall survival (OS) were calculated and a log-rank test was used for comparison. Results: Mean equivalent dose in 2 Gy fractions (EQD2) for the bladder (77.33 vs. 80.24 Gy) and rectum (69.12 vs. 69.87) along with D90 (9.12 Gy vs. 7.20 Gy) were comparable. With a median follow up period of 38 months, 3-year local control rate was 56.6% vs. 46.60% (p = 0.72) and 3-year OS was also similar: 83% vs. 80% (p = 0.8). Conclusions: In a developing country like India, 9 Gy ×2 # is a reasonably good alternative for treating locally advanced carcinoma cervix, keeping the patient compliance and convenience in mind.