Clinical and dosimetric outcomes of carcinoma cervix patients treated with MRI only at first fraction, followed by CT-based image-guided brachytherapy for subsequent fractions.

PURPOSE: Magnetic resonance (MRI)-based image-guided brachytherapy (IGBT) is the gold standard technique for carcinoma cervix. We aimed to evaluate doses to target and organs at risk (OARs), and report clinical outcomes of locally advanced carcinoma cervix (LACC) patients treated with a hybrid approach of using MRI- and computed tomography (CT)-based IGBT.

MATERIAL AND

METHODS

Twenty-two LACC patients, after receiving external beam radiotherapy of 50 Gy in 25 fractions with concurrent cisplatin 40 mg/m2 weekly, underwent 7 Gy in 3 fractions of IGBT planning with MRI alone at first fraction, and CT at second (CT-1) and third (CT-2) fractions. Dose received by at least 90% of volume (D90) for high-risk clinical target volume (HR-CTV), and dose to 0.1 cm3, 1 cm3, and 2 cm3 for OARs was evaluated during each fraction and compared.

RESULTS

The median age was 50 years. Fourteen (63.6%) patients were FIGO (2010) stage II. HR-CTV volumes (mean ±SD) of MRI, CT-1, and CT-2 were 24.23 cc ±9.26 cc, 27.82 cc ±15.37 cc, and 24.82 cc ±11.14 cc, respectively (p = N.S.). HR-CTV D90 (mean ±SD) was significantly higher in MRI-based plans compared with CT-based plans at second fraction (MRI: 108.86 ±24.21% vs. CT-1: 98 ±23.18%, p = 0.03), but not different than CT-based plans at third fraction (MRI: 108.86 ±24.21% vs. CT-2: 106.86 ±17.36%, p = 0.68). No statistically significant differences in doses to the rectum, bladder, and sigmoid colon were observed between MRI- and CT-based plans (all p > 0.05). 5-year loco-regional control, disease-free survival, and overall survival rates were 85.2%, 80.7%, and 79.0%, respectively.

CONCLUSIONS

Hybrid approach in IGBT using MRI at first fraction and CT for subsequent fractions yields comparable dosimetric parameters and decent long-term clinical outcomes. This approach could be considered resource-sparing brachytherapy technique.