MRI-based image-guided adaptive brachytherapy for locally advanced cervical cancer in clinical routine: a single-institution experience

Abstract

Background: MRI-based image-guided adaptive brachytherapy (IGABT) is a new approach for individual dose escalation and control of organ at risk (OAR) doses and toxicities in the treatment of locally advanced cervical cancer.

Methods: Various radiotherapy-related parameters and the feasibility of the treatment based on acute toxicity were analyzed in a total of 50 cases in two cohorts who received a brachytherapy (BT) boost after definitive chemoradiotherapy with either an MRI-based IGABT technique (24 patients) or CT-only image guidance (26 patients). For target volume, OAR delineation, and dose prescription, the EMBRACE II protocol was followed.

Results: The features of the target volumes and dose coverage did not differ between the two groups regarding teletherapy. At BT, however, while the High-Risk Clinical Target Volumes (CTVHR) did not differ the D90 dose coverage was significantly higher in the MRI-based IGABT group than in the non-MRI-based group (7.37 ± 0.55 Gy vs. 6.87 ± 0.84 Gy, p = 0.015). The CTVHR D98 doses showed a strong trend in favor of the MRI-based technique (6.16 ± 0.59 Gy, vs. 5.72 ± 0.95 Gy, p = 0.051). Cumulative doses to the CTVHR by means of both D90 and D98 were significantly higher in the MRI-based treatment group than the other group (86.64 ± 4.76 Gy vs. 81.56 ± 8.29 Gy, p = 0.011 and 77.23 ± 4.39 Gy vs. 73.40 ± 7.80 Gy, p = 0.037, respectively). Regarding OAR exposure, doses to the bladder, rectum, and sigmoid did not differ between the two cohorts.

Conclusion: Our first clinical results support the implementation of IGABT as a key component of image-guided adaptive radiotherapy (IGART) aiming at tumor dose-escalation and OAR protection.

Keywords: MRI-based brachytherapy; adaptive radiotherapy; cervical cancer; image-guided brachytherapy; interstitial brachytherapy.