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

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.