Dr. Richard Pötter
At 5 years, the rate of local control was 92%, and overall survival was 74%. However, nodal and systemic control rates were inferior for node-positive and high-risk patients, and nearly 15% of patients experienced grade 3-5 treatment-related morbidity.
These results were reported at the European Society for Radiology and Oncology 2020 Online Congress.
Historically, brachytherapy dose has been fairly rigidly prescribed, based on dose points defined in two dimensions. By performing imaging before each brachytherapy implant, treatment parameters can be adapted to a patient’s anatomy, taking into account the positions of organs at risk and any tumor regression from prior treatment.
Richard Pötter, MD, emeritus professor at Medical University of Vienna, and colleagues tested MRI-guided adaptive brachytherapy in a multicenter cohort study.
The study’s disease outcome analysis included 1,341 women with cervical cancer of International Federation of Gynecology and Obstetrics stage IB–IVB (52% node positive) being treated with curative intent.
The women underwent definitive external beam radiotherapy (45-50 Gy, using either three-dimensional–conformal radiotherapy or intensity-modulated radiotherapy) with concurrent cisplatin chemotherapy, followed by MRI-guided adaptive brachytherapy based on MRI with the applicator in situ.
“There was no fixed dose prescription for brachytherapy, and there were no constraints for organs at risk,” Dr. Pötter explained. “But there was systematic joint reporting and contouring for the target and organs at risk, and also for doses and volumes.”
Nearly all patients were treated with adaptive MRI-based target and dose-volume and point parameters (99.1%), as well as with individualized multiparametric dose optimization (98.2%). The application technique was adapted, with intracavitary application alone used in 57% of patients, and both intracavitary and interstitial application in 43%.
Efficacy and toxicity
At a median follow-up of 51 months, 7.3% of patients had experienced a local failure, with 3.8% having an isolated local failure and 3.5% having synchronous nodal or systemic failure, Dr. Pötter reported.
The local failure rate was similar going from disease stage IB2 to IVA (8%-9%), even though the target volume more than doubled.
“This favorable result was due to an adaptation of dose, which was quite similar for the different stages and volumes. This is a major message of EMBRACE I,” Dr. Pötter commented.
The Kaplan-Meier–estimated 5-year rate of local control was 92% for the whole cohort. It was 98% in patients with stage IB1 disease and 91%-92% in patients with stage IB2–IVA disease.
The 5-year rate of overall survival was 74% for the entire cohort. It fell with stage, from 83% in patients with stage IB1 disease to 52% in patients with stage IVA disease.
For the entire population, the 5-year pelvic control rate was 87%, the 5-year cancer-specific survival was 79%, and the 5-year disease-free survival was 68%.
Overall, 14.6% of patients experienced grade 3-5 treatment-related morbidity at 5 years: 2.7% developed fistulas, 6.1% had vaginal toxicity, 6.5% had genitourinary toxicity, and 7.6% had gastrointestinal toxicity.