Evaluation of the impact of EMBRACE II protocol in Spanish centers, with a large cohort of patients using a ranking index

PURPOSE: The aim of this paper was to assess development of high-dose-rate (HDR) cervix brachytherapy (BT) implants in three Spanish institutions before and after introduction of EMBRACE II protocol. MATERIAL AND METHODS: 392 patients from three different institutions, treated between 2009 and 2019 were analyzed. D(90) of high-risk clinical target volume (HR-CTV) and D(2cc) of organs at risk (OARs) of all patients were collected. Statistical distribution was analyzed for two different periods of time: before and after EMBRACE II publication. Index I was applied based on collected dosimetric quantities (D(90) and D(2cc)) to enhance equilibrium between HR-CTV coverage and doses to OARs. Variation in dosimetry and index depending on CTV and technique used (IC vs. IC/IT) were also evaluated. RESULTS: Adaptation of institutions to EMBRACE II protocol resulted in a statistically significant increase of D(90) HR-CTV (Institution 1; p < 0.00001) or decrease of D(2cc) OARs (Institution 2; p < 0.04). Increase in the use of interstitial component showed higher coverage of HR-CTV for Institution 3 (p = 0.03), and lower doses to OARs for the same coverage of HR-CTV at Institution 2 (p-OARs < 0.03). Even though index I was only significantly different between periods for Institution 1 (p < 0.0000001), it was able to show a reduction of dose variability related to higher expertise and higher interstitial component. CONCLUSIONS: Depending on local protocol before EMBRACE II, the adaptation through increasing interstitial component and physician and physicist training, resulted in a significant increase of HR-CTV doses or reduction of OARs doses. Index I was able to describe an evolution of equilibrium between CTV coverage and OARs’ sparing.