Implementation of state-of-the-art (chemo)radiation for advanced cervix cancer in the Netherlands: A quality improvement program

Adaptive brachytherapy for cervical cancer in combined 1.5 T MR/HDR suite: Impact of repeated imaging

Introduction

At our department we have a dedicated 1.5 Tesla MRI/HDR brachytherapy suite, which provides the possibility of repeated MRI scanning before, during and after applicator insertion and before and/or after irradiation for patients with advanced cervical cancer. In this study we analysed the effect of this adaptive workflow. We investigated the number of interventions, their impact on organ doses (OAR) and the respective dose differences between total prescribed and total delivered doses.

Materials and methods

Seventy patients with locally advanced cervical cancer FIGO2009 stages IB-IVA, treated from June 2016 till August 2020, were retrospectively analysed. The standard brachytherapy schedule consisted of two applicator insertions and delivery of three or four HDR fractions.OARs were recontoured on the repeated MRI scans. The D2cm3 dose difference between total prescribed and total delivered dose for bladder, rectum, sigmoid and bowel were calculated.

Results

In total 153 interventions were performed, 3 replacements of the applicator, 23 adaptations of needle positions, bladder filling was changed 74 times and repeated rectal degassing 53 times. The impact of the rectal interventions was on average -1.2 Gy EQD23. Dose differences between total delivered and total prescribed D2cm3 for bladder, rectum, sigmoid and bowel were -0.6, 0.3, 2.2 and -0.6 Gy EQD23, respectively.

Conclusions

An MRI scanner integrated into the brachytherapy suite enables multiple interventions based on the scans before treatment planning and dose delivery. This allows for customized treatment according to the changing anatomy of the individual patient and a better estimation of the delivered dose.

Multi-center dosimetric predictions to improve plan quality for brachytherapy for cervical cancer treatment

BACKGROUND AND PURPOSE

Image-guided adaptive brachytherapy (IGABT) is an important modality in the cervical cancer treatment, and plan quality is sensitive to time pressure in the workflow. Patient anatomy-based quality-assurance (QA) with overlap volume histograms (OVHs) has been demonstrated to detect suboptimal plans (outliers). This analysis quantifies the possible improvement of plans detected as outliers, and investigates its suitability as a clinical QA tool in a multi-center setting.

MATERIALS AND METHODS

In previous work OVH-based models were investigated for the use of QA. In this work a total of 160 plans of 68 patients treated in accordance with the current state-of-the-art IGABT protocol from Erasmus MC (EMC) were analyzed, with a model based on 120 plans (60 patients) from UMC Utrecht (UMCU). Machine-learning models were trained to define QA thresholds, and to predict dose D_2cm3 to bladder, rectum, sigmoid and small bowel with the help of OVHs of the EMC cohort. Plans out of set thresholds (outliers) were investigated and retrospectively replanned based on predicted D_2cm3 values.

RESULTS

Analysis of replanned plans demonstrated a median improvement of 0.62 Gy for all Organs At Risk (OARs) combined and an improvement for 96 % of all replanned plans. Outlier status was resolved for 36 % of the replanned plans. The majority of the plans that could not be replanned were reported having implantation complications or insufficient coverage due to tumor geometry.

CONCLUSION

OVH-based QA models can detect suboptimal plans, including both unproblematic BT applications and suboptimal planning circumstances in general. OVH-based QA models demonstrate potential for clinical use in terms of performance and user-friendliness, and could be used for knowledge transfer between institutes. Further research is necessary to differentiate between (sub)optimal planning circumstances.

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. D90 of high-risk clinical target volume (HR-CTV) and D2cc 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 (D90 and D2cc) 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 D90 HR-CTV (Institution 1; p < 0.00001) or decrease of D2cc 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.