A MULTI-ATLAS APPROACH FOR ACTIVE BONE MARROW SPARING RADIOTHERAPY: IMPLEMENTATION IN THE NRG-GY006 TRIAL

Bladder Cancer
07/07/2020

Yusufaly T, et al. Int J Radiat Oncol Biol Phys 2020.

ABSTRACT

BACKGROUND: Sparing active bone marrow (ABM) can reduce acute hematologic toxicity in patients undergoing chemoradiotherapy for cervical cancer, but ABM segmentation based on positron emission tomography/computed tomography (PET/CT) is costly. We sought to develop an atlas-based ABM segmentation methods for implementation in a prospective clinical trial.

METHODS: A multi-atlas was built on a training set of 144 patients and validated in 32 patients from the XXX-XXXXX clinical trial. ABM for individual patients was defined as the sub-volume of pelvic bone above the individual mean standardized uptake value on registered 18F-fluorodeoxyglucose PET/CT images. Atlas-based and custom ABM segmentations were compared using the Dice similarity coefficient (DSC) and mean distance to agreement, and used to generate ABM-sparing intensity modulated radiation therapy (IMRT) plans. Dose-volume metrics and normal tissue complication probabilities of the two approaches were compared using linear regression.

RESULTS: Atlas-based ABM volumes (mean [s.d.], 548.4 [88.3] cc) were slightly larger than custom ABM volumes (535.1 [93.2] cc), with a DSC of 0.73. Total pelvic bone marrow (PBM) V20 and Dmean were systematically higher and custom ABM V10 was systematically lower with custom-based plans (slope: 1.021 [95% confidence interval (CI): 1.005-1.037], 1.014 [95% CI: 1.006-1.022], and 0.98 [95% CI: 0.97-0.99], respectively). We found no significant differences between atlas-based and custom-based plans in bowel, rectum, bladder, femoral heads, or target dose-volume metrics.

CONCLUSIONS: Atlas-based ABM segmentation can reduce pelvic bone marrow dose while achieving comparable target and other normal tissue dosimetry. This approach may allow ABM sparing in settings where PET/CT is unavailable.