Lung SBRT credentialing in the Canadian OCOG-LUSTRE randomized trial

Purpose: To report on the Stereotactic Body Radiation Therapy (SBRT) credentialing experience during the Phase III Ontario Clinical Oncology Group (OCOG) LUSTRE trial for stage I non-small cell lung cancer.Methods: Three credentialing requirements were required in this process: (a) An institutional technical survey; (b) IROC (Imaging and Radiation Oncology Core) thoracic phantom end-to-end test; and (c) Contouring and completion of standardized test cases using SBRT for one central and one peripheral lung cancer, compared against the host institution as the standard. The main hypotheses were that unacceptable variation would exist particularly in OAR definition across all centres, and that institutions with limited experience in SBRT would be more likely to violate per-protocol guidelines.Results: Fifteen Canadian centres participated of which 8 were new, and 7 were previously established (>= 2 years SBRT experience), and all successfully completed surveys and IROC phantom testing. Of 30 SBRT test plans, 10 required replanning due to major deviations, with no differences in violations between new and established centres (p = 0.61). Mean contouring errors were highest for brachial plexus in the central (C) case (12.55 +/- 6.62 mm), and vessels in the peripheral (P) case (13.01 +/- 12.55 mm), with the proximal bronchial tree (PBT) (2.82 +/- 0.78 C, 3.27 +/- 1.06 P) as another variable structure. Mean dice coefficients were lowest for plexus (0.37 +/- 0.2 C, 0.37 +/- 0.14 P), PBT (0.77 +/- 0.06 C, 0.75 +/- 0.09 P), vessels (0.69 +/- 0.29 C, 0.64 +/- 0.31 P), and esophagus (0.74 +/- 0.04 C, 0.76 +/- 0.04 P). All plans passed per-protocol planning target volume (PTV) coverage and maximum/ volumetric organs-at-risk constraints, although variations existed in dose gradients within and outside the target.

Automated summary

This study reports on the credentialing experience of SBRT during the OCOG LUSTRE trial. The results showed inconsistent OAR definitions across centers, and institutions with limited SBRT experience were more likely to violate protocol guidelines.