Improving the Efficiency of Single-Isocenter Multiple Metastases Stereotactic Radiosurgery Treatment

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Purpose Multiple brain metastases can be treated efficiently with Stereotactic Radio Surgery (SRS) using a Single Isocenter Dynamic Conformal Arc (SIDCA) technique. Currently plans are manually optimized, which may lead to unnecessary table angles and arcs being used. This study aimed to evaluate an automatic 4 π -optimization SIDCA algorithm for treatment efficiency and plan quality. Methods and Materials Automatic 4 π -optimized SIDCA plans were created and compared to the manually optimized clinical plans for 54 patients who received single-fraction SRS to 2-10 metastases. The number of table angles and arcs were compared with a paired t-test using a Bonferroni-corrected significance level of p < 0.05 / 4 = 0.0125 . The reduction in treatment time was estimated from the difference in the number of table angles and arcs. Plan quality was assessed through the volume-averaged inverse Paddick Conformity Index (CI) and Gradient Index (GI), and the volume of normal brain surrounding each metastasis receiving 12 Gy (local V12 Gy). For a five-patient subset the automatic plans were manually adjusted further. CI and GI were assessed for non-inferiority using a one-sided t-test with the non-inferiority limit equal to the 95 % inter-observer reproducibility limit from a separate planning study (corrected significance level p < 0.05 / ( 4 − 1 ) = 0.017 ). Results The automatic plans significantly improved treatment efficiency with a mean reduction in the number of table angles and arcs of − 0.5 ± 0.1 and − 1.3 ± 0.2 respectively ( ± standard error, both p < 0.001 ). Estimated treatment time saving was − 2.7 ± 0.5 minutes , 14 % of the total. The volume-averaged CI and GI were non-inferior to the clinical plans (both p < 0.001 ), although there was a small systematic shift in CI of 0.07 ± 0.01 . The resulting difference in local V12 Gy, 0.25 ± 0.04 cm 3 , was not clinically significant. Minor manual adjustment of the automatic plans removed these slight differences whilst preserving the improved treatment efficiency. Conclusions Automatic 4 π -optimization can generate SIDCA SRS plans with improved treatment efficiency and non-inferior plan quality.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.