Impact of daily plan adaptation on organ-at-risk normal tissue complication probability for adrenal lesions undergoing stereotactic ablative radiation therapy

• Published in: Radiotherapy and oncology Vol. 163; pp. 14 - 20
• Main Authors: Chen, Hanbo, Schneiders, Famke L., Bruynzeel, Anna M.E., Lagerwaard, Frank J., van Sörnsen de Koste, John R., Cobussen, Paul, Bohoudi, Omar, Slotman, Berend J., Louie, Alexander V., Senan, Suresh
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.10.2021
• Subjects: Adaptive radiotherapy; Adrenal; Humans; Magnetic resonance; Normal tissue complication probability; Organs at Risk; Probability; Radiosurgery - adverse effects; Radiotherapy Planning, Computer-Assisted; Retrospective Studies; Stereotactic ablative radiotherapy; Stereotactic body radiation therapy; Normal tissue complication probability; Stereotactic body radiation therapy; Adrenal; Stereotactic ablative radiotherapy; Magnetic resonance; Adaptive radiotherapy
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2021.07.026

•MR-guided adaptive adrenal SABR reduces the chance of stomach toxicity.•Reduction in predicted stomach toxicity was mainly for left adrenal lesions.•Consider dose escalation for right adrenal lesions due to low predicted toxicity. Stereotactic ablative radiotherapy (SABR) can achieve good local control for metastatic adrenal lesions. Magnetic resonance (MR)-guidance with daily on-table plan adaptation can augment the delivery of SABR with greater dose certainty. The goal of this study was to quantify the potential clinical benefit MR-guided daily-adaptive adrenal SABR using the normal tissue complication probability (NTCP) framework. Patients treated with adrenal MR-guided SABR at a single institution were retrospectively reviewed. Lyman-Kutcher-Burman NTCP models were used to calculate the NTCP of upper abdominal organs-at-risk (OARs) at simulation and both before and after daily on-table plan adaptation. Differences in OAR NTCPs were assessed using signed-rank tests. Potential predictors of the benefits of adaptation were assessed by linear regression. Fifty-two adrenal MR-guided SABR courses were analyzed. The baseline simulation plan underestimated the absolute stomach NTCP by 10.0% on average (95% confidence interval: 4.7–15.2%, p < 0.001). Daily on-table adaptation lowered absolute NTCP by 8.7% (4.2–13.2%, p < 0.001). The most significant predictor of the benefits of adaptation was lesion laterality (p = 0.018), with left-sided lesions benefitting more (13.3% [6.3–20.4%], p < 0.001) than right-sided lesions (2.1% [−1.6–5.7%], p = 0.25). Sensitivity analyses did not change the statistical significance of the findings. NTCP analysis revealed that patients with left adrenal tumors were more likely to benefit from MR-guided daily on-table adaptive SABR using current dose/fractionation regimens due to reductions in predicted gastric toxicity. Right-sided adrenal lesions may be considered for dose escalation due to low predicted NTCP.