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. 2024 May 22;4(1):96.
doi: 10.1038/s43856-024-00526-7.

Structure-specific rigid dose accumulation dosimetric analysis of ablative stereotactic MRI-guided adaptive radiation therapy in ultracentral lung lesions

J M Bryant  1 , Ruben J Cruz-Chamorro  2 , Alberic Gan  3 , Casey Liveringhouse  2 , Joseph Weygand  2 , Ann Nguyen  3 , Emily Keit  2 , Maria L Sandoval  2 , Austin J Sim  4 , Bradford A Perez  2 , Thomas J Dilling  2 , Gage Redler  2 , Jacqueline Andreozzi  2 , Louis Nardella  2 , Arash O Naghavi  2 , Vladimir Feygelman  2 , Kujtim Latifi  2 , Stephen A Rosenberg  5
Affiliations

Structure-specific rigid dose accumulation dosimetric analysis of ablative stereotactic MRI-guided adaptive radiation therapy in ultracentral lung lesions

J M Bryant et al. Commun Med (Lond). .

Abstract

Background: Definitive local therapy with stereotactic ablative radiation therapy (SABR) for ultracentral lung lesions is associated with a high risk of toxicity, including treatment related death. Stereotactic MR-guided adaptive radiation therapy (SMART) can overcome many of the challenges associated with SABR treatment of ultracentral lesions.

Methods: We retrospectively identified 14 consecutive patients who received SMART to ultracentral lung lesions from 10/2019 to 01/2021. Patients had a median distance from the proximal bronchial tree (PBT) of 0.38 cm. Tumors were most often lung primary (64.3%) and HILUS group A (85.7%). A structure-specific rigid registration approach was used for cumulative dose analysis. Kaplan-Meier log-rank analysis was used for clinical outcome data and the Wilcoxon Signed Rank test was used for dosimetric data.

Results: Here we show that SMART dosimetric improvements in favor of delivered plans over predicted non-adapted plans for PBT, with improvements in proximal bronchial tree DMax of 5.7 Gy (p = 0.002) and gross tumor 100% prescription coverage of 7.3% (p = 0.002). The mean estimated follow-up is 17.2 months and 2-year local control and local failure free survival rates are 92.9% and 85.7%, respectively. There are no grade ≥ 3 toxicities.

Conclusions: SMART has dosimetric advantages and excellent clinical outcomes for ultracentral lung tumors. Daily plan adaptation reliably improves target coverage while simultaneously reducing doses to the proximal airways. These results further characterize the therapeutic window improvements for SMART. Structure-specific rigid dose accumulation dosimetric analysis provides insights that elucidate the dosimetric advantages of SMART more so than per fractional analysis alone.

Plain language summary

Stereotactic MR-guided Adaptive Radiation Therapy (SMART) is a type of radiation therapy for cancer. With SMART, treatment can be adapted based on daily changes in the body seen via imaging. SMART can safely deliver radiation to lung tumors near the center of the body which are risky to treat, due to potential damage to nearby organs. We looked at 14 patients who received SMART to determine how much changing the radiation plan each day improved our ability to safely deliver high doses. We found that SMART not only improved our ability to cover the entirety of the tumor with the dose originally intended, but also reduced dose to nearby organs. Treatment resulted in excellent control of the tumor with few side effects. SMART shows promise for safer and more effective treatment for lung tumors in this part of the body.

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Conflict of interest statement

K.L. and V.F. declare the following competing interests: both received consulting fees from ViewRay, Inc. S.A.R. declares the following competing interests: has been the recipient of research grants, has received an honorarium, and has served on the Lung Research Consortium Advisory Board for ViewRay, Inc. T.D. declares the following competing interests: holds equity shares in Moderna and has received consulting fees from AstraZeneca. Furthermore, he has received both consulting and sponsored travel fees from the NCCN. The other authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Coronal view of a TRUFI sequence used to contour targets and OAR.
The gross target volume (GTV), trachea, esophagus, right upper lobe bronchi, azygous vein, aorta, and heart are contoured in red, yellow, orange, green, blue, magenta, and pink, respectively.
Fig. 2
Fig. 2. Kaplan–Meier curves for LC of the ultracentral lung lesions and LFFS of the ultracentral lung lesion patients treated with SMART.
a Kaplan–Meier curve of the LC of the ultracentral lung lesions treated with SMART. b Kaplan Meier curve of the LFFS for ultracentral lung patients treated with SMART.
Fig. 3
Fig. 3. Kaplan–Meier curves for OS and PFS of the ultracentral lung lesion patients treated with SMART.
a Kaplan–Meier curve of the OS for ultracentral lung patients treated with SMART. b Kaplan–Meier curve of the PFS for ultracentral lung patients treated with SMART.
Fig. 4
Fig. 4. Example of the contours, cumulative delivered dose, and cumulative predicted dose for the highest risk axial slice where the PBT directly abutted and sandwiched a HILUS group B lesion that underwent online daily adaptation for seven out of eight total fractions.
a GTV (red), PTV (pink), and PBT (blue) contours. b The cumulative delivered dose plan demonstrates how daily plan adaptation pushes the higher isodose lines outside of the proximal airway while maintaining excellent target coverage. c The cumulative predicted dose plan demonstrates doses nearing 80 Gy within the thin-walled PBT.
See this image and copyright information in PMC

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