Outcomes of stereotactic body radiotherapy 60\u2009Gy in 8 fractions when prioritizing organs at risk for central and ultracentral lung tumors

Yizhou Zhao,Mitchell Liu,Eman Khawandanh,Susan Zhang,Emma M Dunne,Steven Thomas,Devin Schellenberg

doi:10.1186/s13014-020-01491-w

Yizhou Zhao, Mitchell Liu + Show 5 more

Open Access

https://doi.org/10.1186/s13014-020-01491-w

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Abstract

BackgroundFor stereotactic body radiotherapy (SBRT) to central (C) and ultracentral (UC) lung tumors, our provincial practice has been to prioritize organs at risk (OARs) constraints by compromising target volume coverage if needed. The objectives are to report the treatment’s efficacy and safety.MethodsWe conducted a retrospective analysis of all provincial patients who underwent SBRT at 60Gy in 8 fractions to C and UC lung tumors, from 2013 to 2017.ResultsNinety-eight lesions were treated, 57 (58.2%) C and 41 (41.8%) UC. The median follow-up was 22.9 months (range 2.5–64.8 months). The 1- and 3-year local control (LC) was 97.8 and 84.5% respectively, with no differences between C and UC groups (p = 0.662). Fifty-three (54.1%) cases had optimal dose coverage (V60Gy ITV&PTV > 95%), 29 (29.6%) had compromised PTV coverage (V60Gy ITV > 95%/PTV < 95%), and 16 (16.3%) had both compromised ITV and PTV coverage (V60Gy ITV&PTV < 95%). No significant difference in LC was detected at 2 years between the 3 groups (95.6, 91.8 and 90.9%, p = 0.717). There were 3 episodes of grade 3 toxicity in the C group (2 dyspnea, 1 pneumonitis) and 2 in the UC group (1 dyspnea, 1 hemoptysis). There were no gr4/5 toxicities. On multivariable Cox regression analysis, ITV size was found to be a predictor for LC (p = 0.001).ConclusionsSBRT at 60Gy in 8 fractions achieves high rates of LC with low risks of significant toxicities, even if target volume coverage is reduced to meet OARs constraints.

Highlights

For stereotactic body radiotherapy (SBRT) to central (C) and ultracentral (UC) lung tumors, our provincial practice has been to prioritize organs at risk (OARs) constraints by compromising target volume coverage if needed
Overall better internal target volume (ITV) and planning target volume (PTV) dose coverage were achieved for the patients in the central tumor cohort, as reflected by significantly higher Minimum point dose (Dmin), Mean dose (Dmean), V 60 Volume receiving at least Gy (Gy) and D 99%, as well as lower volumes receiving less than 60Gy
There was no significant difference in local control between primary lung lesions and metastases (p = 0.725), nor between central and ultracentral tumors (p = 0.662)

Summary

Introduction

For stereotactic body radiotherapy (SBRT) to central (C) and ultracentral (UC) lung tumors, our provincial practice has been to prioritize organs at risk (OARs) constraints by compromising target volume coverage if needed. Stereotactic body radiotherapy (SBRT) is widely accepted as the standard treatment for early stage nonsmall cell lung cancers (NSCLC) in patients who are not operative candidates [1,2,3]. An early phase II trial reported risks of severe treatment-related toxicities for a subset of lesions located centrally in the chest [8]. The 2-year freedom from severe toxicity rate was only 54% for central tumors, in contrast to 83% for those that are peripherally situated.

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