Pitfalls in lung stereotactic body radiotherapy—a review of organ toxicities and dose constraints

Stereotactic body radiotherapy (SBRT), which is also known as stereotactic ablative radiotherapy (SABR) has been established as a treatment for early-stage inoperable non-small cell lung cancer (NSCLC) in several international guidelines. One of the earliest phase I study data in lung SBRT was first published in 2003 by Timmerman and colleagues, with the same group subsequently reporting excellent phase II results. These two trials and similar landmark studies, now form the basis for lung SBRT practice internationally. Although SBRT is a standard treatment option for early stage inoperable NSCLC, it is still not available in many developing parts of the world. Because of its noninvasive nature, excellent control outcomes and safe track record. The indications for its use are expanding with more sites being treated as well as increasing use in early stage operable lung tumours and oligometastatic setting. There are still uncertainties with regards to optimal radiotherapy dose-fractionation regimen and because of the large ablative doses used in SBRT, there is a potential for significant side effects. Certain scenarios like treatment of central or recurrent tumors require greater care. In this paper, we elaborate on the common toxicities reported in literature in relation to SBRT of lung tumors as well as factors that may alter these risks.