Of the 72 patients studied, 15 (21%) experienced grade 3 or higher toxicity and 10 (14%) died of bronchopulmonary hemorrhage.
This doesn’t completely write off the use of SBRT for ultra-central lung tumors, according to Joyce Lodeweges, MD, of University Medical Center (UMC) Utrecht in the Netherlands.
“We have to inform the patient very well that there are some high risks to this treatment,” she said at the European Lung Cancer Virtual Congress 2021 (Abstract 61M0).
Dr. Lodeweges noted that keeping the biologically effective dose of radiation to the main bronchus below a certain threshold (< 90 Gy) could reduce the risk of toxicity significantly, making SBRT a viable option for some patients. In addition, MRI-guided daily adaptation of the radiation treatment to organs at risk may make the treatment safer.
Varying definitions, regimens spur debate
SBRT is standard care in peripherally located, stage I non–small cell lung cancer that is inoperable or if the patient refuses surgery, noted study discussant Yolande Lievens, MD, PhD, of Ghent University Hospital in Belgium.
“[SBRT] has good local control rates with low toxicity even in patients with COPD or being elderly,” Dr. Lievens said.
“In more moderately central tumors, there is quite some evidence that risk-adapted fractionation schemes can be delivered in a safe way and lead to high local control rates,” she added. “For ultra-central legions, there’s still not a recommendation to treat with SBRT because we see a lot of increased toxicity.”
“For ultra-central tumors, SBRT is still under debate,” agreed Dr. Lodeweges. “This is because of the varying definitions in the literature and the varying fractionation schemes used.”
How the location of tumors is defined is important. Central tumors are those that are at least 2 cm away from the main bronchial tree, whereas ultra-central tumors are those that butt onto it or overlap it.
In Dr. Lodeweges’s study, ultra-central tumors were defined as those with a planning target volume (PTV) abutting or overlapping the main bronchi, trachea, and/or esophagus.
Study details
Between 2012 and 2020, there were 72 patients with ultra-central lung tumors treated at UMC Utrecht. Most patients (78%) had a PTV covering the main bronchus, with 21% each having PTVs overlapping the trachea or esophagus.
Patients received a protracted SBRT regimen of 60 Gy given in 12 fractions. The median follow-up was 19 months.
The local failure-free survival rate was 98% at 1 year and 85% at 2 years. Overall survival rates were 77% and 52%, respectively.
Receiving a biologically effective dose of more than 90 Gy to the main bronchus increased the risk of grade 3 or higher toxicity. On the other hand, patient age and tumor histology did not affect the risk of adverse events.
The use of antithrombotic therapy didn’t have any bearing on toxicity either, but it’s a possible risk factor to consider, Dr. Lodeweges said. Peri- or endobronchial tumor location is another consideration.