In a phase II study (iSABR) reported in JAMA Oncology, Gensheimer et al found that individualized stereotactic ablative radiotherapy (SABR) for up to four lung cancer tumors was associated with a high degree of local control and the ability to minimize radiation doses.
Study Details
Two hundred and seventeen patients were enrolled in the trial between November 2011 and December 2018 at Stanford University and Hokkaido University, Sapporo, Japan. Patients underwent once-daily SABR for up to four tumors. The sum of three orthogonal diameters had to be ≤ 20 cm if one tumor was treated, and ≤ 15 cm for each tumor if multiple tumors were treated.
Patients received a total of 240 treatment courses. Doses ranged from 25 Gy in one fraction for peripheral tumors with a volume of 0 to 10 cm3 to 60 Gy in eight fractions for central tumors with a volume of > 30 cm3.
Patients were enrolled in three groups:
- Initial diagnosis of non–small cell lung cancer (NSCLC) with T1-3N0M0 tumors (group 1, n = 79 receiving 79 courses)
- T1-3N0M0 new primary NSCLC with a history of prior NSCLC or multiple NSCLCs (group 2, n = 67 receiving 82 courses)
- Lung metastases from NSCLC or another solid tumor (group 3, n = 71 receiving 79 courses).
Patients had a median age of 72 years, and 69% were current or former smokers. The main outcome measure was freedom from local recurrence (same-lobe recurrence) at 1 year in the three groups.
Key Findings
A total of 285 tumors, including 211 peripheral tumors (74%) and 74 central tumors (26%), were treated. The most common dose was 25 Gy in 1 fraction (158 tumors).
Median follow-up was 33 months (range = 2–109 months). Freedom from local recurrence per tumor at 1 year was 97% (90% confidence interval [CI] = 91%–99%) for group 1, 94% (90% CI = 87%–97%) for group 2, and 96% (90% CI = 89%–98%) for group 3. Freedom from local recurrence ranged from 90% in group 1 to 95% in group 3 at 2 years, and from 83% in group 1 to 93% in group 2 at 5 years.
Median overall survival among all patients was 59 months (95% CI = 49–82 months), including 57 months (95% CI = 43 months to not estimable) in group 1, 82 months (95% CI = 46 months to not estimable) in group 2, and 57 (95% CI = 40 months to not estimable) in group 3.
Grade ≥ 2 pneumonitis occurred in 16 patients (7%; grade ≥ 3 in 3 patients, 1%). Grade ≥ 3 adverse events occurred in 5% of patients, including pneumonitis, noncardiac chest pain, pleural effusion, pneumonia, and grade 5 pulmonary hemorrhage considered related to treatment.
The investigators concluded, “The results of this nonrandomized controlled trial suggest that individualized SABR used to treat lung tumors may allow minimization of treatment dose and is associated with excellent local control. Individualized dosing should be considered for use in future trials.”
Billy W. Loo, Jr, MD, PhD, and Maximilian Diehn, MD, PhD, of the Department of Radiation Oncology, Stanford University School of Medicine, are the corresponding authors for the JAMA Oncology article.
Disclosure: Financial support for the study was provided by the Department of Radiation Oncology, Stanford University School of Medicine, and by the Global Center for Biomedical Science and Engineering, Hokkaido University Faculty of Medicine. For full disclosures of the study authors, visit jamanetwork.com.
