Conference Coverage

Single and multifraction SBRT found comparable for lung metastases



Stereotactic body radiotherapy (SBRT) for lung oligometastases nets similar safety and efficacy whether it is delivered in multiple fractions or just one fraction. This was among key findings of a randomized, phase 2 trial reported at the American Society for Radiation Oncology Annual Meeting 2020.

Shankar Siva, PhD, MBBS, of Peter MacCallum Cancer Centre in Melbourne, Australia

Dr. Shankar Siva

“Most patients [with lung metastases] are treated with lifelong anticancer drug therapy only, with little prospect for long-term cancer control,” investigator Shankar Siva, MBBS, PhD, of Peter MacCallum Cancer Centre in Melbourne, said in a news briefing.

“However, some patients may have limited spread to the lungs and may be suitable for either surgery, which is an invasive approach, or SBRT, which is a noninvasive approach, with the aim to prolong long-term cancer control,” he added.

Patients and treatment

Dr. Siva and colleagues enrolled in their phase 2 trial (SAFRON II/TROG 13.01) 90 patients from 13 centers in Australia and New Zealand.

All patients had one to three lung metastases (from nonhematologic malignancies) that measured up to 5 cm in diameter and were located in the periphery.

The most common primaries were colorectal cancer (47%), lung cancer (11%), and kidney cancer (10%). The trial required that all primary and extrathoracic disease had been definitively treated.

The patients were randomized evenly to lung SBRT delivered with a single-fraction regimen (28 Gy in one fraction) or a multifraction regimen (48 Gy in four fractions) that netted the same biological equivalent dose.

Safety and efficacy

The two treatment groups did not differ significantly with respect to any-grade toxicities at 1 year, with the exception of higher rates of esophagitis and radiation dermatitis in the multifraction group, Dr. Siva reported.

The rate of grade 3 or worse toxicity at 1 year – the trial’s primary endpoint – was 5% with the single fraction and 3% with multiple fractions, with overlapping 80% confidence intervals, meeting the prespecified endpoint for acceptable toxicity.

The single-fraction group had two grade 3 events that resolved with intervention and no grade 4-5 events. The multifraction group had a single grade 5 event (fatal pneumonitis in a patient with underlying interstitial lung disease) and no grade 3-4 events.

The single-fraction and multifraction groups were also similar at 1 year on rates of freedom from local failure (93% and 95%, respectively), disease-free survival (59% and 60%, respectively), and overall survival (95% and 93%, respectively), with overlapping 95% CIs for each outcome.

Analyses of quality of life and cost-effectiveness are ongoing.

Applying the results: Useful in a pandemic?

“Single-session SBRT is safe, convenient, and noninvasive, and appears to be effective, to date, for lung secondaries. This approach may be considered as a one-stop, knockout type of approach for patients who have one to three metastases to the lung,” Dr. Siva proposed.

“These findings may have implications for treatment selection in a resource-constrained environment, such as the current global pandemic, when trying to reduce footfall or thoroughfare within a radiotherapy department, and it’s quite a convenient approach for patients,” he added.

Dr. Sue S. Yom

“Stereotactic radiation has an obvious advantage over conventional radiation in several ways and may have a special advantage in the midst of the COVID-19 pandemic to reduce exposure to patients and our hospital personnel,” agreed news briefing moderator Sue S. Yom, MD, PhD, of the University of California, San Francisco.

However, use of stereotactic techniques remains controversial because they require technical precision and additional resources for planning and quality assurance, and they are often more expensive than conventional radiation therapy, she noted. Therefore, there must be evidence to justify their use in a palliative or metastatic setting.

The current trial is noteworthy for pushing the SBRT efficiency envelope, according to Dr. Yom.

“These findings are going to be confirmed by the study team with further follow-up at 3 years,” she pointed out. “If the findings of this study are maintained, it shows that patients with up to three metastatic tumors in the lung can have their treatment given in an extremely efficient manner over one session, which saves them time and hospital resources, and could be very significant to patients’ quality of life.”

The trial is sponsored by the Trans-Tasman Radiation Oncology Group and the Australasian Lung Cancer Trials Group. Dr. Siva disclosed relationships with Varian Industries, Merck, AstraZeneca, Bayer Pharmaceuticals, Bristol Meyers Squibb, and Reflexion. Dr. Yom disclosed no relevant conflicts.

SOURCE: Siva S et al. ASTRO 2020, Abstract 5.

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