September 25, 2016

Single-Fraction SBRT Outcomes Comparable to Multiple-Fraction Regimen for Non-Small Cell Lung Cancer

Study confirms safety and efficacy

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For patients with medically inoperable early-stage non-small cell lung cancer(NSCLC), a single-fraction 30 Gy stereotactic body radiation therapy (SBRT) regimen is as safe and effective as a 60 Gy three-fraction regimen, researchers have found.

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The two different SBRT regimens produced equivalent outcomes in terms of overall survival, progression-free survival and toxicity, according to results of a randomized phase II study. Single-fraction SBRT provides excellent local control, minimal toxicity and overall survival comparable to the higher-dose SBRT schedule, based on this multi-institution study.

Gregory Videtic, MD, Cleveland Clinic Cancer Center’s Director of Thoracic Radiation Oncology, presented the findings at the 2016 annual meeting of the American Society for Radiation Oncology (ASTRO) in Boston.

SBRT is considered the emerging standard of care for medically inoperable lung cancer.

“This study helps confirm the appropriateness of a single-fraction schedule in lung SBRT and further enhances the treatment options for a medically vulnerable population,” Dr. Videtic says. “It corroborates findings from the recently published Radiation Therapy Oncology Group RTOG 0915 study that showed the efficacy and safety of single-fraction SBRT.” That study compared 34 Gy in one fraction to a regimen of 48 Gy given in four daily 12-Gy fractions.

“Participation in this project reflected our interest in advancing knowledge on the applications and indications for lung SBRT,” he says. “We were gratified to be invited to take part.” The study was initiated by Roswell Park Cancer Institute in Buffalo, NY. SUNY Upstate Medical University in Syracuse, NY, also participated. Cleveland Clinic Cancer Center accrued the majority of patients to the trial.

The study’s primary endpoint was toxicity, with secondary evaluation of local tumor control, late toxicity (greater than one year), and progression-free and overall survival.

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Severe adverse events, defined as RTOG grade 3 and higher, were comparable for patients in both arms: those receiving 30 Gy in one fraction (Arm 1); and 60 Gy delivered in three, 20-Gy fractions over 1.5 to 2 weeks (Arm 2). Overall survival and progression-free survival were also comparable between arms. These findings mirrored those of RTOG 0915.

Methodology, results and implications

Patients with documented medical conditions precluding lobectomy for biopsy-proven peripheral (greater than 2 centimeters from the central bronchial tree), T1/T2, N0 (clinically node negative by PET), M0 (nonmetastatic) tumors were eligible.

The 98 patients who participated were randomized to either Arm 1or Arm 2. The study spanned a period from 2008 to 2015. Median follow-up was 24 months. Following SBRT, 10 patients were lost to follow-up: one in Arm 1, and nine in Arm 2.

Summarized adverse event (AE) results are:

RTOG grade 3 AEs

  • Arm 1: 13 (27%)
  • Arm 2: 16 (33%)

Pulmonary-related grade 3 AEs

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  • Arm 1: 8 (16%)
  • Arm 2: 6 (12%)

There were no grade 4 AEs. One grade 5 event occurred in each arm: death of unknown cause in Arm 1, and disease progression in Arm 2.

Although the study shows single-fraction SBRT is safe and effective for early-stage NSCLC, Dr. Videtic cautions against interpreting the findings as a blanket endorsement of the regimen in all cases.

“I’m not suggesting clinicians opt or preferentially choose single-fraction therapy,” he emphasizes. “I’m suggesting that it is a validated schedule that can be considered in appropriate individual patients who match the eligibility criteria of the study. We trust this will spur further implementation of single-fraction therapy in practice. We’re also hopeful that these results will support a randomized phase III trial of lung SBRT schedules, which will have survival as a primary endpoint.”

Results consistent with RTOG findings

Whether there are subgroups of NSCLC patients who might benefit from higher-dose/multiple-fraction SBRT regimens is an area of controversy and investigation, Dr. Videtic notes. Retrospective studies suggest that tumors larger than 3 centimeters might benefit from higher-dose fractionated regimens. There are also indications that histology makes a difference, he adds.

“In the absence of randomized phase III trials, where overall survival would be the primary endpoint, we can only look to clinical judgment regarding the appropriate regimen for a given tumor,” he says.

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