Stereotactic ablative body radiation therapy (SABR) nearly doubled the overall survival of patients with inoperable stage I lung cancer compared to standard radiotherapy, according to results of a multi-center phase III trial published in the Lancet Oncology. SABR also improved local disease control in the patient population.
As part of the CHISEL trial, 101 patients with non-small cell lung cancer (NSCLC) were randomized to receive either SABR (66 patients) or standard radiotherapy (35 patients). Results showed median overall survival was five years in the SABR group compared to three years in the standard treatment group.
At two-year follow-up, 77 percent of those in the SABR cohort were alive compared to 59 percent of patients in the standard radiotherapy group, reported David Ball, MD, with Peter MacCallum Cancer Centre in Melbourne, Australia, and colleagues.
Twenty total patients had their disease progress locally, nine (14 percent) of those in the SABR group and 11 (31 percent) of 35 patients in the standard group. And at two years, the standard radiotherapy group had a cumulative incidence of local treatment rate of 26 percent compared to 10 percent in the SABR group.
“To the best of our knowledge, this study is the first to make a direct comparison that indicates that SABR is associated with improved survival,” the authors added. “The findings of this trial suggest that SABR should be the treatment of choice for this (peripherally located stage 1 NSCLC) patient group.”
In total, the CHISEL trial enrolled 101 patients from 11 hospitals in Australia and three in New Zealand between Dec. 31, 2009, and June 22, 2015. All were either ineligible for or refused surgery.
If tumors were less than 2 centimeters from the chest wall, SABR patients received four 12 Gy fractions totaling 48 Gy. In all other cases, SABR patients received three 18 Gy fractions. In the standard radiotherapy group, depending on the institution, patients received daily 2 Gy fractions totaling 66 Gy or daily 2.5 Gy fractions for a total of 50 Gy.
Additionally, treatment was well tolerated with one grade 4 adverse event in those treated with SABR and seven grade 3 events. In the standard treatment group two grade 3 events were recorded.
Since this trial was completed, Ball et al. noted, there have been two large retrospective non-randomized studies and one systematic review that reported SABR-associated survival benefits compared to standard radiotherapy. Those results are consistent with the CHISEL trial.
“The improvement of both local control and overall survival with SABR shown in this prospective randomized trial provides, to our knowledge for the first time, evidence supporting stereotactic ablative radio- therapy as the standard of care for the treatment of inoperable peripherally located stage 1 (T1N0M0 and T2aN0M0) NSCLC,” the authors concluded.