Stereotactic Ablative vs Standard Radiotherapy in Inoperable Stage I NSCLC
In the phase III TROG 09.02 CHISEL trial reported in The Lancet Oncology, Ball et al found that stereotactic ablative body radiotherapy improved local disease control vs standard radiotherapy in peripherally located, inoperable stage I non–small cell lung cancer (NSCLC).
The open-label trial comprised 101 patients with stage I (T1–T2a, N0, M0) disease from 11 sites in Australia and 3 in New Zealand. Patients were randomly assigned 2:1 between December 2009 and June 2015 to receive stereotactic ablative body radiotherapy (n = 66) or standard radiotherapy (n = 35). Stereotactic ablative body radiotherapy consisted of 54 Gy in three 18-Gy fractions or 48 Gy in four 12-Gy fractions if the tumor was < 2 cm from the chest wall. Standard radiotherapy consisted of 66 Gy in 33 daily 2-Gy fractions, or 50 Gy in 20 daily 2.5-Gy fractions, depending on institutional preference.
The primary endpoint was time to local treatment failure in the intent-to-treat population.
Local Treatment Failure
Five patients (7.6%) in the stereotactic ablative body radiotherapy group and 2 (6.5%) in the standard radiotherapy group did not receive assigned treatment, and an additional 4 patients in each group withdrew before completing the study.
Median follow-up for local treatment failure was 2.6 years in the stereotactic ablative body radiotherapy group and 2.1 years in the standard radiotherapy group. Median time to local treatment failure was not reached in either group. Local progression was observed in 9 patients (14%) in the stereotactic ablative body radiotherapy group vs 11 (31%) of the standard radiotherapy group (hazard ratio = 0.32, P = .0077). Local control at 2 years was 89% in the stereotactic ablative body radiotherapy group vs 65% in the standard radiotherapy group. Median overall survival was 5 years in the stereotactic ablative body radiotherapy group vs 3 years in the standard radiotherapy group (HR = 0.53, P = .027).
Toxicity
Among patients treated with stereotactic ablative body radiotherapy, 1 had a grade 4 adverse event (dyspnea) and 7 had grade 3 adverse events (cough in 2; and hypoxia, lung infection, weight loss, dyspnea, and fatigue in 1 each, respectively) related to treatment. In the standard radiotherapy group, 2 patients had grade 3 adverse events (both chest pain).
The investigators concluded, “In patients with inoperable, peripherally located stage I NSCLC, compared with standard radiotherapy, [stereotactic ablative body radiotherapy] resulted in superior local control of the primary disease without an increase in major toxicity. The findings of this trial suggest that [stereotactic ablative body radiotherapy] should be the treatment of choice for this patient group.”
David Ball, MD, of Peter MacCallum Cancer Centre, Melbourne, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was supported by The Radiation and Optometry Section of the Australian Government Department of Health, with the assistance of Cancer Australia and by the Cancer Society of New Zealand and the Cancer Research Trust New Zealand. The study authors' full disclosures can be found at thelancet.com.
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