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Stereotactic body radiotherapy safe, effective for tumor control in centrally located NSCLC
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High-dose stereotactic body radiotherapy appeared associated with a low rate of dose-limiting toxicities and high rates of tumor control among patients with centrally located non-small cell lung cancer, according to data from the phase 1/2 NRG Oncology/RTOG 0813 trial published in Journal of Clinical Oncology.
“The patients who enrolled into NRG-RTOG 0813 were medically inoperable with early-stage lung cancer, mostly elderly and with comorbidities,” Andrea Bezjak, MD, professor in the departments of radiation oncology and health policy management and evaluation at University of Toronto and staff radiation oncologist at Princess Margaret Hospital, said in a press release. “The 2-year overall survival rates for patients at the two highest doses [of SBRT] were 70%, which is comparable to patients with peripheral early-stage tumors that were treated by SBRT.”
In the multi-institutional, seamless study, Bezjak and colleagues evaluated 100 patients (median age, 72 years; 57% women) with biopsy-confirmed, node-negative, centrally located NSCLC staged T1 (65%) or T2 (35%) by PET. Most patients (45%) had squamous cell carcinoma.
The organs most at risk/in closest proximity to planning target volume included the main bronchus and large vessels.
The researchers assigned patients to a dose-escalating, five-fraction SBRT schedule ranging from 10 Gy per fraction to 12 Gy per fraction administered over 1.5 to 2 weeks. They assessed patients prior to each SBRT fraction, at 6 weeks, every 3 months for 2 years, every 6 months for the next 2 years, and each year thereafter.
Determining the maximum tolerated dose of SBRT — at which likelihood of a dose-limiting toxicity was closest to 20% without exceeding it — served as the primary objective. The researchers defined dose-limiting toxicity as any predefined, treatment-associated, grade 3 or worse toxicity that occurred within the first year of treatment.
Secondary objectives included rates of grade 3 or higher adverse events aside from dose-limiting toxicities, adverse events that occurred beyond the first year, PFS and OS.
Median follow-up was 37.9 months (range, 1.7-75).
Dose-limiting toxicities occurred in five patients within the first year of treatment. The maximum tolerated dose of SBRT was 12 Gy per fraction, the highest dose permitted by protocol. The probability of a dose-limiting toxicity with this dose was 7.2% (95% CI, 2.8-14.5), well below the target rate of 20% specified by protocol.
The 71 evaluable patients in the 11.5 Gy-per-fraction and 12 Gy-per-fraction cohorts demonstrated 2-year rates of 89.4% (90% CI, 81.6-97.4) and 87.9% (90% CI, 78.8-97) for local control; 67.9% (95% CI, 50.4-80.3) and 72.7% (95% CI, 54.1-84.8) for OS; and 52.2% (95% CI, 35.3-66.6) and 54.5% (95% CI, 36.3-69.6) for PFS.
“This trial demonstrated our ability to provide local control and potential for cure in patients with centrally located, node-negative tumors in multiple institutions, while maintaining plan qualities, achieving good patient outcomes and only allowing modest rates of toxicity,” Bezjak said. – Jennifer Byrne
Disclosures: The study was supported by NCI grants. Bezjak reports a consultant/advisory role with AstraZeneca; a speakers bureau role with AbbVie; and travel, accommodations and expenses from AbbVie and AstraZeneca. Please see the study for all other authors’ relevant financial disclosures.
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