SYDNEY – Stereotactic lung radiotherapy for centrally located non–small cell lung carcinomas can result in overall survival outcomes that are similar to those for peripheral tumors, but with an increased risk of local failure and pneumonitis, based on the results of an analysis of a large international data set.
Overall survival at 3 years was similar for 100 centrally located non–small cell lung cancers – defined as being located within 2 cm of the proximal bronchial tree – and for 869 peripheral tumors treated with stereotactic body radiotherapy (50% vs. 51%; P = .70), based on data presented by Dr. Maria Werner-Wasik at a world conference on lung cancer, sponsored by the International Association for the Study of Lung Cancer.
Dr. Maria Werner-Wasik
Also, the two groups did not significantly differ in the incidence of chest wall pain and myositis, rib fracture, and dermatitis. Patients with central tumors had a significantly higher incidence of grade 2 or above pneumonitis (8% vs. 1% in those with peripheral tumors; P less than .001). The incidence of grade 3 pneumonitis was similar between the two groups.
Central tumors were associated with a lower rate of cause-specific survival than were peripheral tumors (75% vs. 88%; P less than .001) and higher local failure rates at 3 years (16.2% vs. 5.9%; P less than .001) and 5 years (20.4% vs. 8.3%; P less than .001).
Dr. Werner-Wasik said central tumors had fallen into a "no-fly zone" for stereotactic body radiotherapy since an earlier trial showed unacceptable levels of toxicities from treating centrally located lung tumors. Thereafter, prospective trials examined only peripheral tumors.
"If you have a central tumor you have to do something. You can always treat with standard fractionation, but that’s not the idea. We want to give those patients (with centrally located tumors) the benefit of a short, effective regimen," said Dr. Werner-Wasik, professor and director of clinical research at the department of radiation oncology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia.
The data from the Elekta Lung Research Groupshowed a higher rate of local failure. Dr. Werner-Wasik said this was still "respectable," especially as the centrally located tumors did receive slightly less radiation than the peripheral tumors did and were significantly larger at baseline (3.1 vs. 2.4 cm; P less than .001).
"The local control was worse for central tumors versus peripheral tumors, presumably because we treated them with lower biologically effective doses," said Dr. Werner-Wasik in an interview. "But also, these tumors were slightly different ... as illustrated by higher values on PET scans."
Results from the upcoming RTOG 0813 study may shed more light on the question of how to deliver stereotactic body radiotherapy to centrally located tumors, she said. "We have to find an effective central dose radiation fractionation and total dose so these patients do not suffer complications and yet are assured local control."
The research was partly supported by a grant from Elekta, makers of stereotactic body radiation technology products. Dr. Werner-Wasik said she had no relevant financial disclosures. The Elekta Lung Research Group includes participants from William Beaumont Hospital in Royal Oak, Mich.; Princess Margaret Cancer Centre, Toronto; Thomas Jefferson University, Philadelphia; Julius Maximilian University of Würzburg (Germany); and the Netherlands Cancer Institute–Antoni van Leeuwenhoek Hospital in Amsterdam.