Does Incidental Irradiation With Doses Below 50 Gy Effectively Reduce Isolated Nodal Failures in Non–Small-Cell Lung Cancer: Dose–Response Relationship
Received 12 April 2008; accepted 7 July 2008.
Purpose
To evaluate the dose–response relationship for a wide range of doses lower than 50 Gy delivered to the hilar and mediastinal lymph node stations from incidental irradiation in 220 patients with non–small-cell lung cancer (NSCLC) treated with three-dimensional conformal radiotherapy. The endpoint was isolated nodal recurrence (INR) in stations that were initially negative.
Methods and Materials
The individual responses of 2596 nodal stations were analyzed. Different fractionation schedules were used in different patients. Total prescribed tumor doses ranged from 52 Gy to 74 Gy given over 16–56 days. There were 1198 nodal stations (46%) within and 1398 stations beyond the elective nodal irradiation (ENI) volumes. The INR incidence was estimated for six dose levels ranging from 5 ± 5 Gy to ≥56 Gy.
Results
There were a total of 25 INRs in 17 patients (8%). The incidence of INR within the electively treated volumes was 0.58%, compared with 1.28% in nodal stations beyond the ENI. Almost 80% of the INRs occurred during 10 months of follow-up. A strong dose–response relationship was seen for the lower “incidental” doses, most of which were less than 50 Gy. As the dose increased from 5 ± 5 Gy to 40 ± 5 Gy, the rate of freedom from INR increased from 12% to 76% (p = 0.005).
Conclusions
There is evidence of a dose–response relationship between a reduction in the rate of INR and doses lower than 50 Gy. This suggests that incidental irradiation can eradicate at least some subclinical metastases in regional lymph nodes.
∗Department of Radiotherapy, Cancer Center, Maria Sklodowska-Curie Memorial Institute, Warsaw, Poland
†Department of Radiotherapy, Center of Oncology, Maria Sklodowska-Curie Memorial Institute, Gliwice, Poland
‡Department of Radiation Oncology, University of California, Los Angeles Medical Center, Los Angeles, CA
Reprint requests to: Bogusław Maciejewski, M.D., Department of Radiotherapy, Cancer Centre, Maria Sklodowska-Curie Memorial Institute, Wybrzeże Armii Krajowej 15, 44-101 Gliwice, Poland. Tel: (+48) 32-231-54-87; Fax: (+48) 32-230-78-07
ABSTRACT