Postoperative radiation therapy does not improve the survival of elderly patients following complete resection of stage III non–small cell lung cancer with N2 lymph node involvement, according to a retrospective study of the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) registry linked to Medicare records.
"Clinicians should refrain from widespread use of PORT [postoperative radiation therapy] in elderly patients with this cancer subtype until we know more," especially given its side effects, said lead author and pulmonologist Dr. Juan P. Wisnivesky of the Mount Sinai School of Medicine in New York, and his coauthors.
Although the value of PORT in N2-positive disease has been uncertain, it’s often used in these patients for whom the extent of lymph node involvement greatly affects prognosis. Long-term survival drops from 70% of patients without lymph involvement to 20%-35% of patients with microscopic N2 disease, the authors noted.
More than 54% (710) of the 1,307 patients identified in the SEER-Medicare database received postoperative radiation. They were all diagnosed between 1992 and 2005. Patients who underwent limited resection, received preoperative chemotherapy or radiation therapy, or died with 30 days of surgery were excluded from the current study. The results were published online Feb. 13 in Cancer (2012[doi:10.1002/cncr.26585]).
The investigators reported patients who received PORT tended to be younger and higher in income than those who did not, but otherwise were evenly matched for race, gender, and comorbidities. Nearly half, 42%, of the PORT group was in the group aged 65-70 years, 34% aged 71-75, and 24% older than 75years.
Tumor status, histology, and rates of lobectomy and pneumonectomy were similar whether patients received PORT or not. Patients in the PORT group were more likely to receive adjuvant chemotherapy; however, 36% did so vs. 23% of the group not given PORT.
PORT did not improve 1 or 3-year survival in an unadjusted analysis or in a Cox model adjusting for propensity scores (HR, 1.11; 95% confidence interval 0.97-1.27). "Analyses limited to patients treated with or without chemotherapy" as well as "intermediate or high complexity [radiation therapy] planning ... showed similar results," the researchers noted.
The SEER study "was powered to detect relatively small benefits of PORT," they said. "The generalizability of our results should be excellent"
SEER doesn’t record disease recurrence, so "we were not able to assess whether PORT is associated with...increased disease-free survival or lower rates of local recurrence." Similarly, because the registry does not record total radiation dose or fractionation schedule, "We were not able to assess the impact of these factors on lung cancer survival," the researchers cautioned.
The results are consistent with the conclusions of the PORT Meta-Analysis Trialists Group, which recommended that PORT use be limited to clinical trials until more data are available, the authors wrote. Dr. Wisnivesky, et al. said the results "highlight the importance" of enrolling patients in the ongoing French-sponsored, phase III Lung Adjuvant Radiotherapy Trial, known as Lung Art.
Dr. Wisnivesky has received a research grant from GlaxoSmithKline and lecture honorarium from Novartis. His coauthors reported no relevant conflicts of interest. The study was funded by the National Cancer Institute.