Postoperative radiotherapy is associated with better survival in non-small cell lung cancer with involved N2 lymph nodes: results of an analysis of the National Cancer Data Base.
BACKGROUND
Use of postoperative radiotherapy (PORT) in non-small-cell lung cancer remains controversial. Limited data indicate that PORT may benefit patients with involved N2 nodes. This study evaluates this hypothesis in a large retrospective cohort treated with chemotherapy and contemporary radiation techniques.


METHODS
The National Cancer Data Base was queried for patients diagnosed 2004-2006 with resected non-small-cell lung cancer and pathologically involved N2 (pN2) nodes also treated with chemotherapy. Multivariable Cox proportional hazards model was used to assess factors associated with overall survival (OS). Inverse probability of treatment weighting (IPTW) using the propensity score was used to reduce selection bias. OS was compared between patients treated with versus without PORT using the adjusted Kaplan-Meier estimator and weighted log-rank test based on IPTW.


RESULTS
Two thousand and one hundred and fifteen patients were eligible for analysis. 918 (43.4%) received PORT, 1197 (56.6%) did not. PORT was associated with better OS (median survival time 42 months with PORT versus 38 months without, p = 0.048). This effect was significant in multivariable and IPTW Cox models (hazard ratio: 0.87, 95% confidence interval: 0.78-0.98, p = 0.026, and hazard ratio: 0.89, 95% confidence interval: 0.79-1.00, p = 0.046, respectively). No interaction was seen between the effects of PORT and number of involved lymph nodes (p = 0.615).


CONCLUSIONS
PORT was associated with better survival for patients with pN2 nodes also treated with chemotherapy. No interaction was seen between benefit of PORT and number of involved nodes. These findings reinforce the benefit of PORT for N2 disease in modern practice using the largest, most recent cohort of chemotherapy-treated pN2 patients to date.
Departments of *Radiation Oncology, †Hematology and Oncology, ‡Surgery, §Biostatistics and Bioinformatics Shared Resource, ‖Rollins School of Public Health, and the ¶Winship Cancer Institute, Emory University, Atlanta, GA.
John L
JL
Mikell
Theresa W
TW
Gillespie
William A
WA
Hall
Dana C
DC
Nickleach
Yuan
Y
Liu
Joseph
J
Lipscomb
Suresh S
SS
Ramalingam
Raj S
RS
Rajpara
Seth D
SD
Force
Felix G
FG
Fernandez
Taofeek K
TK
Owonikoko
Rathi N
RN
Pillai
Fadlo R
FR
Khuri
Walter J
WJ
Curran
Kristin A
KA
Higgins
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy; D003131:Combined Modality Therapy; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D009369:Neoplasms / Q000473:pathology / Q000601:surgery*; D011182:Postoperative Care; D011379:Prognosis; D018714:Radiotherapy, Adjuvant / Q000379:methods*; D012189:Retrospective Studies; D015996:Survival Rate