Pattern of recurrence of pN2 non-small-cell lung cancer: should postoperative radiotherapy be reconsidered?

OBJECTIVES The prognosis of patients with mediastinal lymph node (LN) metastasis (pN2 stage III disease) is still unsatisfactory. Both systemic and local recurrence should be prevented after curative surgery. The aim of this study was to explore the pattern of recurrence in patients with completely resected pN2 non-small-cell lung cancer (NSCLC) in the era of adjuvant chemotherapy. METHODS We investigated 337 patients with completely resected cN0-1 and pN2 NSCLC from 2005 to 2016 at National Cancer Center Hospital, Japan. The patterns of recurrence were compared between patients who were managed by observation alone and those with adjuvant chemotherapy. In patients with regional LN recurrence, the pattern and site of recurrence were also explored. RESULTS There were 195 (58.5%) men and 142 (41.5%) women with a mean age of 63.2 years. Fifty-five (16.3%) patients developed only regional LN recurrence, 116 (32.6%) patients developed only distant recurrence and 65 (19.3%) patients developed both regional LN recurrence and distant recurrence. The difference in the pattern of recurrence between patients with observation alone and those with adjuvant chemotherapy was not statistically significant (P = 0.145). As for the pattern of regional LN recurrence, 68 (20.2%) patients had LN recurrence inside the systematic nodal dissection area. CONCLUSIONS Regional LN recurrence was observed in >30% of patients with completely resected pN2 NSCLC. About 20% of patients had recurrence inside the systematic nodal dissection area. Postoperative radiotherapy might be considered as an additional treatment strategy for these patients.