The intrathoracic lymph node ratio seems to be a better prognostic factor than the level of lymph node involvement in lung metastasectomy of colorectal carcinoma.

OBJECTIVES: Data on thoracic lymph node involvement (LNI) in lung metastasis of colorectal cancer (CRC) are conflicting, with a 5-year overall survival (OS) ranging from 6 to 40%. We aimed to evaluate whether there are subgroups of patients according to the lymph node ratio (LNR).

METHODS: We retrospectively reviewed the data from 106 patients who underwent a thoracic procedure for CRC lung metastasis with pathologically proven thoracic LNI.

RESULTS: In the univariate analysis, the median OS was significantly poorer for a pN2 location of LNI (26 vs 16 months, P = 0.04), LNR ≥50% (30 vs 17 months, P = 0.005), high preoperative CEA (32 vs 16 months, P = 0.02), hepatic metastases (27 vs 11 months, P <0.0001) and disease-free survival < 24 months (32 vs 17 months, P = 0.05). When pN1 and pN2 patients were staged according to the LNR, the median OS was significantly better for an LNR <50% (27 vs 17 months for pN1, 32 vs 12 months for pN2, P = 0.01). In the multivariate analysis, a high preoperative CEA [hazard ratio (HR): 2.256 (1.051-4.841), P = 0.04], pN1 status [HR: 0.337 (0.162-0.7), P = 0.004] and the absence of hepatic metastases [HR: 0.395 (0.180-0.687), P = 0.02] remained significant prognostic factors. There was an upward trend for patients with LNR <50% [HR: 0.565 (0.296-1.082), P = 0.08]. Otherwise, low LNR was significantly associated with a decreased risk of loco-regional recurrence (HR: 0.36, 95% confidence intervals: 0.14-0.96, P = 0.04).

CONCLUSIONS: The LNR seems to be a more reliable prognostic factor than LNI for CRC lung metastasis. Prospective studies are necessary.