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ORAL 34 - Quality/Survival/Prognosis in Localized Lung Cancer (ID 153)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Localized Disease - NSCLC
- Presentations: 1
ORAL34.05 - Survival Implications of Variation in the Lymph Node (LN) Count in ACOSOG Z0030 (Alliance) (ID 654)
16:45 - 18:15 | Author(s): M. Allen
Variation in the thoroughness and accuracy of pathologic lymph node (LN) staging may contribute to within-stage variation in survival after curative-intent resection of non-small-cell lung cancer. Accurate staging mandates effective collaboration between surgeons and pathologists. ACOSOG Z0030 tightly controlled surgeon practice, but not pathology practice. We tested the impact of the thoroughness of pathologic examination (using the number of examined LNs as a surrogate) on detection of LN metastasis and survival.
We reanalyzed the mediastinal LN dissection arm of ACOSOG Z0030, using linear regression to examine the clinical and demographic factors associated with LN count, Cox proportional hazards models to determine the association between the number of LNs examined and survival of patients with pN0 and pN1 disease, and logistic regression to determine association of number of LN examined and the discovery of unexpected N2 LN metastasis. Overall (OS) and recurrence-free survival (RFS), were analyzed without and with adjustment for T-category.
The 524 patients, had a mean age of 66.8 years, and were 52% male. Forty-four percent had adenocarcinoma, 27% squamous, 4% large cell, and 25% ‘other’ histology; 96% had T1/2 disease. Four hundred and thirty-nine (84%) were pN0, 63 (12%) pN1, and 21 (4%) pN2. In patients with pN0, pN1, and pN2 respectively, the mean number of mediastinal LNs examined was 13.5, 12.9, and 17.4; station 10 LNs were 2.4, 2.7, and 2.5; station 11-14 LNs were 4.6, 6.2, and 6.2; total LNs (from all stations) were 19.7, 21.3, 25. Tumor histology and pN-category were the only factors associated with the number of LNs examined: patients with squamous histology tended to have the most number of non-hilar N1 LNs examined (p<0.001); patients with pN1/N2 had more non-hilar N1 nodes than those with pN0 (p=0.005); those with pN2 had more N2 nodes examined than those with pN0 or pN1 (p=0.085). There was a consistent association between the number of LNs examined and survival. Patients with pN0 had better OS (HR 0.96; p=0.12) and RFS (HR 0.97; p=0.2) with examination of more non-hilar nodes; patients with pN1, had better OS and RFS with increased examination of LNs from N2 (OS HR=0.96, p=0.059; RFS HR=0.95, p=0.03) and all stations (OS HR=0.97, p=0.048; RFS HR=0.96, p==0.012). Adjustment for T-category strengthened these relationships between the number of LNs, pN-stage and survival. The likelihood of discovering N2 disease was associated with increased examination of LNs from mediastinal (odds ratio=1.04; p=0.035) and all stations (OR=1.03; p=0.035).
Despite uniformly thorough surgical hilar/mediastinal LN harvesting, the number of LNs examined was associated with the likelihood of detecting nodal metastasis, and survival. Patients with more LNs examined were more likely to have LN metastasis, examination of more LNs was associated with better survival in patients within the same pN-category. This may indicate an effect of variable thoroughness in pathologic examination processes on the accuracy and prognostic value of the pathology nodal staging system. Heterogeneity in the cancer immune response may be an alternative hypothesis to explain these findings.