Survival effect of PET/CT-defined occult lymph node metastasis in the newly proposed ninth edition N descriptors: a
Xinchen Shen1, Tao Chen1, Juemin Yu1
1Department of Thoracic Surgery, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China.
Purpose:
To elucidate the potential reasons for the favourable prognosis of positron emission tomography/computed tomography (PET/CT)-defined occult N2 metastasis and its survival effect in the context of the newly proposed ninth edition N descriptors.
Methods:
A total of 3565 patients who underwent preoperative PET/CT and surgical resection for non-small cell lung cancer were retrospectively included. Survival analysis was conducted using the Kaplan-Meier method and Cox proportional hazards model.
Results:
The incidence of single-station involvement was significantly higher (p < .001) in occult N2 metastasis (117/191, 61.3%) compared to evident N2 metastasis (83/198, 41.9%). The survival rates of patients with occult N2a (single-station N2 involvement) and occult N2b (multiple-station N2 involvement) were comparable to those of patients with clinically evident N2a and N2b, respectively (adjusted p >.20 for all). Conversely, single-station involvement was associated with a markedly superior prognosis than multiple-station involvement, whether for patients with occult N2 metastasis (5-year overall survival [OS]: 62.7% vs 50.1%, adjusted p = .04) or patients with clinically evident N2 metastasis (5-year OS: 50.3% vs 36.2%, adjusted p = .03). Cox regression analysis of the pathological N2 population further indicated that multiple-station involvement was a more robust prognostic factor than occult lymph node metastasis.
Conclusions:
The favourable prognosis of PET/CT-defined occult N2 metastasis may be attributed to the discrepancy in prognosis and proportion between occult N2a and clinically evident N2b. This external validation provided substantial evidence supporting the reasonableness and robustness of the newly proposed ninth edition N descriptors.
