A Preoperative Risk Classification for Synchronous Oligometastatic Non-Small Cell Lung Cancer

Background: In previous multicentre studies, the longest survival was observed in synchronous lung oligometastatic patients without pN2 disease. This paper aimed to identify preoperative favourable prognostic factors and propose a preoperative classification for categorising the synchronous oligometastatic non-small cell lung cancer (NSCLC). Methods: A retrospective review of prospectively collected patients was performed. The inclusion criteria were: synchronous oligometastatic NSCLC (≤5 extrapulmonary metastases), radical surgical treatment of the primary tumour and all metastatic sites (2005–2018). Exclusion criteria were: palliative surgery, recurrent lung cancer, low-performance status, follow-up information unavailable. The reverse Kaplan – Meier method estimated median overall survival (OS) and progression-free survival. A stratified backward stepwise Cox regression model was employed for multivariable survival analyses. A prognostic grouping considering all the relevant prognostic factors simultaneously was constructed, and a Receiver Operating Characteristic (ROC) curve was generated. Hosmer-Lemeshow χ statistics was used for measuring OS calibration within groups. Findings: 281 patients were included. Data from the Cox regression model were used to construct a prognostic risk classification. Four parameters (age ≤65 years, site of metastasis, clinical nodal status, and induction treatment) were used to build a risk classification. Group A: no risk factors (age ≤65 years, lung/brain metastasis, cN0, induction treatment); Group B: one risk factor (age >65 years or no lung/brain metastasis or cN1–2 or no induction treatment); Group C: two risk factors; Group D: ≥3 risk factors. The Area Under the Curve (AUC) was 0.56 (95% CI: 0.49–0.62), Hosmer-Lemeshow χ statistics was 21.3 (3 degrees of freedom, p=0.0042). Interpretations: Patient selection is critical in identifying the proper subsets of oligometastatic NSCLC. After clinical validation, this preoperative risk classification might support decision-making during the multidisciplinary team assessment and patient selection for enrolment in future randomised trials. Funding: This work was partially supported by the Italian Ministry of Health with Ricerca Corrente and 5 x 1000 funds. Declaration of Interest: All authors have no conflict of interest to declare. Ethical Approval: This research was carried out following the Helsinki Declaration 10. The Ethical Committee authorised the study (785/19).