Utility of PET for Nodal Staging in Subsolid Clinical Stage IA (T1 N0) Lung Adenocarcinoma

Abstract

Background: Positron emission tomography (PET) is the standard of care for non-small cell lung cancer (NSCLC) clinical staging, but it may have limited utility in evaluating subsolid lung adenocarcinomas that can have relatively indolent behavior without hypermetabolic activity.

Methods: The sensitivity and specificity of PET for determining pathologic lymph node status and disease-free survival were assessed in patients operated on for cT1 N0 subsolid lung adenocarcinoma from January 2006 to June 2022 (at Stanford University School of Medicine, Stanford, CA). Patients with clinical or pathologic tumor size >30 mm, hilar or mediastinal lymph node size >1cm, and purely solid tumors were excluded.

Results: PET was available in 498 of 534 (93.2%) patients and more often was used in older patients with larger and more solid tumors. The overall pathologic lymph node-positive rate was 8.4% (45 of 534). PET specificity was 95.1%, but sensitivity was only 20.0%. A tumor diameter of 18.5 mm and a solid component percentage of 62.5% had the maximum predictive accuracy for pathologic lymph node positivity, with a 0% and 1.5% rate of pathologic and PET lymph node positivity, respectively, for tumors with values lower than those thresholds. There was no significant difference in 5-year disease-free survival between individuals who did and did not undergo PET scanning (76.6% vs 96.8%; P = .07). Conversely, 134 (26.9%) patients who underwent PET scanning had 171 incidentally detected hypermetabolic lesions unrelated to lung cancer, with only 13 of 134 (9.7%) patients identified as having non-NSCLC premalignant or malignant conditions requiring further therapy.

Conclusions: PET scan use for subsolid lung adenocarcinoma has high specificity but limited sensitivity for predicting pathologic lymph node positivity. PET also has no association with disease-free survival and often detects clinically unimportant findings rather than changing lung cancer management, particularly for patients with smaller and less solid tumors.

Figure

Pie charts depicting that (A) 80% of patients with pathologic lymph node–positive (pN+) disease were missed by fluorodeoxyglucose (FDG) positron emission tomography (PET) and (B) >90% of patients with incidentally detected FDG-avid distant lesions had benign disease.