About 40% of patients with stage I lung adenocarcinoma will have recurrent disease; there are currently no predicting factors that can identify patients at highest risk for recurrence and therefore candidates for more aggressive surveillance and/or adjuvant therapy. The aim of our study was to investigate the predictive value of preoperative 18F-FDG PET/CT SUVmax in stage I lung adenocarcinoma and the correlation with histologic predominant subtypes and the Sica-Travis score (a proposed grading system of lung adenocarcinomas based on histologic pattern).
We identified 152 consecutive patients (103 men, 49 women) with pathological stage I lung adenocarcinoma submitted to lobectomy and mediastinal lymph-nodes dissection between 2007 and 2014. Histologic predominant subtypes were classified according to the IASLC/ATS/ERS lung adenocarcinoma classification and Sica-Travis Score was calculated for all cases. All patients underwent 18F-FDG PET/CT at least 1 month before surgery and SUVmax value was calculated for each lesion (range 1-5 cm). Five-year Disease-Free Survival (DFS) and Overall Survival were assessed on August 2014 in those patients with at least 2 years follow-up (122/152).
Among 152 patients we observed 14 lepidic (9%), 61 acinar (40%), 35 papillary (23%), 34 solid (23%) and 8 other uncommon (5%) predominant subtypes. Mean SUVmax was 3.71±1.39 for lepidic, 7.4±3.93 for acinar, 6.6±3.78 for papillary, 10.7±4.9 for solid, 10.7±2.3 for other uncommon predominant subtypes. Mean Sica Travis score was 3±0.78 (median 3), 4.37±0.68 (median 4), 4.54±0.65 (median 5), 5.85±0.42 (median 6), 5.71±0.48 (median 6) for lepidic, acinar, papillary, solid and other uncommon predominant subtypes, respectively. Different subtypes showed significant differences when SUVmax and Sica Travis Score were compared (Student t-test, p<0.005), except between acinar and papillary and between solid and other uncommon subtypes. After a mean follow-up of 43±20 month, 84 patients were disease-free (DF) whereas 38 patients had recurrent disease (RD); PET/CT SUVmax was 7.56 ±3.21 for DF and 9.8±4.61 for RD patients (Student t-test: p=0.03). Five-year DFS was 100%, 77%, 64% and 47% and 28% for lepidic, acinar, papillary, solid and other uncommon subtypes, respectively (Log-rank test, p=0.0001).
18F-FDG PET/CT SUVmax seems to well correlate with the predominant histologic pattern according to the new IASLC/ATS/ERS lung adenocarcinoma classification and to the Sica-Travis Score.18F-FDG PET/CT SUVmax represents an important prognostic factor in patients with stage I adenocarcinoma of the lung; high SUVmax could be considered for a further stratification of patients with an increased risk of recurrence, and can impact on patients’ management.
*A grading system of lung adenocarcinomas based on histologic pattern is predictive of disease recurrence in stage I tumors. Sica G. et al; Am J Surg Pathol, 2010;34(8):1155-62