Correlation of PET/CT Findings and Histopathology after Neoadjuvant Therapy in Non-Small Cell Lung Cancer

Abstract

Objectives: Prediction of histopathological response with PET/CT scans after neoadjuvant chemoradiotherapy is limited by confounding factors which have been evaluated in this analysis. Methods:¹⁸F-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT findings [standard uptake value (SUV), residual tumor volume] were correlated with histopathological parameters of the resection specimens (tumor cell density, necrosis, scar, macrophage infiltration) in patients with locally advanced non-small cell lung cancer (stage IIIA/IIIB) after neoadjuvant induction chemotherapy (platinum-based doublet) and concurrent chemoradiotherapy (cisplatin/vinorelbine/45 Gy). Results: Sixty patients [40 male/20 female, median age 56 years (34–78)] completed induction therapy, 46 patients (stage IIIA/IIIB: 16/30; squamous cell carcinoma 41%, adenocarcinoma 48%, large cell carcinoma 11%) were resected. Pathologic complete response of the primary tumor was observed in 19 patients (41%) with a broad range of SUV_mean (0.4–9.8, mean 3.0) after neoadjuvant therapy. A high rate of histopathological complete remissions (44%) was observed in tumors with a postinduction SUV >2.5 and volumes larger than the median (7.9 cm³) before resection. SUV_mean was positively correlated with the macrophage score (r = 0.39, p = 0.007) and tumor cell density (r = 0.32, p = 0.03). Conclusions: These observations suggest that postinduction FDG uptake should be interpreted with caution in larger residual tumor volumes, since high SUV levels may be due to macrophage infiltration and not viable tumor tissue.

Is <sup>18</sup>F-FDG-PET/CT a Valid Non-Invasive Predictor for Regression Grade after Neoadjuvant Treatment in Patients with NSCLC Stage III?

“…False positive findings in 18 F-FDG-PET according to primary tumor are mostly due to inflammation or side effects by radiotherapy which could be proved by histology, as shown not only by Poettgen et al but also in our data [38] [39]. Patients with false positive findings in mediastinum represent a special problem, if 18 F-FDG-PET should play an important role as non-invasive predictor to loco-regional and systemic tumor control and basis for future therapy decisions.…”

Integrated imaging of non-small cell lung cancer recurrence: CT and PET-CT findings, possible pitfalls and risk of recurrence criteria

“…PET-CT false-positives can be explained through the increase of glycolysis, and consequently of FDG uptake, due to macrophage infiltration when inflammation is present (Fig. 9) [59]; for the same reason PET-CT should be performed at 3-6 months after irradiation, as radiation-induced inflammatory reactions can persist during this period [60]. When recurrence is suspected by CT or PET-CT, pathological confirmation may be achieved by mediastinoscopy or endo-oesophageal / endo-bronchial needle aspiration techniques (EUS-NA and EBUS-NA) sampling.…”

Predictive factors for survival in stage IIIA N2 NSCLC patients treated with neoadjuvant CCRT followed by surgery

“…For patients receiving neoadjuvant chemotherapy (CTx) or CCRT for locally advanced NSCLC, there is abundant information on histopathologic factors establishing their role in the prediction of tumor response and patient survival [6,7,[10][11][12][13][14][15][16][17][18][19]. In contrast, the predictive value of imaging factors after neoadjuvant therapy for patients' OS and recurrence is still controversial and has been discussed in only a few studies [20][21][22].…”