Value of F-18-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography in non-small-cell lung cancer for prediction of pathologic response and times to relapse after neoadjuvant chemoradiotherapy

Purpose: To determine the value of combined positron emission tomography/computed tomography (PET/CT) during induction chemotherapy (CTx) followed by chemoradiotherapy (CTx/ RTx) for non-small-cell lung cancer to predict histopathologic response in primary tumor and mediastinum and prognosis of the patient. Experimental Design: Fifty consecutive patients with locally advanced non-small-cell lung cancer received induction therapy and, if considered resectable, proceeded to surgery (37 of 50 patients). Patients had at least two repeated F-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT scans either before treatment (to) or after induction CTx (t(1)) or CTx/RTx (t(2)). Variables from the PET/CTstudies [e.g., lesion volume and corrected maximum standardized glucose uptake values (SUVmax,corr)] were correlated with histopathologic response (graded as 3, 2b, or 2a: 0%, > 0-10%, or > 10% residual tumor cells) and times to failure. Results: Primary tumors showed a percentage decrease in SUVmax,corr during induction significantly larger in grade 2b/3 than in grade 2a responding tumors (67% versus 34% at t(1), 73% versus 49% at t(2); both P < 0.005). SUVmax,corr at t(2) was significantly correlated with histopathologic response in tumors smaller than the median volume (7.5 cm(3); r = -0.54, P = 0.02). In the mediastinal lymph nodes, SUVmax,corr values at t2 predicted an ypN(o) status with a sensitivity and specificity of 73% and 89%, respectively (SUVmax,corr threshold of 4.1, r = -0.54, P = 0.0005). Freedom from extracerebral relapse was significantly better in grade 2b/3 patients (86% at 16 months versus 20% in 2a responders; P = 0.003) and in patients with a greater percentage decrease in SUVmax,corr in the primary tumor at t2 in relation to to than in patients with lesser response (83% at 16 months versus 43%; P = 0.03 for cutoff points between 0.45 and 0.55). Conclusions: SUVmax,corr values from two serial PET/CTscans, before and after three chemotherapy cycles or later, allow prediction of histopathologic response in the primary tumor and mediastinal lymph nodes and have prognostic value.