Positron Emission Tomography in T3/T4 Non-Small Cell Lung Cancer After Induction Chemoradiotherapy

Background. To predict pathological response and survival in T3/T4 non-small cell lung cancer after induction chemoradiotherapy by assessing fluorodeoxyglucose uptake with positron emission tomography. Methods. In this retrospective observational study, standard uptake values of whole tumors and extrapulmonary involvement sites were measured after induction chemoradiotherapy. The values were then compared with pathological responses and recurrence-free survival. Results. Fifty-seven patients with clinical T3/T4 tumors were treated by chemoradiotherapy followed by surgery. Pathological complete response was observed in 33% of patients (19 of 57). With the cutoff value of 3.3 for whole tumor fluorodeoxyglucose uptake for estimating complete response, 38% patients (9 of 24) with values lower than the cutoff value were false-negative. Tumor remission at extrapulmonary involvement sites was observed in 82% patients (47 of 57), and the cutoff value of the extrapulmonary uptake was 3.0 without any false negatives. Recurrence-free survival was significantly better in patients with values lower than both the whole- and extrapulmonary-uptake cutoff values than in patients with higher values (P = .016 and P = .001, log-rank test, respectively). Among 7 patients who avoided en bloc resections of involved structures because of lowered extrapulmonary uptakes and negative findings in intraoperative frozen sections, none experienced margin recurrence. Conclusions. Even when whole tumor uptakes in patients with T3/T4 tumors markedly decrease after induction chemoradiotherapy, surgical treatment is still indicated because of possible residual tumors. Tumor remission at extrapulmonary involvement sites could be predicted by extrapulmonary uptake values. Both whole- and extrapulmonary-uptake values after induction chemoradiotherapy could be used to predict prognosis.