Metabolic (FDG-PET) response after radical radiotherapy/chemoradiotherapy for non-small cell lung cancer correlates with patterns of failure.

Background: We previously reported that F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) response correlated strongly with survival after radical radiotherapy (RT)/chemoradiotherapy for non-small cell lung cancer (NSCLC). PET-response, survival and patterns of failure data are presented with long-term follow-up.
Methods: Pre- and post-treatment FDG-PET scans were performed for 88 patients after concurrent platinum-based radical chemo/RT (n = 73) or radical RT alone (n = 15). PET responses were prospectively assessed as either complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), or progressive metabolic disease (PMD).
Results: RT was 60 Gy in 30 fractions in 6 weeks. Follow-up PET was performed at a median of 70 days after treatment. PET responses were: CMR, n = 40 (45%); PMR, n = 32 (36%); SMD, n = 5 (6%) and PMD 11 (13%). Estimated median survival after follow-up PET was 23 months; median follow-up duration 35 months. One and 2 year survival after follow-up PET was 68% and 45%, respectively. Median survival for CMR and non-CMR patients was 31 and 11 months, respectively (p = 0.0001). One-year survival for CMR and non-CMR patients was 93% and 47%, respectively and 2 years survival was 62% and 30%, respectively. Excluding PMD patients, non-CMR patients had higher rates of local failure (HR 2.15, p = 0.009) and distant metastasis (HR 2.05, p = 0.041) than CMR patients. By last follow-up, 20 of 40 CR patients (50%) had PMD, with local failure (n = 8), distant metastasis (n = 2) or both (n = 10).
Conclusions: Attainment of CMR after radical RT/chemoRT for NSCLC bestows superior freedom from local and distant relapse; late local relapse is common.