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The aim of our study was to evaluate the pattern of local failure after stereotactic body radiotherapy (SBRT) of non small cell lung cancer (NSCLC) lesions relating to different type of 18F-FDG positron emission tomography (PET) response.Thirteen NSCLC patients for a total of 15 lesions (primary early or locally advanced and metastases) underwent PET before and 6 months after SBRT. Maximum standard uptake value (SUVmax)2.5 was considered as cut off for complete response (CR) while lesion reductionor =50% with residual value above 2.5 for partial response (PR).With a median follow up of 30 months pre- and post-SBRT mean SUV max values were 8.2 (range 14.2-3.7) and 2.4 (range 12.9-0), respectively. No "in field recurrence" was observed while 3 cases of "out field recurrence" occurred as regional nodes progression at 7.8 and 14 months after treatment. Three years overall survival, local control and distant metastases free survival were respectively 66.7%, 63.3% and 44.4%. Actuarial 75% and 53.3% 3-year local control, 60% and 40% 3-years distant metastases free survival were observed for complete and partial PET response, respectively, after SBRT. Thereafter, 60% and 50% 3-year overall survival were observed for complete and partial response.Clinical results were significantly better for "responder" than "non responder" and for "complete" than "partial response" group. Moreover, our data seem to confirm that a significant subset of patients maintain a low metabolic activity without developing local relapse on longer follow up.