The survival rate of non–small cell lung cancer (NSCLC) patients has remained low over the last few years. To date, the standard treatment response is based on RECIST.
Metabolic changes assessed by 18F-FDG PET/CT imaging are often more indicative of the effects of therapy compared to morphological changes. The aim of this study was to assess the clinical value of PET for an early prediction of tumor response to Erlotinib after failure of at least one prior chemotherapy regimen. The metabolic treatment response using EORTC and PERCIST was compared with RECIST.
20 patients underwent a PET/CT scan before and after administration of 3 doses at 48 h. For 14 patients, a further metabolic follow-up was planned at the end of treatment, 45 days from the start of therapy. Metabolic variations were analyzed according to PERCIST and EORTC. CT scans were performed before and 45 days after the treatment. The morphological response was evaluated by RECIST.
Disease-Free Survival (DFS) and Overall Survival (OS) time of response classifications were calculated. Patients were grouped into responders (complete response –CR- and partial response –PR-) and non-responders (stable disease –SD- and progressive disease –PD-).
Results of metabolic evaluation at 48 h, as regards EORTC, showed 7 PMR, 10 SMD and 3 PMD. According to PERCIST: 2 PMR, 17 SMD, and 1 PMD. The analyses showed that only EORTC proved a significant prognostic factor for predicting DFS and OS with a median of 103 and 410 days in responder patients. Non-responders had a median DFS of 47 days and a median OS of 104 days. PERCIST was not a significant factor associated with DFS and OS.
Results at 45 days were as follows: for RECIST 4 PR and 10 PD; according to EORTC 5 PMR, 5 SMD, 4 PMD whereas PERCIST results are 4 PMR, 6 SMD and 4 PMD. For responder patients, median DFS was 287.5 days for the RECIST and PERCIST and 79.5 days for EORTC. For non-responder patients median DFS was comparable for all response criteria (about 50 days). Only RECIST and PERCIST showed a good prognostic factor for OS: 480 vs 174 days (responders vs non-responders).
An accurate method for monitoring therapy response is mandatory for better patient management. RECIST is known to have some limitations being dependent on anatomic changes whereas metabolic data overcome such limitations. At 48 h, according to the EORTC, this study confirms that PET may be useful in the early identification of patients who would benefit from Erlotinib treatment. For treatment response, at 45 days, PERCIST is closely related to prognosis and could be considered an appropriate method to discriminate responders from non-responders.

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