P23. PET-CT confirms high rate of complete remissions among patients with advanced EGFR positive NSCLC treated with intercalated therapy

Background: With standard radiology, distinction between partial remissions (PR) and complete responses (CR) is often difficult. Here we present experience with positron emission tomography/computed tomography (PET/CT) to evaluate metabolic response to treatment in a single-arm Phase 2 clinical trial of intercalated chemotherapy and erlotinib for advanced epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC).

Patients and methods: Eligible patients were chemo-naive, had advanced NSCLC with activating EGFR mutations, fulfilled the standard criteria for platin-based chemotherapy and provided written consent to participate in the trial. As induction, patients received intercalated therapy with gemcitabine (1,250 mg/m², days 1 and 4), cisplatin (75 mg/m², day 2) and erlotinib (150 mg on days 5-15). This treatment was repeated every 3 weeks for four to six cycles, followed by maintenance erlotinib. In addition to standard radiologic examinations, PET-CT was performed prior to treatment and after 6 months.

Results: Thirty patients entered the trial and were evaluable both by radiology and PET-CT. With the exception of a single patient in Stage IIIB, all others had distant metastases in lung [15], bone [19] and brain [13]. Treatment was well tolerated; grade 4 toxicity included three cases of thrombo-embolic events and two cases of grade 4 neutropenia. PET-CT confirmed CR and PR in 16 and 9 patients, respectively [response rate (RR) 83%]. Correlation between radiologic and metabolic response is shown in the Table 1. Median time to progression was 21.2 months, and median survival was 32.5 months.

Table 1 Correlation between radiologic and metabolic response
Full table

Discussion and conclusions: PET-CT scanning confirmed high efficacy of intercalated chemotherapy and erlotinib for patients with advanced NSCLC harbouring EGFR activating mutations. Assessment of metabolic response confirmed CR also for patients with bone metastases who are not evaluable by standard radiological methods. In small Phase 2 clinical trials, precise evaluation of response to treatment may provide additional information of importance for interpretation of the results.

Keywords: Non-small cell lung cancer (NSCLC); positron emission tomography/computed tomography (PET/CT); epidermal growth factor receptor (EGFR) mutations