PET based target volume delineation in hypofractionated radiotherapy in locally advanced NSCLC: A single institution experience

Background: Chemo-radiotherapy is the standard of care of locally advanced (stage III) unresectable non-small cell lung cancers (NSCLC). Concomitant chemo-radiotherapy reduces local failure compared to sequential schedules but distant failures remain common (about 40%). Conventional radiotherapy is given in 2Gy fractions over 6−7 weeks of treatment (total dose 60−70Gy) conditioning the patent’s quality of life. Stereotactic body radiotherapy (SBRT) is effective for the treatment of early stage NSCLCs not eligible for surgical resection. The integration of positron emission tomography (PET) information for target volume delineation in radiation treatment planning is routine in many centers. We evaluated the feasibility of short course hypo fractionated radiotherapy with PET assisted visual-manual target delineation, given between chemotherapy cycles, in locally advanced NSCLCs. Methods: Patients, with a proven histological diagnosis of NSCLC, were enrolled if deem not resectable. Inclusion criteria were: maximum diameter of the primary tumor <80mm, absence of neoplastic pleural effusion and a conserved pulmonary function (FEV1 >1). All patient underwent 18FFDG PET-CT within 1 month from the beginning of the treatment and mean SUVmax was 12.6 (range 3.8–33.8). A total dose of 40 Gy was given in 5 fractions of 8Gy using volumetric modulated arch therapy and flattening filter free 6MV photon beams. Dose constraints from AAPM task group 101 were respected for organs at risk. Planning target volumes were delineated using the 18F-FDG uptake as reference and included the primary tumor and every clinically evident lymph node metastases. Platinum doublets were the preferred chemotherapy regimen (8 patients). Toxicity was evaluated according to CTCAE v4 and tumor response according to RECIST criteria 1.1 Results: From February 2014 to January 2015, 15 patients (11 males and 4 females) have been enrolled with a median age of 71 years (range 53−86). Performance status was 0 in 5 patients and 1 in the remaining. Eight were adenocarcinomas, 4 squamous cell carcinomas and 3 not otherwise specified NSCLCs. The median size of the primary tumor was 49mm (range 17−77; T1 13%, T2 13%, T3 27%, T4 47%). Five had N2, 3 N1 and 2 N3 lymph node metastases. Side effects were 7% of G1 esophagitis and 7% of G1 cough. Ten patients have been currently evaluated for response: partial responses 8 (80%) and stable disease 2 (20%), no local progression have been observed. Conclusions: Hypofractionated radiotherapy with PET-based target volume delineation is feasible with the current schedule in locally advanced NSCLCs with mediastinal spread and foresees promising results.