Magnetic resonance (MR) imaging for tumor staging and definition of tumor volumes on radiation treatment planning in nonsmall cell lung cancer: A prospective radiographic cohort study of single center clinical outcome

We investigate the impact of magnetic resonance (MR) on the staging and radiotherapy planning for patients with nonsmall cell lung cancer (NSCLC). A total of 24 patients with NSCLC underwent MRI, which was fused with radiotherapy planning CT using rigid registration. Gross tumor volume (GTV) was delineated not only according to CT image alone (GTV(CT)), but also based on both CT and MR image (GTV(CT/MR)). For each patient, 2 conformal treatment plans were made according to GTV(CT) and GTV(CT/MR), respectively. Dose-volume histograms (DVH) for lesion and normal organs were generated using both GTV(CT) and GTV(CT/MR) treatment plans. All patients were irradiated according to GTV(CT/MR) plan. Median volume of the GTV(CT/MR) and GTV(CT) were 105.42 cm(3) and 124.45 cm(3), respectively, and the mean value of GTV(CT/MR) was significantly smaller than that of GTV(CT) (145.71 ± 145.04 vs 174.30 ± 150.34, P < 0.01). Clinical stage was modified in 9 patients (37.5%). The objective response rate (ORR) was 83.3% and the l-year overall survival (OS) was 87.5%. MR is a useful tool in radiotherapy treatment planning for NSCLC, which improves the definition of tumor volume, reduces organs at risk dose and does not increase the local recurrence rate.