R. Eakin

18F-FDG PET-CT SIMULATION FOR NON-SMALL-CELL LUNG CANCER: EFFECT IN PATIENTS ALREADY STAGED BY PET-CT

PURPOSE Positron emission tomography (PET), in addition to computed tomography (CT), has an effect in target volume definition for radical radiotherapy (RT) for non-small-cell lung cancer (NSCLC). In previously PET-CT staged patients with NSCLC, we assessed the effect of using an additional planning PET-CT scan for gross tumor volume (GTV) definition. METHODS AND MATERIALS A total of 28 patients with Stage IA-IIIB NSCLC were enrolled. All patients had undergone staging PET-CT to ensure suitability for radical RT. Of the 28 patients, 14 received induction chemotherapy. In place of a RT planning CT scan, patients underwent scanning on a PET-CT scanner. In a virtual planning study, four oncologists independently delineated the GTV on the CT scan alone and then on the PET-CT scan. Intraobserver and interobserver variability were assessed using the concordance index (CI), and the results were compared using the Wilcoxon signed ranks test. RESULTS PET-CT improved the CI between observers when defining the GTV using the PET-CT images compared with using CT alone for matched cases (median CI, 0.57 for CT and 0.64 for PET-CT, p = .032). The median of the mean percentage of volume change from GTV(CT) to GTV(FUSED) was -5.21% for the induction chemotherapy group and 18.88% for the RT-alone group. Using the Mann-Whitney U test, this was significantly different (p = .001). CONCLUSION PET-CT RT planning scan, in addition to a staging PET-CT scan, reduces interobserver variability in GTV definition for NSCLC. The GTV size with PET-CT compared with CT in the RT-alone group increased and was reduced in the induction chemotherapy group.

18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography–Based Radiotherapy Target Volume Definition in Non–Small-Cell Lung Cancer: Delineation by Radiation Oncologists vs. Joint Outlining With a PET Radiologist?

PURPOSE (18)F-Fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) has benefits in target volume (TV) definition in radiotherapy treatment planning (RTP) for non-small-cell lung cancer (NSCLC); however, an optimal protocol for TV delineation has not been determined. We investigate volumetric and positional variation in gross tumor volume (GTV) delineation using a planning PET/CT among three radiation oncologists and a PET radiologist. METHODS AND MATERIALS RTP PET/CT scans were performed on 28 NSCLC patients (Stage IA-IIIB) of which 14 patients received prior induction chemotherapy. Three radiation oncologists and one PET radiologist working with a fourth radiation oncologist independently delineated the GTV on CT alone (GTV(CT)) and on fused PET/CT images (GTV(PETCT)). The mean percentage volume change (PVC) between GTV(CT) and GTV(PETCT) for the radiation oncologists and the PVC between GTV(CT) and GTV(PETCT) for the PET radiologist were compared using the Wilcoxon signed-rank test. Concordance index (CI) was used to assess both positional and volume change between GTV(CT) and GTV(PETCT) in a single measurement. RESULTS For all patients, a significant difference in PVC from GTV(CT) to GTV(PETCT) exists between the radiation oncologist (median, 5.9%), and the PET radiologist (median, -0.4%, p = 0.001). However, no significant difference in median concordance index (comparing GTV(CT) and GTV(FUSED) for individual cases) was observed (PET radiologist = 0.73; radiation oncologists = 0.66; p = 0.088). CONCLUSIONS Percentage volume changes from GTV(CT) to GTV(PETCT) were lower for the PET radiologist than for the radiation oncologists, suggesting a lower impact of PET/CT in TV delineation for the PET radiologist than for the oncologists. Guidelines are needed to standardize the use of PET/CT for TV delineation in RTP.

P3.16-18 Modern Radiotherapy Increases Patient Access to Curative Intent Radiotherapy in Non-Small Cell Lung Cancer

Background: The authors evaluated the efficacy, patterns of failure, toxicity and cost of body gamma-ray stereotactic ablative radiotherapy (Body Gamma-ray SABR) for patients with medically inoperable, clinical stage I/II non-small cell lung cancer (NSCLC) with 8 years of follow-up. Clinical staging was performed according to the sixth edition of the American Joint Committee on Cancer TNM staging system. Method: Eligible patients who had no previous treatments, with histologically confirmed NSCLC, determined as clinical stage I /II, underwent OUR-QGD type of the body gamma-ray SABR (70 grays in 10 fractions for gross target volume) at the Radiation Oncology Department, People’s Liberation Army Airforce General Hospital, Beijing, China from January 2007 to July 2010. All patients were immobilized by vacuum bag, and then a slow CT scan was performed without any respiration gating. The total radiation dose of 50%, 60%, and 70% isodose line were prescribed in 50, 60, and 70 Grey (Gy) correspondingly, covering 100% of the planning target volume (PTV), 90% of the clinical target volume (CTV), and 80% of the gross target volume (GTV) in 10 fractions. The CT scan and/or positron emission tomography/ computed tomography were every 3 months for the first 2 years, every 6 months for the next 3 years, and then annually thereafter to evaluate the efficacy of the treatment. The primary endpoint was overall survival. Result: A total of 29 patients were eligible for analysis. The median age of the patients was 71 years (55-87), and the median follow-up was 8.1 years (6.8-10.3). The 1-year, 3-year, 5-year and 8year overall survival rates were 93.1%, 72.1%, 59.4% and 44.8%, and the local, regional and distant disease recurrence were 10.3%, 13.8% and 13.8% at 5 years and 10.3%, 17.2% and 20.7% at 8 years. Two patients (6.9%) experienced grade 3 treatment-related adverse events. No patients developed grade 4 or 5 adverse events. The median cost of body gamma-ray SABR is 4838 dollars (4615-4923 dollars). Conclusion: With long-term follow-up, the results of the current study demonstrated outstanding local control and low toxicity after body gamma-ray SABR in patients with clinical stage I/II NSCLC. The dominant failure included regional and distant disease recurrence. And the body Gamma-ray SABR is pretty cost-effective.