A Pilot Trial of Serial 18F-Fluorodeoxyglucose Positron Emission Tomography in Patients With Medically Inoperable Stage I Non-Small-Cell Lung Cancer Treated With Hypofractionated Stereotactic Body Radiotherapy

Purpose: Routine assessment was made of tumor metabolic activity as measured by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in Stage I non-small-cell lung cancer (NSCLC). This report describes PET correlates prospectively collected after stereotactic body radiotherapy (SBRT) for patients with medically inoperable NSCLC. Methods and Materials: 14 consecutive patients with medically inoperable Stage I NSCLC were enrolled. All patients received SBRT to 60-66 Gy in three fractions. Patients underwent serial planned FDG-PET/computed tomography fusion imaging before SBRT and at 2, 26, and 52 weeks after SBRT. Results: With median follow-up of 30.2 months, no patients experienced local failure. One patient developed regional failure, 1 developed distant failure, and 1 developed a second primary. The median tumor maximum standardized uptake value (SUV_max) before SBRT was 8.70. The median SUV_max values at 2, 26, and 52 weeks after SBRT were 6.04, 2.80, and 3.58, respectively. Patients with low pre-SBRT SUV were more likely to experience initial 2-week rises in SUV, whereas patients with high pre-SBRT SUV commonly had SUV declines 2 weeks after treatment (p = 0.036). Six of 13 patients had primary tumor SUV_max >3.5 at 12 months after SBRT but remained without evidence of local disease failure on further follow-up. Conclusions: A substantial proportion of patients may have moderately elevated FDG-PET SUV_max at 12 months without evidence of local failure on further follow-up. Thus, slightly elevated PET SUV_max should not be considered a surrogate for local treatment failure. Our data do not support routine serial FDG-PET/computed tomography for follow-up of patients receiving SBRT for Stage I NSCLC.