Using Fluorodeoxyglucose Positron Emission Tomography to Assess Tumor Volume During Radiotherapy for Non–Small-Cell Lung Cancer and Its Potential Impact on Adaptive Dose Escalation and Normal Tissue Sparing
Received 10 August 2008; received in revised form 28 October 2008; accepted 30 October 2008.
Purpose
To quantify changes in fluorodeoxyglucose (FDG)-avid tumor volume on positron emission tomography/computed tomography (PET/CT) during the course of radiation therapy and examine its potential use in adaptive radiotherapy for tumor dose escalation or normal tissue sparing in patients with non–small-cell lung cancer (NSCLC).
Methods and Materials
As part of a pilot study, patients with Stage I–III NSCLC underwent FDG-PET/CT before radiotherapy (RT) and in mid-RT (after 40–50 Gy). Gross tumor volumes were contoured on CT and PET scans obtained before and during RT. Three-dimensional conformal RT plans were generated for each patient, first using only pretreatment CT scans. Mid-RT PET volumes were then used to design boost fields.
Results
Fourteen patients with FDG-avid tumors were assessed. Two patients had a complete metabolic response, and 2 patients had slightly increased FDG uptake in the adjacent lung tissue. Mid-RT PET scans were useful in the 10 remaining patients. Mean decreases in CT and PET tumor volumes were 26% (range, +15% to −75%) and 44% (range, +10% to −100%), respectively. Designing boosts based on mid-RT PET allowed for a meaningful dose escalation of 30–102 Gy (mean, 58 Gy) or a reduction in normal tissue complication probability (NTCP) of 0.4–3% (mean, 2%) in 5 of 6 patients with smaller yet residual tumor volumes.
Conclusions
Tumor metabolic activity and volume can change significantly after 40–50 Gy of RT. Using mid-RT PET volumes, tumor dose can be significantly escalated or NTCP reduced. Clinical studies evaluating patient outcome after PET-based adaptive RT are ongoing.
∗Department of Radiation Oncology, University of Michigan, Ann Arbor, MI
†Department of Nuclear Medicine, University of Michigan, Ann Arbor, MI
Reprint requests to: Feng-Ming Kong, M.D., Ph.D., Department of Radiation Oncology, University of Michigan, 1500 East Medical Center Drive, UH B2C490 SPC 0500, Ann Arbor, MI 48109. Tel: (734) 769-7426; Fax: (734) 763-7370
Supported in part by a seed grant from the Radiological Society of North America and a 2004 Young Investigator Award from the American Society of Clinical Oncology (F.M.K.).
This study was presented at the 2005 Radiological Society of North America Annual Meeting and won the Resident in Training Award from the American Association of Women Radiologists (M.F.), November 26–December 1, 2006, Chicago, IL.
ABSTRACT