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Tumor volumes derived from PET/CT smaller than those derived from CT alone
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Among patients with non–small cell lung cancer, PET/CT-derived tumor volumes for radiation therapy were smaller than those derived using CT alone.
Jeffrey D. Bradley, MD, associate professor in radiation oncology at Washington University Medical School in St. Louis, presented findings from this phase-2 trial.
Researchers enrolled 47 patients into a prospective trial to compare the effect of PET/CT compared to CT alone on radiation treatment volumes and to determine the rate of elective nodal failures that occurred when using the PET/CT derived volumes. The follow-up duration was 12.9 months for all patients.
Tumor volumes were smaller by approximately 12.5 cm3 when defined by PET/CT, and mean tumor volume and median tumor volume were also smaller. No difference was observed between groups for the number of involved nodes.
For PET/CT, the mean lung dose decreased from 19 Gy to 17.8 Gy (P=.06), according to data presented by Bradley during the presentation. The volume of normal lung treated with more than 20 Gy decreased from 32% to 30.8% when using PET/CT. There was no difference between groups for volume of normal lung treated with more than 20 Gy or mean esophageal dose. Lymph node failure in nontargeted regions only occurred in one of 47 patients (2%), supporting current RTOG trials that omit elective nodal irradiation in NSCLC.
“PET/CT changed tumor contours 51% of the time and did so significantly in 21% of patients, and 2% of the population developed elective nodal failure,” Bradley said.
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- Bradley JD. #4.