LOS ANGELES—Positron emission tomography (PET) can be used to better characterize patterns of local failure after definitive radiation therapy for non-small-cell lung cancer, which may help to improve that therapy, investigators said at ASTRO 2007 (abstract 102).
"Local failure remains a common problem in NSCLC treated with radiation. More importantly, the characteristics of local failure have implications for treatment-planning strategies," said lead author Sonal Sura, MD, formerly of Memorial Sloan-Kettering Cancer Center and currently at George Washington University. "However, evaluating failures with CT scans is difficult because it is hard to differentiate between tumor recurrence and radiation changes."Of 230 NSCLC patients who underwent involved-field radiation therapy, the researchers identified 26 patients who had both a local recurrence and a postrecurrence PET scan that could be registered with the treatment planning CT scan.
Patterns of failure
Local failures were evaluated independently by three radiation oncologists. They categorized each failure according to where it arose (primary tumor vs nodal area) and assigned it to one of four patterns of failure:
• Completely within the gross tumor volume (GTV).
• Within the GTV but extending outward.
• Marginal miss arising from the planning target volume (PTV) and extending outward.