ASTRO: FDG-PET shows promise in lung cancer treatment decisions

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Post-treatment imaging with PET scans has shown promise in predicting which patients with stage II and III inoperable non-small cell lung cancer (NSCLC) have aggressive tumors and need additional treatment, according to the preliminary study results reported at the American Society for Radiation Oncology (ASTRO) Annual Meeting in Miami.

The trial was led by the American College of Radiology Imaging Network (ACRIN) in collaboration with Radiation Therapy Oncology Group (RTOG) and funded by the National Cancer Institute. ACRIN and RTOG participating sites from around the country enrolled 251 patients into the phase III trial and gathered pre- and post-treatment F-18 fluorodeoxyglucose-PET (FDG-PET) scans. Treatments included both chemotherapy and radiation therapy.

It is the largest study of its kind for the evaluation of FDG-PET for patient prognosis.

Mitchell Machtay, MD, of the Seidman Cancer Center at University Hospitals Case Medical Center in Cleveland, and colleagues wanted to determine if the standardized uptake value (SUV), a quantitative measure of how rapidly tumor cells are using the glucose-based FDG radiotracer, obtained on the FDG-PET scans was predictive of patient survival. On every scan, a contouring tool was used to contour every visible hypermetabolic lesion, which were then classified as primary tumor or by lymph node station.

“NSCLC primary tumors are more likely to demonstrate persistent hypermetabolic activity following chemoradiation than involved lymph nodes,” wrote the authors in the study abstract. “High pre-treatment TGA [total glycolytic activity] is an independent predictor of residual disease in both tumors and lymph node stations. Radiotherapy dose escalation to primary tumors and lesions with high TGA values may be warranted.”

Since most cancer cells take up sugar at a higher rate than normal cells, the researchers found that high levels of glucose-based FDG uptake following treatment marked a tumor that was more likely to recur. The higher the SUV in the primary tumor, the greater the recurrence rate and lower the survival rate for patients.

The results also demonstrated a strong correlation between the radiation dose intensity and local control of the cancer.

For patients with stage II and III inoperable NSCLC, the prognosis is poor as only 15 percent of patients survive five years post-treatment. The researchers noted that the results may mean that FDG-PET scans have a role in helping make treatment decisions by providing more definitive prognostic information after the completion of therapy.

"Lung cancer remains the number one cancer killer in the U.S. These findings have the potential to give cancer physicians a new tool to more effectively tailor treatments for patients with locally advanced lung cancer," Machtay said in a statement.