PET Offers Prediction of Early Response to Head and Neck Cancer Treatment

A new study found that positron emission tomography (PET) imaging with 3'-deoxy-3'F-18-fluorothymidine (18-F-FLT) during treatment and early follow-up has the potential to predict therapeutic responses and identify patients needing close follow-up to identify recurring or persistent.

Tumor response to therapy is typically tracked by the assessment of tumor size change by anatomic imaging modalities. Whereas several studies have demonstrated that F-18-fluorodeoxyglucose (FDG) PET may be used to gauge response, the agent may generate false-positive findings. The study’s investigators set out to determine if F-18-FLT, a recently developed imaging compound, would also be valuable in predicting response to HNSCC therapy.

“In experimental models, reduced FLT uptake preceded reduced FDG uptake, suggesting that decreased cell proliferation precedes changes in glucose metabolism,” noted Hiroshi Hoshikawa, MD, from the department of otolaryngology, faculty of medicine, Kagawa University (Kagawa, Japan), and lead author of the study. “However, there are few clinical studies comparing FLT-PET and FDG-PET findings for radiotherapy.” The study’s findings were published in the October 2012 issue of the Journal of Nuclear Medicine.

In the study, 28 patients with HNSCCs underwent F-18-FLT and F-18-FDG PET imaging before radiotherapy treatment, four weeks after the start of therapy and five weeks after the conclusion of therapy. Uptake of both of the agents was calculated in primary and metastatic lesions.

F-18-FLT uptake during the radiation therapy dissipated in 34 of 54 lesions (63%); the negative predictive value was 97%. F-18-FDG uptake also had a high negative predictive value (100%) during radiation therapy, but only nine lesions (16%) demonstrated absence of FDG. Moreover, the specificity and overall accuracy of F-18-FLT were considerably higher than F-18-FDG PET both during and after radiation therapy. These results indicate that F-18-FLT PET is more beneficial for evaluating early loco-regional clinical outcomes and helping to avoiding unnecessary radical surgery.

“With the development of new molecular imaging agents, it’s now up to clinical researchers to utilize them to assess the characteristics of malignant tumors and their therapeutic response to chemotherapy, radiotherapy and molecular targeting therapy,” concluded Dr. Hoshikawa. “We hope that our findings will be helpful in understanding the significance of F-18-FLT-PET.”

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