PET Imaging Useful After Thoracic Radiation Therapy for Lung Cancer Staging

A rapid decline in metabolic activity seen on a positron emission tomography (PET) scan after radiation therapy for non-small-cell lung cancer is correlated with good local tumor control, according to recent findings. Moreover, the researchers also found that the higher the metabolic activity and tumor size on a PET scan before treatment, the more likely a patient is to die from lung cancer.

The study's findings were presented by researchers from Thomas Jefferson University Hospital (Philadelphia, PA, USA) in November 2009 at the 51st American Society for Radiation Oncology (ASTRO) annual meeting, held in Chicago, IL, USA. "PET scanning is an emerging tool of molecular imaging in lung cancer, in contrast to CT [computed tomography] scans and MRI [magnetic resonance imaging] scans, which are anatomic imaging,” said Dr. Maria Werner-Wasik, associate professor of radiation oncology at Jefferson Medical College of Thomas Jefferson University, and the study's lead author. "It has become an important tool in the evaluation of lung cancer staging and evaluation of treatment response.”

Dr. Werner-Wasik and colleagues conducted a retrospective analysis of 50 patients with lung cancer who received PET imaging before and after radiation therapy. They analyzed the prognostic factors for tumor local failure. The investigators measured the metabolic activity using the maximum standardized uptake value (mSUV). They also measured the tumor size (the metabolic tumor volume).

The risk of local failure decreased for each unit decline in mSUV by the first posttherapy scan. When compared to the pretherapy PET scan, the mSUV of the primary tumor declined by 72% in the first posttherapy scan, 76% by the second scan, and 77% by the third scan. Nineteen patients achieved a metabolic complete response at the median time of 10.6 months. Eight patients suffered local failure. Other factors significantly associated with increased local failure included female gender, stage IV disease, and large tumor size.

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