According to a study published in the journal Chest, use of a scanner that combines positron-emission tomography (PET) and computed tomography (CT) provides more accurate information about presurgical lung cancer stage than use of PET alone.
Lung cancer remains the leading cause of cancer death in the US. Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, accounting for 75%-80% of all lung cancers. When a diagnosis of lung cancer is confirmed, determining the stage or extent of spread of the cancer is essential to making treatment decisions.
Imaging techniques such as PET and CT can be used to stage NSCLC before surgery. A CT scan uses computer-controlled x-rays to create a three-dimensional image and shows the extent of the disease. A CT scan is more sensitive and precise than a standard chest x-ray.
PET scans are often used to improve the detection of cancer in lymph nodes. Prior to a PET scan, a substance containing a type of sugar attached to a radioactive isotope (a molecule that spontaneously emits radiation) is injected into the patient’s vein. The cancer cells “take up” the sugar and attached isotope. The low energy radiation emitted by these cells helps physicians locate cancer.
Each of these imaging techniques has some limitations when used alone. In response, an integrated (combined) PET/CT system has recently been developed. In order to evaluate whether use of an integrated PET/CT scanner provides more accurate information about NSCLC stage than use of PET alone, researchers conducted a study among 36 patients with NSCLC. Twenty-five of these patients also had CT performed. For the patients with CT information, a computer program fused the separate CT and PET images, and results from these separately-obtained but fused images were compared to results from the images generated by the integrated PET/CT scanner.
The use of integrated PET/CT resulted in more accurate staging than use of PET alone. Integrated PET/CT produced these results:
- Accurately staged 83% of patients
- Overstaged 10% of patients
- Understaged 7% of patients
In contrast, PET alone had the following, less precise results:
- Accurately 57% of patients
- Overstaged 20% of patients
- Understaged 23% of patients
The separately-obtained but fused CT and PET images appeared to perform well when the fusion process succeeded, though it only succeeded in 68% of patients.
The researchers conclude that integrated PET/CT more accurately stages NSCLC than PET alone. More accurate staging of NSCLC before surgery may result in better treatment.
Reference: Halpern BS, Schiepers C, Weber WA et al. Presurgical Staging of Non-small Cell Lung Cancer. Chest . 2005;128:2289-2297.
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