Integrated PET/CT Scan More Accurately Stages Non-Small Cell Lung Cancer

Understand the role of PET/CT scanning in the management of Non-Small Cell Lung Cancer.

by Dr. C. H. Weaver M.D. updated 4/2019

Imaging techniques such as PET and CT are used to help determine the stage of newly diagnosed NSCLC and evaluate a patients response to treatment once initiated. 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 been developed. In order to evaluate whether use of an integrated PET/CT scanner provides more accurate information about NSCLC than use of PET alone.

Determining The Initial Stage of Cancer

Accurate determination of the initial stage of lung cancer is very important in order to determine which individuals will have early stage cancer that can be cured with surgery and to avoid unnecessary surgery in those who will not benefit. PET scans have been shown to more accurately identify lymph node involvement with cancer compared to CT but both scans appear to have benefit.(1)

The use of combined PET/CT however provides more accurate information about presurgical lung cancer stage than use of PET alone.

The use of integrated PET/CT accurately staged 83% of individuals compared to 57% with PET alone. More accurate staging of NSCLC before surgery results in better treatment.(2)

Doctors from Denmark have reported similar results. They assessed the frequency of "futile thoracotomies". A thoracotomy is surgery to open the chest. This surgery was considered to be futile when the patient was found to have advanced, inoperable cancer; benign lung disease; or death or recurrence within a year of the surgery.(3)

After staging, 60 out of 98 patients with PET/CT group and 73 out of 91 patients in the conventional staging group who underwent thoracotomy 52% of patients in the conventional staging group were found to have had a futile thoracotomy, compared with only 35% in the PET/CT group.

These results suggest that preoperative PET/CT for NSCLC reduces the total number of thoracotomies as well as the number of futile thoracotomies, without affecting survival.

PET Scans May Help Identify Detection of Lung Cancer

According to an article recently published in the Journal of the National Cancer Institute, positron emission tomography (PET) scans may improve the accuracy of imaging in lung cancer.(4)

Researchers from Canada recently reviewed data including the use of PET scans in the diagnosis of lung cancer. This review included 15 trials and 12 reports regarding PET scans in lung cancer.

  • PET scans are able to differentiate between benign masses and cancerous masses as small as 1 cm.
  • PET provides superior results compared with CT scans for accurately detecting the extent of spread of cancer of mediastinal (center of the chest) NSCLC.
  • PET is accurate in determining the extent of spread of SCLC.
  • PET may also aid in identifying patients who have cancer spread to other sites of the body that is not detected with present screening measures.

The researchers concluded that PET scans may help improve accuracy in staging lung cancer or may be an important screening tool for lung cancer. The authors state: “Further trials are necessary to establish the clinical utility of PET as part of the standard preoperative assessment of early-stage lung cancer.”

PET Detects Responders to EGFR Inhibitors in Lung Cancer.

A novel use of positron emission tomography (PET) scans predicts which patients with lung cancer will respond to epidermal growth factor receptor (EGFR) inhibitors, further personalizing cancer care with non-invasive methods. These results were recently presented at the 14th World Conference on Lung Cancer, sponsored by the International Association for the Study of Lung Cancer.(5-8)

The EGFR pathway is involved in cellular growth and replication. In a significant portion of cancers, the EGFR pathway contains a mutation and does not function normally. Novel medications for cancer, referred to as EGFR inhibitors, reduce or stop unchecked cellular growth through this pathway among patients with EGFR mutations.

Patients with lung cancer often undergo testing to determine whether they have mutations within their EGFR pathways, ultimately establishing whether EGFR inhibitors may be effective treatment. This testing involves invasive methods to remove cancerous tissue which undergoes subsequent laboratory testing.

Researchers from Amsterdam recently conducted a clinical trial to evaluate the accuracy with which PET scans using Tarceva® (erlotinib), an EGFR inhibitor, could predict responses to treatment with the drug. The trial included 10 patients with non-small cell lung cancer (NSCLC) who initially underwent standard laboratory testing for EGFR mutations. Five patients had EGFR mutations and 5 patients did not. The patients then underwent PET scanning with radiolabeled Tarceva.

Patients whose cancer absorbed high levels of the radiolabeled Tarceva during the scan were the only patients who responded to subsequent therapy with Tarceva.

Dr. Idris Bahce, the principle investigator of the study, stated that “This is an important finding, as it indicates that this new imaging PET technique may be a non-invasive predictive marker that identifies NSCLC patients who benefit from treatment with [EGFR inhibitors].” Although this was a small, preliminary study, these results provide a novel approach to a personalized and less invasive method of determining which patients will respond to treatment with EGFR inhibitors. Further studies evaluating this type of procedure are being planned.

References:

  1. Birim Ö, Kappetein A, Stijnen T, Bogers J. Meta-Analysis of Positron Emission Tomographic and Computed Tomographic Imaging in Detecting Mediastinal Lymph Node Metastases in Nonsmall Cell Lung Cancer. Annals of Thoracic Surgery. 2005; 79:375-382.
  2. Fischer B, Lassen U, Mortensen J et al. Preoperative staging of lung cancer with combined PET-CT. New England Journal of Medicine. 2009;361:32-9.
  3. Halpern BS, Schiepers C, Weber WA et al. Presurgical Staging of Non-small Cell Lung Cancer. Chest . 2005;128:2289-2297.
  4. Ung Y, Maziak D, Vanderveen J. 18Fluorodeoxyglucose positron emission tomography in the diagnosis and staging of lung cancer: a systematic review. Journal of the National Cancer Institute [early online publication]. November 27, 2007. DOI: 10.1093/jnci/djm232.
  5. Fischer B, Lassen U, Mortensen J et al. Preoperative staging of lung cancer with combined PET-CT. New England Journal of Medicine. 2009;361:32-9.
  6. Lardinois D, Weder W, Hany T, et al. Staging of non-small-cell lung cancer with integrated positron-emission tomography and computed tomography. The New England Journal of Medicine. 2003;348:2500-2507.
  7. Halpern BS, Schiepers C, Weber WA et al. Presurgical Staging of Non-small Cell Lung Cancer. Chest . 2005;128:2289-2297.
  8. Reference: Bahce I, et al. In vivo selection of non-small cell lung cancer patients with activating mutations in the tumor epidermal growth factor receptor using [11C]erlotinib and positron emission tomography. Presented at the 14th World Conference on Lung Cancer. July 3-7, 2011. Amsterdam, Netherlands. Abstract PRS.5.

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