CT Scans for Lung Cancer Screening

Lung cancer screening with low dose CT scans can help detect the disease at an early stage

(RxWiki News) Lung cancer is the leading cause of cancer deaths in the United States. Finding early signs of cancer can make a huge difference in treatment and survival.

Lung cancers can be aggressive and may grow quickly, making treatment at later stages a huge challenge. Diagnosing lung cancer early is considered key to effective treatment.

Computed tomography (CT) scans may help catch the disease but expose patients to harmful radiation.

A new study explored the role of low-dose CT scans, which involve lower radiation risk than traditional CTs, in the early diagnosis of lung cancer.

The results showed that in high-risk patients, low-dose CT scans may have a role in early detection.

"Quit smoking to lower your risk of lung cancer."

This study was conducted by Timothy R. Church, PhD, at the University of Minnesota School of Public Health, and collaborators from other institutions in the US.

The objective of the study was to examine the role of low-dose CT scans in spotting early signs of lung cancer in high-risk patients.

The researchers closely examined data from a previously conducted study called the National Lung Screening Trial. The trial had shown that screening with low-dose CT was more effective in reducing deaths from lung cancer as compared to chest x-rays.

In the first phase of the trial, more than 26,000 participants were scanned using low-dose CT and around the same number of participants received chest x-rays.

Of the participants who were screened with low-dose CT scans, 27.3 percent showed signs of lung cancer as indicated by nodules in the lung and 9.2 percent of the participants who were screened using x-rays showed signs of cancer.

CT scans of older patients and those who had smoked more packs of cigarettes per year were more likely to show signs of lung cancer.

Lung cancer was confirmed using further diagnostic methods in 1.1 percent of participants in the low-dose CT group as compared to 0.7 percent in the radiography group.

In the low-dose CT group, 158 participants were diagnosed early as compared to 70 participants in the x-ray group.

There was no significant difference in the rate of diagnosis in late stage cancer. Low-dose CT scans were thus more effective in detecting early signs of cancer.

The results also indicated that many patients were incorrectly diagnosed as having lung cancer signs by the low-dose CT and did not actually have lung cancer.  

This is a key concern with using low-dose CT scans, since patients who did not have lung cancer would be termed as having cancer, which would cause them to be subjected to unnecessary procedures such as biopsies.

According to the researchers, the number of diagnostic procedures performed on the patients who showed signs of lung cancer on low-dose CT were much lower than expected and the benefits from early detection outweighed the risks.

A majority of patients whose CT scans showed signs of cancer underwent only one diagnostic test following the CT scan (90.4 percent of participants) or x-ray (92.7 percent). And the subsequent diagnostic test was more commonly imaging and not surgery or biopsy.

The researchers believe that the results provide important information for doctors and patients considering lung cancer screening. Typically, the candidates for screening are high-risk patients, specifically smokers and those who have a history of smoking.

According to the study results, there appears to be a role for low-dose CT scans in early diagnosis of lung cancer.

“The recent study substantiates previous encouraging results reported for screening of lung cancer with low-dose CT in high-risk individuals," said Fred Hirsch, MD, PhD, Professor of Medicine and Pathology at the University of Colorado Cancer Center.

"Several questions need to be answered, such as what is the most optimal screening population? The National Lung Screening Trial study included men and women in the age of 55-74 years with a history of 30 pack-years smoking history. However, we don't know the value of screening in other age groups or in individuals with a shorter smoking history record,” said Dr. Hirsch, who was not involved in the study.

“It is not quite clear which nodules need to be followed up after screening or in other words what size and consistency of the screen detected nodule makes it necessary to follow-up, either with a biopsy or serial CT scans?” he said.

“While screening for lung cancer in this population is an attractive approach, many questions are still unanswered, which makes a specific communication between a screening candidate and the physician important before implementation of the results in clinical practice” Dr. Hirsch said.

This study was published in May in The New England Journal of Medicine.

The study was funded by the National Cancer Institute. The National Lung Screening Trial, the original trial from which data for this study came, was funded by various universities across the US.

One of the co-authors, Dr. David Gierada, reported receiving support through his institution, Washington University School of Medicine, St. Louis from VuCOMP, a private company that sells computer-aided detection systems for analysis of medical images. 

No other potential conflicts of interest or financial relationships relevant to the study were reported.

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Review Date: 
May 29, 2013