Understanding Your Chest CT Scan & PET Scan for Lung Cancer Detection

Lung cancer is the leading cause of cancer death in the US, taking more lives annually than the next three most common cancers combined.

Yet, of the 7.6 million adults who are eligible for lung cancer screening – only 2% are actually getting screened. While medical imaging has huge potential to improve the survival rate for lung cancer, getting the right test at the right time, and ensuring your images are interpreted by a qualified radiologist, are both crucial.

To better understand the complexities of lung cancer imaging, we spoke with Dr. Darko Pucar, lung cancer imaging expert and member of the Thoracic Oncology Tumor Board at Yale University. In this exclusive interview, Dr. Pucar discusses the important role a chest CT scan plays in early detection of lung cancer, explains how a PET scan for lung cancer staging is the most powerful tool, and reveals why patients should be getting a second opinion on their scans to prevent diagnostic errors.

Understanding Your Scan: Chest X-Ray vs. Chest CT Scan vs Lung PET Scan

[Doc Panel] What is the difference between a chest x-ray and a chest CT scan?

[Dr. Pucar]

A chest x-ray is the least expensive and quickest imaging test to perform on the lungs, making it a frequently used option for early examination. When compared to a chest CT scan, however, it is quite limited.

While a chest x-ray can detect some lung tumors, it’s not very good at catching them when they’re small – as they are in the beginning stages of lung cancer. Its ability to accurately determine cancer spread is also insufficient. A chest CT scan, on the other hand, can detect tumors in the lungs and chest lymph nodes.

Basically, a chest CT scan is a more detailed type of chest x-ray. It takes dozens of pictures of your lungs and chest and compiles the information together. Because it is able to detect very small nodules in the lung, a chest CT scan is especially effective for diagnosing lung cancer at its earliest, most curable stage.

[DocPanel] Under what circumstances is a patient advised to get a PET scan for lung cancer evaluation?

[Dr. Pucar]

If findings suspicious for cancer have been detected on a chest x-ray or a chest CT scan, a PET scan is the appropriate next step.

PET (positron emission tomography) uses a radioactive substance, called a tracer, that allows doctors to see how things are functioning on a molecular level.

Typically, when we use a PET scan for lung cancer evaluation it’s performed in conjunction with a chest CT scan. Through a process called image fusion, the two scans are merged together so that the radiologist can interpret the combined information.

PET Scan for Lung Cancer Diagnoses

[DocPanel] What are the advantages of using a PET scan for lung cancer detection rather than other imaging tests?

[Dr. Pucar]

A PET scan for lung cancer also has the capability to detect cancer in lymph nodes and organs that appear morphologically normal on a chest CT scan. Plus, since a PET scan typically covers a much larger area of the body (typically from skull to thighs) than a chest CT scan, it provides the best chance of detecting metastatic disease.

However, it’s important to keep in mind that PET/CT interpretation is very complex. Interpretation by a radiology expert is essential in avoiding false-negative and false-positive results.

For example, the tracer used in PET can help an interpreting radiologist distinguish between benign (noncancerous) and malignant (cancerous) masses. This is of course extremely valuable. But – if the radiologist does not have adequate training and extensive experience diagnosing lung cancer, there’s an increased risk for misdiagnosis. Ensuring your PET and CT chest scans are interpreted by a radiology subspecialist can help prevent errors.

PET Scan for Lung Cancer Staging & Treatment

[DocPanel] What role does a PET scan play in lung cancer staging?

[Dr. Pucar]

A PET scan can catch minute changes in glucose metabolism, making it the most powerful tool to stage lung cancer.

It is typically always performed prior to treatment to ensure the most accurate possible staging. It’s also performed to detect if there has been any tumor spreading in the lymph nodes of organs that is not visible on a chest CT scan.

Today there are effective and even potentially curable options for patients whose cancer has spread to lymph nodes or has metastasized outside of the chest. But early and accurate detection of cancer spread is essential for optimal treatment. A PET/CT scan can help with this.

[DocPanel] Which imaging tests can help determine whether or not lung cancer treatment is working?

[Dr. Pucar]

By detecting minute changes in glucose metabolism, a PET scan can pick up on positive treatment effects even before the tumor starts to shrink. So, when we use a PET scan for lung cancer treatment management, we’re able to gauge treatment effectiveness earlier and more accurately than we would be able to with a chest CT scan.

Upon completion of treatment, the tumors may not completely disappear on a CT scan. In this situation, a PET scan can determine if there is still viable cancer in residual tumors that are picked up on with the chest CT scan. This allows doctors to decide if more treatment is needed.

By detecting increased tumor metabolism or tumor sites that are not visible via CT, a PET scan can also let us know when a tumor is not responding to treatment sooner than a chest CT scan is able to. In such scenarios, doctors can quickly change the treatment as needed.

With the advancement of lung cancer treatment, many more options are available to patients now than a decade ago. And, thankfully, doctors can even monitor the success of a medication with PET/CT scans. But again, interpretation can be challenging, requiring a very specialized set of skills. An expert second opinion can make a big difference for patients.

Interpreting a PET Scan – Lung Cancer Accuracy

[DocPanel] What are some other challenges in accurately diagnosing lung cancer?

[Dr. Pucar]

Benign lung nodules can look similar to lung cancer on a chest CT scan. This puts patients at risk of a false-positive. Or, the reverse may happen – a radiologist might dismiss a malignant mass as a benign mass. Either or has negative consequences. This is another reason that patients should seek a second opinion on their chest CT scan.

Another challenge is that lung cancer can be hidden within lung inflammatory changes or scarring. In this situation, a lung PET scan can substantially expedite the diagnosis and management by showing high glucose metabolism in areas of concern and by guiding biopsy to the area of concern. Having a subspecialist look at your scans helps ensure that situations such as these will be recognized and handled appropriately.

[DocPanel] What advice do you have for patients navigating lung cancer screening or a lung cancer diagnosis?

[Dr. Pucar]

As we have discussed, the interpretation of a chest CT scan or a PET scan for lung cancer is complex and can be quite challenging. Consequently, a reading is best performed by a subspecialty radiologist. Getting an expert second opinion can help ensure you get the most accurate information possible and the most optimal lung cancer care possible.

In addition – if your CT chest scan results are inconclusive, consider asking your doctor for a PET/CT scan.

Lung cancer screening with prompt diagnosis and accurate staging can significantly reduce lung cancer-related deaths. By creating more awareness around the capabilities of medical imaging for lung cancer detection, diagnosis, staging, and treatment – people will be more empowered to ask for it.