Table of ContentsView AllTable of ContentsLimitationsMissed DiagnosesFalse-NegativesBetter MethodsLung Cancer ScreeningWhat You Can Do
Table of ContentsView All
View All
Table of Contents
Limitations
Missed Diagnoses
False-Negatives
Better Methods
Lung Cancer Screening
What You Can Do
Achest X-raycreates images of:
It is often the first imaging test a doctor will order if lung or heart disease is suspected. Iflung canceris present, chest X-rays can sometimes detect larger tumors. More often than not, though, they fail to diagnose the disease. Chest X-rays also fall short as a tool forlung cancer screening.
This article looks at chest X-ray and its use for the diagnosis of lung cancer. It also discusses some of the other diagnostic tools a doctor may use if lung cancer is suspected.
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Limitations of Chest X-Rays
X-rays use radiation to create two-dimensional images of internal organs. Organs and tissues that absorb more radiation appear white or gray, while materials that absorb less radiation (such as gases in the lungs) appear black.
It is not uncommon to hear stories of lung cancer that was discovered on an X-ray. When this happens, though, the disease usually is in an advanced stage. The cancer was only seen because the tumor was large and hard to miss.
The problem with this is thatadvanced lung cancerfound instage 3borstage 4is more difficult to treat. With rare exception, these advanced lung cancers are incurable.This is why chest X-rays are poor tools for diagnosing lung cancer.
Low Resolution Images
On a chest X-ray, any abnormal growth in the lung will appear as a relatively solid area of light gray. The growth might be cancer, but it could also be any number ofbenignor noncancerous conditions.
Based on the X-ray alone, all the radiologist can do is describe the growth in general terms, such as:
A chest X-ray alone cannot confirm cancer or something more benign, like a cyst or scar.
Obscured Images
Normal body parts like bones can obscure tumors on an X-ray and make them hard to see. This is especially true if they are small. Disease processes can also make cancerous growths hard to see.Pneumonia, for example, commonly occurs withsymptomatic lung cancer. If you have pneumonia, the pus and mucus that clog the airways can easily hide a tumor.
On an X-ray,tuberculosis (TB)also looks similar to certain lung cancers. These conditions often occur together. When this happens, TB may be diagnosed while the cancer is missed. Even after the TB infection clears up, doctors may assume remaining spots are scars and leave them uninvestigated.
Most Common Forms of Lung Cancer
RecapOn an X-ray, small cancers can sometimes be hidden behind bones or the processes of other diseases like pneumonia or tuberculosis.
Recap
On an X-ray, small cancers can sometimes be hidden behind bones or the processes of other diseases like pneumonia or tuberculosis.
In some cases, a patient may be told their chest X-ray is normal only to learn months or years later that they have cancer. In these cases, the cancer may come to light after advanced symptoms appear. These may include:
This may seem like negligence, but chest X-rays have fundamental limitations. This is especially true when it comes to detecting certain types and sizes of lung cancer. Your medical team can’t diagnose what they can’t see.
Cancer Type and Location
Cancers in certain parts of the lungs are harder to see and are more likely to be missed on a chest X-ray. A 2017 study found that 45% to 81% of missed lung cancers occurred in the upper parts of the lung where the collarbone and other structures obscure the view.
Lungadenocarcinomais the most common form of lung cancer. It usually occurs on the outer edges of the lungs, where it can be hard to spot. This type of cancer is missed more often than cancers that occur near the large airways, such assmall cell lung cancerandsquamous cell carcinoma of the lungs.
Tumor Size
Tumors smaller than 1.5 cm (.6 inch) are more likely to be missed on a chest X-ray than larger ones.
Lung adenocarcinomas often have a diffuse “ground glass” appearance. These kinds of tumors may also be hard to see on an X-ray.
RecapCancers located high in the lungs and on the outer edges of the lungs may be hard to see on an X-ray. Small tumors and those with a diffuse appearance are also easily missed.
Cancers located high in the lungs and on the outer edges of the lungs may be hard to see on an X-ray. Small tumors and those with a diffuse appearance are also easily missed.
Risk Factors
Sometimes lung cancers are missed simply because no one was looking for them. Unless there are symptoms or your doctor knows you are at high risk of lung cancer, there may be no reason to suspect cancer.
Only 65% of physicians ask patients if and how much they smoke.Doctors also often fail to ask about a patient’s past history of smoking if they say they are a “non-smoker.”
Former smokers are often assumed to be of lesser risk even if their past use was high. Similarly, never-smokers fall between the cracks because lung cancer is a less likely cause of respiratory illness in this group. It should be noted, though, thatlung cancer diagnoses are increasing in never-smokers.
In addition, many of the symptoms of lung cancer, such asshortness of breathor fatigue can be easily attributed to things like age or obesity.
As a result:
RecapDoctors may miss lung cancer if a patient’s risk factors are unknown. People considered at lower risk may also receive later diagnoses simply because lung cancer is not common in these groups.
Doctors may miss lung cancer if a patient’s risk factors are unknown. People considered at lower risk may also receive later diagnoses simply because lung cancer is not common in these groups.
How Often X-Rays Miss Lung Cancer
There are surprisingly few recent studies that look at the incidence of missed lung cancer. The research that has been done, though, is sobering.
A 2019 review of 21 studies found that 20% to 23% of chest X-rays in people with lung cancer symptoms werefalsely negativefor lung cancer.This can be disastrous since it only takes an average of 136 days for a lung tumor to double in size.
Stage 1,stage 2, andstage 3alung cancers are considered treatable with surgery. If the disease is allowed to progress, it can quickly move from treatable to inoperable. This not only makes it more difficult to manage, it also significantly reduces the patient’ssurvival time.
How Fast Does Lung Cancer Grow?
How Lung Cancer Is Diagnosed
A chest X-ray might “accidentally” find lung cancer during the investigation of another condition. Still, it isn’t one of the most common tools used to diagnose lung cancer because of the concerns outlined above.
Instead, healthcare providers generally rely on three tests:
If cancer is diagnosed, other tests will helpstage and grade the tumor. This process helps doctors understand how far the cancer has progressed so they can decide on the right treatment.
Positron emission tomography (PET)scans are not usually used for diagnosing lung cancer. They are considered more useful for staging the disease. PET scans don’t take snapshots of the body. Instead, they visualize metabolic processes and can help tell the difference between a growing tumor and scar tissue orbenign growths.
RecapOn X-rays, lung cancer is missed in 20% to 23% of cases. This is why CT is considered a much more reliable tool for diagnosing this disease.
On X-rays, lung cancer is missed in 20% to 23% of cases. This is why CT is considered a much more reliable tool for diagnosing this disease.
Chest X-rays are also notsensitive or specificenough to screen for lung cancer.
A 2011 study followed 150,000 people at high risk of lung cancer. Researchers found that four years of annual chest X-rays did not change the death rate in the group. Some cancers were detected, but the tumors were generally advanced enough that finding them on X-ray did not change the patient’s ultimate outcome.
Instead of chest X-rays, annual low-dose CT scans are recommended for people at high-risk for lung cancer. In this population of adults, screening can significantly reduce the risk of advanced cancer and premature death.
Lung Cancer Screening RecommendationsThe U.S. Preventive Services Task Force (USPSTF) recommends annual chest CT scans if you meetallof the following criteria:Age 50 to 80Smoked at least 20pack-yearsCurrent smoker or quit smoking within the past 15 yearsThe American Cancer Society also recommends annual screening for those in the same age group and pack-year smoking history, but unlike the USPSTF, it does not suggest a time limit on when to stop yearly screening.
Lung Cancer Screening Recommendations
The U.S. Preventive Services Task Force (USPSTF) recommends annual chest CT scans if you meetallof the following criteria:Age 50 to 80Smoked at least 20pack-yearsCurrent smoker or quit smoking within the past 15 yearsThe American Cancer Society also recommends annual screening for those in the same age group and pack-year smoking history, but unlike the USPSTF, it does not suggest a time limit on when to stop yearly screening.
The U.S. Preventive Services Task Force (USPSTF) recommends annual chest CT scans if you meetallof the following criteria:
The American Cancer Society also recommends annual screening for those in the same age group and pack-year smoking history, but unlike the USPSTF, it does not suggest a time limit on when to stop yearly screening.
Most health officials feel the risks of annual CT screening in other groups outweigh the benefits. A 2019 study, though, suggests otherwise.The study’s authors say low-dose CT screening in non-smokers detected a significant number of cancers in the early stages that would have otherwise been missed.
On the downside, it’s not clear if annual exposure to low-dose radiation might actually increase the risk of lung cancer over time.
Understanding Lung Cancer Prognosis
There are things you can do to reduce your risk of a missed lung cancer diagnosis:
Summary
Chest X-rays may occasionally find advanced lung cancers, but they are not good at diagnosing cancer in the early stages. This is because they are low-resolution, and it’s easy for small cancers to be obscured behind other structures.
CT scans are generally better at diagnosing lung cancer. They may also be helpful for lung cancer screening in high-risk patients.
If you think you have symptoms of lung cancer, ask your doctor about a CT scan. Don’t depend on a chest X-ray for a diagnosis.
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