A chest X-ray produces the following images:
- Blood vessel
- sternum and spine
If lung or heart disease is suspected, this is usually the first imaging test your doctor orders. If lung cancer is present, chest X-rays can sometimes detect larger tumors. However, they often fail to diagnose the disease. Chest X-rays are also inadequate as a screening tool for lung cancer.
This article looks at chest X-rays and their use in the diagnosis of lung cancer. It also discusses some other diagnostic tools doctors may use when they suspect lung cancer.
Limitations of chest X-rays
X-rays use radiation to create two-dimensional images of internal organs. Organs and tissues that absorb less radiation will be easiest to see on the image. This includes the lungs and the gas in the lungs.
Stories of lung cancer being found on an X-ray are not uncommon. However, when this happens, the disease is usually in an advanced stage. Cancer is visible because the tumor is large and hard to miss.
The problem is that advanced lung cancer found in stage 3b or 4 is more difficult to treat. With very few exceptions, these advanced lung cancers are incurable. This is why chest X-rays are a poor tool for diagnosing lung cancer.
Overview of lung cancer staging
low resolution images
X-ray images are shown in shades of gray. They need to be interpreted by a radiologist trained in finding abnormalities. Even so, the resolution of the image is not high, and it’s easy to miss fine details. Substances with similar densities such as blood, pus, and water are difficult to distinguish.
On a chest X-ray, any abnormal growths in the lungs will appear as relatively solid, light gray areas.Growth can be cancer, but it can also be of any number benign or non-cancer conditions.
Based on X-rays alone, all a radiologist can do is describe growths in general terms, such as:
- Lung nodules: Points 3 centimeters in diameter or about 1.5 inches or less
- Lung mass: a spot greater than or equal to 3 cm in diameter
- Lung shadows: an imprecise term that can describe anything from tumors to overlapping structures in the chest
- Lung tumor: A term describing any form of “new growth” in the lung, including any benign
- Lung lesions: any abnormality, whether benign or cancerous
A chest X-ray alone cannot confirm cancer or something more benign, such as a cyst or scar.
Normal body parts like bones can mask tumors on X-rays and make them hard to see. This is especially true if they are small. The disease process can also make cancerous changes difficult to see. For example, pneumonia often occurs with symptomatic lung cancer. If you have pneumonia, pus and mucus that block your airways can easily hide tumors.
Tuberculosis (TB) also looks similar to some lung cancers on X-rays. These situations often occur at the same time. When this happens, TB may be diagnosed when it is missed. Even after the TB infection goes away, doctors may consider the remaining spots to be scars without investigating them.
Most common form of lung cancer
On X-rays, small cancers can sometimes hide in the bones or in the course of other diseases, such as pneumonia or tuberculosis.
In some cases, patients may be told that their chest X-rays are normal, only to learn they have cancer months or years later. In these cases, the cancer may be exposed after advanced symptoms. These may include:
- unexpected weight loss
- cough up blood
This may seem like an oversight, but chest X-rays have fundamental limitations. This is especially true when 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 detect and more likely to miss on chest X-rays. A 2017 study found that 45% to 81% of missed lung cancers occur in the upper part of the lung where the collarbone and other structures block the view.
lung adenocarcinoma It is the most common form of lung cancer. It usually occurs on the outer edges of the lungs and is hard to spot. This type of cancer is more likely to be missed than cancers that occur near large airways, such as small cell lung cancer and lung squamous cell carcinoma.
Tumors smaller than 1.5 centimeters (0.6 inches) are more likely to be missed on chest X-rays than larger tumors.
Lung adenocarcinomas often have a diffuse “ground glass” appearance. These types of tumors can also be difficult to see on X-rays.
Cancers located high in the lungs and on the outer edges of the lungs may be difficult to see on X-rays. Small tumors and tumors with a diffuse appearance are also easily missed.
Sometimes lung cancers are missed simply because no one is looking for them. Unless you have symptoms or your doctor knows you are at high risk for lung cancer, there may be no reason to suspect cancer.
Only 65% of doctors ask patients if and how much they smoke. Doctors also often don’t ask patients about their past smoking history if they say they are “non-smokers.”
Former smokers are generally considered to be less at risk, even if they have a high rate of smoking in the past. Likewise, people who never smoked were in the middle, as lung cancer was unlikely to be the cause of respiratory disease in this group. It should be noted, however, that lung cancer diagnoses are increasing among never-smokers.
Additionally, many of the symptoms of lung cancer, such as shortness of breath or fatigue, can easily be attributed to factors such as age or obesity.
- Women tend to be diagnosed later than men.
- Non-smokers are diagnosed later than smokers.
- Younger adults are diagnosed later than older adults.
What are the risk factors for lung cancer?
If a patient’s risk factors are unknown, doctors may miss lung cancer. People considered to be at lower risk may also receive a later diagnosis because lung cancer is uncommon in these populations.
How often X-rays miss lung cancer
Surprisingly, few recent studies have looked at the incidence of missed diagnosis of lung cancer. However, the research that has been done is sobering.
A 2019 review of 21 studies found that 20 to 23 percent of chest X-rays from people with symptoms of lung cancer were falsely negative for lung cancer. This can be catastrophic, as lung tumors take an average of only 136 days to double in size.
Stage 1, 2, and 3a lung cancers are considered treatable. If the disease is allowed to progress, it can quickly go from treatable to inoperable. Not only does this make management more difficult, but it also drastically reduces the time patients live.
How fast does lung cancer grow?
How to Diagnose Lung Cancer
While investigating another condition, a chest X-ray may reveal lung cancer “by accident”. Nonetheless, it is not one of the most commonly used tools for diagnosing lung cancer due to the aforementioned issues.
Instead, healthcare providers typically rely on three tests:
- calculate tomography (CT). This scan takes multiple X-ray images and combines them into three-dimensional “slices”. This makes it easier to see lung abnormalities.
- Bronchoscopy. During this procedure, a pulmonologist uses a camera attached to a thin tube to look inside the airways and lungs.
- Lung biopsy. Use a needle or other method to extract suspicious tissue. This test is usually ordered if a CT scan suggests cancer. The results can provide definitive evidence of the disease.
If cancer is diagnosed, other tests will help stage and grade the tumor. This process helps doctors understand how advanced the cancer is so they can decide on the right treatment.
Positron emission tomography (PET) scans are not usually used to diagnose lung cancer. They are thought to be more useful for staging of disease. PET scans do not take snapshots of the body. Instead, they visualize metabolic processes and can help differentiate between a growing tumor and scar tissue or benign growth.
How to Diagnose Lung Cancer
Lung cancer is missed in 20 to 23 percent of cases on X-rays. This is why CT is considered a more reliable tool for diagnosing this disease.
Lung Cancer Screening
Chest X-rays are also not sensitive or specific enough to screen for lung cancer.
A 2011 study followed 150,000 people at high risk of lung cancer. The researchers found that four years of annual chest X-rays did not change mortality in this group. Some cancers were detected, but tumors were often advanced enough that finding them on an X-ray did not change the patient’s final outcome.
Yearly low-dose CT scans, rather than chest X-rays, are recommended for people at high risk of lung cancer. In this group of adults, screening can significantly reduce the risk of advanced cancer and premature death.
Lung Cancer Screening Recommendations
Interim guidelines from the United States Preventive Services Task Force (USPSTF) recommend annual low-dose chest CT scans if you: all The following standards:
- 50 to 80 years old
- Smoking at least 20 pack years
- Continued smoking or quit smoking within the past 15 years
Using these guidelines, CT screening could reduce lung cancer mortality by 20% in the United States.
Most health officials believe that the risks of annual CT screening for other groups outweigh the benefits. However, a 2019 study suggests otherwise. Low-dose CT screening in non-smokers detects a large number of cancers at an early stage that would otherwise be missed, the study authors said.
On the downside, it’s unclear whether annual exposure to low-dose radiation actually increases the risk of lung cancer over time.
Understanding Lung Cancer Prognosis
what can you do
There are a few things you can do to reduce your risk of missing a lung cancer diagnosis:
- Compare the results: If you have chest X-rays, make sure your doctor knows and can access any old chest X-rays you’ve ever had. Comparisons can often detect subtle changes that might otherwise be overlooked.
- Report symptoms: Make sure all your symptoms and risk factors are on the radiology order. This can add context to the findings and encourage radiologists to look for subtle signs.
- Be your own advocate: If your respiratory symptoms don’t go away and the cause isn’t found, don’t give up. This is especially true if you only had a chest X-ray. Seek a second opinion and ask if a CT scan is a reasonable option.
Advocating for yourself as a cancer patient
Chest X-rays may occasionally find advanced lung cancer, but they are not good at diagnosing cancer early. This is because of their low resolution and the fact that small cancers are easily masked by other structures.
CT scans are often better at diagnosing lung cancer. They may also aid in lung cancer screening in high-risk patients.
If you think you have symptoms of lung cancer, see your doctor for a CT scan. Do not rely on chest X-rays for diagnosis.
If you have symptoms of lung cancer, a chest X-ray cannot rule out the disease. A “normal” result may be reassuring, but don’t let it give you a false sense of security.
Don’t ignore persistent symptoms, especially if the cause remains unknown or the diagnosis you get doesn’t explain them. The same goes for people who never smoke.Lung cancer is the sixth leading cause of cancer-related death in the U.S. in this group
If you are at high risk for lung cancer, talk to your doctor about annual low-dose CT screening. If you meet USPSTF criteria, the cost of screening may be covered in whole or in part by your insurance.