An Overview of Lung Cancer

In This Article

Lung cancer originates in the tissues of the lungs or the cells lining the airways, the bronchi. The disease begins with mutations of normal cells that turn them into cancer cells. These cells divide and multiply at an out of control rate and can eventually form tumors that impede breathing and oxygenation throughout the body. Lung cancer cells can also spread to other regions of the body which, in fact, is the ultimate cause of most cancer deaths. While smoking is a significant cause of the disease, it's not the only one.

The focus on smoking cessation as a way to prevent lung cancer has, in some ways, overshadowed other causes such as radon exposure. For this reason, it is vital that everyone knows the symptoms and causes of lung cancer, as well as how it is diagnosed and treated.

Prevalence

Lung cancer is the leading cause of cancer deaths worldwide, with 1.8 million new cases being diagnosed each year. Overall, 27 percent of cancer deaths in the United States are due to lung cancer.

In the United States, lung cancer has surpassed breast cancer as the most fatal cancer in women. The same is true in men, with the disease being responsible for more deaths than prostate cancer, pancreatic cancer, and colon cancer combined.

Lung cancer in people who have never smoked is the sixth leading cause of cancer deaths in the United States.

Types

There are two primary types of lung cancer:

  • Non-small cell lung cancer is most common, being responsible for 80 to 85 percent of cancers. This is the type of lung cancer more commonly found in non-smokers, women, and young adults.
  • Small cell lung cancer is responsible for around 15 percent of lung cancers. These lung cancers tend to be aggressive and may not be found until they have already spread (especially to the brain). They usually respond fairly well to chemotherapy but have a poor prognosis.

Non-small cell lung cancer is further broken down into three types:

  • Lung adenocarcinoma: Lung adenocarcinoma is responsible for half of non-small cell lung cancers and is currently the most common type of lung cancer. Lung adenocarcinomas are usually found deep in the lungs, where smoke from a filtered cigarette would settle.
  • Squamous cell carcinoma of the lungs: Squamous cell lung cancer was once the most common type of lung cancer, but its incidence has decreased in recent years, possibly due to the addition of filters to cigarettes. Squamous cell cancers tend to occur in or near the large airways—the first place exposed to cigarette smoke.
  • Large cell lung cancer: Large cell carcinomas of the lungs tend to grow in the outer regions of the lungs. These are usually rapidly growing tumors that spread quickly.

Other, less common types of lung cancer include carcinoid tumors and neuroendocrine tumors.

Symptoms

It can be easy to ignore the symptoms of lung cancer, especially if you're not a smoker and, perhaps, not considering that you're also at risk for the disease.

What's more, healthy people usually are not screened for lung cancer unless they have known risk factors like having a family history of lung cancer or being a long-time smoker.

The goal is to detect lung cancer in the early stages, when it is still possible to treat it. Recognizing its symptoms is essential to this.

Overall, the most common symptoms include:

  • Persistent cough
  • Hoarseness
  • Shortness of breath with activity
  • Tightness in the Chest
  • Coughing up blood
  • Unexplained weight loss
  • Chest pain
  • Frequent infections such as bronchitis or pneumonia
  • A general feeling of being unwell

Squamous cell carcinoma and small cell lung cancer tend to cause symptoms early on, which often include a cough and the coughing up of blood.

Lung adenocarcinomas tend to grow for a long time before causing symptoms, which may include mild shortness of breath, subtle weight loss, and a general sense of being unwell.

As the types of lung cancer have changed over the years, the list of possible symptoms has too.

Causes

Lung cancer usually begins several years before it causes symptoms and is diagnosed. Cells in the lungs may become cancer cells after going through a series of mutations that transform them into cancer cells.

You may have a hereditary predisposition to gene mutations, or they may be the result of DNA damage caused by exposure to carcinogens in the environment.

Certainly, smoking is a significant cause of lung cancer, but there are other important causes of lung cancer as well.

Radon exposure in the home, which anyone is at risk for, is the second leading cause of lung cancer and the most common cause in non-smokers. Next in line is secondhand smoke.

Other causes and possible causes include:

  • Occupational exposures
  • Air pollution
  • Wood smoke
  • Cooking with poor ventilation

The human papillomavirus (HPV)—the virus that causes cervical cancer—is associated with some lung cancers, though it's not at all certain if this may be an actual cause of the disease.

Diagnosis

A combination of imaging studies, including computed tomography (CT scan), magnetic resonance imaging (MRI), and positron emission tomography (PET scan) may be used to diagnose lung cancer. In addition, a lung biopsy is usually needed to determine the type.

Until recently, there was no screening test for lung cancer, but that has changed. It's important to note that chest X-rays are not an adequate screening test, as they fail to pick up lung cancers at a stage early enough to improve survival. Lung cancer CT screening is now recommended for people who:

  • Are between the ages of 55 and 80
  • Smoked for at least 30 pack-years (a pack-year is calculated by multiplying the number of packages of cigarettes smoked daily times the number of years smoked)
  • Continue to smoke or quit in the past 15 years

For people with other risk factors, such as a family history of lung cancer, a personal history of chronic obstructive pulmonary disease (COPD), or other risk factors for lung cancer, screening may also be considered.

It is estimated that if everyone who qualified for screening underwent testing, the mortality rate from lung cancer could be decreased by 20 percent.

Staging

After the type of lung cancer is determined, the doctor goes through careful staging—figuring out how extensive a lung cancer is. This step is an important of the diagnosis process because knowing the stage of cancer is instrumental in designing a treatment regimen.

Metastases

Lung cancers can penetrate nearby tissues and spread through either the bloodstream, lymphatic system, or possibly even the airways to distant sites.

The most common sites of lung cancer metastasis (spread) include the brain, bones, liver, and adrenal glands. Some types of lung cancer—for example, small cell lung cancer—are often only diagnosed after the cancer has already spread.

A pathologist can tell that cells are lung cancer cells—and not those related to another type of cancer—based on their appearance under a microscope. This is true even if lung cancer spreads to other regions of the body.

For example, if lung cancer spreads to the brain, cells taken from the metastasis in the brain would be identifiable as and considered to be lung cancer cells. The diagnosis would be lung cancer with metastases to the brain. The lung cancer is the primary diagnosis, while the metastasis is considered the secondary diagnosis.

In contrast, when tumors begin in other parts of the body and metastasize to the lungs, this is not considered lung cancer. Rather, it is referred to as a cancer (e.g., breast cancer) that is metastatic to the lungs.

Treatment

Treatment options for lung cancer have improved significantly in recent years. From surgery and radiation therapy to immunotherapy and chemotherapy, there are a variety of choices and options. Here is an overview of some the more common treatment options.

  • Surgery: There are several types of lung cancer surgery that may be done, depending on the size and location of a tumor.
  • Radiation therapy: Radiation therapy may be given as an adjunct to surgery to decrease pain or airway obstruction due to a cancer, or in high doses to a localized region in an attempt to cure cancer.
  • Chemotherapy: Chemotherapy usually uses a combination of medications to treat lung cancer.
  • Targeted therapies: Targeted therapy drugs are currently available for people who bear tumors with several genetic mutations including EGFR mutations, ALK rearrangements, and ROS1 rearrangements.
  • Immunotherapy: In 2015, two immunotherapy drugs were approved for the treatment of lung cancer. In some cases, these drugs have resulted in long-term survival even for those with the advanced stages of lung cancer.

There are more than 100 medications being studied in clinical trials for lung cancer.

Palliative care, which is designed to address the full spectrum of medical needs for people with cancer (physical, emotional, spiritual), may also be considered as an adjunct. Early studies have found that, in addition to improving quality of life, palliative care may also improve survival.

Integrative treatments, such as acupuncture, may be used to help ease symptoms of cancer and cancer treatments and are now available at many cancer centers.

Though it is rare, lung cancer does, in some cases, just go away. This phenomenon is referred to as spontaneous remission of cancer. Researchers are tapping into this discovery to learn how the immune system ordinarily functions to remove cancer cells, so treatments based on this principle can be developed.

Coping

If you have only recently been told you have lung cancer, you may be very overwhelmed or even frightened. Learning as much as you can about your cancer can help you feel more in control of your treatment and help you play an active role in your care.

You may feel isolated as you face something that, perhaps, nobody in your group of loved ones can understand. Participating in cancer support groups and communities may allow you to connect with others who are walking a similar road.

Be patient with yourself if you are feeling out of sorts. Nobody really knows how they will feel until they are diagnosed. The emotions you experience may span the spectrum from sadness to anger to intense anxiety—sometimes in just a matter of minutes.

A Word From Verywell

For many years, people living with lung cancer have had to cope with not only the stigma of lung cancer being a "smoker's disease," but the myth that it is uniformly fatal. This stigma is changing as people become more aware that, simply put, anyone with lungs can get lung cancer, and that newer and better treatments have recently ​been approved. We still have a way to go, but many people are surviving—and thriving—while living with this disease.

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Article Sources

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  • Learn About Lung Cancer. American Lung Association. https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/lung-cancer/learn-about-lung-cancer/

  • Lung Cancer Screening. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/lung-cancer-screening/about/pac-20385024

  • Pass J, Carbone D, Johnson D. et al. Principles and Practice of Lung Cancer. 4th Ed. Williams and Wilkins: 2010.