Stage 0 Non-Small Cell Lung Cancer

Definition, Symptoms, and Treatment for Carcinoma In Situ of the Lungs

In This Article

Stage 0 non-small cell lung cancer, also known as carcinoma in situ, is the earliest stage at which lung cancer can usually be detected. Lung cancer is rarely found at this stage, and when it is, it is often an incidental finding when testing is done for some other reason. In theory, lung cancer should be completely curable at this stage since it is noninvasive. That said, many people with stage 0 lung cancer have or develop second primary cancers, and learning about cancer prevention is an important part of treatment.


Stage 0 non-small cell lung cancer defines a tumor that is present in only a few layers of cells and has not grown beyond the inner lining of the lungs (something called the basement membrane). Stage 0 (carcinoma in situ) is considered non-invasive, meaning at this stage it is not yet capable of spreading to other regions. In contrast, stages I to IV lung cancer are considered invasive.

Oncologists use the TNM system to further define the stages of lung cancer, with T representing tumor size, N indicating the presence of lymph nodes that contain cancer cells, and M standing for metastases (the spread of the tumor to the other lung or distant regions in the body.

According to the TNM system, Stage 0 lung cancer is defined as:

  • Tis, N0, M0: Meaning the tumor is in situ (present in only the cells in which it started and has not spread to nearby tissues) and has not spread to any lymph nodes or distant regions of the body).


Stage 0 lung cancer is very small and should have minimal, if any, symptoms. In fact, if any symptoms are present, they are likely related to another condition or another lung cancer. Since it is often found “accidentally,” during testing, whatever symptoms prompted testing in the first place are often present. These might include a persistent cough, shortness of breath, pain in the chest, back, or shoulders, or general symptoms such as fatigue.


The treatment of choice for stage 0 lung cancer is surgery. Radiation or chemotherapy is not usually used, though a specialized form of radiation called stereotactic body radiotherapy (SBRT) may be used if the area is inoperable or if a person will not tolerate surgery. Different types of surgery are commonly performed for lung cancer, and, depending on the location of the tumor, one of the less invasive types of surgery (for example a wedge resection) or a segmental resection can often be performed.

In the past, a thoracotomy was often performed, a procedure in which a large incision is made in the chest, part of a rib removed, and tissue removed in this way. More recently, minimally invasive surgery known as video-assisted thoracoscopic surgery has been used for many of these cancers, especially small tumors such as stage 0 tumors, with a more rapid recovery and less pain.

Clinical trials are in progress looking at still less invasive procedures to treat stage 0 lung cancer, such as photodynamic therapy, radiofrequency ablation, or brachytherapy. 


Since stage 0 lung cancer is by definition non-invasive, it should, in theory, be curable with surgery. Unfortunately, many people with stage 0 lung cancer have second primary cancers, and the prognosis depends on the stage of the more advanced cancer. Individuals with stage 0 lung cancer are also at risk of developing another lung cancer in the future.


Studies suggest that learning as much as you can about your cancer improves your outcome. Ask questions. Talk to your doctor about clinical trials that may be appropriate for you. Consider joining a support group. Ask for and allow your loved ones to help. A diagnosis of lung cancer at this early stage is a great opportunity to make changes that might give you a healthier future. Look at your lifestyle and see if you can do anything to lower your risk of developing lung cancer again:

Followup and Prevention

If you've been treated for stage 0 lung cancer, your doctor will want to follow you periodically for the rest of your life. In theory, stage 0 lung cancer should be curable since it is not invasive, but caution is still in order. Importantly, having had lung cancer in the first place is a very significant risk factor for developing a second primary lung cancer. A second primary lung cancer refers to a separate lung cancer unrelated to your first cancer. Talk to your doctor about the best method and timing for followup to make sure that a new primary lung cancer would be caught as early as possible.

Lung Cancer Screening

For those who have not had a previous lung cancer (even stage 0), lung cancer screening is now recommended for people who are:

  • Between the age of 55 and 80
  • Have smoked a total of 30 pack years or more
  • Continue to smoke or quit within the last 15 years
  • Are good candidates for surgery if a tumor is detected.

People with other risk factors may wish to consider screening as well.

Lung Cancer in Never Smokers and Former Smokers

While screening is often recommended for people who smoke, it's important to note that the majority of people who develop lung cancer in 2019 are nonsmokers; they either never smoked or quit in the past. While heart disease drops off rapidly when people quit smoking, the risk of lung cancer persists and rarely returns to normal.

A Word From Verywell

Stage 0 non-small cell lung cancer is the earliest stage of the disease, though there has been debate over whether "carcinoma in situ" should truly be considered cancer. Though the cells are clearly identifiable as cancer cells, there is theoretically no chance that they could spread (if removed). Since we don't currently have a screening tool that reliably detects lung cancer at this stage, many people are accidentally diagnosed are considered fortunate. Hopefully, tests will be developed in the near future that will change the detection of stage 0 lung cancer from being a providental accident to being intentional.

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