Two years ago, in 2023, it came as a shock for fans to learn that veteran actress Sharmila Tagore was battling cancer. She was diagnosed with lung cancer, but at stage zero. Recently, her daughter Soha Ali Khan opened up about the experience of her mother being diagnosed early on and how it helped her in treatment and recovery.In an interaction with Nayandeep Rakshit, she said, "With my mother, she was one of the very few people to be diagnosed with lung cancer at stage zero, and no chemotherapy, nothing. It was cut out of her and she is, touchwood, fine."The first time the conversation about this was made publicly was during Sharmila's appearance on Koffee with Karan. Host Karan Johar had said, "I would offered Sharmila ji the part played by Shabana ji. She was my very first choice. But because of health reasons at that time, she couldn't say yes." To this, Sharmila responded, "After my cancer...they didn't want me to take that risk."What Is Stage Zero Lung Cancer?As per the American Lung Association, Stage Zero is an early-stage lung cancer that is only in the top lining of the lung or bronchus and has not yet spread.Why Is Staging So Important?The American Lung Association notes that once your specific type of lung cancer has been identified, the next crucial step in the journey from diagnosis to treatment is staging. This process determines how far the cancer has spread and helps your care team design the most effective treatment plan for you.To assign a cancer stage, doctors use a combination of imaging tests—such as CT scans and PET scans—and tissue tests like biopsies. These provide a comprehensive view of the cancer’s location and extent.Staging does more than guide treatment—it also offers insight into your overall prognosis, or likely course of the disease. By looking at data from other patients with the same type and stage of lung cancer, doctors can estimate outcomes. However, it’s important to remember that each case is unique, and no doctor can predict exactly how your cancer will respond to treatment or determine your life expectancy with certainty.The staging process can vary depending on the individual case. Generally, it starts before treatment begins, based on the results of imaging and biopsy tests. This is called the clinical stage.For some patients, doctors recommend pre-treatment intranodal staging—also known as invasive nodal staging or intrathoracic staging. This involves examining the lymph nodes in the chest to see if cancer has spread there. Understanding this early can be especially important if the cancer hasn’t yet reached other organs, as it helps doctors determine the full extent of the disease and tailor the treatment accordingly.Pre-treatment intranodal staging is best done before therapy begins and can sometimes alter the clinical stage based on more detailed information. Two procedures commonly used for this are:EBUS-TBNA (Endobronchial Ultrasound with Transbronchial Needle Aspiration): A minimally invasive test that uses a bronchoscope and a needle to collect tissue or fluid samples from chest lymph nodes.Mediastinoscopy: A surgical procedure that allows doctors to examine and take samples from the mediastinum—the space behind the breastbone between the lungs.If a patient undergoes surgery as their first treatment, doctors may assign a pathological stage afterward. This combines the clinical stage with findings from the surgery itself, often providing a more accurate picture of the disease and informing future treatment steps.If the cancer returns after treatment, it will be restaged, often using the same types of tests that were done during the initial diagnosis.What Determines Lung Cancer Stage?Lung cancer staging is based on three main criteria, commonly referred to as the TNM system:T (Tumor): Size of the tumor and its exact location in the lung.N (Nodes): Whether the cancer has spread to nearby lymph nodes, especially in the chest.M (Metastasis): Whether the cancer has spread to other organs in the body.Each of these components is assigned a value, which is then used to determine the overall stage of the cancer. This system helps guide treatment decisions and gives patients and caregivers a better understanding of the disease.