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Lung Cancer: Causes, Diagnosis, & Treatment, As Per Expert

Lung cancer is the leading cause of cancer-related death worldwide. The mortality from lung cancer is more than breast, prostate, colorectal, and brain cancers combined.

Only one out of five lung cancer patients survive for five years and beyond from the time of diagnosis.

In an exclusive interaction with OnlyMyHealth editorial team, Dr Krishna Kiran, Consultant Surgical Oncologist, American Oncology Institute, Hyderabad, elucidates on the diagnosis and treatment of lung cancer.

Causes And Risk Factors Of Lung Cancer

Smoking is predominantly and overwhelmingly the single most important causative factor for lung cancer. Around 80% of lung cancer patients are current or former smokers. The risk increases with the number of cigarettes smoked per day and also the duration of smoking. Even former smokers have an increased risk of lung cancer compared to nonsmokers for up to 15 years after smoking cessation.

People who are in close proximity to smokers are also at an increased risk due to passive smoking. Cigarette smoke contains more than 60 harmful carcinogenic substances. Around 19 types of cancers are associated with smoking and tobacco use.

Other risk factors for lung cancer include industrial pollution, genetic factors, air pollution, etc. In the Asian population, 20-30% of lung cancers occur in people who have never smoked. The cause is not known. However, the genetic mutations in nonsmoker lung cancers are different from those cancers which develop in smokers.

Symptoms Of Lung Cancer

Persistent cough, shortness of breath, and chest pain are the most common symptoms. Sometimes, there may be hemoptysis (blood in the sputum). Unfortunately, these symptoms occur late in the course of the disease which is largely responsible for the high mortality associated with this disease. These symptoms are also present in patients with COPD (chronic obstructive airway disease), which is common in smokers and leads to delay in diagnosis and treatment.

Are there any screening tests for lung cancer?

In people at high risk, that is, current and former smokers, a yearly low-dose CT scan is recommended to identify cancers at an early stage. This strategy has helped in reducing the risk of death from lung cancer by around 20%.

How is lung cancer diagnosed?

There is no other disease in which technology has been used so extensively. In fact, rapid advances in imaging technology, biopsy techniques, molecular biology, and drug development have brought about the paradigm shift in the course of this disease over the past decade. Today it is possible to biopsy the smallest of lung nodules, which was not the case 20 -25 years ago.

Different techniques can be used to biopsy the nodules depending on the size and location. These include bronchoscopic biopsy, radial endobronchial ultrasound-guided biopsy, navigational bronchoscopy, cryobiopsy, an endobronchial ultrasound-guided biopsy of the mediastinal lymph nodes, and CT scan-guided transthoracic needle biopsy. A PET-CT is performed to stage the disease. There are 2 broad types of lung cancer, non-small cell (which accounts for 90% of cases) and small cell. In non-small cells, adenocarcinoma and squamous cell carcinoma are the predominant subtypes.

What are the stages of lung cancer?

There are four stages. In stage1, the tumor is confined to the lung that too in one lobe of a lung. In stage II, the tumor is larger in size or has invaded some of the surrounding structures such as the pleura or chest wall or spread to the lymph nodes draining the affected lobe. In stage III, the tumor has spread to a higher level of mediastinal lymph nodes. In stage IV, cancer would have spread to other organs.

How is lung cancer treated?

Lung cancer treatment involves a team of doctors across various specialties- surgical, medical and radiation oncologists, pathologists, radiologists, and pulmonologists. Treatment decisions are taken in multidisciplinary tumor board meetings and treatment decisions are based on the stage of the disease and the health condition of the patient. In stage 1, for small tumors, surgery is the mainstay of treatment. It involves the removal of the affected lobe and the draining lymph nodes. This is typically performed by a minimal invasive VATS (video-assisted thoracic surgery) approach or robotic approach, which is associated with shorter hospital stay and early recovery.

Alternatively, radiation can be used to treat these tumors in those patients who are not fit for surgery. In stage 2, surgery is performed and followed by postoperative chemotherapy. In stage III, a combination of chemotherapy and radiation is employed. For stage 4 tumors, treatment is largely medical. In the last decade, an explosion of newer targeted therapies has happened in the field of lung cancer. Advances in molecular testing and the development of drugs that target specific driver mutations have revolutionized the treatment of advanced lung cancers.

Today, molecular tests are performed on the biopsy samples using NGS (next generation sequencing) platforms and hundreds of genetic mutations are studied in a short span of time. Medical oncologists then use this data to tailor the treatment for each specific patient. This is known as personalized medicine. Using this approach, prolonged survival is being achieved in some cases of advanced-stage lung cancers.

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