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By Peter Galvin, MD

Over the years, the nature of lung cancers associated with cigarette smoking has changed. Once, most people who smoked used unfiltered cigarettes which caused the smoker to inhale larger particles that lodged in the main bronchi and caused tumors in those areas. These tumors had early symptoms like cough and hemoptysis (coughing up blood) that allowed them to be diagnosed early in the disease pathway. This allowed them to be treated before the tumors spread. Today, smokers mostly smoke filtered cigarettes in which the inhaled particles are very small, which allows the toxins to reach the deeper parts of the lungs, where tumors develop without symptoms until the tumors have spread widely, making treatment much more problematic.

For example, small cell lung cancer is a fast-growing cancer that is strongly associated with tobacco smoking. Small cell lung cancer represents 10% to 15% of all lung cancers, and about 16,000 cases were diagnosed in the U.S. in 2024. The average age at diagnosis is 69 years, and it is more common among men than women. About 95% of patients have a history of smoking. Although the risk decreases with smoking cessation, the risk remains elevated in former smokers for more than 30 years after quitting. Up to 60% of patients with small cell lung cancer have no symptoms at the time of diagnosis. It is often diagnosed with imaging studies performed for a different reason, or in other words, small cell lung cancer is often found by accident.

Because small cell lung cancer is often asymptomatic, only about 30% of patients have limited-stage cancer, while 70% have extensive-stage cancer, where the cancer has spread to distant lymph nodes and other areas of the body, commonly the brain. For this reason, it is recommended that current and former smokers have an annual screening chest X ray. First-line treatment of limited-stage disease is usually chemotherapy and radiation therapy, followed by immunotherapy, which is medication that stimulates the immune system to kill remaining cancer cells. A small number of limited-stage patients may be helped by surgery to remove the cancer. Despite this treatment, about 60% of those with limited-stage cancer will develop disease spread to the brain within three years of diagnosis. To help prevent cancer from spreading to the brain, prophylactic cranial irradiation can be performed, but this is often associated with memory loss and impaired cognitive skills.

Treatment of extensive-stage small cell lung cancer is a combination of chemotherapy and immunotherapy, followed by monthly immunotherapy until the tumor progresses or the patient can no longer tolerate the treatment. With the latest treatment advances, about 56% of patients with limited-stage disease survive at least three years after diagnosis, while the three-year survival rate for extensive-stage disease is just 18%.

For more information go to the website of the National Cancer Institute at www. cancer.gov

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