Cancer continues to be a global health issue associated with tremendous health and economic burdens for both patients and the healthcare system. In the United States, cancer is the second leading cause of death among both men and women. The National Center for Health Statistics projects that in 2022 an estimated  1.9 million new cancer cases and 609,360 cancer deaths will occur in the U.S.

The American Lung Association indicates that an estimated 541,000 Americans living today have been diagnosed with lung cancer at some point in their life. The American Cancer Society (ACS) has stated that lung cancer is the leading cause of cancer-related mortality in both men and women not only in the U.S. but also globally, and that it accounts for an estimated 25% of all cancer deaths. Nearly 53% of lung cancer cases occur in individuals aged 55 to 74 years, and 37% of cases occur in persons aged 75 years and older.

For both men and women, the median age of lung cancer diagnosis is 70 years. Moreover, although lung cancer can occur in young adults, just 10% of cases occur in those younger than age 55 years. Lung cancer is the leading cause of death by any means in men older than age 40 years and in women older than age 59 years.

Cigarette smoking is the most common risk factor for development of lung carcinoma; other risks include passive smoke inhalation, exposure to residential radon, occupational exposures, infection, and genetic susceptibility. In the U.S., active smoking is responsible for nearly 85% to 90% of lung cancer cases. Occupational exposures to carcinogens account for approximately 9% to 15% of lung cancer cases, and outdoor air pollution accounts for 1% to 2% of cases. Exposure to radon is estimated to be the second leading cause of lung cancer, accounting for an estimated 21,000 lung cancer deaths annually. Both exposure (environmental or occupational) to particular agents and an individual’s susceptibility to these agents are believed to be factors that heighten one’s risk of developing lung cancer.

There are two major types of lung cancer: small cell lung cancer (SCLC) and non–small cell lung cancer (NSCLC). In general, about 13% of all lung cancers are SCLC, and 84% are NSCLC. SCLC is considered extremely aggressive, almost always occurs in smokers, and nearly 80% of patients have metastatic disease at the time of diagnosis. There are two types of SCLC: small cell carcinoma and combined small cell carcinoma.

The clinical behavior of NSCLC is more variable and is contingent on histologic type, but about 40% of patients will have metastatic disease outside the chest at the time of diagnosis. The main subtypes of NSCLC are adenocarcinoma, squamous cell carcinoma (SCC), and large cell carcinoma (LCC). According to the ACS, these subtypes, which originate from different types of lung cells, fall under NSCLC because their treatment and prognoses are often comparable.

Oncogenic driver mutations have been identified principally in adenocarcinoma, and research efforts are exploring means to identify comparable mutations in SCC (e.g., fibroblast growth factor receptor 1, discoidin domain receptor 2, and phosphoinositide 3-kinase.

Adenocarcinoma is the most frequent type of primary lung cancer, accounting for about 40% of all lung cancer cases. In the U.S., adenocarcinoma is the primary cause of cancer death and is the most common lung cancer among individuals who have never smoked.

SCC is the second most common type of NSCLC, accounting for about 30% of all NSCLC cases. This subtype is associated with smoking and occurs more frequently in women.

LCC accounts for about 5% to 10% of all lung cancer cases. This subtype can appear on any part of the lung, and it tends to grow and metastasize quickly.

The types of lung cancer occurring in the U.S., as well as in many other countries, have also changed in the past few decades. For example, the frequency of adenocarcinoma has increased, and the frequency of SCC has declined. The majority of lung carcinomas are diagnosed at an advanced stage, which is often associated with a poor prognosis; therefore, there is an urgent need to expand awareness about the significance of early diagnosis and prompt clinical intervention in order to possibly improve clinical outcomes in affected patients.

In the U.S., lung cancer survival rates are improving, although risk of disease development and outcomes vary by age, gender, race, and socioeconomic status. Survival statistics from the ACS also indicate that NSCLC has a 5-year survival rate of 25%, whereas SCLC has a 5-year survival rate of 7%. According to a 2020 review, researchers stated that various factors may significantly improve treatment outcomes and survival rates among individuals with NSCLC, such as obtaining an earlier diagnosis, using a more accurate and detailed classification system for lung cancers, and advances in treatments.

According to the Lung Cancer Research Foundation, there is promising news: The number of new lung cancer diagnoses has been decreasing progressively by 2% annually since the 2000s, and mortality rates due to lung cancer have been cut in half for men and by a third for women.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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