1. The second greatest burden of lung cancer worldwide is attributed to squamous cell carcinoma
2. Large cell carcinoma represents less than 10% of new lung cancer cases in 2020
Evidence Rating Level: 2 (Good)
Study Rundown: Lung cancer is a leading cause of death with a considerable economic burden and an incidence that varies depending on sex and geography. These variations have been attributed to differences in cigarette smoking patterns and chemical composition, as well as the presence of additional lung carcinogens in the environment. This study examined lung cancer incidence in multiple countries for four main histological subtypes of lung cancer (adenocarcinoma, squamous cell carcinoma (SCC), small-cell carcinoma (SmCC), and large-cell carcinoma (LCC)). The primary outcome of this study was the incidence of lung cancer in males and females in 2020 from 185 countries. Additionally, this study examined the burden of lung cancer subtypes in 4 levels of Human Development Index (HDI) values: low, medium, high, very high. In males, there were over 1 million new lung cancer cases, the majority (39%) of which were adenocarcinoma, a quarter were SCC, just over ten percent were SmCC and 8% were LCC cases. In females, there were 770,828 cases. Similarly, adenocarcinoma comprised the majority of new cases, 12% were SCC, 9% were SmCC, and 6% LCC. Males were found to represent the majority sex in those diagnosed with all lung cancer subtypes. The majority of adenocarcinoma, SCC, SmCC, and LCC were found in countries with HDI values of high or very high. These countries comprised 57% of the world’s population in 2020. Limitations to this study include that there were recurrences of poorly specified histology (unspecified morphology), suggesting a requirement for greater accuracy in the morphological data obtained globally. Another limitation of this study arises from the aggregation of regional data to estimate national rates when country-specific data was not available. Additionally, the data compiled by multiple registries within a single country may not accurately represent the nation as a whole. Overall, the results from this study support that adenocarcinoma is the most prevalent lung cancer subtype and the majority of all 4 subtypes of lung cancer were found in high or very high HDI countries.
In-Depth [retrospective cohort]: This study was a retrospective population study that analyzed data from 2020 in 185 countries. There were 1,435,943 new lung cancer cases in males worldwide in 2020. 39% were adenocarcinoma, 25% were SCC, 11% were SmCC and 8% were LCC. During this same period, there were 770,828 cases of new lung cancer in females. As in males, adenocarcinoma represented most new cases at 59%, 12% were SCC, 9% were SmCC, and 6% were LCC. Males were disproportionately diagnosed with lung cancer and comprised 56% of total adenocarcinoma cases, 79% of total SCC, 71% of total SmCC, and 70% of total LCC cases. The greatest contributors to the worldwide male lung cancer burden for 3 of the 4 subtypes (adenocarcinoma, SCC, SmCC) were China, USA, and Japan. The majority of LCC cases were found in China, Indonesia, and India. In females, the countries contributing most to the lung cancer burden were as follows: China, USA, and Japan (adenocarcinoma); USA, China, UK (SCC); USA, China, Germany (SmCC); USA, India, China (LCC).
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