Lung Cancer Rates are Dropping Overall, But Some Subtypes are Still Increasing

As overall lung cancer rates continue to fall, research from the U.S. National Cancer Institute (NCI) shows that some subtypes of lung cancer are increasing.

"The good news is that lung cancer rates are declining. However, it's not as clear for certain subtypes, and we are not exactly sure of the reasons behind these increases," said lead study-author Denise Riedel Lewis, an epidemiologist at the NCI, via WebMD.

Researchers are still uncertain what exactly to peg this decline to. However, they believe that a drop in smoking may explain the general decline as it's estimated that 90 to 95 percent of lung cancers in the United States are caused by smoking, alone. 

However, a subtype of lung cancer that is on the rise called adenocarcinoma accounts for about 40 percent of all lung cancers, according to the American Cancer Society (ACS). The cancer may start in the outer tissues of the lung and gradually transform into other types of lung cancer.

Some believe that these changes could be a result of the way that smokers receive their nicotine fix. 

"The deeper you breathe in smoke, the more likely the cancer-causing tars are going to get into the outer area of the lungs, and that's where adenocarcinoma starts," said Dr. Norman Edelman, a senior medical advisor to the American Lung Association.

Another subtype has health officials worried.  Squamous cell carcinomas, a centrally located cancer that usually hits the larger bronchi or trachea of the lung, account for 30 percent of lung cancers. Thought this type of cancer is declining, the rate is much slower than normal, according to researchers.  

More information regarding the findings can be seen via the journal Cancer.