By Keishi Takahashi

Showbiz reporter Masaru Nashimoto died from lung cancer on Aug. 21, even though he was a nonsmoker.

Cancer is the No. 1 cause of death in Japan, and of all the different types of cancer, lung cancer claims the most lives every year.

Most people know that smoking increases the risk of lung cancer. According to the National Cancer Center, a Japanese male smoker is 4.4 times more likely to develop lung cancer than a Japanese male nonsmoker, and among Japanese women, smokers are 2.8 times more likely to develop the disease than nonsmokers. However, in the United States and Europe, smokers are at least 20 times more likely than nonsmokers to get lung cancer.

However, there has recently been an increase in the number of nonsmokers who develop lung cancer.

Although most people simply say "lung cancer," the disease is actually classified into four types, depending on factors such as the shape of the cancer cells.

Squamous cell carcinoma and small cell carcinoma, both of which often develop near the main bronchi at the entrance of a lung, are strongly related to smoking.

Glandular cancer that develops on the exterior of the lung accounts for more than half of all lung cancer cases, with even nonsmokers being affected. Female nonsmokers with cancer, a group that has received greater attention recently, usually have glandular cancer.

Large cell carcinoma, which also tends to develop on the outside of the lung, is the fourth type of lung cancer.

According to a survey by the Japanese Association for Thoracic Surgery, 30 percent of patients with lung cancer who underwent surgery in Japan in 1997 had squamous cell carcinoma, and 60 percent had glandular cancer. The same survey showed that in 2007, squamous cell carcinoma accounted for 21 percent of cases, while glandular cancer accounted for 68 percent. The ratio of patients with glandular cancer has risen over the past 10 years.

Commenting on the increase of lung cancer in nonsmokers, Prof. Norihiko Ikeda of the department of respiratory and thyroid surgery at Tokyo Medical University said: "Some have said that factors such as air pollution might be behind [the rising incidence], but we're not sure yet. Cancer begins from errors in cell division, and [the rising incidence] may have something to do with a higher probability for these mutations in the aging population."

The effectiveness of anticancer drugs depends on the type of lung cancer. Recently, the type of drug used is being determined based on the examination of cancer cells extracted from the body.

According to a company Nashimoto belonged to, the type of lung cancer he had was not able to be determined even by cellular examination. Even though Nashimoto was not a smoker, it is possible that second-hand smoke contributed to his developing lung cancer.