How asymptomatic are early cancer patients of five organs based on registry data in Japan

One reason for the low cancer screening rate in Japan is that people are not concerned about cancer if they do not have symptoms.

The authors retrospectively analyzed 18,405 cancer patients using hospital-based cancer registry data collected between 2007 and 2013 at the 13 hospitals of Shimane Prefecture, Japan. The symptomatic rates of five cancers (stomach, colorectal, lung, breast, and cervix) at each stage and the time of early diagnosis were investigated. The early detection rates of symptomatic and asymptomatic individuals were investigated.

The percentages of symptomatic cases tended to increase with progressive stages. The odds ratio (OR) of stage IV compared with that of stage I was 12.23 for stomach, 7.21 for colorectal, 16.91 for lung, 10.30 for breast, and 51.62 for cervical cancer. The proportions of early symptomatic cases at the time of diagnosis were low. Compared with the percentage of early symptomatic cases of stomach cancer of 25.5%, the percentage of lung cancer was the lowest, at 8.2% (OR 0.26), and the percentage of breast cancer was the highest, at 30.2% (OR 1.26). The percentages of early symptomatic cases of colorectal and cervical cancer were 18.9% (OR 0.68) and 19.9% (OR 0.73), respectively. The early detection rates of the asymptomatic and symptomatic groups were 77.6 and 36.1%, respectively.

Cancer registry data indicate that early cancers are asymptomatic, and once symptoms appear, treatment may not be effective. Policy makers should inform people of the necessity of cancer screening before they have symptoms.