Dr. Tsubokura's Radiation Lecture Vol.142

Author: Masaharu Tsubokura M.D., PhD.

Editors: Akihiko Ozaki M.D.,PhD., Yuki Senoo MUDr.

283. There are many causes of cancer

The adverse health effects of radiation exposure include a bleeding disorder (difficulty in stop bleeding) and diarrhea. These health effects of radiation are called “deterministic effects of radiation” as it is "determined" to happen to those who received a significantly high dose of radiation exposure.

On the other hand, the risk of cancer from radiation exposure is a bit complicated to explain. The basic principle is that when you receive a high-dose radiation exposure, the risk of developing cancer in the future increases. This does not mean you will "definitely" get cancer in the future, or you will not get cancer if you had not been exposed to radiation. Radiation exposure-induced cancer is thought to occur in a “stochastic manner” because the probability of cancer development increases with the dose of radiation.

　In other words, while we know that when many people are exposed to a high level of radiation at the same time, the "number" of people who develop cancer higher in the group exposed to radiation compared to the group of people who develop cancer did not. However, it is impossible to distinguish between the person who developed cancer caused by radiation exposure and other causes.

This is because you can develop cancer whether you are exposed to radiation or not, and it can be caused by various things, including bad eating habits, smoking, and infections.

　The explanation for the stochastic effect of radiation exposure may sound unclear. For this reason, it is important to know the probability of cancer development given the current air dose rate.

284. The exact cause of cancer cannot be determined

　The previous article explained that the probability of developing cancer in the future increases as the radiation exposure increases. Moreover, this does not mean that anyone exposed to radiation will "definitely" develop cancer, or you will be cancer-free if you are not exposed to cancer.

　Radiation exposure is certainly one of the causes of cancer, however, there are many other risk factors of cancer. Therefore, it is almost impossible to pinpoint the exact cause of cancer.

　At the present day, we understand that as radiation exposure increases, the probability of developing cancer in the future increases. Furthermore, this type of radiation effect is called the “stochastic effect.” This is because radiation damages (mutates) the genes of cells, which develop into cancer cells. The basic idea is that the higher the dose of radiation you are exposed to, the higher probability that mutations occur.

　Cancer cells are often compared to an uncontrolled car with broken accelerators and brakes. Unlike normal cells in our body, since the cancer cells have constantly pressed accelerators or broken brakes, they cannot operate properly cooperating with their surroundings and continue to grow irregularly on their own. The terms “genetic damage” and “mutation” indicate the car's state, having constantly pressed accelerators and broken brakes.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 21st and 26th June, 2020 was reproduced for MRIC Global under the author's permission.