Dr. Tsubokura's Radiation Lecture Vol.101
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
201. It takes a long time for cancer to grow to a detectable size.
According to recent statistics, around one in every two people in Japan will develop cancer in his or her lifetime. Thus, it can be said that cancer has become a common disease that anyone can develop.
The causes of cancer are diverse and include eating habits, heavy drinking, smoking, infectious diseases, and radiation exposure. In fact, it is said that thousands of cancer cells are generated in our bodies every day, even in healthy people. Our bodies’ immune systems eradicate most cancer cells; however, some of them develop genetic changes that help them to escape the immune system. These cancer cells are able to survive, and naturally, cancer gradually increases its mass by proliferation. In most cases, it takes years for cancers to become large enough to be visible after their initial development.
Cancers that are large enough to be diagnosed do not just appear in our bodies all of a sudden. Rather, they have grown in the body for more than a decade or longer, even though they are invisible or not detected by screening tests.
Cancers are diagnosed only as “early-stage cancers” when they grow large enough to be seen or detected via screening. Furthermore, as cancers progress, they are called “advanced cancers.” The aim of cancer screening tests is to detect cancers during the early stage.
202. Cancer treatment is determined by considering multiple perspectives
According to recent statistics, around one in every two people in Japan will develop cancer in his or her lifetime. Thus, cancer has become a common disease that anyone can develop.
Many cancer cells are generated in our bodies every day, and our bodies’ immune systems eradicate most of them. However, some of them develop genetic changes that help them to escape immune detection. These cancers are able to survive and gradually increase their mass via proliferation over time. For this reason, most cancer cells take years to grow to a visible size following their initial development.
Initially, cancer develops in one organ and then later spread (metastasize) to other surrounding organs. For example, cancer that originally develops in the lungs is called “primary lung cancer.” The term “primary” refers to the fact that the cancer developed in a certain organ. Therefore, primary brain cancer refers to cancer cells that originated from brain cells. On the other hand, when colon cancer cells spread to the lungs (metastasis), the cancer cells in the lungs are described as “metastatic lung cancer.” Because the nature of metastatic lung cancer differs from that of primary lung cancer, their treatments are also different.
When cancer is detected, its stage is determined using Roman numerals in four stages (I to IV) according to its size and whether the cancer cells have spread to other organs. When a detected cancer is still small and resides only in its original location, it is determined to be stage I. When cancer spreads to other organs from its original location, it is diagnosed as stage IV.
The cancer treatments, such as the surgical method, chemotherapy, and radiotherapy, is determined according to its primary location (its original location) and its stage (the progression of the disease).