TREATING ADVANCED PROSTATE CANCER: HOW LONG DO HORMONES WORK?
This varies from man to man. Ten percent of men with M+ (D2) disease— metastatic prostate cancer—live less than six months. Ten percent live longer than ten years. The rest fall somewhere in the middle; statistics show that half of these men live three years or less, and only 25 percent are alive after five years. What accounts for the extreme disparity in these numbers? It all has to do with the ratio of hormone-sensitive cells to hormone-insensitive cells, and how fast the cancer grows. In some men, nearly every cell is responsive to hormones; in other men, very few cells are hormone-sensitive. Some cancers take hundreds of days to double in size; others double every few weeks.
There is a mathematical model of how these cancer cells grow, called tumor kinetics. A tumor must double in size thirty times before a doctor can even feel it—before there’s a centimeter of cancer. This growth is logarithmic—two cells, then four, then eight, etc. Say a tumor is at its tenth doubling; it has 1,024 cells. And say that three-fourths of these cells are responsive to hormones. The patient is castrated, and all the hormone-responsive cells drop out of the picture, leaving only 256 cells. What happens? These cells aren’t affected by the hormones; they continue to grow. The now-smaller tumor doubles. There are 512 cells. It doubles again—1,024 cells. It’s back to where it started. And when it doubles again, there will be twice as many cells as before.
Now say only 1 percent of this cancer is not responsive to hormones. It’s going to take many more doublings before this tumor becomes dangerous. So how long hormones work depends on two things: The ratio of hormone-resistant cells to hormone-dependent cells, and how long it takes for the cancer to double in size. Relapse will come a lot sooner in a man whose cancer doubles every 30 days, for example, than in a man whose cancer takes 100 days to double.
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Tags: Erectile Dysfunction, Men’s Health