If you or someone you know has breast cancer, you may wonder how fast the cancer is growing. You might also wonder how fast it will continue to grow.
Doctors don’t have a way to know when your cancer first started, which means they can’t know how long it took to get to the size it is now. It could have been weeks, months, or longer.
Typically doctors will remove breast cancer tumors as completely as possible. So, they can’t usually track how quickly it grows past that point either.
Studies show that even though breast cancer happens more often now than it did in the past, it doesn’t grow any faster than it did decades ago. On average, breast cancers double in size every 180 days, or about every 6 months. Still, the rate of growth for any specific cancer will depend on many factors. Every person and every cancer is different. Doctors refer to breast cancers that are more likely to grow quickly as more aggressive than those that tend to grow slower.
Factors affecting breast cancer growth
Even though no one can say how fast a certain breast cancer will grow, doctors can tell if a tumor might grow and spread quickly or slowly depending on several known factors explained below. These expectations for how a cancer will act help you and your doctors decide how quickly and aggressively to treat it.
Breast cancer growth depends on the following factors:
- Subtype. Breast cancers are sorted into several subtypes. Some subtypes grow faster than others. For example, triple-negative breast cancers grow faster than those that are positive for hormone receptors. Your doctor will test a sample of your tumor to see what type it is and how fast it might grow.
- Stage. Doctors give breast cancer a stage based on whether it’s still in the milk ducts or lobules or has grown out into breast tissue, lymph nodes, or beyond. Breast cancer stages go from 0 to IV. Stage IV means it has spread from the breast to distant parts of the body, such as the brain or other organs. Cancers that have broken through ducts or lobules into breast tissue or spread are more likely to keep growing and spreading faster than those that are still limited to the place where they started.
- Grade. Your doctors also may give your cancer another number from 1 to 3 for its grade. The grade is based on how normal your cancer cells look under a microscope. Cells that appear more normal are usually less aggressive or less likely to grow quickly. Very abnormal-looking cancer cells are more likely to grow faster and spread.
- Your age. Most breast cancers happen in women aged 50 or older. But when breast cancer happens at a younger age, it’s more likely to be aggressive and fast-growing.
- Genetics. Because cancer cells replicate faster than normal cells, they tend to pick up random changes in their genes faster than a normal cell does, too. Some of these changes could make the cells grow more quickly. Some people also are born with certain changes in all of their cells that make cancer both more likely and more likely to grow faster. Changes in genes called BRCA1 and BRCA2 are commonly linked to aggressive breast cancer. Your doctors may recommend genetic testing to check for these changes.
