Dr. Salman Hyder's study focused on who is more prone to getting breast cancer and sheds light on the complicated answer to why people get cancer.

"You can never say that caused breast cancer," said Dr. Michael Trendle, an oncologist.

The question of why some people get breast cancer has few clear answers and many clues.

"What we have shown is the link that was thought to exist does exist," Hyder said.

Hyder has found a clue: the link between hormone replacement therapy and breast cancer.

"There is a tendency for women taking progestin to develop tumors, but it is not known what is progestin doing. What we have shown is that progestin actually causes release of growth factors from tumor cells," Hyder said. "It's always exciting to know why something happens. What we have shown is, yes, there is a need for caution."

Hyder studied the most common hormone replacement therapy drug Medroxy-Progesterone Acetate, or MPA.

"This specific drug is not good for women," Hyder said.

What could be good for women is a drug called Prima.

"Women who have a defective protein are the ones who may get rumors, so these are the women that can get this specific drug," Hyder said.

Prima can correct the defective protein, which is what allows tumor cells to grow in the first place.

"It's good for women to know what is out there to make better choices for themselves," Hyder said.

The study could also help doctors determine women who are prone to tumors. Still, it's important to know other risk factors for breast cancer, like family history.

If you have questions about hormone replacement therapy, you should talk with your doctor.

Click on the KOMU.com Extra to read the whole study.