October is Breast Cancer Awareness Month, and while you’d think everyone is aware of the disease, there are still many myths and misconceptions.

The first myth is that breast cancer is the biggest killer of women in Canada. In fact, it’s not. Many more women die of heart disease every year, while the biggest cancer killer in Canada by far is lung cancer.

Dr. Ann Chambers, Canada's research chair in oncology and a professor of oncology at the University of Western Ontario, helps us dispel a few more myths about the disease:

#1 My breast cancer risk is not affected by how many kids I have

“A woman’s reproductive history has a very strong link with her risk of getting breast cancer,” Dr. Chambers told CTV News Channel. “If you have children when you’re young, you’re at reduced risk. If you have no children, your risk is higher still. If you breastfeed for a long time, your risk is lower. So it’s a complex hormonal situation.”

#2 My weight might affect my risk for heart disease, but not my breast cancer risk

“Obesity is associated with breast and other cancers, as well as heart disease and diabetes. It’s one of the manipulative things you can change to reduce your risk,” says Chambers. “Keeping a healthy weight, eating a healthy diet and exercising are all things you can do to reduce your risk.”

# 3: If my annual mammogram is clear, I'll be OK

“Mammograms are still our best defence for finding breast cancer early,” says Chambers. “The rules about how often to have one are changing. Between 50 and 69, it’s recommended you get one every two or three years. Below age 50, it’s more likely to cause harm than good. But you can have a clear mammogram one year and then two years later, you can have a fast-growing tumour that shows us. So the mammogram is our best defence though it’s not perfect -- no screening tool is.”

#4: Eating soy can increase the risk of breast cancer

“There’s evidence that soy can both increase and decrease your risk of breast cancer,” says Chambers. “The evidence is not strong enough to support taking supplements, but the evidence is also not strong enough to say don’t eat soy. Soy in moderation probably won’t do anything one way or another.”

#5. Getting diagnosed with breast cancer is a death sentence 

“Since the 1980s, breast cancer mortality has dropped by about 40 per cent,” says Chambers. “This is probably due to two factors: increased mammography screening has been finding tumours earlier, when they’re still treatable. And better treatments that are less toxic and more tailored to the individual. So if you get early stage cancer these days, your chances of five-year survival are high. Where we still have issues is with metastatic breast cancer. Once it’s spread from the breast, beyond the lymph nodes to other organs, it’s much harder to treat.”