Risk factors

Any substance or condition that increases a person’s chances of developing cancer is referred to as a risk factor.

There is no single cause of *chest cancer, but some people are more likely than others to develop the disease. Just because you have some risk factors doesn’t mean that you’ll get chest cancer, but it does mean that your chances of developing it are higher.

The main risks for getting chest cancer are:

  • being 50 years old or older
  • being assigned female at birth

The following factors are known to increase the risk of developing chest cancer for the population as a whole (including non-trans men):

  • having had chest cancer before
  • having a family history (for example, a parent or sibling) of chest or ovarian cancer, especially if the family member was diagnosed before menopause
  • having dense chest tissue
  • having hereditary mutations in the BRCA1 or BRCA2 genes
  • having an above-average exposure to estrogen. This could be due to:
    • never having given birth
    • giving birth for the first time after age 30
    • starting cyclical/monthly bleeding at a young age
    • reaching menopause later than average
    • having taken hormone replacement therapy (estrogen and progestin) for more than five years
  • being obese, especially after menopause (menopause may occur because of surgery, hormones, or getting older)
  • consuming more than one alcoholic drink a day
  • taking oral contraceptives that contain both estrogen and progesterone
  • smoking

Trans men are more likely to be exposed to certain chest cancer risk factors and less likely to others. Overall, trans men are more likely to have the following risk factors:

  • not maintaining a healthy weight
  • consuming above-average amounts of alcohol
  • never giving birth
  • giving birth at an older age.

We don’t know conclusively whether taking testosterone (“T”) effects chest-cancer risk. Some studies show that excess testosterone in the body can be converted to estrogen, which may increase cancer risk. More studies need to be conducted on possible connections between testosterone and chest cancer.

Some trans men may have a reduced risk of chest cancer:

  • Trans men who have had top surgery may have reduced risk factors for chest cancer. This is because top surgery, or mastectomy, removes a significant amount of chest tissue. Research suggests that mastectomy may significantly reduce (by about 90%) the chances of developing chest cancer in people with moderate to high risk.

    Even if you’ve had top surgery, though, it’s possible for cancer to develop in the small amount of chest tissue that remains, and there have been documented cases of chest cancer in trans men who have had top surgery. Your risk level depends on many things, including the type of top surgery and the amount of chest tissue that remains. For example, top surgeries that leave the nipple intact tend to leave more chest tissue, which raises your risk of developing chest cancer. If you’ve had top surgery, talk to your doctor about your personal risk of chest cancer and the kind of that’s best for you.
  • Trans men who are taking gender-affirming hormone therapy or who have had hysterectomies, may undergo menopause earlier than non-trans women, and therefore may have less exposure to estrogen, which may reduce chest cancer risk. More studies need to be conducted on the links between hormones and hysterectomies and chest cancer risk in trans men.

A healthcare provider can help you determine your risk of chest cancer and provide you with a personal plan of screening. If you are at higher than average risk, you’ll likely need to get checked more often or earlier. In general, high-risk individuals are those who have a strong personal or family history of chest cancer, and/or have gene mutations such as BRCA1 or BRCA2.

Remember, there is no single cause of chest cancer, but having some risk factors may increase the risk of developing it. Some people develop chest cancer without having any of these risk factors.

Visit cancer.ca for more detailed information about these and other risk factors.

*A note on terminology: In the trans men sections of this website, we refer to cancer in chest tissue as cancer of the chest, and to the tissue itself as chest tissue. This is because we recognize that many trans men and people on the transmasculine spectrum do not identify as having breasts, feel ambivalent about having breasts and prefer the term “chest” on its own. Although we use this terminology where appropriate, we also recognize the fact that some trans men do have breasts.