Breast Cancer | 7 Interesting Facts

Learn something you didn't know about breast cancer.

Since 1985, October has been designated Breast Cancer Awareness Month (BCAM) in the USA, which is now observed by many countries the world over. Originating from an initiative to promote mammography as the most effective way to beat breast cancer, BCAM has since evolved to a really big deal. 

Here are some lesser known or often-forgotten facts about breast cancer.

1. Not just one, single disease

Most of our readers are involved in scientific research in some form, so it’s not so earth‑shattering to reveal that breast cancer is not just one disease: it’s several grouped together. Typing and classifying tumors by their histopathology, grade, stage and even hormone receptor status, is routine in most healthcare settings. It’s well known that different tumor types have different progression rates and prognoses, for example: cancers positive for the estrogen receptor, the progesterone receptor or another receptor molecule called HER2, have more favorable clinical outcomes than those that lack all of these – so called triple negative breast cancers. It’s obvious that tumors falling into distinct categories require different treatment approaches; so why raise this point at all?

Well, we know that the classification and typing criteria we have at present is not the entire picture. Analyzing the genomes of a large cohort of breast cancers tells us that there could be at least 10 distinct subtypes of breast cancer, each with their own unique set of genetic drivers. Moreover, a lesson from the field of blood cancers has taught us that comparing the phenotypic similarities of tumor cells and normal cells can improve cancer classification. Santagata and colleagues set out to repeat this example in breast cancer, and found that there are 11 differentiation states of normal tissue – Until recently, only two cell types have been morphologically described in the human breast: the inner luminal cells and the outer myoepithelial cells. The paper goes on to suggest that the presence of vitamin D and androgen receptors be considered in the classification and treatment of breast cancers.

2. Racial Disparity: Black women are most likely to die of breast cancer

Black women are more likely to die of breast cancer as they are at increased  risk of developing a more aggressive breast cancer subtype. 1 in 5 black women in the US are diagnosed with the triple-negative breast cancer, the most aggressive subtype with poorest prognosis. As these trends in ethnicity and cancer subtype are consolidated, some clinical trials are now factoring this into their selection criteria and treatment groups. Find out more about this in our Breast Cancer Awareness Month blog.

3. Breast cancer survivors are more likely to develop a second cancer

Cancer survivors are twice as likely to develop a second cancer than those of the same age and gender that have never had cancer. Breast cancer can be caused by genetic factors such as the BRCA1/2 mutation, but the treatment received during the treatment of the first cancer can also increase risk of second cancer development. Treatments such as radiotherapy and chemotherapy can weaken the immune system and induce cellular damage, which could trigger tumorigenesis. Find out more in our blog Second cancer after breast cancer.

4. Good news: breast cancer is one of the most survived cancer

The average 5-year survival for breast cancer is now 89% even though it is also the most prevalent cancer type in the world with over 300,000 women diagnosed in 2022. Thanks to significant progress in early detection and treatment options, breast cancer is now the most survived female cancer and the fourth overall after testicular cancer, melanoma and thyroid cancer.

5. Is there actually a link between night work and breast cancer risk?

Working at night and being exposed to light during the night can impact the body’s circadian rhythm and hormone secretion including melatonin and estrogen. Frequent night work is already linked with other health conditions such as gastrointestinal and cardiovascular diseases, depression and obesity. There has been extensive debate over the years whether night shifts increased the risk of developing breast cancer and the results are inconclusive. Some report an increased trend, but without statistical significance, or a very slight increase in risk and only after working night shifts for over three decades.

6. Our pets can get breast cancer too

Cats and dogs are also at risk of developing breast cancer. Dogs especially, as they get older can develop mammary tumors. The disease affects approximately 1 in 4 unspayed female dogs.  Luckily, half of the tumors are benign, and of the malignant ones, a large proportion can be treated by surgical resection. Much like in humans, the causes of cancer in canines is not well understood, but it might be linked with hormones as unspayed dogs are at increased risk. There is thought genetics contribute too, with certain breeds at elevated risk of canine breast cancer. Cats are not as likely to develop mammary tumours, however they are very aggressive if they do, often resistant to chemotherapy and radiation.

7. Plastic (not so fantastic)

Bisphenol A, often referred to as BPA, is a carbon-based synthetic compound found at low levels in a significant amount of plasticware and canned items. BPA is interesting – and also worrying –because of its origins, uses, and effects on the body. First synthesized in the earlier half of the 20th century, it was originally used to enhance the growth of cattle and poultry. Terrifying Fascinating then, that upon the discovery it could mimic estrogen it was briefly used as a means of hormone replacement in women in the 1930's. As it binds weakly to both isoforms of the estrogen receptor, ESR1 and ESR2, it is now classed as a hormone disruptor. So how did it end up in plastic? Well in the 1950's the chemical industry figured out BPA could harden plasticware (go figure) and this delightful chemical has been in a lot of product packaging ever since. It hasn't set off major alarm bells because it is present in low levels, but there is mounting evidence that even at low levels chronic BPA exposure can increase the risk of breast and other cancers. Another way women can reduce their risk of developing breast cancer is to avoid or reduce their risk of BPA exposure. Steps like using glassware for food storage and avoiding certain types of plastic packaging can help. Breast Cancer UK provide more advice on how to reduce BPA exposure and how to advocate for the ban of BPA.