Breast cancer is the most common type of cancer among women in Singapore today. 

1 out of every 13 women in Singapore is likely to be afflicted by breast cancer, with more than 12,000 new cases diagnosed between 2017 and 2021.

Breast cancer is a malignant tumour which occurs when breast cells become abnormal and divide without control or order. 

The majority of breast cancers start in the milk ducts. A small number start in the milk sacs or lobules. Within these two groups, some grow very slowly while others develop more rapidly.

Breast cancer can spread to the lymph nodes and to other parts of the body such as the bones, liver, lung and sometimes to the brain.

Being a woman is a risk factor for developing breast cancer. However, 1% of breast cancers can also occur in men. 

Other important risk factors for breast cancer include:

• Increasing age, 

• Obesity, 

• Excessive alcohol consumption,

• Smoking history and 

• Reproductive history (age when menstrual periods began, age of first pregnancy and use of hormonal replacement therapy). 

• Notably, genetic factors and family history of breast cancer, especially in a first-degree relative (mother, sister or daughter), or two or more close relatives such as cousins and the presence of genetic alterations in certain genes such as BRCA1 and BRCA2 are also associated with significant lifetime risks of breast cancer.

Don't miss this chance to ask Clin Asst Prof Tira Tan if you are at increased risk of breast cancer, what you can do to lower your risk, latest treatment options available and more.

Source: Singapore Cancer Registry Annual Report 2021

About Clin Asst Prof Tira Tan

Clinical Assistant Professor Tira Tan is a Senior Consultant Medical Oncologist at the National Cancer Centre Singapore (NCCS) with a clinical focus in the treatment of breast cancers and early phase drug development. 

Dr Tan chairs the pre-operative and young women’s breast cancer programmes at NCCS and is the divisional deputy director of research as well as a primary and co-investigator on many early and late phase studies specifically in novel therapeutics and treatment strategies in breast cancer.

Questions and answers on breast cancer

1. Question by Leong

Dear Prof Tan,

How does the long-term use (e.g., for a duration of 1 year or more) of letrozole/clomid in pcos patients as part of fertility treatments to treat anovulation impact their risk of breast cancer in future?

Answer by Clin Asst Prof Tira Tan

Studies have not found a significant association between fertility treatment and excess breast cancer risk. Specific to PCOS, a large Swedish registry study involving a cohort of over 3.5 million females, 14,764 of whom had PCOS found that PCOS is positively associated with an increase in overall cancer risk, specifically that of gynecological cancers such as endometrial cancer and ovarian cancer. PCOS was not associated with excess in breast cancer risk even when considering the use of medications. (Yin W et al JAMA Oncol. 2019; 5(1):106-107)

2. Question by Joey

Dear Prof Tira Tan,

May I ask a few questions on the breast cancer:

a) How do I lower the risk of getting breast cancer? Does yearly mammogram screening enough for me to follow up?

b) I had cervical cancer in 2021 and now in remission.  May I know how far apart should I go mammogram and CT scan?

c) Can I go for mammogram twice a year?

d) Does the chances of getting breast cancer depends on genes?

e) Beside screening, what other options to lower the risk of getting breast cancer?

Answer by Clin Asst Prof Tira Tan

The risk for getting breast cancer is due to multiple factors. Some risk factors are simply not modifiable e.g. female sex, age, family history and some risk factors can be change. For example, women who do not exercise / are not physically active, have a higher risk of getting breast cancer. Women who are overweight have a higher risk of getting breast cancer. The risk of getting breast cancer increases with the amount of alcohol consumption and certain hormone replacement therapy which are taken during menopause can increase the risk for breast cancer.

Breast cancer screening means to perform a test or procedure to detect any abnormalities before symptoms appear. Our nation screening guidelines advise that women over the age of 50 should go for mammogram screening once every 2 years and from age 40 to 49, mammogram screening may be considered every year after weighing out the benefits and limitations of having a mammogram done. I would recommend breast self-examination every month. Being aware of what your normal breast feels like means that you are more likely to be able to report early to your doctor if you detect and presence of lumps, skin changes, swelling or nipple discharge. Please note that doing mammograms more frequently does not prevent breast cancer from occurring.

There is no specific requirement for a gap between a CT scan and mammogram. These tests are performed for different purposes and if recommended by your doctor, I would encourage you to proceed for them.

About 5-10% of all cancers are hereditary cancers which means that they are caused by one or more faulty gene(s) that run in the family. Hereditary cancers are usually suspected if there is a strong family history of cancer, the individual is diagnosed with cancer at a young age or if multiple types of cancers develop in an individual. Approximately 10-20% of cancers are familial cancers which means that the cancer is caused by a combination of genes and their interaction with the environment and lifestyle which has contributed to the increased risk of cancer. The vast majority of cancers are sporadic cancers which means they occur by chance with age and environmental factors contributing to the increase in risk of developing such cancers. Exercise, avoiding excessive weight gains, avoiding alcohol intake, maintaining a healthy lifestyle, and consuming a well-balanced diet will stand you in good stead in modifying your breast cancer risk.

3. Question by Pui See

Hi Prof Tan,

I was diagnosed with Stage 0 breast cancer in 2022 at age 47. My mum passed away stage 4 pancreatic cancer in 2017 at sge 68. I did a genetic blood test with Invitae and the result is negative for genetic defects. I would like to ask will there be increase chance of my daughter getting breast cancer? Thanks.

Answer by Clin Asst Prof Tira Tan

About 5-10% of all cancers are hereditary cancers which means that they are caused by one or more faulty gene(s) that run in the family. Hereditary cancers are usually suspected if there is a strong family history of cancer, the individual is diagnosed with cancer at a young age or if multiple types of cancers develop in an individual. Approximately 10-20% of cancers are familial cancers which means that the cancer is caused by a combination of genes and their interaction with the environment and lifestyle which has contributed to the increased risk of cancer.

Whilst the negative genetic test is reassuring, your daughter does still have an increase in cancer risk in view of family history. A faulty gene may exist but was not recognised due to limitations in current technology, perhaps there is a faulty gene which was not tested by the panel which was performed or perhaps the faulty gene may not be inherited.

Your daughter can consider breast self-examination once a month from the time she gets her first menses. And consider mammogram screening from the age of 40 recognising the limitations to mammograms – denser breast tissue in young women which may obscure abnormalities on mammogram.

4. Question by Edwina

Hi Dr,

I have recently found a ball? Lump? When I press down onto my right breast. Is that normal? The ball feels like it can be moved? I just did a medical check-up but not a mammogram. Any advice is appreciated, thanks!

Answer by Clin Asst Prof Tira Tan

Since this lump is a new development, I would advise that you have this examined by a doctor and a mammogram and/or ultrasound scan of the breast be considered to characterise the lump. Please ask your doctor to consider referring you to see a breast surgeon for further evaluation of your breast lump. A biopsy may be considered for diagnostic confirmation.

5. Question by Jeanie

Hi Prof Tan,

Does insertion of hormonal IUD cause or increase the probability of breast cancer? Given there had been a history of breast cancer within the family. Thanks.

Answer by Clin Asst Prof Tira Tan

The IUD, is a small piece of T shaped plastic which sits inside your uterus to function as birth control. A hormonal IUD in addition releases a small amount of the hormone progestin which can help to prevent pregnancy but also can help with heavy and painful periods. 

The use of combined oral contraceptives which contain both oestrogen and progestagen has been associated with a small increase in breast cancer risk. 

Recently, a study conducted in the UK has also provided new evidence that the use of progestogen-only contraception is also associated with a slight increase in breast cancer risk. (Fitzpatrick D et al PLOS Medicine Mar 2023).

That saying, the small increased in risk of breast cancer needs to be considered in the context of other benefits of hormonal contraceptive use. For example, there is a well established decrease in risk of ovarian, endometrial and colon cancer and the intended benefit of prevention of pregnancy. 

Remember, there are other non hormonal methods of birth control that are also good options for you to discuss with your gynaecologists. You can modify risk factors of breast cancer such as exercise, avoidance of alcohol and maintaining a healthy weight.

6. Question by Ms Koh

Hi Dr,

I had atypical ductal hyperplasia (ADH) on my left breast about 2 years ago, a biopsy was done and I subsequently underwent surgery to remove the excessive cells.

Thank God there is nothing amiss after the removed cells were tested and I have since gone back for annual check-ups with my doctor and all is well (will continue to go back for annual check-ups).

I have normal BMI, no high blood pressure, no high cholesterol levels, no high blood glucose levels (last screening done for these was less than a year ago. In any case, I never had these issues in the past and the only medication I take so far is Vitamin D tablets prescribed by my family doc).

I’m careful with what I eat and have regular exercises at least twice a week so when I asked my doctor why I had ADH in the first place, she couldn’t really pinpoint the reasons.

I would like to know:

a) What else can I do to prevent ADH from ever recurring?

b) Is it a myth that one who consumes soya bean drink daily (pure soya bean, no sugar ‘cos I brewed it myself) or have chicken a few times a week would elevate one's hormone (is it estrogen?) level and would affect breast health? (I do consume leafy vegetables, fruits daily as well).

c) Any foods to avoid for breast health?

Thank you for your advice.

Answer by Clin Asst Prof Tira Tan

Atypical ductal hyperplasia (ADH) is not a cancer, but it is associated with an increase in risk of breast cancer. The condition, when left to accumulate can transition into carcinoma in situ or invasive breast cancer. It is not clear exactly what causes ADH. You can modify your breast cancer risk by exercising, maintaining a healthy weight, and avoiding alcohol.

Additionally, you could ensure that you keep up with breast cancer screening with breast self-examination, clinical breast exam by your doctor and annual mammograms. You can speak with your doctor about taking medications e.g. tamoxifen or aromatase inhibitors to reduce the risk of breast cancer. 

However the side effects associated with consumption of these medications have to be considered as well and I would advise you to have a detailed discussion with your breast surgeon.

There are no specific foods which is recommended nor that you need to avoid. There is no clear association between soy products and breast cancer risk. Soy products contain isoflavones, an estrogen-like chemical. Studies which were conducted in laboratories were done in rats showing isoflavone enhances growth of breast cancer cells. Humans process soy differently to rats and there are in fact several health benefits to soy consumption. 

Please maintain a well balanced and healthy diet. Exercise regularly and maintain your weight within a healthy range.

Ref: I23