09 OCTOBER 2017

Learn About Secondary Breast Cancer

When cancer strikes again

Patients who survive cancer can get hit again by a different cancer. Consultant Breast and General Surgeon Dr Esther Chuwa answers questions about secondary cancers.

After a patient has survived cancer, he or she may be hit by a different cancer that develops in other parts of the body. These cancers are called secondary or second cancers, and are usually unrelated to the first cancer. They are not caused by the recurrence or spreading of the first cancer.

How does secondary cancer develop?

Ironically, secondary cancers can develop because of more successful treatments and improved survival outcomes. Having survived longer from the first cancer, these patients are now susceptible to a “second hit”.

First and second cancers may share common risk factors such as genetic predisposition, hormonal factors and lifestyle factors like obesity, alcohol intake and smoking. For example, patients who are genetic mutation carriers of the BRCA gene face higher risks of a second breast cancer, ovarian cancer and colon cancer. Obesity also increases the risk of cancers such as breast, uterine, colon and kidney cancers.

Second cancers can also result from treatment of first cancers. For example, an adolescent girl who undergoes radiotherapy for Hodgkin’s lymphoma faces higher risks of developing breast cancer later. Chemotherapy used in some susceptible individuals may also increase the risk of leukaemia later. Tamoxifen, an anti-hormone drug used to reduce the risks of a relapse of breast cancer, has been found to lead to endometrial or womb cancer in about two out of 1,000 women.

How common is secondary breast cancer?

While it is rare for a woman who gets breast cancer in one breast to develop a second breast cancer in the other breast, BRCA1/2 mutation carriers face higher risks.

The risk of a second breast cancer developing on the contralateral side 10 years after diagnosis of the first cancer is 5 to 10 per cent for a breast cancer survivor without a BRCA1/2 mutation, but about 10 to 30 per cent for a BRCA mutation carrier. Such carriers may thus consider prophylactic or preventive mastectomy in the opposite breast to reduce the risk of a second primary breast cancer.

For non-mutation carriers diagnosed with breast cancer in one breast, however, this operation does not provide any survival advantage unless the second cancer is discovered at an advanced, late stage. In any case, this is an unlikely scenario as all breast cancer survivors receive close monitoring, and are usually given some form of preventive treatment like anti-hormone therapies or chemotherapy.

Having said that, there are certain subgroups of non-mutation carriers who may benefit from contralateral mastectomy:

  • Women who are diagnosed with breast cancer at a young age and who have a significant family history of various cancers but no demonstrable genetic mutations, or who have decided not to undergo genetic testing.
  • Women who have an excessive, crippling fear of being diagnosed with breast cancer again.
  • Those who prefer to have cosmetic symmetry and face limited options for unilateral breast reconstruction because of their physique.
  • Women with extremely dense breasts with or without fibrocystic breast disease (multiple bilateral breast nodules and extensive microcalcifications). This can make surveillance through MRI and biopsies to check for another cancer challenging and costly.

Women should discuss these factors with their doctors before they make a decision to have the other breast removed.

What can cause an increased risk of secondary breast cancer in younger women?

A woman diagnosed with breast cancer at a young age is more likely to be a BRCA1/2 mutation carrier; this mutation also predisposes her to a second breast cancer. Genetic testing is therefore recommended, as it will help doctors manage the risks better and monitor her more closely for other cancers.

Even if this woman is not a BRCA1/2 mutation carrier, being diagnosed at a young age poses a higher risk of the cancer recurring. This means doctors will usually take more aggressive actions to improve their survival outcomes. As a result of surviving longer, they may face an increased risk of other cancers, which may or may not be related to previous cancer treatments.

What are the symptoms of secondary breast cancer?

There are usually no symptoms; secondary breast cancers are commonly detected through surveillance tests.

How curable is secondary breast cancer?

They are extremely treatable as they are usually detected at an early stage. They usually do not affect a patient’s overall survival outcome. Doctors will aim to cure it and treat it as if it is the first cancer.

What is your advice for patients diagnosed with secondary breast cancer?

Patients diagnosed with secondary cancer often see it as a double whammy, and respond strongly. Those who have lost friends or family members to secondary breast cancer, for example, are more likely to undergo prophylactic surgeries, even though there is little benefit in doing so.

However, patients can take heart in the advancements that are being made in diagnostic tests, surgical techniques and therapeutic drugs. The survival rates for many cancers, including those of the breast, bowel and prostate, have more than doubled since the 1970s. With the advent of more targeted cancer treatments, we can expect fewer side effects, better quality of life, and increased survival rates.

Written by Kok Bee Eng

TAGS cancer drugs, cancer mutation, chemotherapy, history of cancer, mastectomy, metastatic cancer
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