Long-term breast cancer survivors face unexpected challenges

For women, breast cancer is the most common cancer and the second-leading cause of cancer deaths. That's according to the Canadian Cancer Society. Better treatments mean longer survival, Overall, if discovered early, more than 90 per cent of women will survive at least five years following a diagnosis of breast cancer. A study published Monday in the journal Cancer concludes that longer life comes with some telling challenges.

Dr. Muneer Al-Husseini and colleagues at Ascension St. John Hospital and the Mayo Clinic Cancer Center in Phoenix examined the records of just over three-quarters of a million women diagnosed with breast cancer from 2000 to 2015. By the end of the study period, nearly one in four of the women had died.

Just under half of the deaths (about 46 per cent) occurred within one to five years following the diagnosis of cancer. Most of those deaths were caused by the cancer. However, of the women who died five to 10 years after being diagnosed with breast cancer, half of them died of causes not related to the cancer. Of the women who died more than 10 years after being diagnosed with breast cancer, the majority of them died not from the cancer but from some other unrelated cause. 

The leading causes of death in women who survived 10 years or less after being diagnosed with breast cancer were heart attacks and heart failure followed by strokes. The leading causes of death in women who lived more than 10 years after being diagnosed with breast cancer were heart disease followed by Alzheimer's dementia. The rate of heart disease in breast cancer survivors was higher than the general population. Long-term breast cancer survivors in the study also had a higher rate than the general population of chronic liver diseases including cirrhosis. 

In general, longer survival can be chalked up in part to early diagnosis when the disease is more localized and easier to cure. Other factors in longer life include better surgical techniques as well as the development of adjuvant treatments like tamoxifen and trastuzumab which is sold under the brand name Herceptin. Adjuvant treatments prolong survival by lowering the risk of recurrence. Overall survival rates kept going up until 2005, when they appear to have plateaued in the U.S.

The exception is Stage 4 breast cancer. Stage 4 means the cancer has metastasized or spread to other parts of the body including the bones or the brain. A U.S. study published in 2018 also published in the journal Cancer found that five-year survival rates for Stage 4 breast cancer have continued to climb. Doctors chalk that up to adjuvant treatments as well as reduced rates of smoking.

Some of the deaths noted in the current study were unrelated to the diagnosis of breast cancer. But some of the deaths might be linked to the treatments used to treat breast cancer.

Regular heart checks advised

As mentioned, heart diseases were the most common causes of death in long-term breast cancer survivors. It is well-known that the cancer chemotherapy drug doxorubicin can be toxic to the heart. The higher the dose, the more likely the drug causes damage to the heart muscle and heart failure. The adjuvant drug trastuzumab can increase the likelihood of damage to the heart muscle after doxorubicin is given.

Many women with breast cancer received radiation treatments. These can damage the coronary arteries and increase the risk of heart attacks especially when the cancer involves the left breast and the radiation is directed to the left side of the chest which is closest to the heart.

Drugs like tamoxifen can increase the risk of strokes. Long-term breast cancer survivors are at increased risk of developing cancers of the lung, uterus and colon as well as lymphomas. 

The bottom line is that breast cancer survivors need to be checked regularly for heart disease. Since they are also at increased risk of additional cancers, they should be screened for these as well. These patients should be informed  regarding the risks and benefits of regular screening for cancer.

As the number of long-term survivors of cancer increases, it might be helpful to build clinics that specialize in their needs.

People who survive breast cancer should not make it through treatment only to fall between the cracks just as they're starting to resume their lives. We owe it to them to be vigilant to the many other conditions that put them at risk.