Doxorubicin is a chemotherapy drug used commonly in women who have undergone surgery for breast cancer to prevent recurrent cancer. Although it is a very effective agent in fighting breast cancer, it can cause permanent damage to the muscle of the heart. Approximately 25% of breast cancers overexpress a gene called HER2 neu. As a result of this change the cancer is more aggressive than a cancer which has the normal amount of this gene. There is a drug called trastuzumab which is very effective in targeting and killing cancers which overexpress HER2 neu. Unfortunately, this drug can cross react with the heart tissue and damage the heart. Currently women with breast cancer who receiver doxorubicin followed by trastuzumab are monitored by nuclear cardiac imaging. However such testing is not very good at assessing cardiac damage.
Dr. Dhesy and colleagues conducted a study to evaluate whether blood tests called cardiac biomarkers (troponins and pro-brain natiuretic peptides) which are sensitive to very small amounts of heart muscle injury can detect very early damage to heart muscle in patients receiving doxorubicin and trastuzumab. If this were to be the case, then these drugs could be discontinued before there was any permanent damage to the heart.
The study accrued 25 participants. Unfortunately, the results showed no relationship between the blood tests and damage to the heart. This is what is called a “negative study”. However, the study had a positive impact from another perspective. It played an important role in stimulating the development of a Cardio-oncology Program. About a decade ago there was a recognition that cancer patients developed unique heart problems. At Hamilton Health Sciences (HHS) there was an interest from cardiologists to partner with oncologists to establish a special program for diagnosing and treating cardiac problems in cancer patients. The CABOT study was one of the first research projects from this collaboration. It was instrumental in the establishment of a special cardio-oncology clinic at HHS where cancer patients with a heart problem can be referred and seen urgently by a cardiologist.
