Some female health check packages available in the market include a Cancer Antigen (CA15.3) blood test, which is claimed as a breast tumor marker test. The Consumer Council wishes to advise consumers that the CA15.3 test is not an effective way to screen breast cancer.
The Cancer Antigen 15.3 blood test result shows the level of cancer antigen in the blood serum. It is mainly used to monitor the effectiveness of the treatment for breast cancer, especially for advanced stage cancer patients.
Hong Kong Breast Cancer Foundation points out the inefficacy of the blood test in detecting breast cancer in the early stage. Less than 10 % of early stage breast cancer patients, and only around 70% of advanced stage patients will have a higher-than-normal level of CA15.3. Hence, patients should still be vigilant even if their level of CA15.3 is normal.
Breast cancer has become the most common cancer affecting women in Hong Kong. In terms of mortality rates of cancers in Hong Kong females, breast cancer ranks the third, after lung cancer and colorectal cancer. Statistics provided by the Department of Health show that at least 1 woman die of breast cancer every day, making the total number of deaths due to breast cancer 561 in 2010.
Hong Kong Medical Association points out that the Cancer Antigen (CA15.3) blood test only provides a reference for monitoring the recurrence of breast cancer in patients who have undergone mastectomy.
Medical expert from the University of Hong Kong stress that the blood test on cancer antigen is a non-sensitive and non-specific test. On the one hand, the level of CA15.3 can remain normal for many breast cancer patients; on the other hand, in some circumstances, such as the presence of lung cancer or other cancers, or Chinese herbal medicine or over-the-counter drugs, a high level of the antigen may result.
In a medical case, a doctor found a lump in a female patient's breast, and arranged for the patient to take the CA15.3 blood test. The test result showed no indication of breast cancer. However, five months later, the patient was diagnosed of breast cancer after a biopsy test. The doctor was subsequently found guilty by the Medical Council of Hong Kong of professional misconduct for inappropriately using the CA15.3 test for screening and delaying the diagnosis of the patient's breast cancer.
The CA15.3 blood test, therefore, is not an effective means for detecting breast cancer, and women should not use it for breast cancer screening.
The latest issue of CHOICE magazine (Issue 431) carries a special feature article on breast health. The article points out that females should be breast aware at the age of 20. In normal circumstances, the earlier the cancer is diagnosed and treated, the greater the chance of surviving the disease.
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