Dear Dr. Roach: Please discuss the significance of blood tests to show the level of cancer markers to identify cancer and track the efficacy of treatments. I am 69 and have metastatic breast cancer, diagnosed in July 2022. The primary cancer was treated in 2018-2019 with surgery, chemotherapy and radiation. During treatment, my oncologist ordered bloodwork to monitor the level of CA-15-3 and CA 27.29. When a PET-CT scan showed no traces of cancer, the levels were in the low 20s.
During my three years of remission, my oncologist never checked the levels of the markers, stating that they weren’t diagnostic tools, but rather were used only to show trends during treatment. In July 2022, I had a breathing crisis, and CT scans showed a new mass. At that point, the markers were in the 130 range. I started treatment and regular bloodwork showed those markers decreasing until February 2023. I’m now receiving new treatment to keep the tumour down. The last lab report showed the cancer markers have decreased, so it looks as if the therapy is working.
Could the markers have been checked during remission to identify a recurrence sooner?
A.A.
I am sorry that your cancer came back. There are a host of new treatments for metastatic breast cancer, much better than what we have had in the past.
Tumour markers, like CA-15-3 and CA 27.29, are blood tests that tend to correlate with specific cancer activity. Prostate specific antigen, or PSA, in prostate cancer is one of the most commonly known, and it’s one of the few found useful for screening. A healthy person should have very low amounts of the tumour marker, while a person with extensive cancer should have a very high level. However, no tumour marker is perfect — they can be elevated when there is no cancer, and low even when there is extensive disease. In people who had a high level when the cancer was first diagnosed, a trend of increasing blood levels strongly suggests cancer recurrence. These markers are most useful in people with breast cancer that is known to have spread to distant sites, such as lung or bones.
While some breast oncologists will order tumour markers or imaging studies such as CT scans in people who are thought to be in remission, the recommendation is not to check these in people who’ve had breast cancer but are feeling fine. Studies to see whether they help have shown no benefit. There is the potential for harm from unnecessary evaluation for false positive results. The current recommendation is for mammograms (unless a person has had a mastectomy) and a physical exam and history.
New technology called “cell-free DNA” (sometimes called “liquid biopsy”) might have the potential to revolutionize both surveillance after treatment and early detection of cancer. Clinical trials are in progress. I suspect we will learn many new lessons about cancer development, similar to the lessons we learned when highly detailed imaging studies such as MRI became available. Let’s hope this new screening and detection tool will lead to improved treatment and cures for early cancers.
Email questions to ToYourGood [email protected]
