Seeds for Relapse of Cancer Planted Early by Wong Seng Weng
The Straits Times July1, 2019
Patients should not blame their diet or lifestyle when they suffer a deterioration because some cancer cells were likely present at the start that could not be detected and later multiplied
When something bad happens in our lives, it is almost human nature to search for something, or someone, to blame. Often we blame ourselves.
"Doctor, is it because I ate something I shouldn't have?" asked Ms Y.
She just suffered a relapse of breast cancer that was first diagnosed two years ago. At the onset, her disease was diagnosed at an early stage - stage 1. The prognosis was good, the outlook bright.
Ms Y was optimistic that she was going to do all right after treatment, until now. She blamed her undisciplined diet for triggering the relapse.
Ms W, at about the same time, suffered a relapse of cancer of the ovary.
She blamed it on the stress at work. She was promoted to a rather demanding regional managerial role in her company about 11/2 years before the relapse was diagnosed.
Are these women right in laying the blame for the relapse of their cancers on their diet or work stress? Would that be scientific?
For that matter, is there something scientific that they can actually blame?
Before searching for the possible culprits causing cancer relapse, it would be insightful to first understand the basis of how a cancerous tumour that has been totally removed by surgery can mysteriously pop up again, often in another location in the body, far from the initial site.
Patients who had undergone the process of diagnosis and treatment of early-stage cancers will recount a similar experience.
At some point, they would be put through a series of medical imaging such as X-rays, computer-assisted tomography (CT scan) or positron-emission tomography (PET-CT scan).
If the cancer happens to be in the early stage, there will be no sign of cancer spread to other organs of the body on imaging.
The doctor would typically give the patient the "all-clear" signal to proceed for surgery to completely remove the cancerous tumour affecting one location in the body. The aim would be to deliver a cure - total and permanent.
In truth, the "all-clear" signal that patients get at this point is more like a "hopefully clear" indication.
There isn't a proven technology in existence today that can reliably pickup a small number of cancer cells hidden away in parts of the body.
The PET-CT scan is arguably the most sensitive form of medical imaging today for the detection of cancer dissemination.
Even with the help of a PET-CT scan to pick up a site of cancer spread, the diameter of the site has to be at least 1cm. And, in that relatively small lump of 1cm, there are approximately one billion cancer cells.
One billion. That is roughly equivalent to the population of a large country.
If, say, five million cancer cells have spread from the original cancer site to a different location, how would the affected area appear on medical imaging?
Five million cancer cells, about the population of Singapore, are not enough to form even a "little red dot" on a PET-CT scan. In short, these cells would be invisible.
With time, these cancer cells will grow to form billions. At this time, a relapse of the cancer becomes apparent.
In other words, the seed for relapse was already planted at the get-go when the seemingly early stage cancer was first diagnosed. The seed was just too small to be detected.
This is the reason I often have to put many patients diagnosed with early-stage cancers through chemotherapy either before or after their surgery. This is a pre-emptive measure to try to wipe out small numbers of undetectable cancer cells that have spread to avoid a future relapse.
How do I make the decision to proceed with pre-emptive chemotherapy if I have no objective evidence of the existence of these small traces of cancer cells that have bolted?
This would be a judgment call.
I work out the statistical probability of there being such traces of cancer cells based on past patients with the same condition.
If the probability is sufficiently high, I will counsel my patient to bite the bullet and go for a "mop up" course of chemotherapy.
Many a times, such a strategy would work and the fate of an inevitable cancer relapse would have been averted.
But, sadly, there are situations where the disseminated cancer cells are resistant to chemotherapy and cannot be mopped up. A relapse eventually surfaces.
But remember, the seeds for relapse were planted at the beginning. So, Ms Y and Ms W shouldn't blame themselves for the relapse.
Family and friends of cancer patients must earnestly keep this understanding in mind. Don't add to the patients' self-blame.
Dr Wong Seng Weng is the medical director and consultant medical oncologist at The Cancer Centre