Cancer is an expert fugitive. Last week, a new mother - a young woman from Johor - was brought into my consultation room on a wheelchair, accompanied by seven family members.

She was teary-eyed and trembling. Between sobs, she poured out her story. She was in her second trimester of pregnancy when she started complaining of bone aches.

'Only wind," she was told by well-meaning friends and family. The following weeks were punctuated with repeated visits to practitioners of assorted massages and 'cupping", or moxibustion, where a cup is placed over the area of pain and heat treatment applied, to relieve her allegedly rheumatic pains.

Then, 33 weeks into her pregnancy, she woke up one morning with numbness and weakness in both legs. She could hardly walk. After a barrage of tests and scans, she was found to have stage 4 colon cancer which had spread to the bones and liver.

She was operated on immediately and delivered a perfectly healthy baby. At the same time, she had colon and spine surgery - in a last-ditch attempt to remove parts of the tumour.

As the surgery was carried out five days after the onset of paralysis, there is almost no chance that she will ever walk again.

The question arises: 'Why was the cancer diagnosed at such a late stage?" After all, she saw her obstetrician every month for her routine pregnancy check-ups.

Her case may seem astounding, but it is not uncommon for cancer - the expert fugitive - to be diagnosed in its advanced stages.

In its early stages, it often has no symptoms. A person can harbour a cancer in the body for a long time. I have seen primary tumours in the liver as big as a grapefruit. Yet the patient was totally unaware of it.

There is so much reserve function in our organs that even the loss of half an organ, like the liver, can still leave the patient in reasonably good physical health.

All too often, by the time a person has symptoms, the cancer will have progressed beyond its early stages. The symptoms may sometimes not even be from the primary tumour but from sites where the cancer has spread.

Symptoms caused by cancer are often not specific. Is it smoker's cough or lung cancer? Bleeding haemorrhoids or colorectal cancer? Gastric pain or stomach cancer? Under some circumstances, it may be worthwhile to see a doctor.

Cancer is a great equaliser. To those who think they cannot get cancer because they have good genes or are on a strict diet, I would say: 'Wake up!"

Cancer doesn't occur only in the elderly. It can strike the young as well. Both men and women are at risk. It has no respect for wealth or social status. It afflicts the tycoon as well as the road sweeper.

There are many ways in which patients contribute to a delay in their diagnosis or treatment.

Some refuse to go for screening tests because they are in denial. Some cancer patients delay diagnosis because they fear the side-effects: loss of self-esteem after losing a breast, the humiliation of hair loss from chemotherapy or the long-term complications of radiotherapy - which may include a higher risk of cancer.

Some turn to bogus faith healers and traditional herbal remedies.

Delay in cancer diagnosis may also be due to doctor-hopping. When a doctor sees a patient complaining of gastric pain, the physician would, in all likelihood, first prescribe medication rather than order costly tests.

If the pain persists despite medication, the same doctor would then be likely to recommend a gastroscopy (a scope to look inside the stomach) or a barium meal (a radiological study of the inner lining of the stomach using contrast) to find out the reason for the pain.

Patients ought to build up a lasting relationship with one doctor, who then serves as a family physician.

As for the young mother from Johor, after emptying half my box of tissues, she finally decided to move on - and stop berating herself and her doctors for the delay, which led to her cancer becoming so advanced.

Acknowledging now that there was no time to lose, she began focusing on what she needed to do to control her cancer - and to begin caring for and delighting in her new-born baby boy.

Dr Ang, the medical director of Parkway Cancer Centre, has been treating cancer patients for nearly 20 years. In 1996, he was awarded Singapore's National Science Award for his outstanding contributions to medical research.

This story was first published in Mind Your Body, The Straits Times, on May 7, 2008.