Once the fact that the cancer is incurable has sunk in, the question that eventually comes up is: "How much time do I have left?"
I watched a colleague handle this question some weeks ago.
He first answered the question with one of his own: "Do you really want to know the truth?"
The patient nodded with some apprehension.
With a straight face, my colleague said: "Don't know."
It was probably the truth but I am not sure that I would have replied quite that way.
Still, each doctor handles such matters differently and, for each situation, we play the hand that we think best suits the patient, his condition and the prognosis.
I began looking after Mr Yeo in November 2004.
He was referred to me by a senior surgeon who had just removed a cancerous portion of his large intestines.
As the cancer had spread to the regional lymph nodes, the patient was deemed to have stage 3 colon cancer.
Despite undergoing six months of chemotherapy, the cancer came back in February 2006.
After a few more cycles of chemotherapy, he finally asked the inevitable question.
With my usual bravado, I replied: "How much time do you want?"
Mr Yeo sheepishly replied: "Ten years, can or not?"
It is quite interesting to hear the answers that patients come up with.
Another patient, a woman in her 40s who had malignant lymphoma and breast cancer, said: "I want to be a grandmother."
Her daughter, who is a talented musician, is only in her teens.
Another woman who had just given birth to a daughter asked if she could be around to watch her daughter enrol in university.
A man in his 50s asked if he could last till his senile mother passed away.
As I flipped through Mr Yeo's case notes the other day, I came across the entry I made on May 25, 2006: "10 years enough."
I reminded him of his long forgotten plea and jokingly said that his time was running out and that he did not need to continue follow-up and treatment anymore.
This may seem an insensitive or a particularly macabre sense of humour, but in taking care of patients who have stared at death in the face for years - I find myself taking the same prosaic attitude as they do.
At the start, it may be difficult for a patient with stage 4 cancer to imagine, at the point of diagnosis, that it is possible to be alive years later.
However, it is a fact that there are patients who can. The journey, however, is not always an easy one.
Mr Yeo was treated with a very aggressive chemotherapy programme when the disease first recurred.
The side effects of treatment include hair loss, nausea and diarrhoea.
Despite "burning" the liver metastasis using radio frequency ablation, the cancer recurred in the liver in March 2007.
He was then operated on again by the senior surgeon and had half of his liver removed.
In May 2008, the cancer appeared in his bones.
Since then, Mr Yeo has been on low-dose chemotherapy together with bone strengthening medicine.
He has an intravenous catheter that is inserted just under his collar bone into a big vein in his chest.
An infusion ball, containing a chemotherapy drug called 5-fluorouracil, is connected to this catheter, and the drug runs into his body every minute of the day.
He changes the infusion ball once a week by himself at home.
Once a month, he sees me to review his condition, adjust his medication and receive Zometa to harden the bones and slow the progression of his cancer.
My colleagues and I have been tracking his disease with PET-CT scans every six months or so.
His disease has remained non-threatening with occasional flares but, at other times, the disease is quiescent.
Through it all, he has remained alive and well enough to continue working.
Last week, I saw a young woman who had just been diagnosed with stage 4 breast cancer.
She underwent surgery for breast cancer a year ago.
Despite advice from her medical oncologist that she needed chemotherapy to prevent the cancer from returning, she refused.
When I saw her, I could sense the sea of emotions tossing in her mind - regret for not having had treatment; fear of the potential side effects of chemotherapy; and apprehension of how little time she may have left.
She had many questions and I spent more than an hour counselling her.
It was not medicine that she was interested in, but more existential issues.
I am not a philosopher but I felt that she trusted me, so I answered to the best of my ability.
Just before she agreed to start treatment, she asked the inevitable question: "Doctor, how much time do I have left?"
I smiled and replied: "How much do you want?"
Dr Ang, medical director of Parkway Cancer Centre, has been treating cancer patients for 23 years. In 1996, he was awarded Singapore's National Science Award for his outstanding contributions to medical research.
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