Recovery still possible for disease that's hard to detect

PUBLISHED : Monday, 19 November, 2007, 12:00am
UPDATED : Monday, 19 November, 2007, 12:00am

Herman Wong Tze-ming, specialist in medical oncology, AmMed Cancer Center

Is non-Hodgkin's lymphoma visible; can it be easily detected?

While visible symptoms can be seen in some kinds of cancer, non-Hodgkin's lymphoma is often not easily detected until it reaches a late stage. This is because the lymph nodes are found inside the body and the problem may not be noticed in a routine check-up. It is much easier to treat a node if it grows in a visible area such as the neck. But in many cases, the node is inside the stomach, brain or mediastinum. The patient is unlikely to know that they have the disease until they feel pain, or suspect that something abnormal is happening in their body This cancer is like a hidden bomb.

What causes non-Hodgkin's lymphoma? Like many types of cancer, the cause remains unknown. Genetics could be one factor. Virus mutation could be another. After receiving radiotherapy, patients face the risk of getting non-Hodgkin's lymphoma, although the chance is relatively low. So far there is no evidence to prove that certain types of food or a polluted environment are the cause.

How does it occur? The lymphatic system is the body's natural defence against infection, and in a normal immune system it induces cells to kill the infection. But if the system malfunctions, the infected lymph node will continue to grow and spread to other parts of the body. When the cells reach a new site, they may keep on splitting up and form a new tumour.

Is non-Hodgkin's lymphoma fatal? Without proper treatment, the disease is fatal. Conditions of the cancer are divided into four stages. The later the stage, the harder it is to be cured.

What are the chances of recovery? This hinges on the patient's age, health, the behaviour of the tumour and the presence of B-symptoms such as fever, weight loss and sweating. A blood test can also detect the size of the tumour.

Kenny Lei Ieng-kit, specialist in medical oncology, Prince of Wales Hospital

Is there any screening programme for non-Hodgkin's lymphoma? There is no proven screening programme. For low-grade lymphoma, most patients do not have symptoms at the onset of the disease.

The diagnosis is often made incidentally when the patient is screened for something else. Nevertheless, survival would not be greatly affected by an early diagnosis.

With aggressive lymphoma, the disease usually develops more rapidly. Patients generally don't have a honeymoon period before diagnosis. The disease occurs and evolves in a relatively short time. Therefore, screening is not needed.

The Hospital Authority's Hong Kong Cancer Registry statistics show that the average number of new non-Hodgkin's lymphoma cases from 2000 to 2004 mostly involved patients aged from 50 to 75. The average number of new non-Hodgkin's lymphoma cases every year for those aged 50 was 48, and for those aged 75 it was 62.

Is it correct to say that the cancer is active in people of middle and old age and why?

Lymphoma is a heterogeneous disease group, comprising of more than 30 distinct disease subtypes with diverse features. The registry's statistics are from a primitive database which only records basic patient data. For lymphoma patients, it is hard to get a clear understanding of each individual lymphoma subtype.

In general, the incidence of lymphoma does rise with age. This has been observed all over the world. A general explanation of this is that the older we get, the more likely we are to be exposed to risk factors (known and unknown) for developing lymphoma and other forms of cancer.

The registry's statistics also show that only about 50 per cent of lymphoma cancer patients survive after five years of treatment. Why is the survival rate so low?

A generalisation should not be made from this data. Different lymphoma subtypes will have a different survival pattern. For low-grade lymphoma, the median survival duration can be as long as eight to 10 years.

For some aggressive lymphomas, the average survival rate of five years is about 50 per cent - and this is not a low survival figure. Of course, there is still room for improvement, especially with the development of new drugs.

But the results of this will only be reflected in the next five years. I cannot explain why the survival rate is low because that depends on the patient population, disease stage and the type and quality of treatment that they were receiving at the time.

Any or all of these factors could have had an influence on the survival rate.