Screening for cancer

The Star: According to the Second Report of the National Cancer Registry, the incidence of cancer in Malaysia was 134.3 per 100,000 males and 154.2 per 100,000 females in 2003.
While cancer affects all ages, it is more common in older people. The median age of cancer in Malaysia is 59 in males and 53 in females.
The common cancers in children up to 14 years old are leukaemia, cancer of the brain, lymphoma, cancers of the connective tissue and kidneys.
The common cancers among those in the 15 to 49 age group are of the nasopharynx, leukaemia, lymphoma, cancers of the lung, colon and rectum in males; and cancers of the breast, cervix, uterus and thyroid, and leukaemia in females.
The common cancers in those above 50 are of the lung, colon, rectum, nasopharynx, prostate and stomach in males; and cancers of the breast, cervix, colon, uterus, lung and rectum in females.

Cancer screening
This means detecting the condition when there are no symptoms. Every individual can help himself or herself by consulting a doctor without delay if there is/are:
# a lump
# a persistent lesion on the body
# changes in an existing mole
# sores do not heal or heal very slowly
# chronic cough or blood is coughed out
# persistent indigestion or difficulty in swallowing
# unusual bleeding or discharge from any of the body’s orifices i.e. mouth, anus, nose, ears, urethra, vagina
# unexplained weight loss
# poor appetite

When the above symptoms occur, it does not mean that there is cancer. They could also be caused by infections, non-cancerous (benign) tumours, or other conditions. It is important that a doctor is consulted so that a diagnosis can be made and treatment is started early. One should not wait for pain to develop before consulting a doctor, as most cancers do not cause pain in its early stages. Even if the symptoms are due to cancer, it is important to remember that cancers are curable if treated early.

There are scientific bases for cancer screening tests:
# There are tests or procedures that make it possible to detect a cancer earlier than if it is detected as a consequence of the development of symptoms.
# There is evidence of an improvement in outcome if treatment is started earlier as a result of screening.

The tests that are used to screen for cancer include:
# physical examination
# laboratory tests (e.g. pap smear, tumour markers, occult faecal blood)
# imaging (e.g. mammography, ultrasound scan)
# procedures (e.g. proctoscopy, colonoscopy)

Depending on the results of the tests, the doctor may advise further tests. This may involve the carrying out of procedures, e.g. colonoscopy in those who have a family history of colon cancer, mammography in those who have breast lumps, etc. When procedures are involved, the benefit has to be balanced against the risks involved.
A diagnosis of cancer can be made from microscopic examination of a biopsy, i.e. a procedure in which some tissue is removed from a part of the body. The diagnosis can also be made from tests other than a biopsy.

Outcomes of cancer
The treatment of most cancers and its success, which affects the person’s survival rate, is affected by the stage of the condition. This forms the basis for the assumption that early detection and treatment would result in better outcome and survival. In general, the larger the cancer, the more likely it is to spread to surrounding structures and to distant sites. The stage of the cancer has an important impact on outcome. That is why all treatment trials require the comparisons of similar stages when evaluating the differences in outcome.
However, the behaviour of cancers is also affected by its biological characteristics like its grade, sensitivity to hormones and gene expression.

Potential harm
Most screening tests are non-invasive or minimally invasive. However, some involve procedures which carry some small risks which are immediate (e.g. perforation from colonoscopy) or delayed (e.g. potential increased risk of cancer from excessive X-rays).
The results may cause unnecessary anxiety and worry. It could also lead to unnecessary procedures that are invasive.
The result can be a false positive (i.e. the diagnosis of a non-cancerous condition that would not be clinically evident had it not been detected by screening). This is becoming a problem because diagnostic methods are increasingly more sensitive at detecting tiny growths. On the other hand, a false negative result can lull a person into ignoring signs and symptoms, with consequent delay in treatment.
Whether to screen or not is not a simple issue. If something can be done to prevent a cancer from developing or to improve the outcome, it is justifiable to screen for it. But if a patient cannot be helped, it may not be helpful to carry out widespread screening for the cancer. However, early and accurate diagnosis can save a lot of time, pain and frustration for the patient and his/her family. An early diagnosis can also help in the understanding of the health issues that the patient will have to face.

It is evident from the above that there are no quick and easy answers in cancer-screening, which many people hope to obtain when they have some laboratory tests carried out. It is advisable to have a regular doctor and to consult him or her for any type of screening, let alone cancer screening, for he or she is in the best position to advise on what is necessary.

Dr Milton Lum is Chairperson of the Commonwealth Medical Trust. This article provides general information only and is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation that the writer is associated with.