Nasopharyngeal Carcinoma (NPC)
Nasopharyngeal Carcinoma (NPC) is the 6th most common cancer among males in Singapore. This disease hits hard because the peak incidence occurs in people who are in the prime of their working and family lives. In Singapore, it is the second and third commonest cancer in males aged 15 to 34 years and 35 to 64 years respectively. The key to the management of NPC is early detection. There is a 90% cure rate if the disease is treated at an early stage.
This cancer has a distinct racial and geographical distribution. The highest incidence of NPC is in the Southern part of China (Guangdong province) and Hong Kong hence the name “Cantonese Tumour”. The incidence is also high among North Africans, the Inuits of Alaska and the Chinese in South East Asian countries. About 92% of NPC sufferers in Singapore are Chinese while 6% and 1% are Malay and Indian respectively. NPC is three times more common in men.
What causes NPC?
It is known that NPC is caused by the Epstein Barr Virus (EBV). This virus is extremely common and more than 90% of people are infected with the virus by the time they reach adulthood. Infection with EBV causes a minor flu like illness in children and occasionally a systemic disease called glandular fever in teenagers and young adults. EBV persists in white blood cells in a dormant phase after the initial infection. The mechanism by which this virus subsequently causes NPC in people is not fully understood and is currently under intense scrutiny by scientists and researchers.
The suspicion that NPC is also associated with the consumption of preserved foods like salted fish came about because of the high incidence of the disease among the boat people of Hong Kong. It is theorized that carcinogens released during the cooking or consumption of these foods primes the cells in the nasopharynx for EBV to cause cellular malignant change. Consumption of these foods at a young age is also thought to be a significant risk factor (weaning children with salted fish was a common practice in Southern China and Hong Kong)
Genes play a significant role in NPC. A study done in Singapore documented that 15.5% of first degree relatives of NPC patients subsequently got the disease. The mean interval to getting NPC between affected siblings was 5.3 years while that between affected parent and child was 24.5 years.
How is NPC diagnosed?
NPC can be difficult to detect because it grows in a ‘hidden’ area at the back of the nose called the nasopharynx. The problem is confounded by the fact that individuals with early disease may not have symptoms. More advanced disease can present as a neck lump, reduced hearing in one ear, nose bleeds, blood stained postnasal drip, blocked nose, headaches and double vision. The symptoms can be quite non-specific and there seems to be a tendency for patients to seek medical attention late. Even doctors can be misled, leading to a delay in referring the patient to the specialist. A Singapore study showed that in nearly one fifth of NPC patients, the diagnosis was delayed by an average of 7.2 months due in part to clinicians not considering a diagnosis of NPC. It is for this reason that NPC is commonly diagnosed at a late stage (stage 3 or 4). This is unfortunate because the cure rate after treatment for stage 3 is only 60% and it drops to below 50% for stage 4 disease. On the other hand, the cure rate for the earliest stage disease can be in excess of 90%.
The best way to examine the nasopharynx is via a nasoendoscopy done by an ENT specialist in the clinic. A biopsy is done if a suspicious mass or irregularity is seen in the nasopharynx. Patients with NPC may also have high titres of certain antibodies to EBV in their blood. Blood tests for these antibodies are available commercially and can be used to screen for NPC in selected high risk patients. An MRI scan with contrast is a useful adjunct in NPC detection because it can sometimes show up a growth even when the nasopharynx looks ‘normal’ on nasoendoscopy.
Treatments for NPC
NPC tumour cells are very sensitive to radiation hence the conventional treatment for early stage NPC is definitive radiation therapy (RT). Late stage disease is treated with a combination of radiation and chemotherapy. During treatment, there is a significant irradiation of the adjacent structures in the head and neck leading to potential RT long term effects like dry mouth, hearing loss, poor vision and temporal lobe necrosis. Improvements in RT equipment over the past 10 years has reduced salivary flow continues to be a problem in majority of patients. Surgical removal of the tumour is a difficult operation and is reserved for disease that recurs after radiation and chemotherapy. These surgeries are usually performed in selected patients. It is a keyhole (scarless) procedure for surgically removing NPC that recurs after primary treatment with radiation and chemotherapy.
This disease can be defanged if detected early. Public education regarding the symptoms of NPC is one way to bring the patients in early. High risk groups like first degree relatives of patients with NPC should be screened for the disease as soon as possible. Doctors and primary care physicians should be thoroughly familiar with the symptoms and signs NPC and have a high index of suspicion for this disease.