Rare disease remains hidden
The recent death of Apple co-founder Steve Jobs has turned the spotlight on pancreatic cancer, which claims about 400 lives every year in Hong Kong. The type of cancer that Jobs had - a pancreatic neuroendocrine tumour (PNET) - is actually a rare form of the cancer. Only eight to 10 new cases of PNET occur in Hong Kong every year, compared to 400 for pancreatic cancer, the sixth leading cause of cancer deaths locally.
Dr Lo Chung-yau, a specialist in endocrine surgery, says PNET is a less lethal form of pancreatic cancer. 'PNET grows relatively slowly,' he says. 'If the cancerous cells have not spread to other parts of the body, 60 per cent of patients will still be alive five years after diagnosis; 20 to 30 per cent of patients can still live 10 years after diagnosis.'
If the cancerous cells spread, however, the survival rate drops to 20 per cent five years after diagnosis, says Lo. However, this rate is still higher than that for the common form of pancreatic cancer - adenocarcinoma - which is close to zero. Jobs was diagnosed at the age of 48 and died at 56.
Because of the slow growth of PNET, the window for treatment is broad, so it's not difficult to cure, according to Dr Peter Teo Man-lung, a specialist in clinical oncology. The flip side, however, is that the lack of clear symptoms usually delays treatment, says Lo.
Because the pancreas lies deep inside the body, it's often difficult to diagnose tumours early because they have yet to interfere with the function of nearby organs such as the stomach, liver or gall bladder. 'While getting a liver scan is easy, normal medical check-ups can't reveal PNET,' says Lo.
If the tumour is located in the head of the pancreas, it will cause an obstruction in the bile duct. The patient's face will turn yellow, and they will have an infection that doctors can pick up. But the chance of having obvious symptoms is lower if the tumour is located in the tail, farthest from the duodenum.
When the tumour grows big and suppresses the large intestine, it will cause obstruction and bleeding, explains Lo. For those whose cardio-respiratory functions are affected, they can show asthma-like symptoms such as shortness of breath. Other symptoms include dizziness and shaky hands.
Lo adds that PNET may cause the pancreas to overproduce certain hormones such as insulin, which makes the patient suffer from low blood sugar levels. Some produce excessive levels of serotonin (known as the 'happy hormone') and suffer severe diarrhoea.
'But some patients can have no symptoms at all,' says Lo. 'The cancerous cells in two-thirds of patients have already spread at the time of diagnosis.'
The pancreas makes juices which are enzymes that help digest food in the duodenum. It also produces important hormones, including insulin, which controls the amount of sugar in the blood. PNET develops in the islet cells, which are clusters of cells that produce hormones. But doctors don't really know what causes it.
The US Food and Drug Administration approved two new drugs - sunitinib and everolimus - last year for the treatment of advanced PNET. Surgical removal is the preferred form of treatment. Chemotherapy, radiofrequency therapy and molecularly targeted therapy in oncology are used for those whose tumours have spread to other parts of the body.
Teo says a liver transplant can extend the life of patients afflicted with PNET, especially for those whose cancerous growth is under control in the pancreas and the cancerous cells have not spread to other organs. However, to prevent the body from rejecting the new liver, patients will have to take immunosuppressant drugs, which weaken the immunity of the body and can make cancerous cells in other parts of the body grow faster. 'It's a dilemma,' says Teo.
Jobs underwent surgery for PNET in 2004 and had a liver transplant in 2009. In his case, however, the cancer had already spread and a cure was impossible. '[Jobs] had to get a transplant to prevent liver failure and instant death,' says Teo.
Lo speculates that before Jobs got the liver transplant in the US, he went to Europe for an experimental hormone-delivered radiotherapy, as the therapy has not been approved by the FDA.
The treatment involves injecting hormones with radioactive substances to kill cancerous cells. Lo says the side effects are much less severe than those associated with chemotherapy, but the treatment costs HK$80,000 to HK$100,000. Only one or two local patients have received the therapy, he says.
PNET is distressing because it tends to afflict people in their 30s and 40s. Overall, pancreatic cancers are increasingly striking people at younger ages. 'In the past, most people who had adenocarcinomas were over 70. But recently I have seen patients who are just over 50,' Teo says.
The risk factors for PNET are largely unknown. Risk factors for pancreatic cancer include not only age, but also cigarette smoking, obesity, diabetes and race. (Blacks are more likely to develop the disease than whites.)
'Although we don't know what causes the disease,' says Lo. 'The best way to prevent it is to stay healthy by exercising regularly and eating less fatty foods.'
