The Cancer Institute NSW hopes new research into unknown primary site cancer – the State’s third-deadliest, but largely hidden cancer – will lead to further scientific efforts to improve treatment and save lives.

A study by the Cancer Institute into 14,500 cases of cancer diagnosed without an obvious organ of origin has found new evidence that some patients may have better survival chances than previously thought by experts around the world.

“Unknown primary cancer takes around 1,000 lives in NSW every year, but until now there has been little study of its prognosis,” Professor Jim Bishop, Chief Cancer Officer and CEO Cancer Institute NSW said on 16 June 2008.

Unknown primary cancer is the fifth most common cancer in NSW women and the seventh most common in men, with around 1,500 new cases diagnosed in NSW each year, representing around 4 per cent of all cancers diagnosed. At 8 per cent of all cancer deaths in NSW, unknown primary cancer ranks equal third with prostate cancer, after cancers of the lung and bowel, as leading causes of cancer death. The median survival for patients with unknown primary cancer that has spread throughout the body is only three months, compared to five months where the primary tumour is known. However, the Cancer Institute study has shown some sub-sets of unknown primary cancer do considerably better and may be treated successfully.

The report shows that cancer of unknown primary of squamous cell type has a good outlook.

“This Cancer Institute research is also important, because it raises the possibility that unknown primary cancers are actually a specific type of cancer in some cases,” Professor Bishop said.

“With this new information, doctors and researchers can now explore how this cancer could be diagnosed earlier – therefore improving a patient’s chances of survival.

“Unfortunately, overall, patients diagnosed with late-stage unknown primary cancer have an 80 per cent greater chance of dying in the first year after diagnosis, compared to the same stage in those with a known primary tumour.

“The study has also raised the possibility that differences in the genetic make-up of unknown primary cancer could lead researchers to new discoveries to improve treatment and survival.”