Patients with similar cancers and at similar stages in their illness have been getting different treatment for their conditions in different parts of the State.
The treatment given depends on which clinician the patient sees, which hospital he or she attends and which health board region he or she lives in, according to a report published by the National Cancer Registry.
The director of the registry, Dr Harry Comber, expressed concern at the situation. "It is a matter of concern that treatment varies between health boards on same stage cancers," he said.
"On a national level it does seem clear that we need guidelines on treatment of common cancers," he added.
There were variations from hospital to hospital and from consultant to consultant in terms of what was considered to be "optimal treatment" for different cancers. In the absence of guidelines it was up to the consultants to decide what was best for their patients, he said.
It was to be hoped, he added, that when patients were treated in a consistent manner, there would also be more consistency in survival rates.
The report, Patterns of Care and Survival from Cancer in Ireland - 1994 to 1998, found there were:
a 33 per cent poorer survival rate for patients with breast cancer living in the Southern Health Board region
a 31 per cent poorer survival rate for female colorectal patients living in the Western Health Board region
and a 21 per cent to 36 per cent poorer survival for male colorectal cancer patients living in the South Eastern, Mid Western, Southern and Midland Health Board areas.
The outcome for lung and prostate cancer did not vary significantly with area of residence.
Overall, patients in the eastern region did better.
"This report provides strong evidence that cancer treatment and survival can depend on where the patient lives," the report states.
Asked where patients should go for best outcomes, Dr Comber stressed that the data studied related to 1994-1998 and did not necessarily reflect the situation at the moment.
He will now study the treatment provided in more recent years to see if things have changed.
The report found rates of surgery, chemotherapy and radiotherapy differed from region to region.
Somewhat surprisingly given the lack of radiotherapy facilities in the south-east, it found that women with breast cancer in that region were 25 per cent more likely to receive radiotherapy than women in the eastern region.
Furthermore, Dr Comber said, there was no particular relationship between the number having radiotherapy for breast cancer and their chances of survival.
"But for a fairly high percentage of breast cancer patients radiotherapy is probably not necessary or appropriate," he said.