Almost four in 10 men who need to be assessed for suspected prostate cancer are not getting an appointment to be seen in a HSE-run rapid access clinic in the recommended time.
Just 65.1pc of men are getting their tests within the 20-day deadline, according to latest figures. Clinics are also failing to meet the target time to provide an assessment for all women who are urgently referred for breast cancer checks.
Only 78.1pc are getting an appointment to be seen in two weeks, although the target is 95pc.
Although the delay is unlikely to affect a patient's prognosis, it adds to the stress and anxiety of not knowing about the cause of the symptoms.
A spokeswoman for the HSE yesterday blamed the rise in the number of return patients to rapid access prostate clinics for putting pressure on the service.
While there has been a fall of 7pc in the number of new patients nationally attending rapid access prostate clinics, they have been coping with a 74pc increase in return patients.
The HSE said the rate of increase in the number of return patients creates a risk of rapid access clinics losing the capacity to promptly see and diagnose new patients.
Referring to breast cancer clinics, the HSE said they have had an increase of around 6pc - some 2,228 - in the number of new patients nationally with a corresponding 4pc rise in return patients between 2010 and 2015.
"Over the same period the number of patients diagnosed with breast cancer increased by 14pc," she said.
The HSE said it expects there to be an increase in cancer cases nationally of about 50pc between 2010 and 2025, with knock-on pressures for treatment services.
"The number of patients having cancer-directed surgery is predicted to increase by 50-55pc between 2010 and 2025, chemotherapy by 42-48pc, and radiotherapy by 32-35pc."
The rapid access clinics were set up for patients with suspected breast, prostate or lung cancer.
These clinics have improved the diagnostic pathway for patients suspected of having breast or prostate cancer, the HSE said.
"Where clinics are not meeting access targets, patients are clinically triaged to ensure that those with the highest risk are seen soonest. Where clinics have ongoing problems, initiatives are put in place to deal with those who have been waiting longer.
"The functioning of all clinics is currently under review to identify opportunities to improve processes within the clinic and also to identify where further investment is needed."
Hospitals that are finding it most difficult to meet the deadlines for breast cancer clinics are St James's Hospital, Dublin, and Letterkenny Hospital, Co Donegal.
The target was also not met by Cork University Hospital.
The target for men with suspected prostate cancer is not being met in the clinics in counties Cork, Waterford, Limerick and St James's Hospital.
The prostate cancer service is facing a key challenging in attracting and retaining consultant urologists.
The uptake of women availing of free mammograms under the Breastcheck programme is ahead of target.
This is aimed at offering checks to women over 50 who do not have symptoms.
However, the service is also under strain due to its efforts to recruit and retain radiography staff.
It now opens its clinic in Dublin on Sundays in a bid to make it easier for women to attend the screening in the form of a digital X-ray.