Some 780 chemotherapy patients at one of Northern Ireland's main treatment centres had treatments in April and May cancelled because the centre does not operate on bank holidays, BBC Northern Ireland reports. Some patients had their treatment rescheduled, but others did not.
The Belfast Health and Social Care Trust told the BBC it tried to rearrange appointments for some patients at the Belfast Cancer Centre but it was not always possible.
The Trust, which runs the centre at Belfast City Hospital, prioritises rescheduling patients who have cancer which has not spread. This means some patients with secondary cancer which has spread did not have their cancelled appointments rescheduled and missed them altogether.
The Trust said it was aware of the "anxiety and inequity" felt by patients affected by bank holiday closures. Chemotherapy for 304 patients will be interrupted in July and August.
The Belfast Trust said it tried to reschedule appointments for some patients, but that this was not always possible due to what it described as "capacity".
It said it received four formal complaints about the issue in the past year, although it is understood more patients had complained informally.
A spokesperson said the Trust tried to reschedule chemotherapy sessions for patients with cancer which had not spread - where a cure was "potentially achievable" - in the same week as their missed session, or the following week.
It said this was because of "some clinical evidence" that supported delivering "the planned dose of chemotherapy on schedule".
It said rescheduling was based on "capacity" and therefore delays happened "across the spectrum of diseases and treatment intentions".
But the spokesperson added that patients whose cancer had spread (secondary cancer patients) were not rescheduled to receive their treatment in the same week because of "less evidence".
BBC News Northern Ireland said it has spoken to a number of patients who did not have their treatment rescheduled at all.