Waikato Hospital says all urgent cancer cases are getting radiation treatment on time, but admits others may face delays.
Waikato Hospital's director of Hospital and Specialist Services, Michelle Sutherland, said all "urgent" cancer cases at Waikato were seen within the national best practice guidelines.
"And at the moment all other cases including routine ones, have at most an average of a one to two week delay to these guidelines."
Patients were prioritised based on their clinical urgency, she said.
"This does mean that some patients may be waiting longer than they or we would like, but we do need to triage patients due to urgency and are working hard to keep waiting times as short as possible, while ensuring all patients receive care within appropriate timeframes."
Advocates say some breast cancer patients are waiting weeks longer than best practice, putting them at risk of the disease recurring.
Breast cancer patients often required different treatment such as surgery or chemotherapy first and needed "recovery time" before starting radiation therapy, Sutherland said.
"This is an established practice in breast cancer radiation treatment, and while it can feel like a long process, we do our best to update our patients on these timeframes during their first specialist appointment."
Breast Cancer Foundation chief executive Ah-Leen Rayner has told RNZ international best practice was for women who have had breast-conserving surgery to get radiation treatment within eight-12 weeks as longer delays can increase the chance of breast cancer coming back.