Te Aho o Te Kahu - the Cancer Control Agency - said Waikato DHB's 73 cancer patients currently receiving treatment would be cared for in Auckland, Wellington and Tauranga.
Te Aho o Te Kahu chief executive Diana Sarfati said while delays in treatment were possible, they hoped to minimise them.
"The very urgent patients are being sent immediately to Auckland, and those patients who have the highest needs for treatment will receive it, and they will receive it in the time that they need it," Sarfati said.
"I don't think we can rule out minor delays, but we're going to be talking more about days or maybe weeks, but not longer than that. The most urgent patients will be being seen urgently."
Decision-making about where patients would be sent was under way, she said.
"All 73 patients who were on treatment at the time of the cyber attack are either already receiving treatment, or have a plan for that to be happening in the next couple of weeks.
"The patients who were on the waiting list to start treatment - there's 121 of those - will be reviewed and prioritised, they will be contacted in the next few days to put a plan in place."
Safarti said sending patients to Australia had always been a less desirable option.
"This is an incredibly stressful time for those patients. The last thing they're going to want is to be going to Australia. Our aim was always to treat people as close to home as we could get.
"We've been working with the DHB staff, who have been working incredibly hard ... to make sure that patients get the care they need with as little disruption as possible under the current circumstances."
Last year Te Aho o Te Kahu reported diagnosis of cancer was significantly disrupted by the pandemic and lockdown, with about 500 fewer diagnosis counted throughout the country between January and April, compared with the year before.
- RNZ