Chief executive Kevin Snee said 22 people were scheduled to have their radiation therapy treatment today, the first time the service has been offered since the attack and an "important milestone".
The DHB had four machines and two were currently back in operation as some other patients were continuing to get care in Tauranga and Wellington hospitals.
"Being able to again provide this important service for our community here in Waikato is a great reward for all the hard work of our IT, support and clinical teams," he said.
"We have four machines and will begin with two this week while we keep a number of our staff in Tauranga and Wellington to ensure continuity of care for those patients who were sent to those areas.
"Once our staff and patients are repatriated to Hamilton, which is expected over the next two weeks, we'll be able to have all four up and running."
Work was continuing to restore all systems across the DHB with a number of key services including the inpatient management system and diagnostic services across the radiology and laboratory services expected to be online this week.