The Cancer Control Agency, Te Aho o Te Kahu, admits ongoing radiation treatment delays for patients in Southland and Otago are "stressful".

Its chief executive, Rami Rahal, said a lot of effort had gone into supporting the Southern Cancer Service after criticism of long wait-times by the Health and Disability Commission last year.

"I am aware the ongoing difficulties to deliver timely radiation treatment services in Southern have been stressful and disruptive for many cancer patients and their whānau," he said.

"Health New Zealand Te Whatu Ora have taken meaningful steps to support Southern cancer services."

As a result of these efforts, the current waiting list for first specialist appointments with a radiation oncologist had nearly halved to 56 people, down from 113 a year ago, he said.

However, specialist shortages continued to plague services, as the Health and Disability Commission has concluded in a follow-up report this week.

Rahal said workforce growth and development were vital to creating "sustainable solutions".

Necessary measures included "intensified efforts" to recruit overseas clinicians, retaining current staff by ensuring a good practice environment, and providing advanced training to nurses, general practitioners, pharmacists and allied health professionals "to take on more of the load from oncologists where safe and effective".

"We are working closely with Health New Zealand on these issues and remain committed to helping drive improvement in Southern and across New Zealand for those living with cancer," he said.