Whanganui DHB service and business planning general manager Paul Malan said the number of patients could be quite small so one or two patients could have a significant impact on percentages.
"Whanganui DHB's result for the faster cancer treatment target in January 2019 accounts for a total of six patients where two of the patients were not seen within the target timeframe," Malan said.
"Those two patients have since been progressed on their treatment pathway."
Malan said the holiday period, planned delays in treatment for clinical reasons, patient choice and "other unexpected pressures" during January may have contributed to the result. Industrial action was not an issue.
For the April to December 2018 period, Whanganui DHB met its target for six of those nine months, three of them at 100 per cent, Malan said.
For the first quarter of 2018, the DHB averaged 88 per cent, and 85.7 per cent for the second quarter.
Cancer Society of New Zealand medical director and Southern DHB oncologist Chris Jackson told the New Zealand Herald while it was shocking to hear how long some patients were waiting for treatment, more emphasis needed to be put on the root causes.
"Our system is failing and that's exactly why we need a national cancer agency to ensure all DHBs are keeping up with a national standard of care."
The Herald approached Minister of Health David Clark for comment in the issue but he declined.
Director-General of Health Dr Ashley Bloomfield said ministry officials were working with DHBs that were not meeting the target to understand what the issues were, and what specific actions were under way to improve performance.
"The Ministry of Health is also working on a national cancer action plan to improve collaboration between DHBs, their clinicians, and the wider cancer care sector," Bloomfield said.
"The aim is to improve national consistency of services, equity, and health outcomes for people with this disease."
Clarification
An earlier version of this story said WDHB ranked second to last nationally in cancer treatment wait times for January. In fact, it ranked second to last among the 13 health boards which provided figures. Out of the 20 district health boards in New Zealand, seven did not provide the relevant statistics.