Patients who may have cancer are suffering “huge anxiety” because of record delays in being tested.
More than one in five people referred for diagnostic checks in Tayside and Fife were not seen within the legal target of six weeks, official figures show.
Staff shortages including a lack of radiologists are driving the delays across Scotland, according to Cancer Research UK.
In Fife, just 77.2% were seen within the six-week standard, compared with 78.8% in Tayside and 79.3% nationally – a record low.
The number of Scots waiting longer than they should for diagnostic procedures such as CT scans, MRI scans and ultrasounds rose from 3,554 at the end of 2015 to 15,956 just two years later, the data published on Tuesday revealed.
Health Secretary Shona Robison said: “The Scottish Government has made £4.85m of funding available to support access to diagnostics for suspected cancer patients, including £2m for improvements to scopes alone.
“I have made it clear to boards that they must continue to treat these patients with the highest priority.”
Gregor McNie, from Cancer Research UK in Scotland, said: “These statistics paint a picture of a service struggling to keep up with growing demand. Waiting to find out if you do or don’t have cancer can cause huge anxiety to patients.
“Staff shortages are partly to blame and the recent initiative to recruit more radiologists will go some way to alleviate current pressures.
“But a more urgent plan for all diagnostic staff is also needed.”
Janice Preston, the head of Macmillan Services in Scotland, said: “Cancer waiting times haven’t been met since 2012 and these latest statistics add to a growing issue that must be addressed head on and a solution found.”
The diagnostic figures were released at the same time as statistics showing the 18-week referral to treatment target was missed and a decline in performance in the 12-week treatment time guarantee for outpatients.
Meanwhile, A&E departments are still not meeting the target for the percentage of patients admitted, transferred or discharged within four hours of arriving.
Anas Sarwar, for Scottish Labour, said: “A decade of SNP mismanagement has left our NHS under staffed an under pressure.”
Helen Wright, who is Fife’s director of nursing, said: “Fife, like much of the rest of the country, has been affected by the well-documented national shortage of radiologists and sonographers, and this coupled with an increasing demand for diagnostic services have made the six week target particularly challenging of late.
“We do appreciate how difficult it is for patients to wait for information about their health and make every effort to see each as quickly as possible.”
An NHS Tayside spokeswoman said: “Our endoscopy service has experienced an increase in demand and regretfully our waiting times are longer than we would like.
“However, it is important to note that the endoscopy service prioritises patients referred with urgent suspicion of cancer and continues to meet the two-week waiting time standard for this.
“For all other endoscopy services, actions have been put in place to address and reduce the waiting times.”