Figures obtained by BBC News Northern Ireland show that some patients in the Western Health Trust are waiting up to 20 weeks to see a specialist consultant after being flagged.
Red flag referrals are made when a doctor believes a patient's symptoms require additional research because they could be cancer-related. .
A number of specialties, including general surgery, are represented in the inpatient and day case statistics.
The Western Trust issued an apology.
Urology, orthopedics, endoscopy, and gynecology are some of the other specialties that are affected.
The statistics have been dubbed "appalling, shocking, and sadly the reality for a growing number of people," according to a GP who practices in Londonderry. .
The figures, according to Dr. Simon O'Hagan, have "gotten out of control" and are "soul-destroying" for both patients and medical professionals.
In the Western Health Trust, eight years is the maximum hospital waiting period for patients in need of orthopaedic surgery.
The statistics from December of last year also show that some people have been waiting seven years for an urgent referral to an ENT specialist.
The Western Health Trust stated that the longest wait for a Red Flag Inpatient/Day Case for General Surgery was 19.9 weeks, with a 16-week average.
According to Dr. O'Hagan, the Western Trust informed one of his patients, who has been diagnosed with Crohn's disease, that specialists will still be seeing patients in 2019.
The patient has "no choice but to self-fund a private appointment for gastroenterology," which is scheduled for Belfast the following week, according to Dr. O'Hagan.
Patients are telling us that they simply can't wait on these lists any longer, claiming that if they do, they won't make it to the front of the line.
Meanwhile, there has been an increase of 1,578 since September according to the Department of Health's most recent quarterly waiting-list statistics.
The current waiting list for a first consultant-led outpatient appointment includes 378,411 patients.
Furthermore, 16,392 patients are awaiting their first consultant-led outpatient appointment for a cataract treatment day-case.
They must wait 400 weeks, and eight years is typical, according to Dr. Nicola Duffy, a general practitioner in Derry.
Without their own fault, those who are on waiting lists, according to Dr. Duffy, go to the emergency department (ED) when they are ill and in need of medical attention.
Dr. Duffy claims that the lack of accountability for Northern Ireland's waiting lists is a contributing factor in the issue.
Some of Colum Eastwood's constituents have been waiting to see a consultant for eight years, the Social Democratic and Labour Party (SDLP) MP said yesterday in the House of Commons.
He questioned the leader of the government about whether he concurred that "the situation can no longer stand and we need a government as soon as possible.".
People in England shouldn't have to wait more than a year to be seen, according to Prime Minister Rishi Sunak's comments from last month.