Use of positron emission tomography-computed tomography (PET-CT) scan in cancer patients: A single Canadian academic oncology center experience

e18691 Background: PET-CT scan is key tool in the diagnosis and follow up of cancer patients. In 2017, a governmental study demonstrated that the use of PET-CT scans in the province of Quebec, Canada was two times more elevated than other Canadian provinces, and similar to the United States (507 vs 510 PET-CT scans per 100,000 persons, respectively). In Quebec, the governmental agency Institut national d’excellence en santé et en services sociaux (INESSS) published recommendations for judicious use of PET-CT scans, derived from evidence-based literature and publications from international oncology societies . We sought to evaluate the use of PET-CT scans in our institution with regards to INESSS guidelines. Methods: A total of 1561 PET-CT scans were performed for oncologic purposes at the CHUM between September 1 st and November 30 th 2019. TEP-CT scans from patients under 18 years of age or who were not followed at our center were excluded. 975 PET-CT scans respected our criteria. We reviewed disease and clinical characteristics of patients, adherence to 2017 INESSS guidelines, imaging indication (staging, response to treatment, or follow up), and type of specialties requesting the exam. Results: Oncologic PET-CT scans were most frequently prescribed by surgeons (39%), followed by oncologists (29%) and radiation-oncologists (12%). 530 (54%) PET-CT scans followed guidelines, 377 (39%) did not, and 68 (7%) were not included in INESSS guidelines. Adherence to guidelines was similar between oncologists and surgeons (54% and 53%, respectively). PET-CT scans ordered by radiation-oncologists followed guidelines in 67% of cases. Lung (29%), breast (19%), and gastro-intestinal cancers (16%) were the sites for which the exam was most requested. Whereas 77% of PET-CT scans requested for lung cancer followed guidelines, only 17% of breast cancer PET-CT scans did. Misuse of this imaging tool was also observed in the investigation of cancer of unknown origin, where only 17% of ordered PET-CT scans followed guidelines. Conclusions: In our institution, 39% of PET-CT scans prescription did not follow guidelines. Variability in adherence to guidelines was significantly more noticeable between primary cancer sites compared to types of specialties requesting the exam. To avoid wasting of resources, we advocate for respecting guidelines and discussing in tumor-boards the off-label use of PET-CT scans. Judicious use of PET-CT scans is particularly important in a public health system for appropriate allocation of resources.