University of Texas MD Anderson Cancer Center Houston, TX
Nitish Mittal, MD, Malek Shatila, MD, Sidra Naz, MD, MPH, Yang Lu, MD, PhD, Anusha Thomas, MD, Hao Chi Zhang, MD, Priyanka C. Iyer, MD, Mimi I. Hu, MD, Yinghong Wang, MD University of Texas MD Anderson Cancer Center, Houston, TX
Introduction: Metformin is a commonly used treatment for diabetes mellitus that has been shown to increase F-18 fluorodeoxyglucose (FDG) uptake in the gastrointestinal (GI) system, which could have a similar imaging presentation as enterocolitis on positron emission tomography/computed tomography (PET/CT) scan. This mimicking feature could lead to confusion of subclinical enterocolitis and impact clinical management, especially in patients on immune checkpoint inhibitors (ICI) as enterocolitis is one of the common adverse events related to ICI. We are interested to study the incidence and characteristics of patients with diagnosis of clinical enterocolitis among patients on metformin and ICI who had PET/CT evidence of FDG uptake in GI tract.
Methods: We conducted a retrospective single-center study among cancer patients concurrently receiving metformin and ICI (01/01/2010-09/30/2022) who underwent a PET/CT scan during their treatment. Cases with reported suspicious positive PET/CT signal for GI tract were extracted and analyzed for colitis incidence, clinical and imaging presentations.
Results: Among 1869 PET scans in 1259 patients in the study window, 361 patients had positive enterocolitis reported on 535 PET/CT scan tests. After manual chart review, 157 patients were included as the final cohort with the following demographics: median age 67 (58-73), male gender (69.4%), cancer type (lung, head & neck in 36.9%, melanoma in 24.8%, gastrointestinal in 8.9%, genitourinary in 6.4%), and ICI treatment (anti-PD-1/L1 monotherapy in 80.8%, combination of CTLA-4 and PD-1/L1 in 19.2%). Total 70 of 157 patients had a clinical diagnosis of ICI enterocolitis (44.6%). The features of positive FDG uptake on PET/CT appeared comparable between patients with clinical enterocolitis and those without which could be due to the metformin effect (Figure 1). No specific characteristics such as standardized uptake value (SUV) level have been observed to differentiate the metformin effect vs immune related enterocolitis.
Discussion: The signal of FDG uptake is comparable between the metformin effect and ICI enterocolitis on PET/CT. The FDG positivity does not necessarily associate with ICI enterocolitis. The management is still relying on the standard clinical and endoscopy evaluation for final confirmation.
Figure: Captions are present in the image already.
Disclosures:
Nitish Mittal indicated no relevant financial relationships.
Malek Shatila indicated no relevant financial relationships.
Sidra Naz indicated no relevant financial relationships.
Yang Lu indicated no relevant financial relationships.
Anusha Thomas indicated no relevant financial relationships.
Hao Chi Zhang indicated no relevant financial relationships.
Priyanka C. Iyer indicated no relevant financial relationships.
Mimi I. Hu indicated no relevant financial relationships.
Nitish Mittal, MD, Malek Shatila, MD, Sidra Naz, MD, MPH, Yang Lu, MD, PhD, Anusha Thomas, MD, Hao Chi Zhang, MD, Priyanka C. Iyer, MD, Mimi I. Hu, MD, Yinghong Wang, MD. P3032 - Similar Features of PET Scan in Gastrointestinal Tract Related to Metformin and Immune Related Enterocolitis, ACG 2023 Annual Scientific Meeting Abstracts. Vancouver, BC, Canada: American College of Gastroenterology.
