Rare but aggressive, cancers of the bile duct can be added to the list of carcinomas for which PET scanning with the radiotracer 18F-FDG adds diagnostic and/or prognostic value, according to the authors of a study running in the August edition of the Journal of Nuclear Medicine.
Jaemin Jo, MD, and fellow researchers at Seoul National University College of Medicine in South Korea prospectively enrolled 75 patients with advanced biliary tract cancer who were about to begin palliative chemotherapy.
The researchers’ primary interest was in the prognostic value of tracking tumor metabolism and chemotherapy-related changes in these patients.
Analyzing associations between SUVmax and clinicopathologic factors (primary tumor site, histologic differentiation, molecular characteristics, laboratory findings, disease extent), as well as comparing clinical outcomes, the team found that patients with higher tumor metabolism showed worse progression-free and overall-survival outcomes than the patients with lower tumor metabolism.
Lesser reductions of SUVmax also were associated with worse survival, both progression-free and overall.
Finally, when the researchers considered both baseline tumor metabolism and chemotherapy-related tumor changes, they found patients with low tumor metabolism and greater reduction in tumor metabolism had the best overall survival (20.7 vs. 6.2 months).
“To the best of our knowledge, the present study is the first prospective study on the prognostic impact of metabolic activity in biliary tract cancers,” the authors write in their discussion. “Metabolic activity was associated not only with overall survival but also with progression-free survival.”
Higher 18F-FDG uptake “might represent higher tumor burden, resulting in poor outcome,” they add. “In support of this view, we found that patients in the high-metabolism group had the tendency to present with initially metastatic status and had higher 18F-FDG uptake at organs and lesions.”
Jo and colleagues also comment on the rise of PET/MRI alongside PET/CT. Noting that PET/MRI has been shown potentially better for depicting anatomic division—besides having the advantage of being radiation-free—they point out that there isn’t much data on PET/MRI for imaging biliary tract cancer.
“Some studies showed the superiority of PET/MRI for the evaluation of liver metastasis, so it seems that PET/MRI has also potential role in biliary tract cancer,” they write. “However, longer scanning time, large volume of data, motion artifacts due to respiration or bowel movements and contraindication of the procedure in patients with metal prostheses are limitations of PET/MRI.”