Background: The aim of the study was to identify the frequency of isolated pelvic metastasis with the goal of determining the utility of pelvic CT as a surveillance strategy in patients with resected biliary tract cancer (BTC).
Methods: Study eligibility criteria included patients 18 years or older with BTC who underwent R0 or R1 surgical resection at University of Michigan between 2004 and 2018, with a minimum 6-month disease-free surveillance period. CT and MRI reports were independently graded by two radiologists as positive (organ metastasis, peritoneal carcinomatosis, or enlarged lymph nodes), equivocal (borderline lymph nodes or non-nodular ascites), or negative (absence of or benign findings) in the abdomen and pelvis separately. A 3rd blinded radiologist reviewed all positive and equivocal scans. Clinic notes were reviewed to identify new or worsening signs and symptoms that would warrant an earlier pelvic surveillance scan. A 95% binomial proportion confidence interval was used to find the probability of isolated pelvic metastasis.
Results: BTC were anatomically classified as extra-hepatic (distal and hilar) cholangiocarcinoma (38; 25%), intra-hepatic cholangiocarcinoma (57; 38%), and gallbladder cancer (56; 37%). 151 patients met eligibility criteria, of which 123 (81%) had no pelvic metastasis, 51 (34%) had localized upper abdominal metastasis, and 23 (15%) had concomitant abdominal and pelvic metastasis. Median follow-up time was 19.2 months. One (0%) subject with resected BTC (intra-hepatic) developed isolated osseous pelvic metastasis during surveillance (95% CI 0.004-0.1; p = 0.0003). 3 (2%) subjects developed isolated simple ascites (equivocal grade) without concurrent upper abdominal metastasis.
Conclusion: Isolated pelvic metastasis is a rare occurrence during surveillance in patients with resected BTCs, and therefore, follow-up pelvic CT in absence of specific symptoms may be unnecessary.
Keywords: Biliary tract cancer; Pelvic CT; Pelvic metastasis; Peritoneal carcinomatosis.