Microscopically Incomplete Resection (R1) of Intrahepatic Cholangiocarcinoma: What's the Next Step?

Intrahepatic cholangiocarcinoma (ICC) carries a poor prognosis, with microscopically positive margins (R1) significantly worsening survival. Despite this, current guidelines provide ambiguous recommendations for adjuvant therapy (AT) in R1 cases, partly due to extrapolation from heterogeneous biliary tract cancers. To critically appraise the scarce evidence on AT following R1 resection for ICC, highlight existing knowledge gaps, and outline priorities for future research. We conducted a focused review of studies evaluating survival benefit of AT after R1 resection in ICC, using PRISMA guidelines. Only two retrospective studies specifically addressed this question. Neither study demonstrated a clear survival benefit for adjuvant chemotherapy in R1 resections. Broader data on biliary tract cancers remain heterogeneous and inconclusive. Recent retrospective studies suggest possible benefit from chemoradiation in select subgroups, but robust, prospective trials are lacking. There is insufficient high-quality evidence to guide AT decisions in R1 ICC. Multi-institutional registries and randomized trials focused specifically on ICC are urgently needed. Until then, individualized, multidisciplinary decision-making remains critical.