1. Approach to adjuvant treatment in mixed intestinal and pancreatobiliary ampullary adenocarcinoma

Ampullary adenocarcinoma is unusual because tumours arising from the ampulla of Vater may differentiate along either an intestinal pathway, resembling colorectal adenocarcinoma, or a pancreatobiliary pathway, resembling pancreatic or distal biliary adenocarcinoma. Some tumours show genuine mixed differentiation. This distinction is clinically relevant because treatment selection increasingly follows histological phenotype.

Pathology review.

The first step should be expert gastrointestinal pathology review of the pancreaticoduodenectomy specimen, ideally within a multidisciplinary setting. The review should confirm:

·       The site of origin of the tumour be it from the ampulla rather than the distal bile duct, pancreas or duodenum.

·       The dominant histological phenotype.

·       Tumour size and pathological T stage.

·       Number of lymph nodes harvested.

·       Histological grade.

·       Lymphovascular invasion.

·       Perineural invasion.

·       Pancreatic and duodenal invasion.

·       Resection-margin status, confirming the reported R0 resection.

This is particularly important because reproducibility of the 'mixed' classification is poorer than for clearly intestinal or pancreatobiliary tumours.

Role of immunohistochemistry

Morphology remains central, but immunohistochemistry can help when differentiation is uncertain. A useful panel includes CK7, CK20, CDX2, MUC1 and MUC2.

Strong CDX2/CK20/MUC2 expression supports intestinal differentiation, whereas MUC1 and CK7 expression with absent CDX2/MUC2 supports pancreatobiliary differentiation. No single marker is completely sensitive or specific, so immunohistochemistry plays a supportive role rather than replace morphological assessment. Mismatch-repair testing should also be performed routinely.

Choosing adjuvant therapy

If expert review continues to classify the tumour as genuinely mixed, it is reasonable to manage it according to the pancreatobiliary pathway when the pancreatobiliary component is substantial or when high-risk pathological features are present.

Pre treatment evaluation should review:

·       ECOG performance status particularly after Whipple surgery.

·       Pathological T and N stage.

·       Tumour grade.

·       Lymphovascular and perineural invasion.

·       Postoperative CA 19-9 after resolution of biliary obstruction.

·       Nutritional status and postoperative weight.

·       Renal, hepatic and bone-marrow function.

·       Pre-existing neuropathy.

·       Comorbidities and frailty.

·       Patient preference, treatment access and anticipated tolerance.

Node-positive disease, pT3/pT4 disease, poor differentiation, pancreatic invasion, lymphovascular or perineural invasion, and an elevated postoperative CA 19-9 strengthen the argument for multi-agent adjuvant chemotherapy.

Evidence is less robust than in pancreatic or colorectal cancer. In the ESPAC-3 periampullary trial, the unadjusted primary analysis did not show a statistically significant survival advantage for chemotherapy over observation, but an adjusted analysis accounting for prognostic factors showed a survival benefit. Therefore, an R0 resection alone should not automatically lead to observation.

2. Adjuvant chemotherapy for confirmed pancreatobiliary subtype

If expert review confirms a pancreatobiliary subtype and the patient has recovered well from surgery with ECOG 0–1 and adequate organ function, the preferred regimen would be modified FOLFIRINOX for approximately six months.

The rationale is both biological and clinical. Pancreatobiliary ampullary cancers share pathological and molecular features with pancreatic and biliary tract cancers, and contemporary guidelines permit pancreatic-type adjuvant chemotherapy. French intergroup guidance also supports six months of mFOLFIRINOX for aggressive pancreatobiliary or mixed tumours, particularly pT3/T4, node-positive, poorly differentiated or otherwise high-risk disease.

More ampullary-specific retrospective evidence has also emerged. A 2025 multicentre study reported better 3-year disease-free survival with adjuvant mFOLFIRINOX than with other treatments. Because this was retrospective and involved a small mFOLFIRINOX subgroup, it should not be interpreted as equivalent to a phase III randomized trial, but it strengthens the rationale for mFOLFIRINOX in a fit patient.

Alternative for a less-fit patient

If postoperative recovery, comorbidities, neuropathy or frailty make mFOLFIRINOX excessively toxic, reasonable alternatives include gemcitabine plus capecitabine, gemcitabine alone, or another fluoropyrimidine-based regimen.

Gemcitabine has randomized periampullary evidence from ESPAC-3. Thus, for a fit 62-year-old with confirmed pancreatobiliary histology, mFOLFIRINOX is a defensible preferred option, while gemcitabine-based treatment is reasonable when tolerance, cost or access makes FOLFIRINOX unsuitable.

3. Molecular biomarkers, targeted therapy and immunotherapy

The patient's question about an oral targeted treatment is reasonable, but targeted therapy should not currently replace curative-intent adjuvant chemotherapy after an R0 resection simply to reduce hospital visits. The strongest role of biomarker-directed therapy is presently in unresectable, recurrent or metastatic disease.

Mismatch repair proteins and microsatellite instability

The tumour should undergo MMR immunohistochemistry for MLH1, PMS2, MSH2 and MSH6, or equivalent MSI testing. If the tumour is dMMR or MSI-high, immune-checkpoint therapy such as pembrolizumab may become an important option in appropriate advanced or recurrent disease. An MSI-high result does not currently justify replacing standard postoperative chemotherapy with pembrolizumab outside a clinical trial.

Tumour mutational burden

Comprehensive next-generation sequencing can report tumour mutational burden. A TMB of at least 10 mutations per megabase may create a tissue-agnostic indication for pembrolizumab in previously treated advanced solid tumours when satisfactory alternatives do not exist. It is not a standard substitute for adjuvant chemotherapy after curative surgery.

NTRK1, NTRK2 and NTRK3 fusions

A DNA/RNA next-generation sequencing assay should include fusion detection for NTRK1, NTRK2 and NTRK3. Although rare, an NTRK fusion is particularly relevant because larotrectinib is an oral TRK inhibitor with a tissue-agnostic role in appropriate advanced NTRK-fusion-positive solid tumours. It would not currently replace postoperative chemotherapy in an otherwise curatively resected patient.

BRAF

BRAF V600E should be assessed as part of broad molecular profiling. In advanced disease, a BRAF V600E alteration may permit treatment with oral dabrafenib plus trametinib under a tissue-agnostic indication after prior therapy when there are no satisfactory alternatives.

HER2/ERBB2

HER2/ERBB2 amplification or overexpression should also be assessed, usually by immunohistochemistry with confirmatory in-situ hybridization or sequencing where required. HER2-positive advanced tumours may be candidates for HER2-directed therapy. This remains primarily relevant to recurrent or metastatic disease.

Additional broad genomic profiling

A sufficiently broad DNA/RNA panel should also evaluate clinically relevant alterations such as:

·       KRAS and NRAS.

·       BRCA1 and BRCA2.

·       PALB2 and other homologous-recombination repair genes.

·       RET fusions.

·       Other uncommon actionable kinase fusions or alterations.

BRCA1/2 or PALB2 abnormalities may suggest greater sensitivity to platinum-containing chemotherapy and may have implications for germline genetic counselling. However, PARP-inhibitor strategies cannot simply be extrapolated into routine adjuvant ampullary-cancer treatment without supporting evidence.

Conclusion:

This patient's case should first undergo expert gastrointestinal pathology review with morphology plus CK7, CK20, CDX2, MUC1 and MUC2 where necessary, together with reflex MMR/MSI assessment. If the tumour remains genuinely mixed, a clinically significant pancreatobiliary component should generally push management toward the pancreatobiliary pathway, while pathological recurrence risk and patient fitness are incorporated into the final decision.

If a pancreatobiliary subtype is confirmed and she is fit with ECOG 0–1, six months of modified FOLFIRINOX would be a reasonable preferred adjuvant regimen, particularly for node-positive, pT3/T4 or otherwise high-risk disease. Gemcitabine-capecitabine or gemcitabine-based treatment would be reasonable alternatives when FOLFIRINOX is unsuitable.

The resection specimen should undergo MMR/MSI testing and comprehensive DNA/RNA profiling, including NTRK fusions, BRAF V600E, HER2/ERBB2, tumour mutational burden and relevant homologous-recombination alterations. These findings may later allow immunotherapy or targeted treatment, including some oral options, but they do not currently replace standard curative-intent adjuvant chemotherapy solely for convenience after an R0 Whipple resection.

Key references

1.         Chiorean EG, et al. Ampullary Adenocarcinoma, Version 1.2023, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2023;21:753–782.

2.         Neoptolemos JP, et al. Effect of Adjuvant Chemotherapy With Fluorouracil Plus Folinic Acid or Gemcitabine vs Observation in Resected Periampullary Adenocarcinoma: ESPAC-3. JAMA. 2012;308:147–156.

3.         Vernerey D, et al. French Intergroup Clinical Practice Guidelines for ampullary tumours. 2024.

4.         Kalem A, et al. FOLFIRINOX: The Best Adjuvant Treatment for Ampullary Adenocarcinoma? Cancers. 2025.

5.         Brescia International Multidisciplinary Consensus Guidelines on pathology assessment of ampullary/periampullary neoplasms.