Current Status (as of Jan 15, 2026)

• NED on imaging: MRI abdomen shows post-surgical changes only, no new hepatic lesions. CT chest: stable pulmonary nodules (9 mm RLL, stable >15 months).
• CEA 1.8 (Siteman, 01/15) — approaching baseline of 1.4 from initial diagnosis (11/2021). Lowest value since treatment began.
• Labs completely normal: CBC, CMP, LFTs all within range. Creatinine 1.16 (eGFR 77). Platelets recovered to 170 (from nadir of 131 on chemo).
• ECOG 0 — fully active, no symptoms.
• Guardant 360 MRD: NEGATIVE — no circulating tumor DNA detected.
• Guardant Tissue: NEGATIVE — tumor-informed ctDNA assay also negative.

The Decision Point

At our Jan 15 visit, Dr. Tan outlined three options:

1. Observation — frequent CEA and scans
2. “Adjuvant” chemotherapy — 5-FU-based
3. FOLFOX + panitumumab — given RAS wild-type status and possible lung metastasis

We agreed to await the Guardant results before deciding. The results are now back: negative for both assays.

Why I Still Want to Discuss Escalation

The ctDNA-negative result is genuinely good news. But my clinical history gives me pause about relying on surveillance alone:

• Two recurrences — the second came while on active 5-FU maintenance (Nov 2025 MRI showed new liver lesions during cycle 7-8 of 5-FU)
• First liver resection had a positive margin (segment 2, May 2025)
• CEA was unreliable — it was falling (3.3 → 2.6) while new metastases were forming. And at initial diagnosis, CEA was only 1.4 with a pT4 tumor.
• Disease escaped maintenance therapy — 5-FU alone has empirically failed to prevent recurrence in my case

The negative ctDNA shifts the calculus but doesn’t resolve it. The false-negative rate is 5-15%, and may be higher for tumors with low ctDNA shedding — which mine may be, given the consistently low CEA pattern.

What I’d Like to Discuss

On treatment strategy:

• Given my recurrence history, does the ctDNA-negative result change your recommendation? Or does the clinical pattern still warrant some form of treatment?
• At our last visit you mentioned FOLFOX/panitumumab as option 3. Anti-EGFR therapy has never been used in my case — is this the right time to deploy it?
• Would a middle path make sense? For example, 5-FU/LV + panitumumab (no oxaliplatin initially), with serial ctDNA monitoring — escalating to full FOLFOX only if ctDNA turns positive?
• If we do use oxaliplatin, can we use a stop-and-go approach (4-6 cycles then maintenance without oxaliplatin)?

On colonoscopy surveillance:

Comprehensive Clinical Analysis: CEA Kinetics, ctDNA, and Treatment Strategy

Prepared for Discussion with Dr. Benjamin Tan — February 2026

Patient: Alexander R. Towell, age 50, male Primary Oncologist: Benjamin R. Tan, MD — Washington University / Siteman Cancer Center Hepatobiliary Surgeon: William Chapman, MD — Washington University

Clinical data extracted from three EHR systems exported 01/30/2026: (1) Siteman/BJC — 76 Epic CDA XML documents (DOC0001–DOC0076), (2) Anderson Hospital — 80 MEDITECH CCDA XML files + FHIR Bundle (691 resources), (3) SIHF Healthcare (athenahealth) — 16 PCP encounters (Sep 2021–Jan 2026), 260 lab results, 125 vitals, 29 medications, 12 conditions, PHQ-9 screenings, immunizations, and behavioral health notes. Guardant 360 MRD and Guardant Tissue results received via MyChart message (both negative). All claims are cross-referenced against the actual medical record unless otherwise flagged.

1. CEA Kinetics Analysis

The 17-Point Time Series

Cross-Laboratory Assay Note

Anderson Hospital uses the Ortho Clinical Diagnostics immunoassay (ref range 0.0–3.0 ng/mL). Siteman/BJC uses a different assay (ref range 0.0–5.0 ng/mL). The Anderson FHIR data explicitly notes: “CEA results determined by assays using different manufacturers or methods may not be comparable.”