A 58-year-old man with stage III colorectal cancer (T3N1M0) has completed adjuvant chemotherapy with 5-fluorouracil and leucovorin. He now presents for follow-up. Which drug is the preferred first-line option if he develops metastatic disease?

Question

Accepted Answer

C. 5-Fluorouracil + Leucovorin + Oxaliplatin (FOLFOX). ## First-Line Chemotherapy for Metastatic Colorectal Cancer

**Key Point:** FOLFOX (5-FU + Leucovorin + Oxaliplatin) is the gold-standard first-line chemotherapy regimen for metastatic colorectal cancer (mCRC) in patients with good performance status.

### Rationale for FOLFOX

1. **Superior efficacy**: FOLFOX achieves higher response rates (45–50%) and improved overall survival compared to 5-FU/LV alone.
2. **Doublet backbone**: Combines a fluoropyrimidine (5-FU) with a platinum agent (oxaliplatin), providing synergistic cytotoxicity.
3. **Established standard**: Recommended by ASCO, ESMO, and NCCN as first-line for fit patients.
4. **Biologic add-ons**: Bevacizumab (anti-VEGF) or cetuximab (anti-EGFR, if RAS wild-type) are added to FOLFOX, not used as monotherapy initially.

### Role of Biologic Agents

| Agent | Mechanism | Role in mCRC |
|-------|-----------|-------------|
| **Bevacizumab** | Anti-VEGF monoclonal antibody | Added to FOLFOX/FOLFIRI; improves OS and PFS |
| **Cetuximab** | Anti-EGFR monoclonal antibody | Added to chemotherapy if RAS/BRAF wild-type; monotherapy only in rare chemo-refractory cases |
| **Panitumumab** | Anti-EGFR monoclonal antibody | Alternative to cetuximab; RAS wild-type selection required |

**High-Yield:** FOLFOX is the backbone; biologics are added, not substituted. Monotherapy with any single agent is not standard first-line.

**Clinical Pearl:** Patient selection matters — FOLFOX is preferred in fit patients; simplified 5-FU/LV or capecitabine may be used in elderly or frail patients.

[cite:Harrison 21e Ch 297]

Answer

A. Bevacizumab monotherapy

Answer

B. Cetuximab monotherapy

Answer

D. Irinotecan monotherapy

A 58-year-old man with stage III colorectal cancer (T3N1M0) has completed adjuvant chemotherapy with 5-fluorouracil and leucovorin. He now presents for follow-up. Which drug is the preferred first-line option if he develops metastatic disease?

Explanation

First-Line Chemotherapy for Metastatic Colorectal Cancer

Rationale for FOLFOX

Role of Biologic Agents

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Agent	Mechanism	Role in mCRC
Bevacizumab	Anti-VEGF monoclonal antibody	Added to FOLFOX/FOLFIRI; improves OS and PFS
Cetuximab	Anti-EGFR monoclonal antibody	Added to chemotherapy if RAS/BRAF wild-type; monotherapy only in rare chemo-refractory cases
Panitumumab	Anti-EGFR monoclonal antibody	Alternative to cetuximab; RAS wild-type selection required