What is CAPOX?
- CAPOX (also called XELOX) is a chemotherapy regimen combining:
- Capecitabine (oral fluoropyrimidine, prodrug of 5-FU)
- Oxaliplatin (platinum-based alkylating-like agent)
Mechanism of Action
- Capecitabine → 5-FU
- Inhibits thymidylate synthase → blocks DNA synthesis
- Incorporates into RNA → disrupts RNA function
- Oxaliplatin
- Forms DNA crosslinks → inhibits replication and transcription
- Causes apoptosis
Clinical Indications
- Colorectal cancer (adjuvant and metastatic)
- Gastric cancer (sometimes combined with other drugs, e.g., CAPOX in perioperative FLOT-like regimens)
- Off-label: other GI malignancies where fluoropyrimidines + platinum are used
Dosing (Typical Cycle = 21 days)
- Oxaliplatin: 130 mg/m² IV on day 1
- Capecitabine: 1000 mg/m² orally BID on days 1–14, then 7 days off
- Repeat every 3 weeks
- Duration in adjuvant colon cancer: typically 3–6 months (depending on stage and risk category, per IDEA trial data).
Toxicities & Monitoring
From Oxaliplatin:
- Neurotoxicity
- Acute: cold-induced paresthesias, pharyngolaryngeal dysesthesia
- Chronic: cumulative peripheral neuropathy
- Myelosuppression
- Nausea, vomiting
From Capecitabine (5-FU–like):
- Diarrhea
- Hand–foot syndrome
- Mucositis
- Myelosuppression (less common than with bolus 5-FU)
- Rare: cardiotoxicity (angina, vasospasm)
Monitoring
- CBC, renal function (capecitabine needs renal dose adjustment), liver function
- Neuropathy assessment
- GI toxicities, hand–foot syndrome
- Watch for DPD deficiency if severe unexpected toxicity
Key Clinical Pearls for Oncology Pharmacist
- Oral convenience: CAPOX is often preferred over FOLFOX for patients who want to avoid a central line and continuous 5-FU infusion.
- Efficacy: CAPOX and FOLFOX are considered equivalent in adjuvant colorectal cancer.
- Renal function: Reduce capecitabine dose if CrCl <50 mL/min; avoid if <30 mL/min.
- Neurotoxicity is dose-limiting → may need oxaliplatin dose reduction or discontinuation while continuing capecitabine.
- Combination with biologics: CAPOX can be paired with bevacizumab or other targeted agents in metastatic colorectal cancer.