S-1 (Tegafur) Dosing for BSA 1.6 m²
For a patient with body surface area (BSA) of 1.6 m², the standard S-1 dose is 80 mg/m²/day, which calculates to 128 mg/day total, typically administered as 60 mg twice daily (morning and evening) after meals for 28 consecutive days followed by 14 days rest. 1
Dose Calculation and Administration
- Standard dosing: S-1 is administered at 80 mg/m²/day, given orally twice daily after meals 1
- For BSA 1.6 m²: 80 mg/m² × 1.6 m² = 128 mg/day total dose
- Practical dosing: Round to 60 mg twice daily (120 mg/day) or 65 mg twice daily (130 mg/day) depending on available capsule strengths
- Treatment schedule: 28 days of consecutive administration followed by 14 days rest constitutes one cycle 1
- Duration: Treatment is typically repeated for four cycles initially 1
Dosing Adjustments Based on Toxicity
- If neutrophil count <1500/μL or platelet count <100,000/μL: Postpone treatment for maximum 2 weeks 2
- If neutrophils 1000-1500/μL or platelets 70,000-100,000/μL after delay: Reduce dose by 50% 2
- If counts remain below these thresholds: Discontinue treatment 2
Expected Toxicity Profile
- Common adverse reactions (78% incidence): Generally mild and manageable 1
- Grade 3-4 toxicity (20% incidence): Includes decreased hematocrit, leucopenia, granulocytopenia, diarrhea, malaise, and proteinuria 1
- Gastrointestinal toxicity: Most frequent side effect, with grade 3-4 occurring in approximately 17.5% of patients 2
- Hematological toxicity: Minimal severe toxicity expected 2
- Hand-foot syndrome: Occurs in approximately 5% of patients 2
Clinical Context
- Response rate: Approximately 49% in advanced gastric cancer and 32.5% in metastatic colorectal cancer 1, 2
- Combination with streptozotocin: In pancreatic neuroendocrine tumors, S-1 has been combined with STZ at doses of 350-1000 mg/m² weekly or 500 mg/m² days 1-5 every 6 weeks 3
- Advantage over IV therapy: Oral administration improves quality of life while maintaining similar efficacy to IV fluorouracil regimens 2, 4