About This Information

This information provides clinical context for the Lonsurf® (trifluridine/tipiracil) dose calculator. It summarizes key aspects of dosing, administration, and safety based on official prescribing information to support healthcare professionals in applying the calculator’s outputs.

Outputs Explained

The calculator provides the following key outputs to guide dosing:

• Body Surface Area (BSA): Calculated in m² using the selected formula (e.g., Du Bois, Mosteller), which is the basis for dose determination.
• Calculated Dose: The precise dose in mg derived by multiplying the patient’s BSA by the selected dose level (e.g., 35 mg/m²).
• Final Rounded Dose: The calculated dose rounded to the nearest 5 mg increment for practical administration. This is the dose to be given per administration (twice daily).
• Total Daily Dose: The final rounded dose multiplied by two, representing the total amount of Lonsurf® the patient will receive each dosing day.
• Tablet Breakdown: The recommended number of 15 mg and 20 mg tablets required to achieve the final rounded dose.
• Dose Capping Alert: A notification appears if the calculated dose exceeds the maximum recommended dose of 80 mg per administration, which is then capped at 80 mg.

How to Use the Calculator

1. Enter Patient Data: Input the patient’s height and weight, ensuring the correct units (cm/in and kg/lbs) are selected.
2. Select BSA Formula: Choose the desired Body Surface Area calculation method from the dropdown menu. The Du Bois formula is a common standard.
3. Set Prescribed Dose: Select the appropriate dose level based on the treatment plan (e.g., 35 mg/m² for starting dose, or a reduced level for dose modification).
4. Review Results: The calculator automatically updates to display the calculated BSA, rounded dose, and required tablet combination for each administration.

Dosing Overview

The recommended starting dose of Lonsurf® is 35 mg/m² administered orally twice daily with food. The dose should not exceed 80 mg per administration.

Administration Schedule

Lonsurf® is administered on a 28-day cycle:

• Week 1: Twice daily on Days 1 through 5.
• Week 2: Twice daily on Days 8 through 12.
• Weeks 3 & 4: Rest period with no Lonsurf® administration.

The calculated total daily dose should be divided and administered as two equal doses. Doses are rounded to the nearest 5 mg.

Switching Therapy

The decision to switch a patient to or from Lonsurf® therapy should be made based on a comprehensive clinical evaluation, including disease progression, performance status, and prior treatments. There are no specific washout periods mandated in the label, but sufficient time should be allowed for the resolution of any persistent toxicities from prior therapies before initiating Lonsurf®.

Missed Dose

If a patient misses a dose, they should be instructed not to take the missed dose. They should resume their normal dosing schedule with the next planned dose. Patients should not take two doses at the same time to make up for a missed one.

Safety Alerts & Dose Modifications

Frequently Asked Questions (FAQ)

Why is Body Surface Area (BSA) used for Lonsurf® dosing?

BSA is a common method for dosing cytotoxic chemotherapy agents. It provides a more accurate measure of a patient’s metabolic mass than body weight alone, which helps standardize dosing across patients of different sizes.

Which BSA formula is the most accurate?

The Du Bois formula is widely used and is often the default in clinical practice. However, other formulas like Mosteller may be preferred in certain populations. The choice should be based on institutional guidelines and clinical judgment.

Why does the calculator round the final dose?

The dose is rounded to the nearest 5 mg increment to allow for practical administration using the available 15 mg and 20 mg tablet strengths.

What is the maximum dose of Lonsurf®?

The maximum dose is 80 mg per administration (160 mg total daily dose). The calculator will automatically cap any higher calculated dose at this 80 mg limit.

Why does the calculator offer lower dose levels like 30, 25, and 20 mg/m²?

These represent the recommended dose reduction levels for managing treatment-related toxicities. If a patient experiences certain side effects, their oncologist may decide to continue treatment at a reduced dose.

Should Lonsurf® be taken with or without food?

Lonsurf® should be administered orally with food within one hour after completion of the morning and evening meals.

What should be done if the rounded dose cannot be made with 15 mg and 20 mg tablets?

This is a rare scenario. The tool notes when a combination is not possible. In such cases, the prescriber should consult the full prescribing information or contact the manufacturer for guidance, which may involve further rounding.

Is the “Total Daily Dose” the amount for a single administration?

No. The “Total Daily Dose” is the sum of the morning and evening doses. The “Final Rounded Dose” is the amount to be taken for each administration (twice daily).

References

• LONSURF® (trifluridine and tipiracil) tablets, for oral use. Prescribing Information. Taiho Oncology, Inc. Accessed via FDA.gov.
• Lonsurf: EPAR – Product Information. European Medicines Agency (EMA). Accessed via ema.europa.eu.
• Dosing & Administration. Lonsurf® (trifluridine/tipiracil) HCP Site. Taiho Oncology, Inc. Accessed via lonsurfhcp.com.
• Mayer RJ, Van Cutsem E, Falcone A, et al. Randomized trial of TAS-102 for refractory metastatic colorectal cancer. N Engl J Med. 2015;372(20):1909-1919. doi:10.1056/NEJMoa1414325. Accessed via NEJM.org.