What is Lonsurf?
Lonsurf is an oral chemotherapy drug used to treat adults with metastatic colorectal cancer and metastatic gastric (stomach) or gastroesophageal junction (GEJ) adenocarcinoma. It is typically prescribed after other chemotherapy treatments have been tried. The medication is a combination of two active ingredients: trifluridine and tipiracil. Because it affects fast-growing cells, it can impact both cancerous and healthy cells, which leads to side effects.
How Lonsurf Works
Lonsurf's efficacy comes from its dual-component mechanism:
- Trifluridine: This is a nucleoside analog that gets incorporated directly into the DNA of cancer cells, disrupting their ability to multiply.
- Tipiracil: This component inhibits an enzyme called thymidine phosphorylase, which would otherwise quickly break down trifluridine. By blocking this enzyme, tipiracil allows trifluridine to remain active longer, enhancing its anti-cancer effect.
Serious Side Effects of Lonsurf
The most significant serious side effect of Lonsurf is severe myelosuppression, a decrease in bone marrow activity leading to lower blood cell counts. This condition is potentially life-threatening and requires prompt medical attention.
Key aspects of severe myelosuppression include a significant drop in neutrophils (severe neutropenia), increasing the risk of serious infections; a deficiency of red blood cells (severe anemia), causing symptoms like fatigue and shortness of breath; and a low platelet count (severe thrombocytopenia), which can lead to unusual bleeding or bruising. In clinical trials, grade 3 or 4 neutropenia occurred in 38% of patients taking Lonsurf, while severe anemia and thrombocytopenia were reported in 17-18% and 4-5% of patients, respectively.
Patients experiencing fever, chills, unusual bleeding or bruising, or extreme fatigue should contact their healthcare provider immediately. Blood counts are monitored before treatment and during cycles.
Common Side Effects of Lonsurf
Beyond serious blood count issues, patients may experience various common side effects. A major clinical study (RECOURSE) identified the most common reactions in Lonsurf patients, occurring more often than in the placebo group. These include:
- Blood-related: Anemia (77%), Neutropenia (67%), and Thrombocytopenia (42%).
- General: Fatigue/Asthenia (52%) and fever (19%).
- Gastrointestinal: Nausea (48%), decreased appetite (39%), diarrhea (32%), vomiting (28%), and abdominal pain (21%).
- Other less frequent side effects include hair loss, taste changes, and mouth sores.
Comparison of Common vs. Serious Lonsurf Side Effects
| Side Effect Category | Common Manifestations (≥20% incidence) | Serious / Severe Manifestations (Grade 3-4) & When to Call a Doctor |
|---|---|---|
| Blood Counts | Anemia, neutropenia, thrombocytopenia | Call doctor immediately for fever >100.5°F (38°C), chills, unusual bleeding/bruising, severe fatigue, pale skin, shortness of breath. |
| Gastrointestinal | Nausea, diarrhea, decreased appetite, vomiting, abdominal pain | Contact doctor for vomiting 4-5 times in 24 hrs, severe diarrhea (4-6 episodes/day), inability to eat/drink, or signs of dehydration. |
| General Wellness | Fatigue, weakness, fever | Contact doctor for extreme fatigue where you are unable to perform self-care activities. |
Managing Side Effects
Managing side effects is crucial for maintaining quality of life. Your healthcare provider may adjust the dose or pause treatment if side effects become severe. Management strategies include:
- For Low Blood Counts: Close monitoring with blood tests. Avoid sick individuals and prevent injuries to reduce infection risk. G-CSF medications may be used to boost white blood cell production.
- For Nausea/Vomiting: Use prescribed anti-nausea medication. Eat small, frequent meals and avoid rich foods.
- For Diarrhea: Stay hydrated with clear liquids and eat low-fiber foods. Anti-diarrheal medication may be prescribed.
- For Fatigue: Balance light activity with rest and short naps. Ask for help with chores if needed.
Conclusion
Lonsurf is a valuable treatment for advanced colorectal and gastric cancers, but it carries risks of significant side effects, particularly myelosuppression. Common adverse reactions include low blood counts, fatigue, nausea, and diarrhea. Regular monitoring by a healthcare team and open communication about symptoms are essential for safe treatment management. Many common side effects can be managed with medication and lifestyle adjustments.
For more information directly from the manufacturer, you can visit the official Lonsurf® patient website.
