Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) (Zanosar + 5-FU) — Clinical FAQs

Question 1

What is Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) FDA-approved to treat?

Accepted Answer

Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) is FDA-approved for the following oncology indications: 1. Metastatic islet cell carcinoma of the pancreas — streptozocin is FDA-approved for use in combination with 5-fluorouracil for this indication.

Question 2

How does Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) work (mechanism of action)?

Accepted Answer

Two-drug cytotoxic combination for advanced pancreatic neuroendocrine tumors. Streptozocin alkylates DNA via O6-guanine methylation, exploiting GLUT2-mediated preferential uptake into pNET cells. 5-Fluorouracil (5-FU) is a fluoropyrimidine antimetabolite that inhibits thymidylate synthase (TS), depleting dTTP and causing thymineless cell death, and also incorporates into RNA, disrupting RNA processing and protein synthesis. These mechanisms are complementary: streptozocin induces direct DNA alkylation damage while 5-FU impairs the nucleotide pools required for DNA repair of that damage, providing biochemical rationale for their combination. Additionally, 5-FU may diminish MGMT (O6-methylguanine-DNA methyltransferase) activity over time, reducing the primary resistance mechanism against streptozocin's O6 alkylation.

Question 3

How is Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) administered?

Accepted Answer

Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) is administered Intravenous (IV). Standard dosing (5-day schedule, adapted from Moertel data): Streptozocin 500 mg/m² IV daily on days 1–5 + 5-Fluorouracil 400 mg/m² IV daily on days 1–5, repeated every 6 weeks (42-day cycle).

Question 4

What are the most common side effects of Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU)?

Accepted Answer

The most commonly reported side effects of Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) (≥10% incidence) include: Severe nausea and vomiting (>90% with streptozocin; highly emetogenic), Diarrhea (5-FU; may be dose-limiting with bolus schedules), Mucositis and stomatitis (5-FU), Myelosuppression — neutropenia, thrombocytopenia, anemia (from both agents, though streptozocin contributes less than anthracyclines), Renal tubular dysfunction — glucosuria, proteinuria, hypophosphatemia (streptozocin) and others (8 total). Consult your oncologist for complete prescribing information.

Question 5

Does Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) have a black box warning?

Accepted Answer

Yes. Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) carries FDA black box warning(s) regarding: 1. Streptozocin — Renal Toxicity (Dose-Limiting): Cumulative nephrotoxicity including azotemia, Fanconi syndrome (glucosuria, phosphaturia, aminoaciduria, tubular acidosis), and irreversible renal failure. Monitor renal function before each course; reduce or discontinue based on renal impairment. 2. Streptozocin — Hepatotoxicity: Monitor LFTs before each cycle. 3. Streptozocin — Myelosuppression: Obtain CBC before each course. 4. 5-Fluorouracil — Cardiotoxicity: Coronary vasospasm, angina, myocardial infarction, and sudden death have been reported, particularly with continuous infusion. Obtain baseline ECG; discontinue if chest pain or cardiac symptoms occur during infusion. 5. 5-Fluorouracil — DPYD Deficiency: Patients with dihydropyrimidine dehydrogenase (DPYD) deficiency have severely reduced 5-FU clearance and are at high risk for severe or fatal toxicity (mucositis, diarrhea, neutropenia). Test for DPYD deficiency (genotyping or phenotyping) before initiating 5-FU.

Question 6

Is Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) safe during pregnancy?

Accepted Answer

Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) pregnancy safety: Category D — Both streptozocin and 5-fluorouracil are teratogenic and fetotoxic. 5-FU causes fetal harm in animal models; streptozocin is embryotoxic. Effective contraception required during treatment. Do not use during pregnancy.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Streptozocin + 5-Fluorouracil Regimen (STZ + 5-FU) — Drug Monograph

Mechanism of Action

FDA Indications

Common Side Effects

Clinical Pearl

Related Therapies & Mechanisms