Chemotherapy and Cancer Pharmacology

General Principles and Mechanism of Chemotherapy

• Definition and Purpose: Chemotherapy drugs are administered to slow or stop the growth of tumors. They achieve this by directly inhibiting the cellular growth of cells within the body.

• Mechanism of Action: Chemotherapy is often nonspecific, meaning it does not target cancer cells exclusively. It targets all fast-growing cells in the body.     * Metaphor: Chemotherapy is described as an "atomic bomb" or a "nuke" where no one is spared. It kills both "the good guys" (healthy cells) and "the bad guys" (cancer cells).

• Afflicted Cell Types: Because the drugs target the fastest-growing cells, the following are significantly affected:     * Tumor cells: Fast-growing cells that stop growing and die.     * Skin cells: Resulting in weak, fragile skin.     * Hair follicles: Leading to hair loss (alopecia).     * Bone marrow: Leading to profound suppression of blood cell production.

Bone Marrow Suppression: Life-Threatening Complications

• General Risk: Bone marrow suppression is the most critical side effect to understand for the NCLEX and nursing exams because it is the most deadly. The mnemonic provided is "chemo is bad to the bone."

• Physiological Impact: The bone marrow produces essential blood cells for perfusion, oxygenation, and immune protection. Suppression results in decreased cell counts across three primary categories:

• 1. Red Blood Cells (RBCs) and Anemia:     * Normal Range: Typically between $4.5 \times 10^6$ and $6.0 \times 10^6 \text{ cells/mm}^3$.     * Effect: Chemotherapy decreases these levels, resulting in anemia, low blood volume, and reduced oxygenation.

• 2. Platelets and Thrombocytopenia:     * Normal Range: $150,000$ to $400,000 \text{ cells/mm}^3$.     * Thrombocytopenia Threshold: A platelet count less than $100,000 \text{ cells/mm}^3$.     * Risk: Massive bleeding.     * Nursing Interventions/Patient Teaching:         * Use electric shavers instead of razor blades.         * Avoid bearing down during bowel movements; use stool softeners.         * Fall precautions: Avoid rugs and ensure hallways are well-lit.

• 3. White Blood Cells (WBCs) and Leukopenia:     * Normal Range: $5,000$ to $10,000 \text{ cells/mm}^3$.     * Leukopenia Threshold: A WBC count less than $4,000 \text{ cells/mm}^3$.     * Metaphor: WBCs are the "WBC elite squad" or the "police of the body." When chemo drops its "atomic bomb," these defenses are wiped out, turning the body into a "deserted ghost town" or the "wild wild west" where infection can run rampant.     * Conditions: Immunodeficiency and being immunocompromised.     * Priority Finding: Fever is the absolute priority. A temperature over $100.3^{\circ}F$ ($38^{\circ}C$) is a critical indicator of infection. The tip provided is "$38$ is not great."     * Neutropenic Precautions (Reverse Isolation):         * No fresh flowers.         * No fresh fruit.         * Avoid crowds and sick individuals.

Specific Chemotherapy Agents: Doxorubicin and Cisplatin

Doxorubicin

• Memory Trick: Think of a "ruby red body" like a fever.

• Critical Fever Threshold: Kaplan specifies that a temperature over $100.5^{\circ}F$ ($38^{\circ}C$) is the highest priority for this drug. Fever is always the priority with chemotherapy.

• Hyperglycemia: Doxorubicin causes decreased insulin sensitivity. Without effective insulin to move sugar into cells, glucose remains in the bloodstream.     * Nursing Action: Monitor for high blood sugar (hyperglycemia).

Cisplatin

• Primary Toxicity: Renal toxicity (nephrotoxicity) , bone marrow suppression

• Memory Trick: "Cisplatin because he can't pee-splatin."

• Nursing Assessment: Monitor Intake and Output ($I \& O$).

• Lab Values for Kidney Function:     * Creatinine: Values over $1.3$ indicate impaired kidney function.     * BUN (Blood Urea Nitrogen): Values over $20$ are considered significantly high.     * Urine Output: Output of $30\,mL/hr$ or less indicates the kidneys are in distress.

• Management:     * Administer antiemetics (anti-nausea medication) prophylactically.     * Perform a saline rinse before and after meals.     * Increase fluid intake for the following $3$ days.     * Manage fatigue.

• Hydration Indicators: Satisfactory hydration status is evidenced by stable blood pressure, good skin turgor, capillary refill less than $3\,\text{seconds}$, and urine output over $30\,mL/hr$.

• Ototoxicity,tinnitus,hypokalemia,hypomagnesemia

Other Chemotherapy Agents: Cyclophosphamide and Vincristine

Cyclophosphamide

• Mechanism: Stops protein synthesis to treat tumors and cancer.

• Side Effects: Standard bone marrow suppression (anemia, neutropenia, thrombocytopenia), leading to high risks for infection and bleeding.

• Precaution: Be vigilant regarding sound-alike drug names.

Vincristine

• Mechanism: Halts cell division during mitosis.

• Key Distinction: This is the only chemotherapy drug that does not cause bone marrow suppression. It is "kind to the bone."     * Memory Trick: Vincristine is a "very cool Christian" who is kind to the bone marrow.     * Result: No anemia, no neutropenia, and no thrombocytopenia. There is no increased risk for bleeding or a weakened immune system.

• Side Effect: Peripheral neuropathy (nerve damage) causing weakness, numbness, and pain in the hands and feet. This is notably not a high-priority tested item but is a known effect.

Breast Cancer Treatment: Tamoxifen

• Mechanism: Estrogen modulator that blocks estrogen receptors in the breast. It treats estrogen-dependent cancers (breast cancer) and endometrial cancer.

• Priority Findings: Heavy periods and excessive bleeding must be reported immediately. On the NCLEX, "report" signals a priority situation. Bleeding is a circulation issue ($ABC$s).

• Clot Risk: Any drug modifying estrogen increases the risk for emboli.     * Memory Trick: Use the double "E"s in Tamoxifen: "E" for Emboli risk and "E" for Endometrial cancer.

• Contraindications: History of Deep Vein Thrombosis ($DVT$, clot in the leg) or Pulmonary Embolism ($PE$, clot in the lung).

• Common/Expected Side Effects: Hot flashes (nicknamed "Hot Tamoxifen"). These are normal and do not need to be reported.

Cell Stimulators and Immunotherapy

Oprelvekin

• Action: Increases platelet production and stimulates hematopoietic stem cells.

• Indication: Given to chemotherapy patients with thrombocytopenia to reduce bleeding.

• Adverse Effects: Fluid retention, Atrial Fibrillation ($A\text{-}fib$), and anaphylaxis.

Filgrastim (Neupogen) and Pegfilgrastim

• Action: Stimulates White Blood Cell ($WBC$) or neutrophil production.

• Expected Outcome: Increased neutrophil count.

• Note: It has no effect on hemoglobin levels; that is the function of erythropoietin.

Interferon

• Action: Immunotherapy that stimulates the immune system to detect and kill cancer cells and viral infections.

• Memory Trick: "Inter-flu-on."

• Side Effects: Flu-like symptoms are expected and normal, including fever, muscle aches, weakness, and chills.

General Nursing Considerations for Chemotherapy

• Temperature Checks: Never use rectal thermometers. Because skin and rectal linings are extremely sensitive, a thermometer can lead to a perforated bowel.

• Nausea Management: Nausea and vomiting are common. In a pediatric or adult scenario where nausea occurs during administration:     1. Stop the chemotherapy infusion.     2. Flush the line.     3. Administer anti-nausea medication such as Ondansetron (brand name: Zofran).