Rectal Cancer Medication

Updated: Jun 07, 2022
  • Author: Burt Cagir, MD, FACS; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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Medication

Medication Summary

Pharmacotherapy in rectal cancer involves the use of multiple chemotherapy agents in combination regimens, often given together with radiation therapy. Chemotherapy is given before surgery to down-stage the tumor and help induce remission, and after surgery to prevent recurrences.

In metastatic rectal cancer, biologic agents are used in combination with chemotherapy. Biologic agents used in Bevacizumab in combination with chemotherapy is indicated in patients with positive or negative resectable synchronous metastases. For colon and rectal cancer, bevacizumab in combination with chemotherapy is also indicated in patients with unresectable synchronous metastases.

FOLFOX is not indicated for good-risk or average-risk stage II patients. In patients in whom 5-fluorouracil treatment has failed, capecitabine should be avoided. Patients who experience no benefit from bevacizumab regimens should avoid continuing the therapy. Cetuximab should not be replaced with panitumumab. Patients with KRAS mutations should not be treated with cetuximab or panitumumab, as these mutations confer resistance to epidermal growth factor receptor (EGFR) inhibitors.

 

 

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Antineoplastic agents

Class Summary

These agents inhibit cell growth and proliferation. They are generally used in combination regimens.

Fluorouracil (5-FU, Fluorouracil, Adrucil)

Blocks methylation of deoxyuridylic acid to thymidylic acid, thereby interfering with DNA synthesis. Dose is body-weight dependent and varies with specific protocol in which patient is involved.

Vincristine (Vincasar PFS, Oncovin)

Mechanism of action uncertain. May involve decrease in reticuloendothelial cell function or increase in platelet production. It is mitotic spindle inhibitor.

Leucovorin (Wellcovorin)

Potentiates effects of fluorouracil. Reduced form of folic acid that does not require enzymatic reduction reaction for activation. Allows for purine and pyrimidine synthesis, both of which are needed for normal erythropoiesis.

Given just prior to fluorouracil.

Irinotecan (Camptosar, Camptothecin-11, CPT-11)

Inhibits topoisomerase I, inhibiting DNA replication and, consequently, cell proliferation.

Oxaliplatin (Eloxatin)

A platinum-based antineoplastic agent used in combination with an infusion of 5-fluorouracil (5-FU) and leucovorin for the treatment of metastatic colorectal cancer in patients with recurrence or progression following initial treatment with irinotecan, 5-FU, and leucovorin. It forms interstrand and intrastrand Pt-DNA crosslinks that inhibit DNA replication and transcription. The cytotoxicity is cell-cycle nonspecific.

Cetuximab (Erbitux)

Recombinant human/mouse chimeric monoclonal antibody that specifically binds to the extracellular domain of human epidermal growth factor receptors (EGFR, HER1, c-ErbB-1). Cetuximab-bound EGF receptor inhibits activation of receptor-associated kinases, resulting in inhibition of cell growth, induction of apoptosis, and decreased production of matrix metalloproteinase and vascular endothelial growth factor. Indicated for treating irinotecan-refractory, EGFR-expressed, metastatic colorectal carcinoma. Treatment is preferably combined with irinotecan. May be administered as monotherapy if irinotecan is not tolerated.

Bevacizumab (Avastin)

Indicated as a first-line treatment for metastatic colorectal cancer. Murine-derived monoclonal antibody that inhibits angiogenesis by targeting and inhibiting vascular endothelial growth factor (VEGF). Inhibiting new blood vessel formation denies blood, oxygen, and other nutrients needed for tumor growth. Used in combination with standard chemotherapy.

Panitumumab (Vectibix)

Recombinant human IgG2 kappa monoclonal antibody that binds to human epidermal growth factor receptor (EGFR). Indicated to treat colorectal cancer that has metastasized following standard chemotherapy.

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