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Introduction ⬇

Radiolabeled monoclonal antibodies (mAbs) are used to image several different cancers. Like other radiopharmaceuticals, mAbs and peptides have two parts: a radioisotope linked to a substance specific to a target organ. In the case of mAbs, that substance is an antibody that has been cloned and mass produced. Because all the daughter antibodies are identical, a high yield of very specific antibodies can be produced. Antibody and peptide tumor imaging is used to detect the location and size of known extrahepatic malignancies. These procedures are not screening techniques.

  1. OncoScint CR/OV (111In satumomab pendetide) was the first mAb radiopharmaceutical to be approved by the U.S. Food and Drug Administration and mass marketed. OncoScint CR/OV is indicated for the detection of ovarian and colon cancer. OncoScint is an antibody linked to 111In.

  2. ProstaScint® (capromab pendetide) is a murine mAb approved for the detection of lymph node metastasis from prostate cancer.

  3. OctreoScan (111In pentetreotide) is a radiopharmaceutical peptide used for localizing neuroendocrine tumors.

Procedure ⬆ ⬇

  1. Inject the patient with the radioisotope over a period of 5 minutes. Observe the patient for any reaction to the radiopharmaceutical agent.

  2. Optimal whole-body scans are obtained between 2 and 4 days after injection; additional images may be obtained at 24 hours and at 5 days.

  3. Perform SPECT imaging if necessary.

  4. See Chapter 1 guidelines for safe, effective, informed intratest care.

Clinical Implications ⬆ ⬇

  1. Abnormal distributions are found in tumors. Any change in the distribution provides information regarding the effectiveness of surgery or therapy.

  2. Abnormal results have been observed in nonspecific areas such as inflammatory bowel disease, colostomy sites, and postoperative bowel adhesions.

  3. The patient’s medical history should be reviewed carefully.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the purpose, procedure, benefits, and risks.

  2. Refer to standard NMI pretest precautions.

  3. Establish an IV line before injecting the radiopharmaceutical.

  4. Advise the patient that a cathartic is required to differentiate bowel activity from abnormal pathology.

  5. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Refer to standard NMI posttest precautions.

  2. Review test results; report and record findings. Modify the nursing care plan as needed.

  3. Observe the patient for 1 hour after injection of OncoScint CR/OV for antibody reactions (e.g., chills, fever, nausea).

  4. Realize that some patients develop human antimouse antibody (HAMA) titers after OncoScint CR/OV injection.

  5. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

Following OncoScint CR/OV imaging, HAMA titers may result in falsely elevated immunoassay levels for CA 125

Interfering Factors ⬆ ⬇

Radioactivity in the bowel may interfere with colorectal assessment. Follow-up imaging is useful after administration of a cathartic to clarify equivocal findings.

During the ProstaScint® scan, the close proximity of the prostate to the bladder requires that a urinary catheter be placed during the delayed imaging. The catheter allows for the bladder to remain empty during the entire scanning session of the prostate and the surrounding body area. The catheter is removed immediately after the 1- to 2-hour scanning session.

Reference Values ⬆

Normal

Distribution occurs in the normal liver, spleen, bone marrow, and bowel.