MONOCLONAL ANTIBODY TUMOR IMAGING STUDIES

Radiolabeled monoclonal antibodies (MoAbs) can be used for imaging of a number of different cancers. Several different procedures are available through the Section of Nuclear Medicine. Call the Section at 6-3966 for a consultation as to patient eligibility for a monoclonal antibody imaging study.

APPROVED AGENTS:

  1. In-111 B72.3 MoAb (OncoScint CR/OV) approved for the detection of primary and recurrent colorectal cancer. It is also approved for the detection of recurrent ovarian carcinoma.
  2. Tc-99m Anti-CEA (CEA Scan) approved for the detection of primary and recurrent colorectal cancer.

INDICATIONS:

  1. Detection of extrahepatic sites of primary and/or recurrent colorectal and ovarian cancer. Note that Tc-99m Anti-CEA is not approved for the detection of recurrent ovarian cancer. Positive antibody scans add important diagnostic information to that supplied by other imaging modalities.
  2. Certain subsets of colon cancer patients have been shown to benefit particularly from antibody imaging. For patients with one to three well-localized hepatic metastasis, RIS is the only method to detect evidence of spread in the extra hepatic abdomen. The second set of colon cancer patients who may benefit from an antibody study are the 16% to 25% of patients with primary colorectal cancer who have synchronous lesions at initial laparotomy.
  3. Women with suspected recurrent ovarian cancer.

PATIENT PREPARATION:

No specific measures are needed before the examination. However, patients should be informed of the following:

  1. Patients undergoing OncoScint imaging should be informed that they will received an injection and be asked to return in 5 days for delayed imaging. These patients will also be asked to take a cathartic the night before imaging.
  2. Patients undergoing the CEA-scan will receive their injection early in the morning and be imaged 6 hours later. A cathartic is usually not require with this test.

RADIOPHARMACEUTICALS:

  1. 5 mCi of In-111 labeled MoAb B72.3 (1 mg of intact antibody)
  2. 25-30 mCi of Tc-99m labeled MoAb IMMU-4 (0.5 mg of anti-CEA Fab' antibody).

SCANNING TIME:

See information to patient under patient preparation.

OTHER CONSIDERATIONS:

Antibody imaging is complimentary to and not in place of high resolution imaging such as CT and MRI.Also keep in mind that Antibody imaging can be performed multiple times but should not be requested any more frequently than one examination every 6 months.

RATIONALE:

Radioimmunoscintigraphy (RIS) is a functional examination that allows for the in vivo imaging of abnormal pathologic processes such as infections, infarcts and malignant tumors. This is accomplished using radiolabeled antibodies and standard gamma scintillation cameras. Each patient receives a total body survey. The body survey is performed as a full-length anterior and posterior total-body acquisition. In each case, selective planar images of areas of known or suspected disease (including oblique and lateral views) are obtained in order to increase the accuracy of lesion size and location.

Noninvasive differentiation of benign from malignant disease has emerged as an important diagnostic challenge in this age of health-care cost containment. Most physicians today acknowledge that early and accurate detection of cancer is the key to successful treatment. Antibodies have been developed and used to detect and treat tumors. In the next few years, several radiolabeled antibodies will likely receive FDA approval for imaging colorectal, lung, and prostate carcinomas, thus expanding and improving the physician's ability to detect and follow cancer in patients. Presently, there is ample evidence in the literature which suggests that imaging with labeled antibodies is clinically useful for detecting colorectal cancer in patients with suspected recurrence, presumed isolated resectable liver metastasis, and in patients at high risk for the development of recurrence.