Monoclonal antibody imaging of colorectal and ovarian cancer.

Abstract

A MONOCLONAL ANTIBODY labeled with indium 11 1, satu- momab pendetide (OncoScint CRIOV), was recently approved by the United States Food and Drug Administration and now is routinely available for the imaging of colorec- tal and recurrent ovarian cancers.The radiopharmaceutical is given intravenously, and imaging is done within three to five days.OncoScint CR/OV is more sensitive than computed tomography (CT) for the detection of cancer in the pelvis (OncoScint CR/OV 74%, CT 57%), mesentery, and retroperitoneum (OncoScint CR/OV 66%, CT 34%), but less sensitive in the liver (41% versus 84%).It can detect metastatic disease in normal-sized lymph nodes and can distinguish between scar tissue and recurrent cancer.The positive predictive value of OncoScint CR/OV is 97% for colorectal cancer and 83% for recurrent ovarian cancer.Consequently, a focus of uptake usually indicates disease.The negative predictive value, however, is only 19% and 29%, respectively, so a normal scan does not rule out re- current disease.When used appropriately, OncoScint CR/OV can be both clinically efficacious and cost-effective.Its use can cause a false-positive elevation in carcinoembryonic anti- gen levels for several months, however.The $2,000 eval- uation can help avoid even higher costs and influence patient management in the following four clinical set- tings:* Patients with a previous history of colorectal or ovarian cancer who present with an elevated carcinoem- bryonic antigen or CA 125 level are at high risk for recurrent disease.In this setting CT, magnetic resonance imaging, and ultrasonography show low sensitivity and specificity.OncoScint CR/OV may identify the site of re- currence and enable earlier surgical intervention.* Patients with "resectable" recurrence of colorectal cancer (such as a solitary liver metastasis) may be candi- dates for surgical resection with curative intent.If OncoScint CRIOV imaging before surgical therapy iden- tifies unexpected nonresectable disease elsewhere, a futile operation may be avoided.* Following resection and chemotherapy, cases of ovarian cancer are often restaged surgically because of a lack of an accurate imaging procedure for detecting resid- ual disease.In these patients, abnormal uptake on OncoScint CR/OV imaging may make a second-look laparotomy unnecessary, or the scan can be used to direct a limited laparoscopic procedure for tissue confirmation.Because of its poor negative predictive value, however, a