Radioimmunoguided surgery challenges traditional decision making in patients with primary colorectal cancer

Initial experience with the radioimmunoguided surgery system (RIGS) has been found to impact on decision making in patients with recurrent colorectal cancers. Reported here is experience with RIGS-influenced therapeutic decisions in patients with primary colorectal cancer.

Thirty-six evaluable patients with primary cancers were injected with the second-generation anti-tumor-associated glycoprotein antibody CC49 labeled with 1 to 2 mCi iodine 125. Pharmacokinetic determination and precordial counts were obtained after injection and weekly until levels were less than 20 counts/2 sec. At surgery abdominal and pelvic explorations were performed, first traditionally by inspection and palpation and then with the hand-held, gamma-detecting probe. RIGS-positive tissue was considered cancerous and removed if possible.

Thirty patients (83%) had positive antibody localization at surgery. Of those patients with localization, in 24 (80%) additional information was obtained at the time of surgery. In 11 patients (34%) staging changes were made as a result of RIGS exploration. New findings resulted in operative changes in nine patients (25%). Eleven (30%) of the original 36 patients became eligible for adjuvant chemotherapy based on current recommendations because of RIGS findings.

In conclusion, the RIGS system provides immediate staging information that impacts on therapeutic interventions, challenging the adequacy of traditional procedures alone for primary colorectal cancer exploration.