Intraoperative gamma detection of I-125-lanreotide in women with primary breast cancer

Background: Somatostatin receptors are present in most human breast cancers . We performed a pilot trial of intraoperative tumor-gamma detection using the radiolabeled somatostatin analog I-125-lanreotide in 13 women with 14 p rimary breast carcinomas. Methods: All patients were given I-125-lanreotide intravenously before surg ery. Patients underwent lumpectomy, and postresection margins were evaluate d with the gamma probe. Axillary dissection specimens were evaluated ex viv o. Results: Seven of 13 women had gamma probe-positive or clinically suspiciou s margins reexcised at the time of lumpectomy. Four of six probe-positive m argins were histologically positive, and two of six probe-positive margins were histologically negative; a single clinically suspicious margin was his tologically positive. A total of 270 axillary lymph nodes were evaluated ex vivo by gamma probe and histology. McNemar's contingency tests demonstrate d a highly statistical correlation between histology and gamma probe counts (P < .0001). Conclusions: The overall accuracy of nodal evaluation with I-125-lanreotide /intraoperative gamma detection was 77%; the negative predictive value of t his technique was 97%, however. This technique predicted the presence of tu mor in 20% of axillary lymph nodes that were negative by routine histology. This technique appears safe and is able to detect positive tumor resection margins and accurately predict axillary lymph node negativity. Further tri als of this technique are required to validate its utility.