Radioisotope-Guided Surgical Biopsy of Suspected Osseous Metastases.

BACKGROUND: Radioisotope bone scanning is frequently used to stage patients with suspected or proven malignancies. Since false-positive results are common, especially in the ribs, open biopsy is often necessary. The conventional approach of visual inspection of the bone scan image to guide the surgeon usually requires excision of a large area of one or two ribs to assure that the biopsy was performed on the correct rib. A more precise method to guide the biopsy is desirable. METHODS: One technique to localize the suspicious area of bone intraoperatively for accurate biopsy involves percutaneous injection of the bone abnormality with a radioisotope followed by injection of methylene blue into the periosteum and subsequent open surgical biopsy. A more recent technique uses a hand-held gamma probe in a sterile sleeve in the operating room to locate the bone "hot spot" directly in the wound to guide the biopsy. RESULTS: Both techniques are effective in pinpointing the bone scan abnormality, but use of the gamma probe is less cumbersome and consumes less time and fewer resources. In one series of 10 patients undergoing gamma probe-guided biopsies of 13 rib and 1 sternal bone scan lesions, this technique showed a sensitivity of 100% in locating the area of abnormal radioisotope uptake. All biopsies yielded an abnormal diagnosis to account for the bone scan abnormality, but only 4 of 14 (29%) demonstrated metastatic tumor. CONCLUSIONS: Techniques described for radioisotope-guided localization of areas of increased tracer uptake in asymptomatic suspected bone metastases are accurate, sensitive guides to the open biopsy of these bony abnormalities. Due to the high false-positive rates in these asymptomatic but suspicious bone scan abnormalities, a diagnosis should be histologically confirmed.