[The problem of false positives in bone scintigraphy in patients with breast neoplasms. A follow-up at 10 years]

Bone scanning plays a pre-eminent role in tumor staging procedures, but its reliability is often questioned because of the high incidence of false positive results; not even bone biopsy can always clarify these questionable findings. To verify what actually becomes of the pathological hot spots lacking radiological evidence, we studied 49 patients with this discrepancy and followed them for an average period of 10 years (range: 8-11). The patients were divided into 3 subgroups: 1) 13 N+ patients with multiple hot spots (greater than 2) (N+ IM); 2) 24 N+ patients with single hot spots (less than or equal to 2) (N+ IS); 3) 12 N- patients with single hot spots (less than or equal to 2) (N- IS). Bone metastasis-free survival rate (SLMO) was calculated, which was confirmed by radiology, and overall survival rate (SG). SLMO was considered to coincide with the percentage of "true" false positives. At 10 years SLMO was 7%, 65%, and 83%, whereas SG was 15%, 70%, and 90%, respectively, in the 3 subgroups N+ IM, N+ IS, and N- IS. The Log-rank test demonstrated a highly significant difference (p less than 0.001) between SLMO and SG in these subgroups, due to the poor prognosis of N+ IM patients. The cumulative examination of all N+ N- patients with single hot spots (36 patients) demonstrated 75% probability of "true" false positives at 10 years. Moreover, the risk of bone metastases resulted higher in the hot spots of the spine than in those of the skull and ribs. The possible role is discussed of microfractures and bone traumatisms in the genesis of "true" false positives.