Bone scintigraphy in breast cancer: a ten-year follow-up study.

Two-hundred and sixty patients with T2-T3a, pN1, M0 (TNM classification) breast cancer underwent clinical and instrumental follow-up (mean 122 months) including periodic bone scintigraphy. A total of 1971 scintigraphic examinations were performed (range 3 to 15 scintigraphies/patient, mean 8). The results of scintigraphy were compared to standard radiographs and to the clinical history of the patients. Bone metastases occurred in 71% of 122 patients who suffered from tumor recurrence during the study. Bone lesions (alone or associated with other tumor lesions) represented the most common site (42%) of first tumor relapse and occurred as first site of distant metastases in 11% of 29 patients with locoregional relapse. Bone metastases were symptomatic in 41% of cases. The sensitivity and specificity of bone scintigraphy were 98% and 95%, respectively; the positive and negative predictive values were 73% and 100%; the accuracy was 96%. Scintigraphic false positive results occurred particularly in the skull and in the ribs and generally when the examination detected less than three focal abnormalities. This study demonstrates that the number of positive scintigraphies during follow-up increases over the years, reaching a plateau only at approximately 8-10 years. It is therefore not advisable to stop performing bone scintigraphies after the first years of follow-up as this may lead to the loss of important information.