What do breast cancer patients benefit from staging bone scintigraphy?

A review and analysis of breast cancer treatment records were conducted to establish criteria for performing disease staging by bone scintigraphy in Japanese breast cancer patients.

Records from 5538 consecutive Japanese breast cancer patients from January 1988 to December 1998 were reviewed and analyzed to determine bone metastasis status at the time of initial treatment. Correlation between metastasis to bone and factors known before and after surgery was analyzed using logistic regression.

The overall incidence of metastasis to bone was 2.13% [95% confidence interval (CI): 1.77-2.55%, 118/5538]. Multivariate logistic analysis revealed that tumor size, nodal involvement and histopathology correlated with metastasis to bone. Patients with tumors larger than 30 mm had a significantly higher probability of metastasis to bone, as did patients with lymph node evaluation results N > or = 1. The incidence of metastasis to bone was 0% in patients with stage 0 disease, 0.08% in stage I patients, 1.09% in stage II patients, 9.96% in stage III patients and 34.04% in stage IV patients. Stage II patients were sub-classified by tumor size T (small, 21-30 mm; and large, 31-50 mm), nodal involvement N and histopathology. The incidence of metastasis to bone in stage II patients was higher in patients with large tumors, scirrhous carcinoma or invasive lobular carcinoma or both.

Bone metastasis correlated with tumor size (T), lymph node involvement (N) and histopathology. Using the criteria that bone scintigraphy is not necessary in populations with a < 1% incidence of bone metastasis, but is recommended at incidence > 3%, the following conclusions were drawn. Staging by bone scintigraphy provided no benefit to patients whose disease was stage I or less, stage II with small tumors or stage II with large tumors marked by low-grade histopathology (papillotubular cancer). Bone scintigraphy is recommended in patients whose disease is stage II with large tumors marked by high-grade histopathology (scirrhous or invasive lobular cancer), stage III or stage IV. Consequently, staging by bone scintigraphy could be avoided in 71% (3943/5538) of Japanese breast cancer patients.