Clinical outcome for patients of solitary bone only metastasis.

BACKGROUND: Solitary bone only metastasis (SBOM) is a rare condition in which metastasis is limited to a single skeletal lesion originating from a previously treated or controllable primary lesion. The study objective was to evaluate the clinical features and survival regarding this rare condition and to clarify its treatment strategy. METHODS: A total of 1453 patients with bone metastasis registered in our hospital database were enrolled. To assess the primary and/or metastatic lesion we used plain X-ray images, CT, MRI and FDG-PET scans as well as bone scans. RESULTS: Among the patients, only 27 (1.8%) had SBOM. The primary cancers responsible for SBOM were lung in seven patients, breast in five, kidney in four, prostate in two, uterus in two and other types in seven. Treatment of SBOM involved resection in four patients, radiotherapy only in 17, radiotherapy in combination with zoledronate in six and chemotherapy with zoledronate in one. Local recurrence did not develop in the four cases treated with resection. However, in-field recurrence was found in 4 of 22 (18%) patients who underwent radiotherapy. All three patients who received >40 Gy did not develop in-field recurrence. The overall and event free survival rates at 5 years were 63% and 41%, respectively. CONCLUSIONS: Solitary bone only metastasis should be treated with wide resection or long-course radiotherapy at doses 40-50 Gy to achieve long lasting local tumor control.