[A case of advanced rectal cancer with bone metastasis successfully treated with chemo-radiation therapy].

A 62-year-old man presented to a hospital with left buttock pain, and sacral neoplasia was suspected. He was referred to our hospital. Colonoscopy( CS) and bone biopsy showed rectal cancer with metastasis to the sacrum. There was no bleeding or ileus associated with the primary lesion, and the sacral metastasis was unresectable; therefore, we decided to provide palliative care for pain relief. Radiation therapy( 40 Gy) was performed on the sacral metastasis and included the primary lesion, and zoledronate was administered concomitantly. Both CS and computed tomography (CT) showed tumor regression of both the primary and metastatic lesions, and the patient's carcinomatous pain was alleviated. Irinotecan, 5- fluorouracil, and Leucovorin (FOLFIRI)+cetuximab was administered to reduce the progression of the primary lesion. After 3 months, CT showed significant tumor regression of both the primary and metastatic lesions. The sacral metastasis was no longer evident on the CT images, and positron emission tomography( PET)-CT did not show fluorodeoxyglucose (FDG) accumulation. The primary lesion had shrunk and become flat, but biopsy indicated residual lesion. Although clinically the frequency of bone metastasis of colon cancer has been reported to be 8.6 to 10.7%, single metastasis is not often seen. In this report, we present a case of advanced rectal cancer with bone metastasis, which was successfully treated with chemo-radiation therapy.