Combination radiation therapy for bone metastases in thyroid cancer

Full text: Distant metastases of thyroid carcinoma (TC) occur due to dissemination of cancer cells through the lymph and blood vessels. They develop in 10-15% of patients with differentiated thyroid carcinoma and are the main cause of death in cancer patients. Appearance of distant metastases depends on a number of factors, i.e. the age of the patients (chiefly in children and those over 45); small size tumors; invasive growth of the tumor outside the thyroid capsule; involvement of the sentinel lymph nodes; poor differentiation of the tumor; incomplete surgical removal of the tumor. Distant metastases mainly localize in the lungs and/or bones. In thyroid cancer patients with suspected bone metastases the latter are revealed radiologically on the primary examination (approximately in 95.9% of cases). In 25% of them, they are seen at body scan with I-131 on residual activities. Probability of visualization of iodine-positive bone metastases is higher at ablation of residual thyroid tissue. When the metastases are revealed by x-ray study, they cannot be treated using I-131, which emphasizes the necessity of other methods of treatment: surgery and distant radiation therapy. But due to multiple character of bone metastases surgery for these metastases is impossible. Within the period of 1999-2004 we studied 310 patients with differentiated TC aged 22-72 (of them 254 women and 56 men). Bone metastases were revealed in 15 (4.8%) patients, of them 13 women and 2 men aged 46-68. As to the stage of the tumor with bone metastases, the patients were grouped as follows: T1 N0 M0 -1 (6.7%), T2-3 N0 M0 -1 (6.7%), TxNxMo-4 (26.7%), T1-4 N0 -1M1-9 (60%) patients. Of the 15 patients with bone metastases, papillary cancer was verified in 5 (33.3%) patients, follicular in 5 (33.3%) papillary cancer follicular variant in 1 (6.7%), medullary in 4 (26.3%). Together with bone metastases, 5 (33.3%) had metastases to the lung parenchyma, diffuse and solitary; 12 (80%) had metastases to sentinel and distant lymph nodes. The presence of bone metastases was revealed using x-ray study and confirmed using bone scan with Tc-99m pyrophosphate. During the treatment the patients with bone metastases were administered 1480-14,134 MBq of I-131. Of all patients with bone metastases, bone metastases accumulated I-131 only in 4 (19%) patients. Thus, treatment of TC with bone metastases only with I-131 did not produce a desirable palliative effect as well as did not control the progress of metastasizing. Therefore, together with I-131 treatment the patients received P-32 (sodium phosphate) treatment. P-32 treatment was started not earlier then 4 months after treatment with I-131. P-32 was administered orally in 100 ml of 10% glucose solution on an empty stomach, 74-120 MBq pert treatment with 4-7- day intervals. Total P-32 activity during one course of treatment made up 296-444 Mbq. Combination radionuclide therapy with I-131 sodium iodide and P-32 sodium phosphate was given to 4 patients with papillary and follicular TC with bone metastases which did not accumulate I-131. Two of these patients had diffuse metastases to the lung parenchyma. The patients received 305-369 MBq of P-32. The radiation load on the red bone marrow was 1098-1328.4 mSv at oral P-32 administration that on the body was 823.5-996.3 mSv. The signs of myelosuppression were not observed during the stay at the Institute. One patient had insignificant reduction of thrombocyte level up to 91.0 x 109 /l and leukocyte level to 2,4 o-tilde 109/l 2 month after the treatment. Three months after systemic radionuclide therapy the signs of inconsiderable myelosuppression disappeared. Pain syndrome disappeared 5-12 days after combination systemic radionuclide therapy, and the patients were able to care for themselves. Flare phenomenon was not seen. A positive feature of combination radionuclide therapy with I-131 sodium iodide and P-32 sodium phosphate together with treatment of bone metastases is possibility continue the treatment of metastases to the sentinel lymph nodes and lung parenchyma, which often accompany bone metastases. Observation of the patients for a year demonstrated that all the patients, which had received combination radionuclide therapy, were alive, pain syndrome was absent in two, in two this was moderate but better then the pain before the beginning of the treatment. All patients did not accumulate I-131 sodium iodide in the lymph nodes. Combination systemic radionuclide therapy with I-131 sodium iodide and P-32 sodium phosphate in TC with metastases to the bones is a method of choice and allows performing adequate treatment of the patients with a continuing process in the thyroid with metastatic involvement of the sentinel lymph nodes and lung parenchyma. (author)