Experimental application of boron neutron capture therapy to undifferentiated thyroid carcinoma.

Purpose: Undifferentiated thyroid carcinoma (UTC) lacks an effective treatment. Boron neutron capture therapy (BNCT) is based on the nuclear reaction (10)B(n,alpha) (7)Li. These particles destroy the tumor locally due to their high linear energy transfer (LET). Mice transplanted with the human cell line of UTC ARO have a selective uptake of (10)B-borophenylalanine (BPA). The complete BNCT was performed to explore its possible application.

Methods And Materials: Mice were distributed into four groups: (1) no treatment; (2) neutron beam alone; (3) 350 mg/kg body weight (b.w.) BPA plus irradiation; (4) 600 mg/kg b.w. BPA plus irradiation. Follow-up was performed by measurement of tumor volume, histologic analysis, and assessment of DNA damage using the comet assay.

Results: The tumor continued to grow in Groups 1 and 2. In Group 3, a slow-down of tumor growth was observed in all mice, and a complete stop was observed in 100% of mice of Group 4. Complete disappearance of the tumor was observed in 50% of the mice that had an initial tumor volume of less than 50 mm(3) (Groups 3 and 4). DNA damage showed a progressive increase from Group 1 through 4.

Conclusion: These data show, for the first time, that UTC is amenable to treatment by BNCT.