Undifferentiated
thyroid carcinoma (UTC) is an aggressive
tumor with a poor prognosis due to the lack of an effective treatment.
Boron neutron capture therapy (BNCT) is based on the selective uptake of
boron by the
tumor and its activation by a neutron beam, releasing
lithium-7 and an alpha particle that will kill the
tumor cells by their high linear energy transfer (LET). In previous studies we have shown a selective uptake of borophenylalanine (10BPA) in a human UTC cell line (ARO) and in NIH nude mice implanted with this cell line. When these animals were injected with BPA and irradiated with an appropriated neutron beam, we observed a 100% of
tumor growth control and a 50% of histological cure when the initial
tumor volume was 50 mm3 or less. Further studies with BOPP (tetrakis-carborane carboxylate ester of 2,4-bis-(alpha, beta-dihydroxyethyl)-deutero-porphyrin IX) showed that when this
porphyrin was injected 5-7 days before BPA, and the animals were sacrificed 60 min after the i.p. injection of BPA, a significant increase in
boron uptake by the
tumor was found (45-38 ppm with both compounds vs. 20 ppm with BPA alone). The application of BNCT using the combination of
boron compounds showed a 100% of complete remission in
tumors with initial volumes under 50 mm3. Dogs suffer spontaneous UTC, with a similar
biological behavior to the human
tumor, and a selective uptake of BPA. These results open the possibility of applying BNCT to UTC.