DISEASE CHARACTERISTICS: Histologically or cytologically proven medullary thyroid carcinoma Unresectable local-regional disease OR Distant metastases Autologous peripheral blood stem cells (PBSC) or bone marrow available Diffuse bone/marrow involvement allowed if: Autologous bone marrow or PBSC with no greater than 5% tumor involvement available Radiation dose to marrow no greater than 3000 cGy until 6 patients have been treated safely at that dose level At least 1 site confirmed by CT targeted by pretherapy indium In 111 monoclonal antibody MN-14 imaging