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Association of thyroid carcinoma with malignant lymphoma
Abstract:
Radiation-associated thyroid carcinoma is of clinical importance in modern radiation therapy of both Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL), because anatomically the thyroid is often in the radiation field. We have reviewed the records of HD and NHL patients seen at Roswell Park Memorial Institute (RPMI) between 1910 and 1960 to determine associated occurrence of thyroid cancer. Radiation therapy was the major therapeutic modality with the occasional use of single agent chemotherapy with nitrogen mustard, triethylene melamine (TEM), chlorambucil and prednisone. There were 519 patients with HD and 863 with NHL. The thyroid glands of 439 (84%) HD and 544 (63%) NHL patients were included in the field of radiation. The mean age of patients with HD was 39 yr while for those with NHL, it was 53 yr. The mean survival in HD was 4.2 yr and in NHL 3.8 yr. There were three cases of thyroid cancer among the HD patients occurring 31, 44 and 48 yr, respectively, after radiation therapy. When compared with the number of thyroid cancers expected to develop, the incidence was significantly greater (p less than 0.005). In contrast, three NHL patients were found to have thyroid cancer at the time of surgery or postmortem examination. This number is again greater than expected in such a population (p less than 0.005); however, in only two cases could the cancer be considered as a sequela to NHL treatment. In all three cases the cancer turned out to be subclinical thyroid carcinoma, incidentally found at surgery or autopsy. One of the patients is still alive without evidence of either disease. The reason for this difference between patients with HD and NHL treated with a similar principle is unclear. Some of the factors contributing to this difference may include: the younger age of HD patients at diagnosis; the longer survival of patients with HD as compared with those with NHL; differences in the sites of radiation and type of treatment given; and possible differences in immunological status between the two groups.