Prognostic value of nuclear DNA content in papillary and follicular thyroid cancer

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Abstract
The relative importance of prognostic factors in papillary and follicular thyroid cancer was studied in 113 patients using Cox's proportional hazards model. Prognostic factors studied were: histology, tumor grade, extrathyroidal growth, nodal involvement, distant métastases at diagnosis, nuclear DNA content, age at diagnosis, and sex. Nuclear DNA content was measured in primary tumors by flow cytometry. Total thyroidectomy and postoperative131I ablation was the standard treatment. The results showed that nuclear DNA content correlated significantly with histologic type and, in papillary cancer, also with tumor grade. The presence of distant metastases at diagnosis was, by far, the most important prognostic factor. In the patient group without distant metastases (n=91), multiploidy (i.e., presence of 2 or more aberrant stemlines) was the only significant prognostic factor for overall survival. With respect to diseasefree survival, multiploidy was second only to the age factor. In the patient group with distant métastases (n=22), all 6 patients with multiploid tumors died compared to 8 (50%) of 16 of those with other ploidy tumors. However, the small number in this group precluded significant results. The present study demonstrates that nuclear DNA content is a prognostic factor in those patients with papillary and follicular thyroid cancer without distant metastases at diagnosis.