Papillary thyroid carcinoma: factors influencing prognosis and current therapy.

Abstract

D ESPITE THE LARGE BODY of knowledge that has accrued over the past several decades concerning the behavior of papillary thyroid carcinoma, considerable controversy persists regarding its management. Of the various issues debated, the two over which the widest differences of opinion exist are the extent of thyroid surgery that is optimal, and the indications for postoperative radioiodine therapy. To some extent, these differing opinions arise from the remarkable variability in the clinical behavior of this tumor. In many instances, it is quite indolent and follows a protracted course, whereas in others it displays striking aggressiveness that results in a rapidly fatal outcome. This natural variability in clinical behavior, which poses some difficulty in the analysis of therapeutic efficacy, must be considered to make such an analysis valid. Another problem in the study of this disease is caused by its typically protracted course that requires large numbers of patients to be followed over several decades before a clear picture emerges regarding the impact of therapy upon survival. Because this is a relatively uncommon tumor, many clinical reports summarize the experience of large referral centers where a single therapeutic approach is often favored, making a critical analysis of treatment difficult. Perhaps for these reasons large multicenter therapeutic trails have not been done and our understanding of the treatment of this disorder comes largely from retrospective clinical studies. There is clearly a need for a large national multicenter therapeutic trial to address many of the issues over which debate continues. Nonetheless, certain principles concerning the management of this tumor seem reasonably evident at this time. In 1977 we reported’ a retrospective analysis of all papillary thyroid carcinoma patients who had been treated by US Air Force physicians worldwide between 1958 and 1972, and in which the pathologic diagnoses had been verified by the Armed Forces Institute of Pathology. Treatment of these 576 patients reflected the clinical situation and bias of the attending physician and follow-up was nearly complete, which permitted a unique opportunity to study the impact of specific types of therapy upon tumor recurrence and survival. Since then, 117 new cases treated by the same physicians have been added to the original study group. This paper will present the most recent analysis of this series and will review the factors influencing prognosis in these 693 patients. From an analysis of our series and a review of the literature, certain patient and tumor features emerge as reliable predictors of outcome. Other prognostic features remain uncertain or require further clarification. Based upon our present knowledge, however, one can use a selective approach to therapy that avoids unnecessarily aggressive treatment for tumors that are likely to follow a benign course, and inadequate therapy for others anticipated to display aggressive behavior. It is for tumors in the middle of this spectrum that the most disagreement prevails and for which the most clinical judgment is required.