International Journal of Radiation Oncology*Biology*Physics
Clinical investigationThyroidThe role of postoperative external-beam radiotherapy in the management of patients with papillary thyroid cancer invading the trachea
Introduction
Despite the proximity of the thyroid gland to the upper aerodigestive tract, thyroid cancer only rarely invades the adjacent structures, such as the larynx, trachea, or cervical esophagus (1, 2). The prevalence of airway invasion by well-differentiated thyroid cancer reportedly ranges from 1% to 13% (3). However, airway invasion is an important clinical problem when locally advanced thyroid cancer involves the laryngotracheal airway. Although surgical resection is the cornerstone of treatment for such patients, there is considerable controversy regarding the extent of surgery and the appropriate postoperative adjuvant treatment. If the cancer is either close to or invading a segment of the upper aerodigestive tract, the decision to remove the structures is a difficult therapeutic dilemma because of the generally indolent nature of most thyroid cancers. If technically feasible, tracheal resection by means of a sleeve or window is the preferred treatment for patients with intraluminal invasion (4). Alternately, “shave” resection of all gross tumors involving the trachea might be possible unless well-differentiated thyroid cancer infiltrates the tracheal perichondrium (5, 6). In fact, a few experts have advocated for a conservative “shave” procedure that might be a better treatment in the case of limited involvement of the trachea, because this approach shows a lower morbidity and a similar survival rate when compared with “en bloc” resection of the tumor and adjacent vital structures (7, 8).
Several investigators, however, have reported that tracheal invasion is a significant and independent negative prognostic factor for survival when surgery alone is used (5, 7, 9). It is well known that patients with locally advanced thyroid cancer with tracheal invasion have a higher recurrence rate, a higher incidence of cervical node metastases, and a higher mortality rate (4, 7, 8, 9, 10). Nonetheless, the role of adjuvant therapy for such patients has not yet been clearly established in the literature. Although postoperative radioiodine ablation with thyroid-stimulating hormone (TSH) suppression is imperative after surgical resection of locally advanced thyroid cancer (11), external-beam radiotherapy (EBRT) has not been widely used even in patients with microscopic or small gross residual disease after surgical resection. Until recently, the beneficial role of EBRT had not been investigated systemically, particularly among the subsets of patients with tracheal invasion by thyroid carcinoma. The aim of the present study was to evaluate the potential role of postoperative adjuvant EBRT in the management of patients treated with conservative surgery for locally advanced thyroid cancer invading the tracheal cartilage.
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Patients and treatments
Between 1986 and 1997, 1,098 patients with well-differentiated thyroid cancers were treated surgically at the Yonsei Cancer Center, Yonsei University, College of Medicine (Seoul, Korea). Among them, 75 (7%) were found to have tracheal invasion at the time of admission. Of these, 2 patients with follicular carcinomas and 1 patient with medullary carcinoma were excluded to make the study population more homogeneous. Four patients who had either metastasis to the mediastinal lymph nodes or distant
Clinical profiles
To determine the role of adjuvant EBRT given after tracheal resection or tracheal cartilage “shave,” we divided all patients into two groups according to the administration of external radiotherapy: (1) the control group (n = 43) and (2) the EBRT group (n = 25). Clinical profiles of both groups are listed in Table 1. There were significant and marginal differences in the sex and age distribution of the two groups, respectively. The serum levels of thyroglobulin were similar between the two
Discussion
This study was undertaken to examine the role of adjuvant EBRT administered after “shave” excision of the tracheal cartilage in the management of patients with locally advanced thyroid carcinoma adhering to or invading the trachea. Clinically, approximately 7% of 1,098 patients undergoing surgery for thyroid cancer were found to have tracheal invasion at the time of initial diagnosis in our series. Our data also demonstrated that patients who received EBRT had a lesser likelihood of local
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