50th Annual Meeting of the American Society of Clinical Oncology (ASCO):

Multifocality Associated with Poorer Prognosis in Patients with Papillary Thyroid Carcinoma

In patients with intrathyroid papillary carcinoma, multifocality is associated with poorer prognosis, suggest results of a study presented on May 31, 2014, at the Annual Meeting of the American Society of Clinical Oncology in Chicago, Illinois.

The significance of multifocality has not been well understood, noted study author Ivan Markovic, MD, MSc, and colleagues in their presentation. The reported incidence of multifocality in papillary thyroid cancer (PTC) has varied widely, from 18% to nearly 88% of cases; moreover, the mechanisms of multifocal spreading and the effect of multifocality on prognosis are unclear.

To try to gain a better understanding of the importance of multifocality, Dr. Markovic and his colleagues from the Institute for Oncology and Radiology of Serbia evaluated the significance of multifocality and other clinical variables on outcomes in 153 patients with PTC who underwent total thyroidectomy at a single institution. Patients with locally invasive tumors or initial distant metastases were excluded.

About the Study
Patients were predominately female (74%) with a median age at diagnosis of 42 years and a median tumor diameter of 15 mm (range, 2-95 mm). Multifocality was found in 28% of specimens and 80% of patients had lymph node metastases. Rates of multifocality were significantly higher in patients older than age 45 at diagnosis (P < .05) and in patients with a tumor diameter greater than 4 cm (P < .01).

Surgical biopsy was undertaken in the lower jugular ipsilateral compartment for frozen-section histology in 67% of patients. All patients with lymph node metastases in the lower jugular lymph nodes underwent modified radical neck dissection.

All patients initiated postoperative lifelong thyrosuppressive therapy and the 12.4% of patients with postoperative I131 uptake in the neck greater than 2% received radio-iodine ablation therapy. Nine percent of patients received external radiotherapy for gross lymph node metastases and/or perinodal infiltration observed by histology.

Adverse Clinical Outcomes Noted
Despite the “generally good prognosis of PTC,” the researchers explained, some patients did develop adverse clinical outcomes during the median follow-up of 138 months, including 8.4% with regional relapse in nondissected lymph nodes, 1.3% with distant metastases, and 5.2% who died from PTC.

Multifocality was associated with significantly worse outcomes than solitary tumors in regards to relapse rate (P < .001), relapse-free survival (P = .0095), and overall survival (P = .0004). In multivariate analyses, multifocality and male sex were independently associated with relapse; and multifocality, age > 45 years at diagnosis, and male sex were independently associated with shorter survival.

Given the higher risk for relapse and shorter survival associated with multifocality, the researchers concluded that total thyroidectomy should be considered the optimal treatment for patients with PTC, with the aim of removing all tumor foci, reducing the risk of relapse, and improving disease-free and overall survival.

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