Determinants of Worsening Response to Therapy in Patients Diagnosed With Papillary Thyroid Carcinoma in a Tertiary Hospital

Introduction: Papillary thyroid cancer (PTC) is generally considered to be an indolent disease with relatively good prognosis. However, some studies have shown that the Filipino population has a higher risk for disease recurrence compared to non-Filipino patients and hence early identification and management during the follow-up period would be beneficial, especially those in whom risk factors for recurrence were identified. Objective. This study aims to identify determinants for disease recurrence of patients with papillary thyroid carcinoma (as defined by the American Thyroid Association (ATA) guidelines 2015) diagnosed from January 1, 2013-December 31, 2017, seen at the University of Santo Tomas Hospital (USTH) outpatient endocrine clinic and underwent total thyroidectomy with or without radioactive iodine ablation therapy. Methodology: Retrospective review of outpatient medical records of 82 patients with PTC who underwent total thyroidectomy with or without radioactive iodine (RAI) therapy and achieved excellent response (ER) to therapy was performed. Baseline clinical profile such as age at diagnosis, sex, family history of thyroid cancer, family history of goiter, histopathology result, serial thyroglobulin (Tg), anti-thyroglobulin (anti-Tg) levels, whole body scan reports, neck ultrasound reports and RAI doses were collected. Logistic regression analysis was used to identify determinants to the development of worsening response. Results: Of the 82 patients, 18 (21.9%) developed worsening response to therapy. Predictors of poor outcomes identified from previous studies such as age, sex, extent of disease, size and multifocality of tumors, ATA risk classification and initial dynamic risk assessment, RAI therapy, level of thyroid-stimulating hormone (TSH) suppression were analyzed. After logistic regression analysis, there was no significant association between variables and progression to worsening response that were previously identified in other studies. Conclusion: Even though no significant association between investigated variables and worsening response were identified in this study, previous studies with larger populations that had exhibited positive association should be considered and hence current Philippine guidelines for the management of PTC must still be applied. Keywords: Thyroid cancer, papillary thyroid carcinoma, excellent response, disease recurrence