Prognostic significance of surgically treated malignant struma ovarii with or without adjuvant thyroid‐related therapy: A systematic review and meta‐analysis

AIMS: The aims of this study are to determine the long-term overall survival (OS) after surgically treated malignant struma ovarii (MSO) and to evaluate prognostic effect of adjuvant thyroid-related therapy (ATRT) in this setting. METHODS: A systematic review in compliance with Preferred Reporting Items for Systematic reviews and Meta-Analyses standards was conducted. MEDLINE, CINAHL, CENTRAL, Scopus, trial registries, and gray literature were searched. Due to rarity of the disease, all case reports including patients with surgically treated MSO were pooled to create a single cohort which was then compared with the eligible case series. The OS and survival time were primary outcomes. The OS was determined using Kaplan-Meier survival statistics, and the predictors of OS were determined using the stepwise Cox proportional-hazards regression model. RESULTS: The study included 376 patients (95 from case reports and 281 from case series). The median age was 44 years; 79% (75/95) were symptomatic. In terms of ATRT, 39% (37/95) received thyroidectomy, 28% (27/95) radioactive iodine, 28% (27/95) hormone suppression therapy, and 55% (52/95) received no therapy. Recurrence occurred in 27% (26/95) with the median time to recurrence of 4 years. The pooled OS was 91% at 10 years and 87% at 20 years. The OS was not predicted by age (p = 0.320), symptomatic status (p = 0.371), follicular histology (p = 0.934), metastatic disease (p = 0.981); omentectomy (p = 0.523), total thyroidectomy (p = 0.371), radioactive iodine therapy (p = 0.285), and thyroid hormone therapy (p = 0.994). CONCLUSIONS: Surgically treated MSO may have excellent long-term prognosis with or without ATRT. It is possible that thyroid-specific treatments in MSO constitute overtreatment, with no demonstrable survival benefit. Limitations in the evidence base limit the ability to produce definitive conclusions.