Impact of body mass index on survival outcome in patients with differentiated thyroid cancer

Increased body mass index is known to be associated with the high prevalence of differentiated thyroid cancers; however data on its impact on survival outcome after thyroidectomy and adjuvant therapy is scanty.

We aimed to evaluate the impact of body mass index on overall survival and disease free survival rates in patients with differentiated thyroid cancers.

Between 2000 and 2011, 209 patients with differentiated thyroid cancers (papillary, follicular, hurthle cell) were treated with thyroidectomy followed by adjuvant radioactive iodine-131 therapy and thyroid-stimulating hormone suppression. Based on body mass index, patients were divided into five groups; (a) <18.5kg/m² (underweight); (b) 18.5-25kg/m² (normal weight); (c) 26-30kg/m² (overweight); (d) 31-40kg/m² (obese) and (e) >40kg/m² (morbid obese). Various demographic, clinical and treatment characteristics and related toxicity and outcomes (overall survival, and disease free survival) were analyzed and compared.

Median follow up period was 5.2years (0.6-10). Mean body mass index was 31.3kg/m² (17-72); body mass index 31-40kg/m² was predominant (89 patients, 42.6%) followed by 26-30kg/m² seen in 58 patients (27.8%). A total of 18 locoregional recurrences (8.6%) and 12 distant metastasis (5.7%) were seen. The 10 year disease free survival and overall survival rates were 83.1% and 58.0% respectively. No significant impact of body mass index on overall survival or disease free survival rates was found (p=0.081). Similarly, multivariate analysis showed that body mass index was not an independent prognostic factor for overall survival and disease free survival.

Although body mass index can increase the risk of thyroid cancer, it has no impact on treatment outcome; however, further trials are warranted.