Patterns of Treatment Failure in Anaplastic Thyroid Carcinoma

Background: Anaplastic thyroid cancer (ATC) is one of the most lethal forms of cancer with a high mortality rate. Current guidelines support surgery for resectable ATC followed by external beam radiation therapy (EBRT) with or without chemotherapy. Treatment for those who are unresectable is palliative. Our goal was to examine first-line therapies as well as the role of genomic profiling in an effort better understand how to approach ATC.

Methods: This is a retrospective study of ATC patients who were seen at our institution from January 2013 to October 2015. Median overall survival (OS) and time to treatment failure (TTF) were calculated by the Kaplan-Meier method.

Results: Fifty-four patients were included. Median age at diagnosis was 63 years and 29/54 (54%) were women. The majority had stage IVC disease at diagnosis (50%), followed by IVB (32%), and IVA (18%). Approximately 93% had somatic gene testing. Initial treatment was surgery in 23 patients, EBRT with or without radiosensitizing chemotherapy in 29 patients, and systemic chemotherapy in 2 patients. Nineteen patients had all three treatment modalities. For the entire cohort, median OS was 11.9 months with 39% survival at 1 year and median TTF was 3.8 months. The majority of patients (74%) developed new distant metastasis or progression of existing metastatic disease. Patients who received trimodal therapy consisting of surgery, EBRT, and chemotherapy had a median OS of 22.1 months versus 6.5 months in those who received dual therapy with EBRT and chemotherapy (p = 0.0008). The TTF was the same in the two groups (7.0 and 6.5 months, respectively). Men were three times more likely to die from ATC than women (p = 0.0024). No differences in OS or TTF were noted based on tumor size (5 cm cutoff), age (60 years cutoff), or presence of any mutation. There was a trend toward shorter TTF in patients with somatic mutations in TP53.

Conclusion: Patients with ATC amenable to aggressive tri-modal therapy demonstrate improved survival. The short TTF, due primarily to distant metastatic disease, highlights the potential opportunity for improved outcomes with earlier initiation of systemic therapy including adjuvant or neoadjuvant therapy.