Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2024

Outcome of metastatic, radioactive-iodine refractory differentiated, medullary and anaplastic thyroid carcinoma – A single institution’s experience (#425)

Bella Nguyen 1 , Zheng Fong 1 , Richard Gauci 2 3 , Jo Keyser 1
  1. Department of Medical Oncology, Fiona Stanley Hospital, Perth, Western Australia, Australia
  2. Department of Endocrinology, Fiona Stanley Hospital, Perth, Western Australia, Australia
  3. Department of Nuclear Medicine, Fiona Stanley Hospital, Perth, Western Australia, Australia

Background:
There is a growing incidence of thyroid cancer (TC). Whilst TC largely has good prognosis, treatment of patients who have metastatic radioactive iodine refractory differentiated TC (RAIR DTC), metastatic medullary TC and anaplastic TC remains challenging. Given relative rarity of these conditions, real world outcomes can be informative in assisting clinicians to make treatment decisions. This poster explores the outcome of different treatments for metastatic RAIR DTC, metastatic medullary TC and anaplastic TC at a single institution.

Method:
Patient electronic medical records were reviewed to retrospectively retrieve the patient’s clinical details. Clinicopathological data were collected including molecular characteristics, lines of treatments, and time of disease progression and death.

Results:
The study included 23 patients. Of these, 16 have metastatic RAIR DTC, 4 with metastatic medullary TC, and 3 with anaplastic TC. In the metastatic RAIR DTC group, overall response rate (ORR) to lenvatinib is 89%, with median progression free survival (PFS) not reached, but exceeding that of 20 months. Most common side effects were consistent with those reported in the SELECT trial, however 89% ended up with dose reduction and treatment breaks. Four patients in this group underwent redifferentiation with BRAF & MEK inhibitor or a MEK inhibitor alone, and 3 out of 4 showed successful redifferentiation response. All metastatic medullary patients were found to have RET mutations and responded to RET-inhibitors. Of the 3 anaplastic TC patients, one had BRAF V600E mutation and showed complete response to BRAF & MEK inhibitor. Another anaplastic TC patient had complete and sustained, long term response following combination of pembrolizumab and lenvatinib.

Conclusion:
Our study showed real world data of patients with RAIR DTC, metastatic medullary TC, and anaplastic TC with promising real-world response rate to lenvatinib, redifferentiation therapy, RET inhibitors, long-term response to BRAF & MEK inhibitor combination and immunotherapy with lenvatinib combination.