The current role of adjuvant radiotherapy in management of medullary thyroid carcinoma: A single institute analysis.

Objectives: Medullary thyroid carcinoma (MTC) accounts for only about 5% of total thyroid cancers. It usually presents as an advanced disease carrying a poor prognosis than well-differentiated thyroid cancers. While the treatment of choice is surgery, the role of adjuvant radiotherapy is still unclear. This retrospective study aims to understand the role of adjuvant radiotherapy in MTC and its effect on survival.

Materials and methods: We did a retrospective two study to estimate the effect of adjuvant external beam radiotherapy (EBRT) on survival outcomes in MTC. A total of 30 patients who were diagnosed with nonmetastatic MTC during the period 2015 to 2020 were included in the study. Fifteen patients underwent only total thyroidectomy with cervical lymph node dissection. Rest 15 patients received adjuvant EBRT following surgery. A median dose of 60 Gy in 30 fractions, 2 Gy per fraction, 5 days per week, was given by conventional radiotherapy technique. Survival outcomes were estimated using Kaplan-Meier method. A univariate analysis using log rank test was performed to estimate the association of various prognostic factors including age, sex, tumor size, nodal involvement, and surgical resection status on survival outcomes.

Results: Median age of presentation in our study is 47 years (inter quartile range: 36-55 years). Median follow-up time is 4 years. Male to female ratio is 2:3-70% of patients presented with T3 lesions and 77% with N1b disease. There was no significant difference in overall survival (OS) in patients who received adjuvant RT following surgery in comparison to patients who underwent only surgery (92.9% vs. 71.4% P value = 0.202). Similarly, there was no improvement in locoregional recurrence-free survival (LRFS) (100% vs. 85.7%, P value-0.157), Distant metastasis-free survival (DMFS) (64.3% vs. 71.4%, P value = 0.725), and Disease-free survival (DFS) (64.3% vs. 64.3%, P value = 0.91). Age, gender, nodal involvement, and surgical resection status (R0, R1, R2) did not have any effect on survival outcomes. DFS (100% vs. 63.6% P value = 0.008), LRFS (100% vs. 94.7% P value = 0.002), and DMFS (100% vs. 63.2% P value = 0.006) were significantly better in T2 lesions compared to advanced lesions.

Conclusion: Adjuvant EBRT failed to show any significant improvement in survival outcomes and locoregional control in MTC. Further prospective randomized clinical trials are needed to validate the role of EBRT in MTC. Clinicians should proceed with caution before advising adjuvant radiotherapy in MTC and make an informed decision after weighing the pros and cons of giving adjuvant EBRT.