Findings from a study examining the therapeutic effect of stereotactic radiotherapy in patients with medullary thyroid cancer (MTC) demonstrated that 87.5% of 16 lesions stabilized following the procedure.

Partial regression was achieved in 20% of lesions and in 30% of lesions that were progressive prior to radiotherapy stabilization. High-dose fractionated stereotactic radiotherapy allowed for attainment of MTC disease control in all soft-tissue metastases after 83% (5 of 6 soft-tissue lesions) demonstrated progression prior to radiotherapy. None of the lesions progressed following the procedure.

“The ability to stabilize spinal metastases is crucial because progression could lead to spinal cord injury, significantly worsening patients’ quality of life,” the study authors wrote. “Tumors in the neck are the second group of lesions whose progression can cause significant damage to the patient’s health. Timely radiotherapy can prevent dysphagia and shortness of breath caused by tumor expansion in the neck.”


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The study provides clinical information demonstrating stereotactic radiotherapy has beneficial outcomes for locally advanced MTC or focal MTC metastases that are surgically unresectable. The authors suggest, “the short time, satisfactory efficacy, and the lack of severe treatment-related complications of stereotactic radiotherapy allow applying it in patients in a more severe general condition, [who are] not amendable for surgery or systemic treatment.”

Study Methods

The researchers enrolled 11 patients with MTC with a total of 16 lesions. The investigators applied the CyberKnife (CK) system using accelerators which focused several hundred beams from multiplanar treatment angles for 11 lesions, while they used a conventional linear accelerator to treat the other 5 lesions. The radiation doses ranged from 5 to 12 Gy for fractionated radiation and from 8 to 44 Gy for total radiation. The clinicians used a single radiation fraction to treat 6 lesions, 2 fractions to treat 3 lesions, 3 fractions to treat 6 lesions, and 9 fractions to treat 1 lesion.

The locations of the lesions differed, with 10 lesions that metastasized to bone, 2 to lymph nodes, 2 to the liver, one primary thyroid tumor, and one MTC recurrent thyroid bed tumor. Follow-ups after stereotactic radiotherapy averaged 3 years with a range between 1 and 9 years.

The main limitation of this study included the small sample size due to the rarity of MTC, which prevented the investigators from drawing more precise conclusions using a more complete statistical assessment that is possible in larger groups.

Reference

Kukulska A, Krajewska J, Kołosza Z, et al. Stereotactic radiotherapy is a useful treatment option for patients with medullary thyroid cancer. BMC Endocr Disord. 2021;21(1):160. doi:10.1186/s12902-021-00832-4