Usefulness of Stereotactic Radiotherapy Using the CyberKnife for Patients with Inoperable Locoregional Recurrences of Differentiated Thyroid Cancer

Abstract

Background Surgical resection is the preferred treatment for locoregional recurrence of differentiated thyroid cancer (DTC). However, some recurrences are unresectable because of their aggressive invasion or severe adhesions. On the other hand, stereotactic radiotherapy (SRT) enables high‐dose irradiation to target lesions, and its usefulness for various cancers has been reported. The objective of the present study was to investigate the feasibility and efficacy of SRT as salvage treatment for locoregional recurrence of DTC. Methods Between August 2011 and December 2017, 52 locoregional recurrent lesions in 31 patients with recurrent DTC were treated by SRT using the CyberKnife system. Information on the adverse events associated with SRT was retrospectively collected from the patients’ medical records. Of the 52 lesions, 33 could be evaluated for therapeutic effectiveness by follow‐up CT, and response was assessed using the RECIST criteria. Results Twenty‐five patients had papillary carcinoma, 5 had follicular carcinoma, and 1 had poorly differentiated cancer. SRT was delivered in one to 20 fractions, and the median dose was 30 Gy (range 15–60 Gy). Adverse events were not frequent, but 1 patient developed bilateral vocal cord palsy that required emergent tracheostomy. The median follow‐up period of 33 lesions was 14 months (range 1–54 months). Complete response, partial response, stable disease, and progressive disease were seen in 10, 11, 9, and 3 patients, respectively. The 3‐year local control rate was 84.6%. Conclusion SRT using the CyberKnife system was found to be a feasible and effective treatment to suppress the growth of locoregional recurrence of DTC.

Stereotactic radiotherapy using the CyberKnife is effective for local control of bone metastases from differentiated thyroid cancer

“…With this system, one can irradiate a target with less damage to proximal organs by moving the robot arm, which has a wide range of motion. With SRT, precise delivery of high-dose radiation to the target can be achieved using a small number of fractions [7]. SRT compared with conventional 3D conformal radiotherapy demonstrated a higher efficacy in tumor control of bone metastases and in limiting radiation to the spinal cord, especially in patients who needed repeat irradiation [3].…”

“…Thus, TKIs should be considered for progressive, symptomatic and/or imminently threatening DTC in which satisfactory control using RAI therapy or directed approaches (e.g. surgery, radiation therapy including SRT) is not considered likely [3, 7]. In our view, SRT appears to be a useful preliminary step to TKI treatment.…”

“…Few studies have yet addressed the efficacy of SRT for thyroid cancer including bone metastases, and there has been no study of SRT for non-spine bone metastases from thyroid cancer. In a recent report, we showed the usefulness of SRT for locoregional recurrence of DTC, with a local control rate (LCR) of 84.6% at 3 years [7]. The aim of the present study was to examine the feasibility and efficacy of SRT using the CyberKnife (Accuray, Sunnyvale, CA, USA) as a salvage treatment for bone metastases from DTC, including spine and non-spine lesions.…”

“…One study reported local tumor progression in as many as 70% of patients at 1 year as evaluated by radiographic findings after EBRT [5]. On the other hand, compared with conventional EBRT, stereotactic radiotherapy (SRT) demonstrated higher efficacy in tumor control by enabling delivery of high-dose irradiation to lesions [3, 7]. Recently, a single Japanese institution reported the efficacy of SRT for spine metastases from various cancers.…”

Multisession CyberKnife Radiosurgery for Advanced Follicular Thyroid Cancer

“…Kawabe et al reported a case of recurrent lymph node metastasis of papillary thyroid carcinoma successfully treated with CyberKnife [7]. Ishigaki et al reported successful SBRT by CyberKnife for 52 locoregional recurrent lesions in 31 patients with recurrent differentiated thyroid cancer [8]. But their cases are mostly papillary carcinoma, and there were only five patients of follicular carcinoma.…”