Serious Concern Regarding Omission of Local Control in a Large Sacral Metastasis

To the Editor,

We wish to raise a serious concern regarding the management described by Nguyen et al ¹ in their article “Sacral Metastasis in Follicular Thyroid Carcinoma: Cytology Pitfalls and Serum Thyroglobulin Utility.” The case involved an ≈8 cm lytic sacral mass with cortical destruction, paraspinal muscle invasion, and multifocal osteolytic disease in the spine and pelvis. Despite these high-risk features, external-beam radiotherapy (EBRT) and surgical consultation were deferred because pain was “well controlled.” The patient received only 200 mCi of radioiodine and died six months later. As orthopedic and spinal surgeons, we are concerned that this management contradicts current evidence and international guidelines on mechanical instability, neurologic risk, and local control of spinal and sacral metastases.

1. Structural Instability Requires Assessment Independent of Pain

Modern oncologic spine practice applies validated frameworks such as the Spinal Instability Neoplastic Score (SINS) and the NOMS (Neurologic–Oncologic–Mechanical–Systemic) decision algorithm. ² A lesion of this size, lytic morphology, and sacral involvement would yield a SINS ≥ 7, warranting urgent surgical or interventional consultation even in the absence of pain. Mechanical pain is often a late finding; deterioration may occur abruptly with fracture or neural compression. The absence of documented mechanical assessment or multidisciplinary referral represents a deviation from accepted standards and a missed opportunity for early stabilization.

2. Prophylactic Radiotherapy Prevents Skeletal Events and Improves Outcomes

The ASTRO 2024 Clinical Practice Guideline on Palliative Radiotherapy for Bone Metastases explicitly recommends EBRT—conventional or stereotactic—not only for palliation but also prophylactically in structurally unstable or high-risk lesions to prevent skeletal-related events (SREs). ³

This recommendation is supported by a multicentre randomized phase II trial by Gillespie et al, which showed that prophylactic RT to asymptomatic or minimally symptomatic bone metastases reduced SREs to 1.6, decreased hospitalizations, and improved overall survival compared with standard observation. ⁴ These data demonstrate that “watchful waiting” until pain escalation is inconsistent with evidence-based care.

3. Radioiodine Alone is Rarely Effective for Lytic FTC Bone Disease

The authors themselves note that remission rates for bone metastases from differentiated thyroid carcinoma (DTC) after radioiodine therapy are only 10–17 %. However, this finding underscores—not excuses—the need for local control. Reviews of DTC bone metastases emphasize that combined local therapy (surgery ± EBRT/SBRT) and bone-modifying agents are essential to prevent SREs and improve survival. ⁵ Deferring EBRT and structural stabilization conflicts with disease-specific evidence.

4. Request for Clarification

Because this case was published in a peer-reviewed journal with broad clinical readership, the omission of local control measures could inadvertently suggest that radioiodine monotherapy is sufficient for large sacral lesions when pain is minimal. We respectfully urge the authors and editors to clarify this management decision in accordance with current guidelines, emphasizing that:

• Pain control is not a reliable indicator of stability.

• Formal SINS/NOMS assessment should guide multidisciplinary referral.

• Prophylactic EBRT or SBRT and stabilization should be considered for lytic, high-risk sacral or spinal lesions, irrespective of pain severity.

Such clarification will help prevent misinterpretation and promote safer, evidence-based care for patients with bone-dominant follicular thyroid carcinoma.