Role of Radiotherapy in Papillary Thyroid Cancer
External beam radiotherapy (EBRT) is indicated in papillary thyroid cancer only when there is incomplete surgical resection or lack of radioactive iodine uptake in the tumor. 1
Primary Treatment Approach
The management of papillary thyroid cancer follows a step-wise approach:
- Total or near-total thyroidectomy is the initial treatment of choice for differentiated thyroid cancer (DTC), including papillary thyroid cancer (PTC), whenever the diagnosis is made before surgery 1
- Less extensive surgical procedures may be acceptable for small, intrathyroidal unifocal tumors with favorable histology 1
- Surgery is typically followed by radioactive iodine (RAI) ablation in intermediate and high-risk patients, not external beam radiotherapy 1
Specific Indications for Radiotherapy
Radiotherapy has limited applications in papillary thyroid cancer:
- External beam radiotherapy should be considered when surgery is incomplete or there is lack of radioactive iodine uptake in the tumor 1
- For locoregional recurrent disease, treatment is based on a combination of surgery and radioiodine therapy, supplemented by external beam radiotherapy only if surgery is incomplete or there is lack of RAI uptake 1
- For T4 tumors with surgically evident gross extrathyroidal extension, radiotherapy may be considered after radioiodine ablation 1
Risk Stratification and Treatment Selection
Treatment decisions should be based on risk stratification:
- Low-risk patients: Radiotherapy is not indicated 1
- Intermediate-risk patients: Radiotherapy is not a first-line treatment; radioiodine ablation is the preferred adjuvant therapy 1
- High-risk patients: Radiotherapy may be considered for specific scenarios (incomplete resection, non-RAI-avid disease) 1
Treatment of Metastatic Disease
For metastatic papillary thyroid cancer:
- Distant metastases are more successfully treated if they are radioiodine-avid, small, and located in the lungs 1
- For bone metastases, a combination of radioiodine therapy and external beam radiotherapy may be used 1
- For brain metastases, surgical resection and external beam radiotherapy represent the main therapeutic options 1
Common Pitfalls and Caveats
- Radiotherapy is not routinely used in the initial management of papillary thyroid cancer 1
- Overuse of radiotherapy may lead to unnecessary complications without survival benefit 1
- Radiotherapy should not replace radioiodine ablation for RAI-avid disease 1
- For central neck recurrence, consider preoperative vocal cord assessment before radiotherapy 1
Special Considerations
- For solitary brain metastases, neurosurgical resection or stereotactic radiosurgery is preferred over conventional radiotherapy 1
- When radiotherapy is used for metastatic disease, it should be image-guided to maximize effectiveness and minimize toxicity 1
- In patients with distant metastases and RAI-avid disease, radioiodine treatment should be tried before considering external beam radiotherapy 1
In conclusion, external beam radiotherapy plays a limited but important role in the management of papillary thyroid cancer, primarily reserved for cases with incomplete surgical resection, non-RAI-avid disease, or specific metastatic scenarios.