External Beam Radiotherapy

External Beam Radiotherapy: Insights and Applications

Introduction to External Beam Radiotherapy (EBRT)

External Beam Radiotherapy (EBRT) is a widely used treatment modality for various cancers. It involves directing radiation from outside the body onto the cancerous tissues. This article synthesizes recent research findings on the efficacy and applications of EBRT in different cancer types, highlighting its role in palliative care, adjuvant therapy, and combination treatments.

Stereotactic Body Radiotherapy vs. Conventional EBRT for Spinal Metastases

Pain Management in Spinal Metastases

Conventional EBRT is a standard palliative treatment for spinal metastases, but its complete response rates for pain relief are relatively low, ranging from 10-20%. A recent multicenter randomized trial compared conventional EBRT with Stereotactic Body Radiotherapy (SBRT) in patients with painful spinal metastases. The study found that SBRT, delivering 24 Gy in two daily fractions, significantly improved complete pain response rates at three months compared to conventional EBRT (35% vs. 14%). This suggests that SBRT is more effective for pain management in these patients.

EBRT in Cervical Cancer: Boosting Techniques

Comparison with Brachytherapy

In the treatment of locally advanced cervical cancer, EBRT is often used as a boost. However, a review by the Gynaecology Study Group in the Italian Association of Radiation and Clinical Oncology (AIRO) found that high-tech EBRT does not outperform image-guided brachytherapy in delivering a boost. The review highlighted the need for prospective clinical studies to better compare these modalities.

Adjuvant EBRT in Endometrial Cancer

Impact on Survival and Recurrence

Adjuvant EBRT has been investigated for its role in treating early-stage endometrial cancer with intermediate or high risk of recurrence. Pooled results from the ASTEC and EN.5 trials showed that while EBRT reduces the risk of isolated local recurrence, it does not improve overall survival compared to observation alone. This indicates that routine use of adjuvant EBRT for improving survival in these patients is not recommended.

EBRT Combined with Brachytherapy for Prostate Cancer

Relapse-Free Survival

A phase-III trial compared EBRT alone with EBRT combined with high-dose-rate brachytherapy boost (HDR-BTb) in localized prostate cancer. The combination treatment significantly improved relapse-free survival (RFS) compared to EBRT alone, with a 31% reduction in the risk of recurrence. This benefit was maintained over a 12-year follow-up period, demonstrating the long-term efficacy of combining EBRT with HDR-BTb.

EBRT in Thyroid Cancer

Locoregional Control

EBRT is not a first-line treatment for differentiated thyroid carcinoma (DTC) but is recommended as an adjuvant therapy in certain high-risk cases. A systematic review found that EBRT improves locoregional control in patients over 45 years old who are at high risk of locoregional recurrence. However, there is a need for long-term prospective studies to further validate these findings.

EBRT in Neuroendocrine Tumors

Efficacy and Safety

The role of EBRT in treating gastroenteropancreatic neuroendocrine tumors (GEPNETS) is less clear due to limited data. A systematic review indicated that EBRT is generally well-tolerated and shows encouraging activity in selected patients, particularly those with pancreatic neuroendocrine tumors (PNETs). However, more well-designed prospective studies are needed to clarify its role.

Conclusion

EBRT remains a cornerstone in the treatment of various cancers, offering significant benefits in specific contexts such as pain management in spinal metastases and relapse-free survival in prostate cancer. However, its role as an adjuvant therapy in endometrial and thyroid cancers requires careful consideration, and further research is needed to optimize its use in neuroendocrine tumors and cervical cancer.

Summary

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