High-Dose-Rate Brachytherapy for Localized Prostate Cancer: An Opportunity for Improvement over Intensity- Modulated Radiotherapy

Advances in conformal radiotherapy techniques such as IG-IMRT have improved local tumor control and survival rates while decreasing GI and GU toxicities compared to 3D-CRT. However, the question remains if further dose escalation could improve the PSA relapse-free survival rate beyond 70% for highrisk patients? Treatment of high-risk patients using IG-IMRT remains challenging as these patients may present with occult distant disease. The potential benefits of high-dose rate (HDR) brachytherapy (BT) for localized prostate cancer are two folds: dose escalation to the target with possible boosting of the regions known to contain disease; and dose sparing to the urethra, bladder, rectum, and neuro-vascular bundles. Available clinical data for the use of HDR BT a boost or monotherapy confirm that HDR BT is capable of delivering a conformal, radiobiologically effective, very high radiation dose to the targeted tumor region without compromising gastrointestinal and genitourinary dose constraints. MRI-guided HDR BT potentially allows clinicians to deliver adaptive radiation to high-risk tumor subvolumes including the dominant intraprostatic legion, or even areas of recurrence. In addition, MRI-guided HDR offers a therapeutic advantage for those patients with visualized extra-capsular disease extension, as extra-capsular disease may be included in the radiation target volume.