Interstitial Prostate Brachytherapy

• Implantation of small radioactive sources into the prostate gland
• Recommended initial therapeutic strategy for patients with low-risk prostate cancer
  • Difficult to perform in patients with very small or very large prostates, bladder outlet obstruction symptoms, or previous transurethral resection of the prostate (TURP)
• Recommended doses:
  • 120 Gy (palladium)
  • 140 Gy (¹²⁵I) with postoperative dosimetry

Low Dose-Rate Brachytherapy

• Uses permanent low-energy seeds (Iodine-125, Palladium-103, Cesium-131) for implantation that delivers adequate doses
• Recommended for patients with the following:
  • Stage T1b-T2a N0 M0
  • ISUP grade 1 with ≤50% biopsy cores involved or ISUP grade 2 with ≤33% biopsy cores involved
  • ≤10 ng/mL initial PSA level
  • <50 cm³ prostate volume International Prostatic Symptom Score (IPSS) ≤12 and urinary flow test result of>15 mL/min
• May be given to patients with intermediate to high-risk together with external beam radiation therapy (EBRT)
• Recommended dose:
  • Iodine-125: 145 Gy [110 Gy with 40-50 Gy EBRT]
  • Palladium-103: 125 Gy [90-100 Gy with 40-50 Gy EBRT]

High Dose-Rate Brachytherapy

• Uses temporary radioactive sources (eg Iridium-192) inserted into different locations in the prostate gland
• Recommended for patients with intermediate- to very high-risk localized or locally advanced prostate cancer
  • Showed improved biochemical control when given together with ADT and EBRT (45-50 Gy), but with more side effects
• Recommended dose:
  • Monotherapy: 13.5 Gy x 2 fractions
  • With EBRT: 9.5-11.5 Gy x 2 fractions; 5.5-7.5 Gy x 3 fractions; 4-6 Gy x 4 fractions

External Beam Radiation Therapy (EBRT)

• Recommended initial therapeutic strategy for patients with low-high risk prostate cancer
• Limited radiation fields are preferred over extended field radiotherapy for localized and locally advanced prostate cancer
• May be given with or without ADT or with brachytherapy with or without ADT in patients with unfavorable intermediate risk
• Recommended to be given concomitantly with ADT as initial therapy in patients with high or very high risk 
• Localization of prostate with image-guided radiation therapy (IGRT) is necessary with either 3-dimensional conformal radiation therapy (3D-CRT) or intensity-modulated radiation therapy (IMRT) for reducing target margin and ensuring treatment accuracy
• Recommended dose for patients with low-risk prostate cancer is 75.6-79.2 Gy; intermediate- to high-risk and metastatic prostate cancer is 81.0 Gy

Stereotactic Body Radiotherapy (SBRT)

• Uses high conformal, high-dose radiation delivered precisely using imaging techniques
• May be considered as an alternative to conventionally fractionated regimens or to EBRT in unfavorable intermediate- or high-risk patients when combined with ADT when EBRT is medically challenging

Proton Beam Therapy

• Delivers less radiation to surrounding normal tissues thereby decreasing long-term treatment morbidity
• Further studies are needed to prove the efficacy of proton therapy against prostate cancer and its superiority to photon-based radiation therapy

Radiopharmaceutical Therapy

• Eg Radium-223 dichloride, ß-emitting agents (Strontium-89, Samarium-153)
• Option for palliative treatment of patients with metastatic disease

Beta-Emitting Radioactive Agents

• Eg Strontium-89 (Sr-89, 89Sr), Samarium-153 (Sm-153, 153Sm)
• Used for treatment of painful bone or widespread metastases that are not eligible for chemotherapy

Radium-223 dichloride

• An alpha particle-emitting radioactive agent used for metastatic castration-resistant prostate cancer (CRPC) with symptomatic bone metastases but without visceral involvement
  • Studies have shown that patients given Radium-223 had better overall survival and time to appearance of symptomatic bone events than those given placebo