For how many weeks after a Lutetium-177 (Lu-177) infusion will prostate cancer cells continue to die from radiation effects?

Duration of Cancer Cell Death After Lutetium-177 (Lu-177) Infusion

Lutetium-177 continues to kill prostate cancer cells for approximately 6-7 days after infusion, which corresponds to its physical half-life of 6.73 days. 1

Radiation Properties of Lu-177

• Lu-177 is a β- and γ-emitting radionuclide with a physical half-life of 162 hours (6.73 days) 1
• It has lower maximum and mean β-particle energies (0.498 MeV and 0.133 MeV) compared to other radiopharmaceuticals like Yttrium-90 1
• These properties translate to maximum and mean soft-tissue penetration depths of 1.7 mm and 0.23 mm, respectively 1
• Lu-177 has two main gamma emission lines: 113 keV (6% relative abundance) and 208 keV (11% relative abundance), which allow for post-treatment imaging and dosimetry assessments 1

Radiation Effect Timeline

• The therapeutic effect of Lu-177 is directly related to its physical half-life of 6.73 days 1
• The radiation emitted by Lu-177 continues to kill cancer cells as long as the isotope remains radioactive in the body 1, 2
• After one half-life (6.73 days), the radioactivity decreases by 50% 1
• The highest levels of radiation exposure and cancer cell death occur during the first 2 days after administration, when urinary excretion levels are highest 1

Clinical Implications

• Patients should observe rigorous hygiene precautions for 1 week following Lu-177 treatment due to continued radioactivity 1
• Special precautions for radiation safety are recommended during the first week after treatment, including:
  • Double toilet flush after urination 1
  • Thorough hand washing after urination 1
  • Avoiding contamination of underclothing or areas around toilet bowls 1
• Women should avoid pregnancy for at least 6 months after treatment due to the potential effects of radiation 1

Treatment Protocols

• Standard Lu-177 treatment protocols involve administering 5.55–7.4 GBq (150–200 mCi) per cycle 1
• Treatment typically consists of three to five cycles with 6–12 weeks intervals between cycles 1
• This interval allows for recovery from potential side effects while maintaining therapeutic efficacy 1

Side Effects During Active Radiation Period

• The most common side effects during the active radiation period include:
  • Hematologic toxicities: anemia, thrombocytopenia, and lymphopenia 2
  • Fatigue 2
  • Nausea and vomiting 2

Clinical Considerations

• Radiation dosimetry can provide valuable information about organ-specific radiation absorbed doses and help assess the risk of delayed organ toxicity 1
• Patient-specific factors may influence the duration and effectiveness of radiation effects, including tumor burden, prior treatments, and individual metabolism 1
• The combination of Lu-177 with other therapies may affect the duration and effectiveness of cancer cell death 3