Treatment - Radiation

Radiation Therapy

  • Role of Radiation Therapy 
    • Cure
    • Control
    • Palliation
  • Overview:  Radiation Therapy
    • Used for over 100 years (Mustard gas in World War I)
    • Since cancer cells grow at a faster rate than normal cells, radiation therapy can be very effective
    • Usually a local treatment (whole body not exposed)
    • About half of all people who are diagnosed with cancer undergo radiation  
  • Mechanism of Cellular Damage
    • Direct damage to cell’s DNA/ chromosomal structures
    • Indirect effect causing toxic changes to cells

Cellular Death

  • May be immediate
  • May occur when cells attempt to divide
  • May occur from cell degeneration
  • Takes days to weeks

Sensitivity to Radiation Damage

  • Fast growing
  • Well oxygenated cells
  • Phase of cell cycle
  • Degree of cellular differentiation

Types and Sources of Radiation

  • External (external beam, teletherapy)
  • Electromagnetic sources
    • X-rays (photons)
    • Gamma rays
  • Particle Sources
    • Electrons
    • Protons/neutrons
  • Brachytherapy (internal)
    • Sealed radionuclides (implants)
    • Intracavity
    • Interstitial sources
  • Types
    • High-dose rate (HDR) implants (tubes skin / breast)
    • Low-dose rate (LDR) permanent implants (prostate cancer – seeds)

Radiation Treatment Frequency

  • Accelerated fractionation
  • Larger daily or weekly doses to reduce number of weeks of treatment
  • Hyperfractionation
  • Smaller dose given more than once per day
  • Hypofractionation
  • Larger doses given once a day or less often to reduce number of treatments

Types and Sources of Radiation

  • Internal – brachytherapy
    • Tandem and Ovoids (e.g., a small, round metal tube, which is placed inside the woman's uterus to treat cervical cancer)
    • 15-20 min dwell time – multiple days
    • Machine feeds source in, then removes
  • Uterus/Cervix
    • Unsealed sources
  • Oral; IV
    • Intraperitoneal; Intrapleural
  • Episcleral
    • Source attached to eye – ocular melanoma

Steps in Radiation Therapy

  • Consultation
  • Treatment Planning
  • Pretreatment studies
  • Simulation
  • Computer planning
  • Construction of blocks
  • Treatment Experience and Follow-up

Additional Radiation Techniques

  • Stereotactic radiosurgery
  • Gamma knife/CyberKnife
    • Non-surgical radiotherapy
    • Precisely targeted radiation
    • Preserves health tissue
  • Intraoperative radiotherapy (IORT)
    • Single dose RT to tumor bed