Radiation Oncology

1. Kazumi Chino, M.D. Faith Hope and Love Cancer Center Radiation Oncology

2. Radiation Therapy 50-60% of all cancer patients will receive radiation therapy in the course of their illness That's almost 1,000,000 people a year in the US

3. A Brief History of Radiation... 1895 Wilhelm Rontgen discovers x-rays 1896 Victor Despeignes uses x-rays in a stomach cancer: the tumor shrinks and the patient has less pain but isn't cured 1900 Francis Williams describes cure of a breast cancer, and recommends early tx of breast cancers to prevent metastasis

4. What is Radiation? Energy from a source, traveling through material or space So light, heat, and sound are all forms of radiation Therapeutically, we think of photons and sub-atomic particles, moving through the body to deposit their energy in the target: cancer cells

5. Linear Accelerator

6. X-rays penetrate to a certain depth based on their energy, and then interact with tissue:

7. Compton Electron The freed e- (free radical) then interacts with whatever is nearby (3-5 nm): Ionization or ion pair formation by stripping an electron from critical molecules in the cell (DNA) = direct effect Or ionization of water molecules, making reactive oxygen species = indirect effect

9. DNA Damage

10. Radiation Action Local: within 3-5 nm of initiation, the free radical is spent Normal tissues have mechanisms to halt division and repair DNA damage Tumors have frequently lost those checks on replication, making them more easily killed by radiation damage Other rapidly dividing cells (bone marrow, gut mucosa) are more easily killed as well

11. Dividing the radiation dose into fractions further exploits the difference between tumor and normal tissue

12. Side Effects of Radiation Rapidly dividing cells are more easily killed by radiation Side effects are local: within the field of treatment or on it's edge Early effects occur during treatment Late effects can occur months to years after treatment

13. Radiation Dermatitis Hair loss is also seen in the treatment field

14. Mucositis, Esophagitis Nausea and diarrhea are also caused by injury to GI mucosa

15. More Early Side Effects Fatigue Muscle aches in the treatment field, costochondritis with treatments in the chest Radiation cystitis: increased frequency or urgency of urination, dysuria, hematuria, and an increased susceptibility to UTI

16. Radiation and Bone Marrow As low as 2-4 Gy can significantly decrease bone marrow cellularity 30-40 Gy (with conventional fractionation) is enough to ablate bone marrow LD 50 = 4.5 Gy to the whole body

17. Active Bone Marrow in Adults

18. Late Effects From Radiation Neurocognitive deficits: 1/3 of patients receiving whole brain irradiation will have a decrease in MMSE score, peaking about 4 months after tx Bone marrow may be replaced with fat or fibrosis, and damage to osteogenic cells can increase bone demineralization or impair healing from fractures

19. Fibrosis Radiation can cause fibrosis throughout tissues In joints, this can limit range of motion In lymph channels, this causes lymphedema

20. Pulmonary Fibrosis Radiation pneumonitis is an intermediate effect, occurring 2-12 months after treatment Sx: SOB, low grade fever, dry cough Inflammation is seen within the tx field Pneuomonitis does not necessarily entail pulmonary fibrosis in the future