Download Radiation Oncology

Radiation Oncology
Kazumi Chino, M.D.
Faith Hope and Love Cancer Center
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
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
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
Linear Accelerator
X-rays penetrate to a certain depth based on
their energy, and then interact with tissue:
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
DNA Damage
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
Dividing the radiation dose into fractions
further exploits the difference between tumor
and normal tissue
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
Radiation Dermatitis
Hair loss is also seen in
the treatment field
Mucositis, Esophagitis
Nausea and diarrhea
are also caused by
injury to GI mucosa
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
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
Active Bone Marrow in Adults
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
Fibrosis
Radiation can cause fibrosis throughout tissues
In joints, this can limit range of motion
In lymph channels, this
causes lymphedema
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