Radiation Oncology Flashcards
high energy radiation that is given off from radioactive materials
sufficient energy to eject an electron
Ionizing Radiation
Low-energy radiation like radio wave and microwaves
Non-ionizing radiation
the amount of radiation absorbed by a person’s body
radiation dose
Example of internal radiation contamination through inhalation of radiation exposure
radon
Radiation can be ______ or ______
particles or waves
What are the biological effects of radiation
damages mammalian cells by deposition of ionizing radiation at or near DNA
-random and discerete
33% of time radiation hits DNA leading to direct damage (single or double strand breaks)
67% of time radiation creates ROS leading to indirect damage
Radiation causes mostly what type of cell death
Mitotic Cell Death - DNA damage breaks and leading to abnormal chromosome set that is unable to be pulled apart
but some tissues under go apoptotic death
What tissues have significant apoptotic death
some normal tissues (lymphocytes, salivary glands, lacrimal glands) and some tumor types (lymphoma) have significant apoptotic death
-Round cell tumors? like mast cells and thymoma but 50-50
hypofractionated
<10 doses
fractionated
10+ doses
high dose per fraction radiation therapy delivered over a short (<5fractions) period of time
Requires a CT scan
Sterotactic (body) radiation therapy
conformal radiation therapy based on CT scan
intensity modulated radiation therapy (IMRT)
piece on the linear accelerator where the radiation comes from
gantry
piece on the linear accelerator that helps to scope dose to area being treated
multi-leaf collimator/beam
most common primary bone tumor in dog
occurring near the metaphysis of the bone
Osteosarcoma
Where does osteosarcoma typically occur
-Proximal humerus
-Distal Radius
-Distal Femur
-Distal tibia
-Proximal tibia
What are considerations for using stereotactic body radiation for OSA patients
1) Integrity of the bone on CT (4 characteristics to look for fracture risk)
2) Degree of lameness on physical examination
3) Skin -if open wound, wont heal
4) Size of the lesion- worse if larger lesions
What is the biggest risk when doing stereotactic body radiation therapy for OSA
Fracture
Skin changes
What is stereotactic body radiation
-Implies hypofractionation
(1-5 treatment)
-High dose/fraction
-Semi-rigid immobilization
-Target localization (contouring and on-bard imaging)
-Spares normal tissues by avoidance
How does stereotactic body radiation therapy spare normal tissues
avoidance
What are the qualifications of sterotactic body radiation therapy (SBRT)
1) Gross disease - dont cut out target
2) Intact healthy skin
3) Ct for planning
What disqualifies a cancer from being able to use Stereotactic body radiation therapy on?
1) Pathologic fracture
2) Oronasal fistula
3) Inability to adequately avoid normal tissues
What are the goals of stereotactic body radiation therapy
-Curative
-Durable palliation
a sterotactic body radiation type that uses Cobalt 201 sources
rigid framework for immobilization
driven by neurosurgeons to deliver a single large dose of radiation to inoperable lesion
Gamma Knife
tumor perfusion deficits following SBRT lead to
acute hypoxia and changes in DNA repair mechanisms
What is needed for SBRT
1) CT scan
2) Immobilization
3) Target localization
Palliative radiation therapy is
short, less intense protocol
-Reduced side effects
-Very simple set up- radiograph and some physics math
What is the goal of palliative radiation
improve quality of life and decrease pain
but not necessarily extend the quantity of life
-improve function
-improve hygiene
-unobstruct urethra/ureter
-stop bleeding
What are the proposed mechanisms on how radiation might improve pain
-Radiation effect on pain mediators and inflammatory cytokines
-Disruption of neuronal transmission of pain
-Radiation associated inhibition of osteoclast activity and resulting bone absorption
How do you diagnose Urogenital carcinoma
Cytology
Histopathology
BRAF test: ~95% of TCC/UC cases
What is the biggest challenges with making a radiation plan for urogenital carcinoma
it frequently changes in size with the bladder
non-uniform dose delivery
-modulated dose output
can be fractionated or hypofractionated
Intensity modulated radiation therapy (IMRT)
What are the advantages of Intensity modulated radiation therapy (IMRT)
Treat complex tumor shapes
minimize dose to normal tissues
What does Intensity modulated radiation therapy (IMRT) require
on-boarding imaging (OBI)
-MV portal films
-Kv-KV images
-KV-CBCT
How many fractions is Intensity modulated radiation therapy (IMRT) typically in vet med?
1-20 fractions
What are the risk factors when a patient is being treated with radiation
1) Total radiation dose
2) Dose per fraction
3) Number of fractions
4) Energy of beam
5) Treatment time
6) Field Size
7) Previous treatments
8) Concurrent medications
What are types on non-malignant conditions that can be treated with radiation therapy
1) Sialocele
2) Osteoarthritis
3) Meningoencephalitis of unknown origin
4) Pulmonic stenosis
5) Feline idiopathic cystitis (single low dose)
What medication is a risk factor to the gastrointestinal tract for patients receiving radiation
Toceranib phosphate (Palladia)
What medication is a risk factor to the heart for patients receiving radiation
Doxorubicin
What are the skin specific risk factors for patients receiving radiation therapt
1) Presence of skin folds in the field
2) Individual variation
3) Use of Bolus
4) Kilovoltage radiatio
5) Electrons
6) Infection
7) Wound/Ulcerations
What are heart specific risk factors for patients receiving radiation therapy
1) Doxorubicin tx
2) Valvular stenosis
3) Arrhythmias
Does KD or MD radiation accumulate more in bone
KD
acute radiation reffects that impact the rapidly dividing cells such as the skin, GI tract, and hematopoietic system usually occurs within
during or shortly after radiation therapy
-within the first 3 months
Acute radiation shortly after radiation therapy or within the first 3 months typically affects what tissues
rapidly dividing cells
-skin
-GI tract
-hematopoietic system
radiation therapy
early delayed effects
2 weeks to 4 months after RT to neurologic tissues
-suspected to be caused by demyelination or edema associated with cell death
Early delayed effects from RT within 2 weeks to 4 months target
neurologic tissues
-suspected to be caused by demyelination or edema associated with cell death
When do late radiation effects occur
3 months to years after RT
-generally irreversible
-late responding tissues are predominantly slowly dividing tissues such as lung, kidney, heart, bone and liver
Late radiation effects >3months after RT target
late responding tissues are predominantly slowly dividing tissues such as lung, kidney, heart, bone and liver
*generally irreversible
radiation effects occur within
the radiation field and are releated to the tissues that have been exposed to radiation
Radiation effects to skin/fur/hair
Acute: alopecia, epilation, erythema, dry desquamation, moist desqyamation, ulceration, necrosis, pain, hemorrhage
Chronic: alopecia, hyperpigmentation or hypopigmentation, leukotrichia, fibrosis, necrosis, pain, induration causing physical impairment, nonhealing wound
Why is the a rapid reaction of mucous membranes to RT
because the lifespan of the mucous membranes is much shorter than the epidermis
What are the effects of radiation to mucous membranes
Acute: erythema, mucositis, edema, confluent or patchy white/yellow membrane formation, ulceration, pain, secondary bacterial/fungal infection
Chronic: non-healing ulceration, hyperpigmentation, discoloration
What are the effects of radiation to the head/neck
Acute: stomatitis, mucositis, pharyngitis, reverse sneezing, esophagitis, xerostomia, thick secretions, cheilosis, ulceration, pain, dysphagia, secondary infection, nasal planum cracking
Chronic: chronic rhinitis, osteoradionecrosis (bone pain, swelling, evidence of infection, exposed bone, nonhealing gingival uclers), xerostomia, trismus with reduced capacity to open mouth
What are the effects of radiation to the eyes
Acute: keratitis, KCS, blepharospasm, periocular swelling/crusting, corneal edema, corneal ulceration, epilation, conjunctivitis, iritis, retinal edema
Chronic: KCS, telangiectasia, scleral melting, cataract. retinitis, blindness, corneal neovascularization, necrosis
How does radiation affect bone
Chronic- fracture, necrosis, infection, osteopenia, growth arrest, secondary tumor
How does radiation affect the heart
Acute and Chronic: pericarditis, restrictive cardiomyopathy, fibrosis, pericardial effusion, cardiac tamponade, pleural effusion, dyspnea, arrythmias, exercise intolerance, heart failure
How does radiation affect the bladder
Acute/Chronic:
pain on palpation, cystitis, stricture, pollakiuria, stranguria, incontinence, hematuria, fibrosis
How does radiation affect the lung
Acute/Chronic:
clinical or radiographic signs of pneumonitis (alveolar/interstitial infiltrate) usually 2-8 weeks after radiation,
chronic fibrosis, pneumothorax
With radiation, when do you see the radiographic signs of pneumonitis (alveolar/interstitial infiltrate)
2-8 weeks after radiation
How does radiation affect the GI tract
acute/chronic:
diarrhea, vomiting, inappetance, enteritis, hematochezia, sense of urgency, incontinence, stricture, fistula
How does radiation affect the CNS
Acute/Chronic: neurologic deficits, seizures, ataxia, blindness, paralysis, dementia, somnolence, endocrinopathies, herniation, headache, nausea/vomiting
What causes the nausea and vomiting that occurs within hours of irradiating the abdomen
5-hydroxytrptamine (5-HT) is released in response to radiation therapy and can stimulate the vomiting center
-Treat with Ondansetron
What causes the fatigue that occurs after irradiation of large volume
mitochondrial dysfunction and genes related to the regulation of the production of ROS
Most effects from radiation are from cell death but what else can occur
1) Nausea/Vomiting from 5-HT release
2) Fatigue from mitochondrial dysfunction
3) Somnolence several hours after brain irradiation
4) Acute edema/erythema from inflammation and vascular leakage
5) Pneumonitis due to destruction of type I pneumocytes and an accumulation of inflammatory cells
Most cells die by radiation through
mitotic cell death which can take time
Degranulation with mast cell tumors can occur minutes to weeks after RT. What are the signs? *
-Erythema
-Edema
-Hypotension
-Vomiting
-Hyporexia
-Melena
-Coagulation abnormalities
What can help you differentiate between tumor recurrence vs infection vs radiation adverse reaction
biopsies (fine needle or tissue)
What is the goal of treating acute radiation effects
improve patient quality of life by minimizing pain, establishing a return to function and ruling out tumor progression/recurrence
What should you do for acute skin treatments after radiation
-Protect skin from prolonged exposure to heat, cold, sunlight (protect from friction)
-Cleanse irradiated area, if necessary with water, normal saline, or mild diluted soap solution, do not scrub the area, may need sedation/anesthesia
-Antibiotic therapy only if evidence of infection
-Anti-inflammatory therapy with NSAID
-Prevent licking/scratching at irradiated skin, e-collar and hobbles for hind feet
-Oral analgesia medications
controversial: aquaphor, 2% lidocaine helly, SSD
How should you treat xerostomia
readily available clean water to increase water intake
maintain good oral hygiene
How do you treat cracked/dry nasal planum
apply balm with soothing ingredients such as hempseed oil, shea butter, cococnut oil, jojoba, vitamin E
How should you treat acute stomatitis/mucositis/esophagitis
-Maintain good oral hygiene
-soft, bland diet at room temp; avoid salty or acidic foods
-enzymatic mouth rinses, sucralfate solution - magic mouthwash, viscious lidocaine, diphenhydramine, loperamide
-NSAIDs, gabapentin, other oral analgesia meds
-Antibiotic therapy if indicated
-Nutritional support possibly requiring a temporary feeding tube
How do you treat eye effects after radiation
-topical antibiotics and steroids if no corneal ulceration is present
-topical antibiotics and anesthetics if corneal ulceration present
-supplement eye lubrication if evidence of decreased tear production- Optixcare
How do you treat the heart effects of acute radiation
Pericarditis managed by prevention on the RT side
-NSAIDs, anti-arrhythmic meds considered, subtotal pericardiectomy if clinical signs present
-Avoid doxorubicin or other anthracyclines, concurrently with RT to the heart
How do you treat the bladder effects seen with acute radiation
maintain hydration and increase fluid intake to dilute urine
treat underlying infections and use NSAIDs
How do you treat the lung effects seen with acute radiation
-glucocorticoids, rest, and oxygen therapy for pneumonitis
-antibiotics if needed
-supportive care with expectorants and bronchodilators
-Antitussive medications considered to aid in appropriate sleep
How do you treat the CNS effects seen with acute radiation
Anti-inflammatory doses of steroids and anticonvulsants as necessary
For herniation from acute edema, consider mannitol or hypertonic saline
With chronic treatments, how do you treat fibrosis (chronic)
physical therapy, hyperbaric oxygen, pain management, glucocorticoids, pentoxifylline and Vitamin E
With chronic treatments, how do you treat lymphedema
manual lymphatic drainage (massage), compression bandages, weight management, exercise, skin care, pressure gradient sleeves
With chronic treatments, how do you treat chronic rhinitis
-Antibiotic therapy if evidence of secondary bacterial infection: consider azithromycin, doxycycline, or metronidazole
-Anti-inflammatory drugs (NSAID or steroids): nasal steroid spray
With chronic treatments, how do you treat esophageal stricture
dilations and semi-solid diet, feeding tubes, hydrocortisone injection at the stricture site
How do you treat osteonecrosis, a chronic manifestation of radiation
surgical debridement/intervention
antibiotics
hyperbaric oxygen therapy
-Pentoxifylline and vitamin E
How do you treat pulmonary fibrosis, a chronic manifestation of radiation
-ameliorated be captopril in human oncology
-oxygen and glucocorticoids as needed
-pentoxifylline and vitamin E
How to you treat the bowel effects seen with chronic radiation treatments
-increased dietary fiber and probiotics
-analgesia as needed
-viscous lidocaine or silver sulfadiazine for anorectal irritation
-sucralfate enemas for bleeding
How do you treat the CNS effects seen with chronic radiation treatments
-glucocorticoid ideal in early-onset radiation necrosis
-Pentoxifylline and vitamin E may help in preventing fibrosis
-Consider surgical resection if necrosis is focal and localized
What does pentoxifylline do
improves blood perfusion by increasing erythrocyte deformability and decreased blood viscosity
antioxidant that protects membrane phospholipids from oxidative damage by scavenging reactive oxygen species that are generated during oxidative stress
Vitamin E
What combination therapy has been shown to decrease risk and even reverse evidence of radiation fibrosis in women who have received breast irridation
Pentoxifylline and Vitamin E
What can exacerbate radiation side effects
Some chemotherapeutics
-Dacarbazine
-Lomustine
-Doxorubicin
-Cisplatin
-Gemcitabine
-Paclitaxel
-Toceranib (for GI ulceration)
Why might antioxidants interfere with radiation cell killing
antioxidants protect against the damage from the radiation and protect against the humor
dont start during radiation therapy
What are possible ocmplications to the oral cabity when doing radiation therapy
-Fistula formation
-Candida albicans yeast infection can increase severity of stomatitis/mucositis
How do you prevent against side effects from radiation therapy
1) IMRT/conformal RT techniques allows for increased dose to tumor while increasing sparing of normal tissues
2) Acute skin effects: reduce skin folds in the treatment field, avoid topical agents immediately before RT, ensure surgical wounds have healed before initiating RT
3) Chronic skin effects- early detection and treatment/management
4) Head and neck effects: pre-RT dental prophylaxis and removal of unhealthy teeth to decrease severity of mucositis and risk of osteonecrosis
