Radiation for Symptom Management Flashcards
1
Q
Radiation: Mechanism of Action
A
- Ionizing radiation causing damage to DNA
- XRs produced by an XR machine or linear accelerator
- Alternatively, gamma rays produced from a radioactive source
- Cancer cells are more susceptible to radiation damage, as they are less able to repair and dividing more rapidly
DNA damage
- Direct (base deletions, breaks in the DNA chain
- Indirect (free radicals produced from interaction between radiation and water molecules) - most important cause of cell death
- Damage to endothelial cells and interrupted blood flow (when high single doses of >10Gy are given)
2
Q
Radical radiotherapy
A
- Aim is complete tumour eradication, while minimizing long term normal tissue damage
- Radiation dose built up in fractionation to allow for higher doses can be given
- Treatment may be ‘accelerated’ (multiple doses in a day over a shorter period of time) to reduce opportunity for tumour cells to repopulate
- Treatment may be ‘hyperfractionated’ (smaller doses over a longer period of time to deliver a higher total dose with greater sparing of normal tissues)
- Typically 6-8 weeks in duration
3
Q
Palliative radiotherapy
A
- Aim is symptom control
- Majority of tumour cells (60-80%) killed in first one or two radiation doses, so initial radiation effect may be adequate for symptom control and long radiation course may not be necessary
- Short, relatively low dose schedules results in less acute reaction and minimal risk of late damage to normal tissue
4
Q
Components of radiation treatment planning
A
Immobilization
- Small movements could result in irradiation to critical structures
- May involve sandbags, or a plastic shell with individualised facemask
Treatment volume localisation
- Typically with CT, but in some cases plain XR is adequate (e.g. bone mets or primary lung tumour)
Dosimetric planning
- Once volume is defined, dose and field arrangements are planned
- May involve stereotatic rads, 1-4 beams, etc.
- Most machines provide 1 Gy/minute, so the treatment itself is brief
Verification
- Defined beam arrangement is checked by imaging on the treatment machine
5
Q
Acute effects of radiation
A
- Due to loss of epithelial cells
- Results in erythema or desquamation
- Depending on the site, can result in mucositis, esophagitis, sterile cystitis, GI irritation, pneumonitis, transient demyelination (Lhermitte’s sign)
- Repair of the denuded surface occurs once treatment is completed over a period of days or weeks
- Poor healing may occur if there is secondary infection/trauma, both risk factors for radionecrosis
6
Q
Late effects of radiation
A
- Some patients are genetically predisposed to lower tolerance for radiation, which is typically due to vascular damage
- ‘Progressive endarteritis obliterans’ - closure of small blood vessels and potential tissue ischemia
Skin
- Atrophy, fibrosis
- Telangiectasias, necrosis
GI tract
- Stricture
- Telangiectasias, bleeding
- Perforation
- Malabsorption
- Chronic enteritis/colitis/proctitis
Bladder
- Reduced volume
- Telangiectasies, bleeding
- Urethral/ureteric stricture
- Fistual
Oral cavity
- Mucosal atrophy
- Telangiectasias, bleeding
- Dental caries
- Mandibular necrosis
Lung
- Fibrosis
CNS
- Myelitis
- Necrosis
- Local edema
Eye
- Cataract
- Entropion or ectropion
- Dry eye
7
Q
Management of radiation side effects: Skin
A
- Desquamation rare after palliative doses - little in the way of acute effects
- Mild skin reactions typically require no treatment, but if needed, starch powder is recommended over talcum, gentian violet, etc.
8
Q
Management of radiation side effects: GI
A
- Nausea typically responds to antiemetics, such as metoclopramide or ondansetron
- If antiemetics are ineffective, dex may be helpful
- Consider prophylactic dosing if the GI tract will be captured in the field
Diarrhea
- low residue diet (avoid fibre, fruit etc.)
- Loperamide or Codeine if an antimotility is needed
9
Q
Management of radiation side effects: Cystitis
A
- Tamsulosin (alpha blocker) may be helpful for severe bladder spasm
- Cranberry juice or potassium citrate are anecdotally effective, but have no evidence
- If there is significant dysuria, consider systemic analgesics
- Rule out secondary infection
10
Q
Management of radiation side effects: Oropharyngeal mucositis
A
- Maintain regular oral hygiene with chlorhexidine mouthwash and prophylactic anti-candidals (e.g. nystatin)
- Local relief of pain with soluble aspirin mouth wash
- In severe cases, feeds via NG may be required
- In radical radiotherapy, pre-treatment assessment by a dentist and meticulous oral hygiene is important (but not required for simple, low dose palliative rads)
- Avoid alcohol and smoking as it worsens effects
11
Q
Management of radiation side effects: Pneumonitis
A
- May occur up to four months after treatment
- Dry cough, dyspnea
Imaging:
- Radiograph showing patchy shadowing confirming to radiation field
Treatment:
- 2-3 week course of steroids and antibiotics for secondary infection
Late radiation fibrosis may occur
12
Q
Radiation for bone pain
A
Indications
- Bone pain (highly effective and long lasting effect)
- Pathologic fracture
- Pressure on nerves
Outcomes
- 40% of patients can expect at least 50% pain relief
- Slightly less than 30% can expect complete pain relief at one month
- Pain relief typically within 10 days, some experience it as rapidly as 24 hrs. Others may not experience relief until a month after!
Single dose vs multi-dose
- No difference in pain outcomes between single and multiple fractions
- Single-fraction may result in higher rate of re-treatment, more pain flares, and potentially greater risk of fracture
- Multiple-fraction is preferred for previously irradiated areas, to treat or prevent pathologic fractures, and for spinal cord or cauda equina involvement
13
Q
Wide field treatment for bony mets
A
- Useful in cases where there are multiple sites of disease
- Delivers treatment to an area that may include up to half the body
- Dose of 6 Gy to upper half body (dose limited by lungs)
- Dose of 8 Gy to lower body
- Associated with greater toxicity (typically GI or a period of bone marrow suppression)
14
Q
Radiopharmaceuticals and application to bony mets
A
- Radioactive agents administered IV, which localize to metastatic bone sites and deliver radiation in a highly focal manner
- Strontium-89 and Smarium-153
- Systematic review shows improved pain control and decreased analgesic consumption
- Main adverse effects are thrombocytopenia and neutropenia
- Onset of analgesia may not occur for MONTHS
Indications:
- Multiple painful bone mets where conventional analgesics are ineffective and local field rads is not possible
- Must consider performance status, marrow function, use of other marrow suppression agents (e.g chemo/rads), alternative treatments, and prognosis
15
Q
Pain flare following rads for bone pain
A
- Occurs within first few days of rads
- Generally lasts 1-2 days and is managed with increased doses of opioids
- Prophylactic dosing of dex has been explored but is not generally recommended
16
Q
Rads for pathologic fracture
A
- An option when surgery is not possible or indicated
- May also be used post-op internal fixation to prevent further progression of the remaining metastatic tumour (not appropriate if there is widespread mets, limited survival, and adequate pain control)
- Typically single dose of 8 Gy for pain relief (higher doses for healing)
- Goal is pain relief and to enable bone healing
17
Q
Rads vs surgery for cord compression/cauda equina
A
- Both rads and decompressive surgery are effective
- One study showed a significant advantage with a surgical approach in terms of functional status and survival
Consider referral to surgery followed by rads if:
- Good performance status
- No mets elsewhere
- Single level of cord compression
Also consider surgery in patients with extensive vertebral collapse with intrusion into the spinal canal, as these patients need surgical stabilization and radiation is unlikely to be of benefit
18
Q
Rads for cord compression/cauda equina
A
- Typically simple treatment with a single posterior field
- Most often 20-30 Gy in 5-10 fractions
19
Q
Prognostication in patients with cord compression
A
- Typically correlates with severity of deficits
- Most patients who have lost ambulation for >24hrs will not regain it
- 3/4 of patients retain the ability to walk if they begin treatment while ambulatory
- > 3/4 have pain relief
Myeloma and lymphoma respond the best to rads
20
Q
Rads for brain mets
A
- 10% of cancers spread to brain
- Isolated brain mets are unusual, typically patient has widespread metastatic disease
- If there is a solitary met, consider referral to surgery with post op rads
- In cases where performance status is very poor, rads is likely inappropriate
Options include:
- Radiosurgery (e.g. gamma knife/stereotactic rads)
- Whole brain rads (better for multiple cerebral mets)
Median survival after brain rads is less than 6 months, as typically it means there is widespread, advanced metastatic disease
