Post on 05-Apr-2018
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IAEAInternational Atomic Energy Agency
PREVENTION OF ACCIDENTALEXPOSURE IN RADIOTHERAPY
Part 4: Clinical consequences of accidentalexposures in radiotherapy
IAEA Training Course
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IAEA
Prevention of accidental exposure in radiotherapy 2
Overview / Objectives
• Module 4.1: Clinical consequences of accidentalexposures in radiotherapy
Objectives:
To provide basic knowledge of clinical consequencesfrom the major case histories and to outline the
clinical detection of radiotherapy accidents
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IAEAInternational Atomic Energy Agency
Module 4.1: Clinical consequences ofaccidental exposures in radiotherapy
IAEA Training Course
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IAEA
Prevention of accidental exposure in radiotherapy 4
Outline
• Therapeutic ratio
• Acute and late reactions
• Normal tissue tolerance and reaction scoring
• Accidental under- and over-exposure
• Clinical consequences• Organ specific
• Clinical detection of accidental exposure• Lessons & recommendations
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IAEA
Prevention of accidental exposure in radiotherapy 5
Therapeutic ratioin radical radiotherapy
• Radiation doses given for curative treatmentof cancers are at the limit of normal tissuetolerance.
• Late complications can be expected for acertain proportion of cure rate.
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IAEA
Prevention of accidental exposure in radiotherapy 6
0.0
0.2
0.4
0.6
0.8
1.0
0 20 40 60 80 100
Absorbed Dose (Gy)
Tissue response vs. absorbed dose
D1 = Low cures, no complications
D3 = High cures high complications
D2 = Moderate cures, minimal complications
Tumour control
Normal tissue damage
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IAEA Prevention of accidental exposure in radiotherapy 7
Therapeutic ratioin radical radiotherapy
• “Acceptable” complications depend on
• Rate of complications
• Organ concerned
• Severity of effect
• The risk level may differ between cliniciansand patients
• Usual acceptable level is 5%
• Lower levels are accepted for serious complicationse.g. spinal myelitis
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IAEA Prevention of accidental exposure in radiotherapy 8
Side-effects & complicationsof radiotherapy
• Radiation reactions are divided according totime scale
• Acute - < 6 months from exposure
• Sub-acute - 6 - 12 months post-exposure
• Late - > 12 months post-exposure
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IAEA Prevention of accidental exposure in radiotherapy 9
Acute reactions
• Acute reactions are a part of normal radiotherapy.
• Less important as they are usually minor and transient
• Usually observed in tissues with rapid cell turnover
(skin, mucosa, bone marrow …) • Due to decreased cell replacement
• Manifested according to normal tissue turn-over time
• Overexposure may increase the frequency andseverity (up to necrosis)
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IAEA Prevention of accidental exposure in radiotherapy 10
Acute reactions
• Determinant factors for acute reactions are:• 1) total delivered dose
• 2) total time of exposure
• 3) organ concerned
• 4) size of irradiated volume
• 5) concomitant drugs (chemotherapy) or disease, e.g. diabetes, previous surgery
• For a given dose, little correlation of early reactionswith fraction size unless fraction size is high
• For specified doses that are protracted, damage isreduced
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IAEA Prevention of accidental exposure in radiotherapy 11
Acute reactions
• Usually do not correlatewith late effects thereforerelatively high frequencyacceptable
• Except when reactions aresevere leading toconsequential latereactions
• Examples:• mucositis
• skin changes
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IAEA Prevention of accidental exposure in radiotherapy 12
Acute reactions - reporting
• Evaluation of radiation reactions are mostlysubjective
• To enhance uniformity, reactions are graded
• e.g. skin grade 2, mucosa grade 1• Commonly used scales include:
• NCIC
• RTOG• EORTC
• LENT-SOMA
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IAEA Prevention of accidental exposure in radiotherapy 13
Acute Morbidity Scoring SystemGrade [ 0 ] [ 1 ] [ 2 ] [ 3 ] [ 4 ]
UPPERG.I.
Nochange
Anorexia with<=5% weight
loss frompretreatmentbaseline/ nauseanot requiringantiemetics/ abdominaldiscomfort notrequiringparasympatholyti
c drugs oranalgesics
Anorexia with <=15%weight loss from
pretreatmentbaseline/nausea &/ orvomiting requiringantiemetics/ abdominalpain requiringanalgesics
Anorexia with >15% weightloss from pretreatment
baseline or requiring N-Gtube or parenteral support.Nausea &/or vomitingrequiring tube or parenteralsupport/abdominal pain,severe despitemedication/hematemesis ormelena/ abdominaldistention (flat plate
radiograph demonstratesdistended bowel loops
Ileus, subacute oracute obstruction,
performation, GIbleeding requiringtransfusion/abdominalpain requiring tubedecompression orbowel diversion
LOWERG.I. INCL.PELVIS
Nochange
Increasedfrequency orchange in qualityof bowel habitsnot requiring
medication/ rectal discomfortnot requiringanalgesics
Diarrhea requiringparasympatholyticdrugs (e.g., Lomotil)/ mucous discharge notnecessitating sanitary
pads/ rectal orabdominal painrequiring analgesics
Diarrhea requiringparenteral support/ severemucous or blood dischargenecessitating sanitarypags/abdominal distention
(flat plate radiographdemonstrates distendedbowel loops)
Acute or subacuteobstruction, fistula orperforation; GI bleedingrequiring transfusion;abdominal pain or
tenesmus requiringtube decompression orbowel diversion
Example for some tissues from the RTOGAcute Morbidity Scoring System
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IAEA Prevention of accidental exposure in radiotherapy 14
Reaction grading summary
Grade Symptoms Intervention Radiation
0 Nil Nil Cont.
1 Mild Nil Cont.
2 Moderate Medication Cont.
3 Severe Supportive ?Delay / Stop
4Life
threateningSupportive ++ Stop
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IAEA Prevention of accidental exposure in radiotherapy 15
Acute side effects - grades
Grade 1
Erythema
Grade 2
Drydesquamation
Grade 3Moist
desquamation
Grade 4Necrosis
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IAEA Prevention of accidental exposure in radiotherapy 16
Late reactions
• Manifest >12 monthsfrom exposure
• but may occur earlierif severe overdose
• Incidence increasesover time
Bladder and rectal complicationsfollowing radiotherapy for cervical cancer
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IAEA Prevention of accidental exposure in radiotherapy 17
Late reactions
• Mainly observed in tissues with slowly proliferating cells• complications are due to arteriolar / capillary narrowing which occur
over time• causes hypoxic damage
• Late complications can also manifest on rapidly
proliferating cells• in addition to and after acute effects
• They are irreversible and often slowly progressive• late reacting tissue are considered as dose-limiting for conventional
radiotherapy
• Late complications can also be consequential to severeacute reactions• they are slowly progressive, and potentially possible to delay using
vascular modifiers
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IAEA Prevention of accidental exposure in radiotherapy 18
Late reactions
• Determinant factors:• total delivered dose
• fraction size and dose rate
• In the case of accidental exposure, the increasedfraction size may amplify the effects (this was thecase in some accidents)
• Late responding tissue are more sensitive toincreases in fraction size than are early reacting
tissues (low α / β ratio)
• organ concerned• e.g. nervous system, lung, rectum, bladder
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IAEA Prevention of accidental exposure in radiotherapy 19
Late reactions
• In serial organs (spinal cord,intestine, large arteries), alesion of a small volumeirradiated above threshold
may cause major incapacity,for example paralysis
• In organs arranged in parallel,such as lung and liver,
severity is related to theirradiated tissue volumeabove threshold
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IAEA Prevention of accidental exposure in radiotherapy 20
Late reactions
• Complications aremore severe and areirreversible
• Example: radiationmyelitis
• Measured as risk,therefore not inevitable
• Expected only in very lowfrequency
• Given as % per 5 years
Necrosis
Ulcer
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IAEA Prevention of accidental exposure in radiotherapy 21
Radiation tolerance doses (cGy)
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IAEA Prevention of accidental exposure in radiotherapy 22
Late Radiation Morbidity Scoring
ORGANTISSUE
Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade5
SPINALCORD
None Mild L'Hermitte'ssyndrome
Severe L'Hermitte's syndrome Objective neurological findings ator below cord level treated
Mono, para quadraplegia
BRAIN None Mild headacheSlight lethargy
Moderate headache Great lethargy Severe headaches Severe CNSdysfunction (partial loss of poweror dyskinesia)
Seizures or paralysis Coma
LARYNX None HoarsenessSlight arytenoidedema
Moderate arytenoid edema Chondritis Severe edema Severe chondritis Necrosis
LUNG None Asymptomatic ormild symptoms(dry cough)Slight
radiographicappearances
Moderate symptomatic fibrosis orpneumonitis (severe cough) Low gradefever Patchy radiographic appearances
Severe symptomatic fibrosis orpneumonitis Dense radiographicchanges
Severe respiratoryinsufficiency/ Continuous O2/ Assisted ventilation
SMALL &LARGEINTESTINE
None Mild diarrheaMild crampingBowelmovement 5times daily Slightrectal dischargeor bleeding
Moderate diarrhea and colic Bowelmovement >5 times daily Excessiverectal mucus or intermittent bleeding
Obstruction or bleeding requiringsurgery
Necrosis/ Perforation Fistula
LIVER None Mild lassitudeNausea,dyspepsiaSlightlyabnormal liverfunction
Moderate symptoms Some abnormalliver function tests Serum albuminnormal
Disabling hepatitic insufficiencyLiver function tests grosslyabnormal Low albumin Edema orascites
Necrosis/ Hepatic coma orencephalopathy
BLADDER None Slight epithelialatrophy Minortelangiectasia(microscopichematuria)
Moderate frequency Generalizedtelangiectasia Intermittent macroscopichematuria
Severe frequency and dysuriaSevere generalized telangiectasia(often with petechiae) Frequenthematuria Reduction in bladdercapacity (<150 cc)
Necrosis/ Contracted bladder(capacity <100 cc) Severehemorrhagic cystitis
Deathdirectlyrelatedtoradiationeffects
Example for some tissues from the RTOGLate Morbidity Scoring System
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IAEA Prevention of accidental exposure in radiotherapy 23
Accidental medical exposure
• Under-exposure
• Over-exposure
• Total dose
• Dose per fraction
• Site / area of exposure
• Normal tissue tolerance
• Normal tissue irradiation
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IAEA Prevention of accidental exposure in radiotherapy 24
Consequences of accidental exposure
• Reduced tumour control rate
• Acute complications
• Late complications
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IAEA Prevention of accidental exposure in radiotherapy 25
Accidental medical exposure
• Accidental exposure may be• Random (one-off)
• Minimize by double-checking and independentcalculations
• Under-exposure can be compensated by, e.g. accelerated treatment
• Over-exposure may cause increased reaction andalso compromised tumour control
• Systematic• Due to failure of system, e.g. calibration, calculation,
TPS, etc.
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IAEA Prevention of accidental exposure in radiotherapy 26
Random accidental exposure
• Involves one or a few patients only
• Examples
• Wrong calculation
• Wedge not inserted
• Wedge factor calculation
• Source displacement
• Movement after insertion
• Wrong source strength
• Higher activity than ordered
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IAEA Prevention of accidental exposure in radiotherapy 27
Systematic accidental exposure
• This is due to failing in the system ofplanning and delivery of radiation therapy
• Includes• Calibration of machine or source
• TPS related
• Systematic manual miscalculation
• More serious than random event as itpotentially affects all patients in a timeperiod
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IAEA Prevention of accidental exposure in radiotherapy 28
Systematic under-exposure
• Accidental under dosage effects are difficultto detect clinically through reduced sideeffects and may only manifest as poor
tumour control.• May only be apparent years later after audit or
not detected due to change in treatment
patterns• This may involve large number of patients
Case 1: Incomplete understanding
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IAEA Prevention of accidental exposure in radiotherapy 29
Case 1: Incomplete understandingand testing of a TPS (UK 1982 – 90)
• SSD correction for distance were usually done bythe technologist
• When a new TPS was acquired, same correctioncontinued• however the TPS already corrected for distance
• Therefore double distance correction was donecausing under dosage of up to 30%
• The problem not discovered for 8 years,1045patients affected
• 492 patients developed local recurrence
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IAEA Prevention of accidental exposure in radiotherapy 30
TCP vs. absorbed dose
Data from Hanks et al 2002
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IAEA Prevention of accidental exposure in radiotherapy 31
Accidental medical over-exposure
• Over-exposure may be
• Localized
• Related to treatment by EBRT or brachytherapy
• Whole body
• Accidental non-medical exposure, e.g. industrialexposure or public exposure
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IAEA Prevention of accidental exposure in radiotherapy 32
Localized over-exposure
• Depends on treatment area
• Organ specific but skin usually involved
• Radiation modality
• Photon
• Deeper tissues involved
• Electrons
• Superficial tissues
• Brachytherapy
• Local tissues
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IAEA Prevention of accidental exposure in radiotherapy 33
Accidental systematic over-exposure
• Wrong calibration of source
• Use of incorrect decay curve for 60Co, USA 1974 –1976
• 22 months of no beam measurement• Reuse of outdated computer file for 60Co
treatment, USA, 1987 –1989
• Beam miscalculation of
60
Co, Costa Rica,1996• During beam calibration reading of the timer wasconfused, leading to underestimation of the dose rate
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IAEA Prevention of accidental exposure in radiotherapy 34
Accidental systematic over-exposure
• TPS related• Untested change of procedure for data entry into
TPS, Panama, 2000• Calculated treatment time double the normal value
leading to 100% overdose
• Change in practice - use of trimmer bars(computer file not updated, USA, 1987-1988• Patients received 75% higher dose
• Accelerator software problem, USA andCanada,1985-1987
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IAEA Prevention of accidental exposure in radiotherapy 35
Accidental systematic over-exposure
• Machine related
• Incorrect accelerator repair andcommunication problems, Spain, 1990
• Electron energy was misadjusted• Dose monitoring system
• Białystok incident Poland
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IAEA Prevention of accidental exposure in radiotherapy 36
Types of overdose
• According to AAPM-Tg35
• Type A > 25% overdose
• Dose range may put patient in LD 50 / 5 range, i.e. 50%risk of death in 5 years
• Type B 5-25% overdose and mostunderdosage
• Not life threatening
• Increased risk of complications or reduced tumourcontrol
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IAEA Prevention of accidental exposure in radiotherapy 37
Clinical consequences of over-exposure
• Severe over-exposure (off the chart)• Early manifestation of symptoms
• Skin erythema, nausea & vomiting, diarrhea
• Often leads to death
• USA 1974 –1976 300 of 450 died within 1 year
• Panama 2000 8* of 28 died
• USA / Canada 1985 –1987 3 of 6 died
• USA source left in patient 1 of 1 died
• Survivors usually have chronic organ related symptomse.g. diarrhea, bleeding, etc.
• 88% of survivors in USA had severe complications
*5 patients - radiation related
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IAEA Prevention of accidental exposure in radiotherapy 38
Radiation tolerance doses (cGy)
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IAEA Prevention of accidental exposure in radiotherapy 39
Clinical consequences of over-exposure
• Skin (Białystok)
• Erythema usually develops after 1 week
• Erythema after few hours
• Moist desquamation (usually does not occur)• Moist desquamation after few weeks
• Ulceration
• 5 of 5 patients• Late effects include fibrosis
M i d i
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IAEA Prevention of accidental exposure in radiotherapy 40
Moist desquamation
Ul i
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IAEA Prevention of accidental exposure in radiotherapy 41
Ulceration
N i
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IAEA Prevention of accidental exposure in radiotherapy 42
Necrosis
Cli i l f
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IAEA Prevention of accidental exposure in radiotherapy 43
Clinical consequences of over-exposure
• Gastro-intestinal (Panama)• Mild diarrhea (grade 1 – 2) usual
• Severe diarrhea (G3) or necrosis (G4) in at least 20 of 28patients
• 8* patients died
• Symptoms usually resolve by 1 month post radiation
• Chronic symptoms about 100 – 230 days
• Long term
• Bowel stenosis, malabsorbtion, chronic diarrhea & dysentry
* 5 patients - radiation related
B l l ti
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IAEA Prevention of accidental exposure in radiotherapy 44
Bowel ulceration
B l i
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IAEA Prevention of accidental exposure in radiotherapy 45
Bowel necrosis
Necrosis
Hemorrhagic rectal mucosa:
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IAEA Prevention of accidental exposure in radiotherapy 46
Hemorrhagic rectal mucosa:two days before death
St i & b t ti
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IAEA Prevention of accidental exposure in radiotherapy 47
Stenosis & obstruction
R t l d
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IAEA Prevention of accidental exposure in radiotherapy 48
Rectal over-dosage
Cli i l f
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IAEA Prevention of accidental exposure in radiotherapy 49
Clinical consequences of over-exposure
• Nervous system (brain)• Tolerance dose is 50 Gy
• Younger patients with developing brain are at higher
risk• Cerebral atrophy, leucoencephalopathy,
calcification
• Reduced IQ & dementia
• Spasticity
• Necrosis
Leucoencephalopathy
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IAEA Prevention of accidental exposure in radiotherapy 50
Leucoencephalopathy
Beam miscalibration of 60Co
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IAEA Prevention of accidental exposure in radiotherapy 51
Beam miscalibration of 60Co
• Whole brain radiation• 8 Gy in 4 fractions
• 50 Gy in 16 fractions
• Dose equivalent• 69.25 Gy (72 Gy)
• Child affected byoverdoses to brain andspinal cord, and the childlost his ability to speak andwalk
Clinical consequences of over exposure
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IAEA Prevention of accidental exposure in radiotherapy 52
Clinical consequences of over-exposure
• Nervous system (spinal cord)• Tolerance dose is 45 Gy (1-5% risk)
• Serially arranged therefore damage will manifest at
all lower levels• Acute myelitis occurs 2-4 months post-radiation
• Delayed myelopathy occurs at mean of 20months
Patient 80 Undifferentiated Ca Pharynx
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Patient 80 – Undifferentiated Ca Pharynx
Spinal cord myelopathy
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Spinal cord myelopathy
• Young woman whobecame quadriplegicas a result of
accidentaloverexposure to thespinal cord
• Dose
• 51.7 Gy in 16 #= 64.4 Gy (67.6 Gy)
Clinical consequences of over exposure
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Clinical consequences of over-exposure
• Lung• Pneumonitis
• Sub-acute reaction
• Dry cough, dyspnea,
fever• Prolonged course of high
dose steroids required
• 5% risk at 20 Gy
• 50% risk at 30 Gy
• Fibrosis as latecomplication
Other organs
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Pleural Effusion Pericardial Effusion
Other organs
Other risks
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Other risks
• Heart
• Ischaemic heart disease
• Bladder
• Bleeding, frequency
• Bone
• Fractures, necrosis
• Alopecia
• Non-specific life shortening& pain
Osteo-radionecrosis
Subcutaneousfibrosis
Clinical detection of over exposure
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Clinical detection of over-exposure
• Careful clinical follow up may detect accidentaloverdose through early enhanced reactions
• This may be easier in uniform patient population
• Experienced radiation oncologists may be able todetect clinically, during regular weeklyconsultation, dose variations of 10%
• In practice this is difficult due to varying radio-sensitivity
between patients• Some overdoses may cause late severe effects
without abnormal early effects
Clinical detection of over exposure
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• In case of unusual reactions of a singlepatient, other patients treated in the sameperiod may need to be recalled
• Re-check all treatment parameters• Check concomitant medications
• Check concomitant therapies
Clinical detection of over-exposure
Evaluation of accidental exposure
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Evaluation of accidental exposure
• Determine if emergency or non-emergency• Look for early prodromal symptoms
• Skin may be a clue to radiation injury
• Appear similar to thermal injury but patient hasno recollection of injury
• Associated with intractable pain
Guide for the management of radiation
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ginjuries based on early symptoms
Clinical signs Corresponding dose(Gy)
Decisions
WBE LE WBE LE
No vomiting No early erythema <1 <10 Outpatient with five weeksurveillance period (blood, skin)
Vomiting 2-3 hafter exposure
Early erythema orabnormal
sensation 12-24 hafter exposure
1-2 8-15 Surveillance in a general hospital(or outpatient for 3 weeks
followed by hospitalization ifnecessary)
Vomiting 1-2 hafter exposure
Early erythema orabnormalsensation 8-15 hafter exposure
2-4 15-30 Hospitalization in anhaematological or surgical(burns) department
Vomiting earlier
than 1 h afterexposure and/orother severesymptoms e.g. hypotension
Early erythema
within the first 3-6h (or less) afterexposure of skinand/or mucosawith oedema
>4 >30 Hospitalization in a well equipped
haematological or surgicaldepartment with transfer to aspecialized centre forradiopathology
Skin injury
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Skin injury
Evaluation of radiation exposure
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Evaluation of radiation exposure
• Determine type of exposure• Whole body
• Local
• Inhaled / ingested
• Determine site, exposure dose and number offractions
• Calculate dose equivalent for organ in terms of
Biological Equivalent Dose (BED) and 2 Gy equivalent• Estimate risk of complications according to organ(s)
concerned
Treatment of injuries
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Treatment of injuries
• Acute phase• Symptomatic
• Pain relief, antibiotics
• Vasodilators, anti-platelets
• Chronic phase
• Symptomatic
• Pain relief,
• Rehabilitation
• Surgical
• Debridement
• Grafts
Healing of radiation injuries
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Healing of radiation injuries
• Depends on extent ofdamage
• Healing by secondaryintention
• Slow process
• Takes months
• Results in scarring
• Results in functionalloss
• Skin, small bowel, etc.
June2001
Dec2001
Progression of late injury
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Progression of late injury
• Injuries may worsendue to
• Increasing vascularcompromise
• Infection
• Concomitant disease,e.g. diabetes
• Early surgicalintervention indicated iftumour controlled
June2001
May2002
Surgery for radiation necrosis
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Surgery for radiation necrosis
Omentum flap
Skin graft
Lessons learned
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Lessons learned
• Working with Awareness and Alertness• Maintain awareness for unusual and complex treatments
• Procedures
• Use comprehensive acceptance, commissioning, qualitycontrol and documentation
• Training and Understanding
• Responsibilities
• Functions and responsibilities should be allocated
Recommendations for prevention
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Recommendations for prevention
• A quality assurance program, involving:• Organization
• Education and training
• Acceptance testing and commissioning• Follow up of equipment faults
• COMMUNICATION
• Patients’ identification and charts
Summary
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Summary
• Accidental exposure can be catastrophic and affectmany patients• Effects are often irreversible, progressive and increasing
in frequency• Careful clinical follow-up may detect overdoses of 10%
or more• Underdosage is more difficult to detect clinically
and may affect long term cures• A Quality Assurance program is a key element in
prevention of accidental exposures.• Good communication and lines of responsibility are
essential
References
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References
• IAEA publications
• Accidental Overexposure of Radiotherapy Patients in Bialystok(2004)
• Investigation of An Accidental Radiation Exposure of RadiotherapyPatients in Panama (2001)
• Accidental Overexposure of Radiotherapy Patients in San José(1998)
• Safety Report Series No.2• Nuclear Radiation Commission USA reports
• Principles and practice of radiation oncology, Brady & Perez, 4thedition, Lippincott Williams
• Radiobiology for radiologists, E.J. Hall, 5th Edition, Lippincott (2003)
• Hanks G E et al . Dose response in prostate cancer with 8-12 yearsfollow-up, IJROBP 54: 427-435 (2002)
• AAPM report 56. Medical accelerator safety considerations. Report ofAAPM Task Group 35
• TecDoc no 88.