rx planning and post rx care of radiation therapy patient
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RADIATION THERAPY : TREATMENT PLANNING AND
POST TREATMENT CARE
Vinay Pavan Kumar K2nd year PG student
AECS Maaruti College of Dental Sciences
Radiation therapy
Introduction
History
General factors
Treatment modalities
Dose Dental
management
Implants in irradiated
bone
Rationale
Early dental intervention is most important factor
to prevent possibility of infection during Rx
Frequently, the patients are elderly, have poor oral
hygiene, low economic status, receive limited
dental care
Patient should be explained about the short term
and long term side effects of the treatment
The use of high energy radiations from X-rays,
gamma rays, neutrons and other sources to kill
cancer cells and shrink the tumor
Era of discovery (1895 - 1920s) Roots of RT were established
Atom and various electromagnetic particles, their
therapeutic use
Lack of knowledge of the biological effects
As the era progressed, biologists began to
understand the relationship between time and dose
Slater J.M, From X-rays to Ion beams: A short history of radiation therapy, Biological and Medical Physics, pp:3-18
Regaud demonstrated that fractionated therapy;
Coutard – External beam radiation therapy
Coolidge developed a practical X-ray tube, to
deliver higher-energy X-rays (180–200 KV) to
deeper tumors
Rutherford, 1919, the structure of atom
Two major divisions of radiation medicine –
diagnosis and therapySlater J.M, From X-rays to Ion beams:A short history of radiation therapy, Biological and Medical Physics, pp:3-18
Orthovoltage era (1920 – 1950s)
Treatment of deep tumors - Radium-based
intracavitary and interstitial irradiation
A transitional period : Physical developments that
led to supervoltage (approx. 500 KV–2MV) RT
were being made
Slater J.M, From X-rays to Ion beams:A short history of radiation therapy, Biological and Medical Physics, pp:3-18
The first supervoltage X-ray tubes, built by
Coolidge were the basis of the linear accelerator
Electron beam therapy became a practical and
useful therapeutic option in 1940, when Kerst
developed the betatron. The first machine
produced 2 MeV electrons; later devices yielded
up to 300 MeV
Slater J.M, From X-rays to Ion beams:A short history of radiation therapy, Biological and Medical Physics, pp:3-18
Megavoltage era (1950 – 1985) Tumors located in deep tissues - the development
of cobalt teletherapy machines and megavoltage
linear electron accelerators
Cobalt teletherapy was capable of producing
beams equivalent to approximately 1.3 MeV X-rays
During this era, radiation medicine advanced as a
discipline
Slater J.M, From X-rays to Ion beams:A short history of radiation therapy, Biological and Medical Physics, pp:3-18
Era of intensity modulated X-ray therapy ( 1970s)
Background started in 1946, with Wilson claiming
the use of protons in medical treatments
Wilson reasoned that protons, among the charged
particles, offered the longest range for a given
energy and were the simplest and most practical
for medical use
Slater J.M, From X-rays to Ion beams:A short history of radiation therapy, Biological and Medical Physics, pp:3-18
Kelly J A, Beumer J, Dental management of irradiated patients, ppt
Physical principles
Absorption of radiation by tissues
Biologic effects
Dosimetry
Radiation curves
GENERAL FACTORS
Physical principles
Electromagnetic waves
Photons
Particulate Radiations
Electron, proton, neutrons
Absorption of radiation by tissues
Electromagnetic waves
Photoelectric effect
Compton effect
Pair production
Particulate radiations
Biologic effects
DNA – Confined to
intranuclear damage –
most cell deaths
Water – Abundant
compared to DNA
Anoxia – 3x resistant to radiation
Cell cycle – Asynchronous
Radiation – Series v/s fractioned dose
Reoxygenation
Redistribution
Repopulate
Repair
Dosimetry
Amount of energy absorbed by the tissues
subjected to radiation
(rads = 100ergs/gm)
Radiation curves
Isodose curves – Electromagnetic waves
Particulate radiations
Single beam
Multiple beam
Single beam curve (photons) – Dose decreases from surface to depth Low energy X-rays – Surface receives highest dose High energy X-rays – ‘Skin-sparing’ effect
Single beam curves (particulate radiations)
Homogeneous from surface to depth depending
on the energy of beam
Treatment planning Simulation
Maintain same position
Body molds, face masks, tattoos
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
After simulation, the exact area that will be
treated, the total radiation dose, dose allowed for
the normal tissues, and the safest angles (paths)
for radiation delivery
150-200 cGy / fraction
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Modalities available
The type of cancer
The size of the cancer
The cancer’s location in the body
Approximity to normal tissues
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
How far into the body the radiation needs to travel
The patient’s general health and medical history
Whether the patient will have other types of
cancer treatment
Other factors, such as the patient’s age and other
medical conditions
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
External beam radiation therapy
Internal beam radiation therapy
Systemic radiation therapy
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
External beam radiation therapy
Coutard
3D conformal RT (3D-CRT)
Delivered using Linear Accelerator (LINAC)
Sophisticated computer software and advanced
treatment machines to deliver radiation precisely
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Intensity modulated rt (IMRT)
Numerous tiny radiations – Collimators Allows change in intensity – Modulation Inverse treatment planning Greater dose in areas required
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Image guided rt (IGRT)
Repeated imaging scans
Current condition of the patient
Accurate radiation treatment, allows reductions in
the planned volume of tissue to be treated
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Stereotactic body rt (SBRT)
Cyberknife
Radiation in fewer sessions
Small radiation fields and higher doses
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Tomotherapy
Type of IMRT
CT imaging scanner + external beam RT
Both imaging and treatment
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Internal radiation therapy
Brachytherapy Radiation source placed in or on the body
Interstitial – Within the tumor Intracavitatory – Within surgical or body cavity Episcleral – Melanoma (eye)
Permanent – Low dose treatment Temporary – Low or high dose treatment
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Systemic radiation therapy
Swallows or receives an injection of radioactive
substance
Radioactive I, samarium, strontium, ibritumomab
tiuxetan
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Dose
External beam radiation therapy – One dose
Minimizes damages to the normal tissues
Exposing cancer cells at right stage of cell cycle
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Regaud – Fractionated therapy
Accelerated fractionation – Large daily or weekly
dose
Hyperfractionation – Smaller fraction more than once
a day
Hypofractionation – larger dose once a day or less
often
www.cancer.gov, National Cancer Institute, Radiation therapy for cancer
Kelly J A, Beumer J, Dental management of irradiated patients, ppt
Dental management
o Dental examination before radiation therapy and
treatment plan
o Dental management during radiation therapy
o Dental management following radiation therapy
Before radiation therapy
Dental extractions
Minor surgical procedures
Pre – radiation prosthodontic care
Criteria for pre – radiation extraction
Dental awareness of the patient
Condition of the residual dentition
Urgency of treatment
Mode of therapy
Radiation fields
Mandible vs Maxilla
Prognosis for tumour control
To ensure best results following extraction prior to radiation therapy -
Radical alveolectomy to ensure primary closure
Teeth should be removed in segments
Antibiotics should be administered during the
healing period
Risk of bone necrosis due to dental extractions
prior to radiation therapy was 12.7%
Kelly J A, Beumer J, Dental management of irradiated patients, ppt
Pre radiation prosthodontic care
Dentures
Avoid relining ill fitting dentures
Avoid soft temporary reline
Advised not to wear denture
Metallic crowns or fixed partial denture
Custom made soft plastic stent
o Mucositiso Xerostomiao Change in oral microflorao Loss of tasteo Increased sensitivity to spicy food
RADIATION EFFECTS OF ORAL CAVITY
Short term effects
Long-term effects
o Reduced bone healing – Osteoradionecrosis
o Permanent loss of salivary function
o Increased potential for dental caries
o Increased susceptibility to infections – Candidiasis
o Trismus
During radiation therapy
Mucositis
Earliest
2-3 week and subsides within 8-10 week
Slight erythema-desquamation-frank
ulceration, pain and dsyphagia, weight loss
Severe cases may require stopping the
therapy
Maintaining good oral hygiene, frequent brushing
Oral mouth rinses - Combination of salt and sodium
bicarbonates in water or dilute hydrogen peroxide
Loss of taste Radiation to tongue and palate (5000 cGy) 1-2 week and returns to normal once treatment is
completed Damage to taste buds and microvili, disrupted
innervation, lack of saliva
Xerostomia and dental caries 60 rads Decrease in salivary flow rates, increase in
acidogenic bacteria Prevention by daily use of topical fluoride
Stannous and Sodium fluoride
Saliva substitutes and sialogogues Most persistent morbidity is dry mouth 1 week and worsens with time Sialogogues are used to stimulate salivary flow Salivary substitutes
Trismus and fibrosis Shortly after radiation begins May worsen by surgery prior to radiation Primary treatment - excercising by using tongue
blades, or bite openers
positioning and sheilding stents
Positioning stents
Maintaining position of structures to be treated
Removing structures from the radiation field
Positioning peroral cones
Positioning dosimetric devices
Recontouring tissues to simplify dosimetry
Positioning radioactive source
Shielding stents
Only used with electron beam therapy
After radiation therapy
Mucositis and loss of taste Subsides gradually Heavy smokers or drinkers may experience longer
delay in healing Continue mouth rinses
Xerostomia and dental caries Salivary loss is permanent Long term salivary substitutes and sailogogues Fluoride application for tooth Maintainence of oral hygiene
Candidiasis
Mainly because of xerostomia
Trismus and fibrosis
Increase in severity with time
Only way to benefit is by regular exercising
Post radiation extractions
Greater risks of bone necrosis as high as 100%
has been reported
Periodontally compromised and mobile tooth can
be extracted with minimal risk
Localized periapical infection can be managed
conservatively with anbibiotics avoiding the need
for removal
Osteoradionecrosis
Regaud,1922
“when bone in the radiation field was exposed for atleast 2 months in the absence of local neoplastic disease” - Beumer
“an area greater than 1 cm of exposed bone in a field of irradiation that had failed to show any evidence of healing for atleast 6 months” - Marx
The reported incidence of ORN of the mandible
varies widely, ranging from 2-39 per cent
Trauma, exposure of radiated bone, infection
Hypovascular, hypocellular and hypoxic
conditions of the bone
Type of radiation treatment, dosage, tissue
volume
ORN
Stage I
30 Dive of HBO
Healing Non
responder
10 Dive of HBO
Stage II
Non responder
Stage III
Local surgical debridement
Wound dehiscence
Nonresponder to stage II
Healing 10 Dive of
HBO
Total of 30 Dive of HBO
Surgical resection
10 Dive of HBO
Patient pain free
Reconstruction surgery
Stage IIIR
Staging of ORN
Three types of ORN –
Type 1 –
Radiation therapy within 21 days of tooth extraction
Type 2 –
Induced by trauma
It generally occurs 3-6 months after radiation therapy
Type 3 –
Spontaneously 6 months to 2 years after radiation therapy
Associated with higher radiation doses, brachytherapy
(Cronje, 1998)Hyperbaric oxygen therapy for prophylactic treatment after head and neck radiation to prevent osteoradionecrosis of the mandible, Group health - A clinical review
Radiation
Irreversible cell damage
Tissue breakdown
Hypocellularity
Osteoblasts death – direct RT damage
ORN
Vascular damage
Endarteritis obliterans
Thrombosis of vessels
Gradual ischemia
Damage to bone tissue
Loss of reparative
and synthetic function
Lyons A, Ghazali N, Osteoradionecrosis of the jaws:Current understanding of its pathophysiology and treatment, Brit J Oral Maxillofac Surg, 2008;46:653-660
Treatment modalities
Conservative measures
Hyperbaric oxygen (HBO)
PENTO or PENTOCLO
Surgical
Kelly J A, Beumer J, Dental management of irradiated patients, ppt
The HBO treatment –
20 sessions each at 2.4 ATA for 90 minutes,
followed by a 30 minute ascent back to one ATA.
This is known technically as a 14/90/30 cycle
Followed by surgery and then 10 further 14/90/30
sessions
Vudiniabola S et al, Hyperbaric oxygen in the prevention of osteoradionecrosis of the jaw, Aust Dent J, 1999;44(4):243-247
Increases diffusion distance of oxygen in tissue of
the compromised vascular beds
Improves the wound environment, resists infection,
and enhances wound repair
Lin YC et al, Scientific rationale of hyperbaric oxygen therapy for osteoradionecrosis of the jaw, Clin Dent J, 2005;24(1):1-14
Lin YC et al, Scientific rationale of hyperbaric oxygen therapy for osteoradionecrosis of the jaw, Clin Dent J, 2005;24(1):1-14
Enhance the killing ability of leucocytes to
stimulate fibroblast growth
Increase collagen formation - promotes
growth of capillaries
Toxic to aerobic and anaerobic bacteria, and
inhibits bacterial toxin formation
Vudiniabola S et al, Hyperbaric oxygen in the prevention of osteoradionecrosis of the jaw, Aust Dent J, 1999;44(4):243-247
PENTO
PENtoxifylline – Improves peripheral vasculature
400 mg b.i.d
TOchopherol (Vit.E) – Anticoagulant, scavangers
1000 IU (600 and 400 IU)
Kelly J A, Beumer J, Dental management of irradiated patients, ppt
Post radiation prosthodontic care
Often candidates for new dentures
To prevent trauma due to dentures – 6 months
Social status
Conventional techniques to be followed
Border extension should be carefully evaluated
Implants in irradiated bone
Systematic review and meta-analysis was done to
evaluate the failure rate of dental implants placed in
irradiated bone between 6 and 12 months and after 12
months from the cessation of radiotherapy
Placement of dental implants between 6 and 12
months post radiotherapy was associated with a 34%
higher risk of failure
Placing implants in bone within a period shorter than
12 months after radiotherapy may result in a higher
risk of failureClaudy M P et al, Time interval after radiotherapy and dental implant failure:Systematic review
of observational studies and meta analysis, Clin Imp Dent Rel Res, 2013:1-10
Kelly J A, Beumer J, Dental management of irradiated patients, ppt
conclusion
Referenceso Taylor T D , Clinical Maxillofacial Prosthetics, 1st
edition, 2000, Quintessence publications, Illionis, pp 37 – 52
o Beumer J, Curtis TA, Firtell D N, Maxillofacial Rehabilitation : Prosthodontic and Surgical Considerations, 3rd edition, 1996, Mosby, St. Louis, pp 23-78
o Slater J.M, From X-rays to Ion beams:A short history of radiation therapy, Biological and Medical Physics, pp:3-18
o www.cancer.gov, National Cancer Institute, Radiation
therapy for cancer
o Marx R E, A New Concept in the Treatment of
Osteoradionecrosis, J Oral Maxillofac Surg, 1983;
41:351-35
o Lyons A, Ghazali N, Osteoradionecrosis of the
jaws:Current understanding of its pathophysiology and
treatment, Brit J Oral Maxillofac Surg, 2008;46:653-
660
o Kelly J A, Beumer J, Dental management of irradiated
patients, ppt
Hyperbaric oxygen therapy for prophylactic
treatment after head and neck radiation to prevent
osteoradionecrosis of the mandible, Group health -
A clinical review
Vudiniabola S et al, Hyperbaric oxygen in the
prevention of osteoradionecrosis of the jaw, Aust
Dent J, 1999;44(4):243-247
Lin YC et al, Scientific rationale of hyperbaric
oxygen therapy for osteoradionecrosis of the jaw,
Clin Dent J, 2005;24(1):1-14
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