rx planning and post rx care of radiation therapy patient

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


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


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


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


Modalities available

The type of cancer

The size of the cancer

The cancer’s location in the body

Approximity to normal tissues


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


External beam radiation therapy

Internal beam radiation therapy

Systemic radiation therapy


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


Intensity modulated rt (IMRT)

Numerous tiny radiations – Collimators Allows change in intensity – Modulation Inverse treatment planning Greater dose in areas required


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


Stereotactic body rt (SBRT)

Cyberknife

Radiation in fewer sessions

Small radiation fields and higher doses


Tomotherapy

Type of IMRT

CT imaging scanner + external beam RT

Both imaging and treatment


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


Systemic radiation therapy

Swallows or receives an injection of radioactive

substance

Radioactive I, samarium, strontium, ibritumomab

tiuxetan


Dose

External beam radiation therapy – One dose

Minimizes damages to the normal tissues

Exposing cancer cells at right stage of cell cycle


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


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%

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


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)


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

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

rx planning and post rx care of radiation therapy patient

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