Radiotherapy /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


INTRODUCTION
With discovery of X-rays in 1895 by Wilhelm
Rontgen, much advancement has taken place
in the field of radiology.
Radiation oncology is a medical specialty that
utilizes ionizing radiation to treat many
different types of malignancies.
Oral cancer – 3.5% of all malignancies.

For more early stage of oral cancer radiation
therapy and surgery are effective.
For intermediate stage radiation therapy used
as an adjuvant role to surgery.
For advanced tumors radiation therapy is
extensively used.
The success of radiation therapy as a treatment
modality depends on differences in repair
capabilities between normal & malignant cells.

OBJECTIVE OF TREATMENT
The choice of treatment depends on
Cell type
Degree of differentiation
Location of primary lesion
Site and size
General condition of patient


Patients age
Lymph node status
Bone involvement
Preservation of functions
Physical and mental status of patients
Complications

MECHANISM OF RADIOTHERAPY
Radiation kills cells by interaction with water
molecules in cells, producing charged molecules
that interact with bio-chemical process in the
cells
•

DNA is damaged

•

Chromosomal damage

•

Incapable of cell division

Radiotherapy deals with use of ionizing
radiation

in

treatment

of

malignant

neoplasm.
Ionizing radiation
Photons (X-rays and Gamma-rays)
Particulate Radiation (Electron, Protons,
Neutrons, Alpha and Beta)

BIOLOGICAL EFFECT OF
RADIATION
Depends
On dose per fraction
The number of fractions per day
Total treatment time
Total dose of radiation


ROLE OF RADIOTHERAPY IN
CANCER
Combined
Adjuvant
Alone
Pallative


INDICATIONS OF RADIOTHERAPY
Posterior 1/3 of tongue
Oropharynx
Tonsillar pillar
Exophytic lesions
Well differentiated carcinomas

ADVANTAGES
Extensive lesions.
Treating the disease in-situ.
Avoid the surgical removal of tissue.
To operate in accessible site.
Choice of treatment for T1 and T2 tumors.
Lymph node metastases.
To eradicate well oxygenated tumor cells at the
periphery.


DISADVANTAGE
Radio resistant tumors
Treatment of hypoxic cells
Complications of radiotherapy


PRINCIPAL OF RADIATION
To deliver a precise dose of radiation to a
definite tumor volume with minimal damage.
The goal of radiotherapy is sterilized is tumor
and avoid causing un-acceptable degree of
toxicity to the surrounding normal tissue.


The first dose of radiation kills cells that are
well oxygenated and in sensitive phases of cell
cycle.
Palliation and prevention of symptoms of
disease.
Absorption of x-ray in the medium is an
important factor for radiation therapy
Gy).

(Dose :

Before the delivery of next dos of radiation sublethal damage repair can occur in both the tumor
and normal tissues.

Because a substantial

number of cells within the tumor have been
killed by the first dose of radiation, there is less
competition for the available oxygen, and some
of the hypoxic tumor cells can re-oxygenate and
become more radiosensitive.

Radiotherapy works in most cases not because
the tumors are more radiosensitive than the
normal tissues, but rather because normal tissues
are better at repair and repopulation within the
context

of

clinically

utilized

fractionation

schemes.
Cells tend to be more radiosensitive in mitosis
and late G1 - early S phase than in early G1 and
G2 phases. So, radiation perferentially kills cells
in the more sensitive phase of cell cycle.

FRACTIONATION SCHEMES
Early or acute responding tissues - skin and
pharyngeal mucosa.
Late responding tissue - spinal cord.
The early responding tissues limit both the size
of dose fraction and the degree to which time
course of radiation can be compressed.

The late responding tissues limits total radiation
dose, so giving smaller dose per fraction allows
higher total dose to be given.
This is the basic rationale for giving multiple
smaller fractions of radiation per day instead of
single daily dose.
The require of minimum time is approximately 6
hours for normal tissue to repair.

HYPER FRACTIONATION
Reduce the size of individual radiation fractions
in an attempt to reduce normal tissues late effect
and to allow a higher total dose of radiation.
ACCELERATED FRACTIONATION
Same dose delivered rapidly to treat the rapidly
proliferating tumors.

CONTINUOUS HYPER FRACTIONATION
RADIOTHERAPY (CHART)
Extreme accelerated schedules
Consists of giving three daily radiation
treatments of 1.5Gy each to a total dose of
54Gy without giving any weekend breaks.


CANCER STAGING
• Commonly used staging UICC-TNM
• T – Size of tumor
• N – Lymph node spread
• M – Metastasized to other organs of body
•

T1 - <2cms

N1 – Ipsilateral single <3cms

•

T2 - >2 to 4cms

N2 – a. Ipsilateral single >3 to 6cms

•

T3 - >4cms

b. Ipsilateral multiple <6cms

•

T4 – Adjacent structures.

c. Bilateral, Contralateral <6cms
N3 - >6cms


TOLERANCE LIMITS
Tongue / Lips : High tolerance (70 to 80 Gy)
Floor of the mouth : Intermediate Tolerance
Alveolar ridges / Mandible: Lowest Tolerance
T1 & T2 tumors : 65 to 70 Gy in 7 Weeks
T3 & T4 tumors : 75 to 80 Gy
Tongue alveolus : 45 to 50 Gy.
N2 & N3 nodes : Radiation followed by surgery

TREATMENT PLANNING
The radiation treatment plan is determined by
tumor site and size, the total volume to be
radiated, the number of treatment fractions, total
number of days of treatment, tolerance of patient
and the sparing of uninvolved tissues or organs.
Type of treatment includes external therapy
•

External therapy (Teletherapy)

•

Internal therapy (Branchytherapy)

EXTERNAL THERAPY (Teletherapy)
X-rays Source / Point of Origin is at a distance away
from patients body.
In

external

therapy

two

principal

field

arrangements are parallel opposed fields and
wedged pair fields.

The wedged pair fields

allow a therapeutic dose to unilateral disease
while sparing high dose to the opposite side.

When a large tumor are midline lesion is present
a parallel opposed field setup may be needed,
which produced a uniform exposure for midline
disease.
Fields of modified by placing a wedges in the
beam to accommodate variation in tissue contour.
Radiation


Epithelial malignancy 1.8 to 2 Gy per fraction for 5
weeks (6000 to 6500cGy).
Lymphomas 180 to 200cGy per day (3500 to
5000cGy).
Superficial tumors : Low penetration
Lip and Skin : Low Kilovolt
Parotid : Electron beam therapy
Deep seated lesions : Neutrons

INTERNAL THERAPY (Branchy Therapy)
X-rays source is placed in contact with the tumor.
One way of concentrating the radiation dose in
the tumor tissue and the limiting the dose to the
surrounding normal tissues.
Branchy therapy is used as a boosted dose of
radiation to specific site or for treatment for
recurrence.

The isotopes used include cesium, irridium,
iodine, radium and gold.
Directly implanted source may be used to deliver
the radiation by covering the unexposed areas
with bandages, holders, wax and shields.
THREE CATEGORIES
Molds / Plaques
Interstitial implants
Intra cavitary / intra luminal

MOLDS / PLAQUES
Radioactive source is loaded into a surface mould
and placed within the tumor.
INTERSTITIAL IMPLANTS
Radioactive source is past through and through
the tumor.
INTRA CAVITARY / INTRA LUMINAL
Radioactive source placed in natural body cavities.

PRE AND POSTOPERATIVE
THERAPY
Preoperative radiation are used for destruction of
peripheral tumor cells, the potential control of
sub-clinical disease.
Postoperative therapy can be used to treat cells
that remain the margin of resection and to control
sub-clinical disease. Example (Carcinoma, extracapsular extension of tumor).

COMPLICATION OF
RADIOTHERAPY
Acute reactions - During the course of
radiotherapy due to tissue toxicity and
resolve over several weeks.
Chronic reactions - develops slowly over
months to years.

Mucositis
Xerostomia
Candidiasis
Caries
Tissue necrosis
Speech and mastication problem
Nutritional deficiency
Mandibular dysfunction
Dentofacial abnormalities
Pain


MUCOSITIS
Epithelial

thinning,

altered

vascular

supply,

fibrosis in connective tissue, friable mucosa and
hyalinization of collagen (1 to 2 weeks).
TREATMENT
Diluting agents/saline, hydrogen peroxide rinse
Coating agents – Kaolin-pectin and hydroxy
popylcellulose.


MUCOSITIS
LIP LUBRICANTS
Topical anesthetics – Xylocaine HCl.
Analgesic agents.


XEROSTOMIA
Acinar cell atrophy, hypo-vascularity, altered
neurologic function, decrease buffering capacity,
altered oral microbial flora treatment.
Sialagogues – sugar free gum or candies
Pilocaropine – 15mg per day
Saliva substitute (Carboxymethylcellulose)

CANDIDIASIS / CARIES
Opportunistic

infection

due

therapy.
TREATMENT
Tropical anti-fungal agents


to

radiation

Loss of remineralization, loss of buffering
capacity, gingival third and the incisal
cusp tips – caries.
TREATMENT
Fluorides, occlusive splints, chlorhexidine
gel 2%.

TISSUE NECROSIS
Hypo vascular, hypo cellular and hypoxic tissue
unable to repair – tissue necrosis.
Clinical features – discomfort, bad taste, parasthesia,
fistula, infection and fracture.
TREATMENT
Hyper baric oxygen therapy, IV fluids, nutritional
supplement,

removing

of

underlying

tropical antibiotic and antiseptic.

etiology,

SPEECH AND MASTICATION
PROBLEM
Abnormal speech after radiation affects tongue
mobility mandibular movement, soft palate
function and palatal defect.
TREATMENT
Speech therapy and prosthesis.

NUTRITIONAL AND
MANDIBULAR DYSFUNCTION
Radiation therapy produces changes in taste,
smell and secondary infection (>3000 Gy).
TREATMENT
Nutritional counseling and ↑caloric intake.


Due to fibrosis stress of muscles.
TREATMENT
Physiotherapy, excises, muscle relaxants and
analgesics injection.


DENTOFACIAL
ABNORMALITIES / PAIN
Affects the facial skeleton, growth and development
agenesis

of

teeth,

abnormal

micrognathia.


root,

trismus,

Pain due to tumor or recurrence or progression
of tumor.
TREATMENT
Tropical

anesthetics,

inflammatory

muscle

analgesic,
relaxants

depressants.


and

antianti-

CONCLUSION
Radiation

therapy

place

an

integral

role

in

management of most head and neck malignancies.
Hence proper use requires basic understanding of
how it affects both tumors and normal tissues.
Research

will

continue

and

investigations

of

radiation

fractionation,

radiosensitizers

therapy.

may

include

source,

radiation

and

combined

Advances

in

radiation

3-Dimensional

treatment planning and delivery – paranasal sinus.
High LET Radiotherapy – Neutrons.
Laser guided radiation.


Radiotherapy /certified fixed orthodontic courses by Indian dental academy

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