BASICS IN RADIATION ONCOLOGY

RADIATION ONCOLOGY

• Radiation oncology is that discipline of human

medicine concerned with the generation,

conservation, and dissemination of knowledge

concerning the causes, prevention, and

treatment of cancer and other diseases

involving special expertise in the therapeutic

application of ionizing radiation.

• Medical Oncology is that discipline of human

medicine specializes in diagnosing and treating

cancer using chemotherapy, hormonal therapy,

biological therapy, and targeted therapy.

• Surgical Oncology branch of surgery applied

to oncology; it focuses on surgical

management of tumours mainly cancerous

tumour.

RADIATION THERAPY

• Radiation therapy is the clinical modality dealing

with the use of ionizing radiations in the treatment of

patients’ with malignant neoplasias (and occasionally

benign diseases).

• The aim of radiation therapy is to deliver precisely

measured dose of radiation to a defined tumour

volume with as minimal damage as possible to the

healthy surrounding tissue, resulting in eradication of

the tumour, high quality of survival and prolongation

of survival at competitive cost.

CELL CYCLE

• G0 – Cell rests and does normal work in the

body

• G1 – RNA and proteins are made for dividing

• S – Synthesis ( DNA is made for new cell )

• G2 – Apparatus for mitosis is built

• M – Mitosis ( The cell divides into 2 cells )

• Radiation kills cells that are actively dividing.

• It also causes damage to the surrounding

tissue.

• Radiation doesn’t kill cells instantly, it may

take day to weeks depending on the cell

• Skin, bone marrow, lining of intestines affects

quickly.

• Nerve, breast, brain, and bone tissue show

affects later

TYPE OF RADIATION

• IONIZING

– PHOTON THERAPY ( X- RAYS AND GAMMA

RAYS )

– PARTICLE THERAPY ( ELECTRONS,

PROTONS, NEUTRONS, CARBON IONS,

ALPHA PARTICLES AND BETA PARTICLES )

• NON – IONIZING

– RADIO WAVES, MICROWAVES, VISIBLE

LIGHT

• RADIOCURABILITY – It refers to the

eradication of tumour at the primary or

regional site and reflects a direct effect of the

irradiation ; but this does not equate with

patients cure from cancer.

• RADIOSENSITIVITY – is the measure of

tumour radiation response, thus describing the

degree and speed of regression during and

immediately after radiotherapy

Factors affecting Radiosensitivity

• Histologic type

– High sensitivity: Malignant lymphoma, Seminoma, etc.

– Moderate sensitivity: Epithelial tumour (Carcinoma)

– Low sensitivity: Osteosarcoma, Malignant melanoma, etc.

• Oxygen concentration in tumour tissue:

Radiosensitivity is low in the hypoxic state.

• Cell cycle: Radiosensitivity is high in M phase and

low in S phase.

• Cancer-related genes: p53, Bel-2, Fas, VEGF, etc.

4 R’s of Radiotherapy

• Repair (few hours)

– Lethal damage

– Sublethal damage

– Potentially lethal damage

• Reassortment (few hours)

• Repopulation (5 – 7 weeks)

• Reoxygenation (hours to few days)

RADIOTHERAPY

• PRIMARY

• ADJUVANT

• NEO-ADJUVANT

• CONCURRENT

• PALLIATIVE

Planning and conduct of course of

Radiation Therapy

• Indication for radiotherapy

• Goal of radiation therapy

• Planned treatment volume

• Planned treatment technique

• Planned treatment dose

EXTERNAL BEAM RADIATION

• 2D RADIOTHERAPY

• 3D CONFORMAL RADIOTHERAPY

• INTENSITY MODULATED RADIOTHERAPY

• IMAGE GUIDED RADIOTHERAPY

• STEREOTACTIC RADIOTHERAPY / SURGERY

• INTRAOPERATIVE RADIOTHERAPY

• ELECTROMAGNETIC GUIDED RADIATION THERAPY

BRACHYTHERAPY

• CESIUM, GOLD, IODINE, IRIDIUM, PALLADIUM

• MAIN TYPES OF INTERNAL RADIATION

– INTERSTITIAL

• PERMANENT BRACHYTHERAPY

• TEMPORARY BRACHYTHERAPY

– HIGH DOSE RATE BRACHYTHERAPY

– LOW DOSE RATE BRACHYTHERAPY

– INTRACAVITARY

– INTRALUMINAL

– SURFACE

• Radiation Oncologist - Plans treatment.

• Radiation Physicist – Working of radiation

equipment & delivering the radiation dose.

• Dosimetrist – Helps the doctor plan and calculate

the needed number of treatment.

• Radiation therapist – operates the equipment.

• Radiation therapy nurse – cares the patient and

advice them on radiation treatment & dealing with

radiation side efftects.

PLANNING

• IMMOBILIZATION

• CT Simulation

• Treatment Planning System – Target delineation

– Dose prescription

– Beam placement

– Dose calculation

– Plan evaluation & Approval

– Quality assurance

• RADIATION DELIVERY

IMMOBILIZATION

• GOALS

• DEVICES

– PLASTIC HEADHOLDERS AND SPONGES

– THERMOPLASTS

– PLASTER OF PARIS

– VACUM MOULDED THERMOPLASTS

– POLYURETHANE FOAMS

THERMOPLAST

IMMOBILIZATION

Video

• TARGET DELINEATION & DOSE

PRESCRIPTION

– Gross tumour volume – 60 – 70 Grays

– Clinical target volume

• High risk – 45 – 54 Grays

• Low risk – 45 Grays

– Planning target volume.

COMBINATION THERAPY

• CONCURRENT CHEMOTHERAPY

– CISPLATIN

• 40mg/m² in 1pint NS IV over 20mins ( Cover bottle with black paper) after premedication

• CARBOPLATIN , TAXOL

• MONOCLONAL ANTIBODIES

– BioMap

TARGETED THERAPY

• Targeted therapy blocks the growth and spread of cancer by preventing cancer cells from dividing or destroying them directly.

• EGFR monoclonal antibodies

– cetuximab, panitumumab, zalutumumab, nimotuzumab

• EGFR tyrosine kinase inhibitors

– gefitinib, erlotinib, lapatinib, afatanib, dacomitinib

• Vascular endothelial growth factor receptor (VEGFR) inhibitors

– bevacizumab, sorafenib, sunitinib, vandetanib

SIDE EFFECTS

ORAL MUCOSITIS

• Symptoms include pain, Dysphagia,

Odynophagia, Nausea, Vomiting, Diarrhoea –

GI Toxicity.

• Prevention

– Midline mucosa sparing blocks

– 3D treatment planning and conformational dose

delivery

– Topical benzydamine – anti inflammatory,

analgesic and anti microbial effect

• Treatment

– Lidocaine, milk of magnesia, chlorhexidine and

diphendhydramine

– Antibiotic lozenges or sucralfate

DERMATITIS

• Erythema, desquamation, oedema, necrosis or ulceration

(dose and duration )

• Sweat glands and hair follicles – damaged

• Alopecia permanent – Follicular fibrosis.

• Treatment

– Gentle cleansing with mild agent, washing with water.

– Petrolatum based, castor oil, trolamine.

– Steroids ameliorate the symptoms, but do not prevent.

– Ulcers – Gention violet, Hydrogel dressings

• If infected – Ionic silver powder, topical antibiotics

• Recent years – Topical granulocyte-macrophage-colony

stimulating factor, tacrolimus, platemet derived growth

factor

• Chronic skin changes

– Oral pentoxifylline (800mg/day)

– Vitamin E (1000IU/day)

• For 6 months

– Prophylactic use of Pentoxifylline reduces late skin

changes, fibrosis and soft tissue necrosis

XEROSTOMIA

• Subjective experience of dry mouth.

• 50 – 60% decrease – 1st week

• Continues in dose dependent fraction

• Symptoms

– Systemic problems – loss of apetite, chronic

oesophagitis, gastroesophageal reflux

– Local problems include dental caries, periodeontal

disease, atrophy and ulceration

• Prevention– Surgical transplantaion of salivary gland.

• Submandibular gland to submental space.

– Intensity modulated RT.

– Amifostine therapy.• 200mg/m² 15 – 20mins prior irradiation

• Treatment– Dietary and oral hygiene

– Saliva substitution

– Medications ( carboxymethylcellulose, porcine, bovine mucin)

– Increase flow – Chewing gums, Lozenges, Vitamin C

– Oral pilocarpine• 5 -10mg TID

SPINAL CORD

• Transient myelopathy ( 2 – 4 months later ).

• LHERMITTE SIGN or LHERMITTE

SYNDROME.

• Rarely, Permanent paralysis, presumed to be

from acute infarction of cord.

HEARING

• Cochlear damage – SNHL ( ˃60grays ).

• Concurrent Chemotherapy with Cisplatin

increases risk.

THANKYOU