سـم ماللهب ــ الرحمـن الرحي

What is Radiotherapy?

an introduction for Oncologists

Ashraf Hamed Hassouna

Professor of Radiation Oncology

NCI, Cairo University

• Mode of action

• Treatment Policy

• Combined modalities

• Patient care before and during RT

• Techniques

• Planning

• Dose & fractionation

• QA

• Side effects

Contents

Mode of Action

RT effects

▪Cell death

• Tumour cell death

• Normal tissue side effects

▪ Cell transformation

• Mutations

• Carcinogenesis

▪ Radiosensitive

• Leukemia

• Lymphoma

• Myeloma

• Ewing

• SCLC

▪ Radioresponsive

• HNSCC

• Breast

• GIT

• Bladder

• NSCLC

▪ Radioresistent

• Melanoma

• Osteosarcoma

• STS

• GBM

• RCC

Therapeutic ratio

Treatment PolicyRadical, Adjuvant, Palliative

Brain mets

Combined Modality Treatment

Pre-operative Radiotherapy

Cons

• Treatment based on clinical

stage, may overtreat patients.

• Potential increase in intra-

operative and post-operative

surgical complications.

• Delay primary treatment.

• Disrupt surgical staging of the

tumor and/or the expression of

histologic or

immunohistochemical

prognostic factors.

Pros

• Smaller RT volumes and doses and potential decreased RT side

effects.

• Sterilization of tumour bed in preparation for surgery.

• Avoidance of surgery in those who progress with systemic disease.

• Tumour down-staging, improved resectability.

• Unaltered blood supply leading to decreased proportion of radio-

resistent hypoxic cells.

• Potential for short-duration hypo-fractionation for patient

convenience and improved resource allocation.

Post-operative Radiotherapy

Cons

• Larger RT volumes and difficulty of RT planning.

• Usually higher RT doses due to altered blood

supply and decreased oxygenation to the tumour

bed.

• Protracted treatment schedule.

• Reduced functional status or delayed patient

recovery after surgery may preclude the use of

postoperative RT.

• Delay in initiation of RT until wound healing is

completed.

Pros

• Treatment decision based on true

pathologic stage, avoids RT in

patients who may not require it.

• More accurate assessment of disease

extent to allow for delineation of

disease involvement.

• Less concern about increase in

perioperative morbidity and mortality

after preoperative induction.

Chemo-Radiotherapy

Types

• Sequential C-RT

• Concurrent C-RT

• Radiosensetizer

Pros

• Lower dose

• Synergistic effect

• Overcome resistance

Cons

• Higher toxicity

• Tolerability

Examples

• HNSCC

• GIT

RT techniques2D, 3DCRT, IMRT, SRS, Brachytherapy

Cobalt Machine

Linear Accelerators (LINACs)

IMRT2D

Novalis System

Cyberknife

Treatment session

Patient care

before and during RT

Oral Hygiene

Naso-Gastric tube

Percutaneous Endoscopic Gastrostomy

PEG

RT Planning

Immobilization

Simulation

LN Contouring

RT

Dose & Fractionation

Altered Fractionation

• Hyperfractionation

• Hypofractionation

• Accelerated fractionation

5Rs of Radiobiology

• Repair

• Repopulation

• Redistribution

• Reoxygenation

• Radiosensitivity

Conventional Fractionation

• 2Gy / Fraction

• 1 Fraction / Day

• 5 Days / Week

Doses

• Radical: 70Gy/35F/7W

• Adjuvant: 50Gy/25F/5W

• Palliative: 30Gy/10F/2W

RT QA

EPID

DRR EPID

CBCT

RT Side Effects

Site

• H&N

• CNS

• Chest

• Abdomen

• Pelvis

Grade

• 0-4

Time

• Early (acute)

• Late (chronic)

Management

• Before RT

• During RT

• After RT

Factors

• Total dose

• Fractionation

• Tissue type

• Volume

Xerostomia

Mucositis

Skin Reaction

Osteoradionecrosis

Thank You

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