Radiotherapy Flashcards Preview

Oncology + Palliative > Radiotherapy > Flashcards

Flashcards in Radiotherapy Deck (26):
1

What is radiotherapy - how is it delivered, what effect does it have on cancer?

Strongly targeted rays of ionising radiation

Destroys or inactivates cancer Disrupts cell division Invisible, silent + pain free

Delivered by a linear accelerator - delivering high energy, short wavelength x rays

2

Electrons vs photons

Photons = high energy x ray treatments = penetrate deep. Cause DNA damage

Electrons = used for skin tumours

3

What is a differential cell kill?

Kills more cancer cells than healthy cells Due to cancer cells having ineffective DNA repair pathways

4

Units of measurement + dose

Gray (Gy)

Delivered as series of small doses (fractions)

5

What is IMRT?

Intensity modulated radiotherapy

Given continuously as it moves in arc around the patient - delivered quicker + greater accuracy

6

What is VMAT?

Volumetric modulated arc therapy - type of IMRT

Protects more healthy tissue MLC movement throughout beam delivery so head can move around (patient not fixed)

7

What is MLC?

Multi leaf collimator Part of RT machine, helps to shape beam of radiation

8

What is the margin for setting up?

Extra margin added due to tumour moving slightly

9

Treatment schedule for category A cancers

5 days a week throughout treatment as can't give cancer cells time to regenerate

10

What is the toxicity skin reaction in RT?

Radiation dermatitis

Eventually causes fibrosis Borders are defined

11

Side effects of RT

Mucositis

Cystitis

Proctitis

Long term urinary frequency + urgency due to bladder fibrosis

Bronchitis/ pneumonitis (can occur 4 weeks - 6 months post treatment)

Fatigue

Diarrhoea

12

Grading for radiation dermatitis

Grade 1 = faint erythema, dry desquamation 2 = moderate erythema, moist desquamation, confined to skin folds 3 = moist desquamation other than skin folds 4 = skin necrosis or ulceration 5 = death

13

RT in prostate pts - requirements, SE

Need to have a full bladder, empty bowels 

SE: skin reaction, fatigue, diarrhoea, tenesmus, cystitis, urinary frequency

14

RT in head and neck cancer - SE

Worst SE - intensive mouth care needed

Held in place by thermoplastic shells

SE: skin reaction, fatigue, mouth soreness, difficulty swallowing, voice changes, hair loss, tinnitus Long term risk of tooth decay, hearing changes, difficulty swallowing + xerostomia (dry mouth)

15

What is brachytherapy + what are the types?

Inserting radioactive material into affected area

intracavity = into body cavity eg uterus

intrastitial = into target eg prostate

16

What cancers use brachytherapy?

Prostate, cervical + womb, head and neck

17

What is the skin sparing effect?

X rays penetrate deep into body tissue, sparing overlying skin Reduces skin toxicity reactions

18

Which cancers are more radio sensitive?

Seminoma Hodgkins disease

19

Which cancers are radio resistant?

Glioblastoma multiforme

20

Why is concurrent chemo helpful?

Acts as radiosensitiser

Improves efficacy

21

What is the radiotherapy pathway?

Diagnosis

MDT discussion

Patient consents

Immobilisation CT scan

Disease delineation by oncologist

Margins added

Treatment plan developed

Pt has daily treatments

Review + monitoring

Follow up

22

What is the most common type of RT used?

External beam - 3D conformal RT Treatment based on 3D shape of their tumour

23

What is the GTV, CTV + PTV?

GTV = gross tumour volume CTV = clinical target volume (margin has been added) PTV = Planning target volume (added margin due to patient + tumour movement)

24

Long term toxicity effects of RT

Lung fibrosis, skin atrophy + infertility

Secondary malignancy

25

What are radioisotopes + what is it commonly used for?

Unstable form of chemical element

Emits radiation when it decays

Commonly used is radiactive iodine I-131 - used in thyroid cancer

26

What is stereotactic RT?

Delivered using VMAT technique

Image guided radiotherapy

works for small + well defined tumours

Large dose of RT given in small number of large fractions