Radiotherapy

Question 1

In what cancers can radiotherapy be used as the sole treatment?

Answer 1

Prostate

Question 2

When can radiotherapy be used as a neoadjuvant treatment?

Answer 2

Rectal cancer

Question 3

When can radiotherapy be used as an adjuvant treatment?

Answer 3

Breast cancer

Question 4

How can radiotherapy be delivered?

Answer 4

Photons/X-rays: External beam RT (most common)
Electrons
Radio-isotopes
Protons

Question 5

What is the science behind radiotherapy?

Answer 5

X-rays at one end of electromagnetic spectrum
Very high energy, very short wavelength
Delivered by LINAC machine penetrating deep into tissue sparing overlying skin
Produce secondary electrons & free radicals causing DNA damage

Question 6

What is radiation dose measured in? What is the number of treatments referred to as?

Answer 6

Gray

Fractions

Question 7

What is the therapeutic index?

Answer 7

Balance between tumour control and the SE of radiotherapy

Question 8

What is the gross tumour volume & clinical target volume& the planning target volume?

Answer 8

GTV: Main bulk of the tumour
CTV: Margin added for microscopic disease spread
PTV: Margin added to allow minor daily variations in patient & tumour position

Question 9

What are the acute SE of radiotherapy?

Answer 9

Develop during treatment
Usually after first 5-10fractions
Often peak few weeks after treatment
Due to damage of normal tissue & ability of normal cells to repair damage
Localised skin reaction
Oral mucositis
Diarrhoea

Question 10

What are the late SE of radiotherapy?

Answer 10

Develop at least 3months-years after treatment
Often irreversible
Develop due to damage to normal cells, partly due to fibrosis & blood vessel damage in irradiated tissue
Lung fibrosis
Skin atrophy
Infertility

Question 11

What is brachytherapy?

Answer 11

Form of radiation treatment where radiation sources are placed within/close to the tumour allowing delivery of localised high radiation dose to a small tumour volume inc chance of control

Question 12

What cancers can be treated with brachytherapy?

Answer 12

Prostate
Gynae
Oesophageal
Head & neck

Question 13

What are the 2 types of brachytherapy?

Answer 13

Intracavity: Radioactive material placed inside a body cavity (uterus, cervix)
Interstitial: Material put into the target (prostate)

Question 14

What is the most commonly used radio isotope?

Answer 14

Iodine I-131
Thyroid cancers
Iodine taken up and concentrated in any remaining thyroid tissue normal or malignant ablating thyroid cells

Question 15

How does RT delivered by photons work?

Answer 15

Causes DNA damage to both cancer and normal cells
Targets deep tissues but spares overlying skin
Produces secondary electron in tissues

Question 16

How does RT delivered by electrons work?

Answer 16

Directly damages DNA
Deliver dose superficially (just below skin surface)
Normal cells can repair themselves and survive

Question 17

What are the specific side effects of RT for prostate cancer?

Answer 17

Proctitis (rectum)
Cystitis (bladder)
Long-term: Telangiectasia of bladder/rectum
Incompetent bladder & inc urination

Question 18

What are the specific side effects of RT for breast cancer?

Answer 18

Acute: Fatigue, skin problems (dry/moist desquamation), pain around scar, skin thickening w/oedema/lymphoedema
Chronic: Shrinking of the breast w/fibrosis, pulmonary fibrosis

Question 19

What is the scoring system for RT side effects for breast cancer?

Answer 19

RTOG 0: No visible changes
RTOG 1: Faint/dull erythema (frequent moisture)
RTOG 2a: bright erythema/dry desquamation, sore, itchy, tight
RTOG 2b: Patchy, moist desquamation, moist erythema
RTOG 3: Confluent moist desquamation, yellow/green exudate
RTOG 4: Ulceration, bleeding, necrosis

Question 20

What is the preparation required for RT for prostate cancer?

Answer 20

Full bladder: Moves S.bowel up & out of radiation field, L.bowel move out of field so smaller radiation dose
Empty rectum: micro-enema

Question 21

What are the side effects associated with RT to the head and neck?

Answer 21

Skin changes
Jaw stiffness
Tooth decay
Fatigue
Soreness of mouth/throat
Xerostomia
voice and taste changes
changes in hearing
changes in skin texture