1

What is radiotherapy?

Radiotherapy represents the use of ionising radiation to treat diseases, usually to control or kill malignant cells.

It has a role in many thoracic malignant diseases, including lung cancer, oesophageal cancer, thymic tumours, mesothelioma and germ cell tumours.

The amount of ionizing radiation is measured in gray (Gy), with the dose varying according to the site of the tumour and indication for treatment.

There have been tremendous technical advances in the planning and delivery of radiotherapy over the last two decades.

2

How is radiotherapy classified?

External beam radiation (commonest form) – where the radiation is delivered (externally) by a linear accelerator.

Brachytherapy – where a radioactive source is placed within the body either directly in the tumour itself or in close proximity to it. An example is lung cancer, where the radioactive material is placed endoscopically near the tumour.

3

How does radiation damage cells?

Radiation deposits energy into cells as it travels through the patient, ultimately resulting in:

a)

breakage of chemical bonds;

b)

damage to the deoxyribonucleic acid (DNA) and cell structure;

c)

prevention of replication;

d)

cell death.

4

What are the potential side effects of thoracic radiotherapy?

Acute effects (within 3 months after the end of treatment):

a)

oesophagitis (most common toxicity), which usually subsides within 2 weeks of treatment;

b)

pneumonitis;

c)

anorexia, nausea and vomiting;

d)

alopecia;

e)

bone marrow suppression.

Late effects (beyond 3 months after the end of treatment):

a)

pneumonitis and pulmonary fibrosis;

b)

rib fracture;

c)

hypothyroidism;

d)

cardiac fibrosis and dysfunction.

5

What are the indications for radiotherapy?

Stand-alone treatment:

a)

radical radiotherapy – where the treatment is given with a curative aim in patients with operable tumours, who are medically unfit or choose not to undergo surgical resection;

b)

palliative radiotherapy – where the treatment is given for symptom relief in patients where a cure is not possible.

Combination therapy with surgery and/or chemotherapy:

a)

induction therapy – treatment given with the aim of down-staging a tumour from an inoperable to an operable stage;

b)

neoadjuvant therapy – pre-operative treatment aimed at improving the survival rate in an operable tumour;

c)

adjuvant therapy – postoperative treatment aimed at improving the survival rate in an operable tumour.

6

What are the uses of radiotherapy in thoracic diseases?

Non-small cell lung cancer (NSCLC) – mainly as stand-alone curative or palliative therapy but also can be used as induction or adjuvant therapy.

Small cell lung cancer (SCLC) – curative therapy in combination with chemotherapy or as prophylactic cranial irradiation.

Mesothelioma – palliation and prophylactic at chest drain or biopsy sites.

Oesophageal cancer – pre-operative chemoradiation and palliation.

Thymoma – as adjuvant therapy or following induction chemotherapy.

7

Which patients are suitable for radiotherapy?

Patients with a good performance status (WHO 1-2), as patients with a poor performance status rarely benefit from radiotherapy.

Certain chemotherapy drugs, such as cisplatin and carboplatin in NSCLC, can potentiate the effects of radiotherapy.

Certain tumours are particularly radiosensitive, including lymphoma and germ cell tumours, whereas most epithelial tumours, including NSCLC and oesophageal adenocarcinoma, are only moderately radiosensitive and hence may require larger doses of ionising radiation.

8

What are the different radiotherapy treatment regimens used for NSCLC?

Conventional radiotherapy:

a)

typically given 5 days a week in daily divided doses, for 5 weeks;

b)

planning with computed tomography (CT) scanning needs to consider:

i)

tumour volume;

ii)

movement of the tumour during respiratory and cardiac cycles, which can be up to 5cm vertically during respiration if the tumour is at the base of the lung;

iii)

acceptable dose to the surrounding structures, especially the heart and spinal cord;

c)