HOW TO TREAT 35
ausdoc. com. au 20 JUNE 2025
HOW TO TREAT 35
Box 1. Indications for radiotherapy
• Tumour sites treated with radiotherapy include but are not limited to:— Skin, any site.— Breast.— Genitourinary: prostate, bladder.— Gynaecological: cervix, uterus.— Head / neck: orbits, sinuses, nasopharynx, oropharynx, hypopharynx.— Gastrointestinal: oesophagus, gastro-oesophageal junction.— Colorectal: anal canal, rectum.— Lung.— Central nervous system: brain, spinal cord.— Haematological; total body irradiation, localised site.— Metastases: brain, bone, lung.
Figure 4. Volumetric modulated arc therapy combined the principles of intensity modulated radiation therapy with the movement of the treatment machine around the patient, further improving conformality of treatment plans.
• Benign processes may also be treated with radiotherapy:— Meningioma.— Acoustic neuroma.— Pituitary adenoma.— Arteriovenous malformations.— Plantar fasciitis.— Keloid scars.— Dupuytren’ s contracture.— Thyroid eye disease.
is more common, as complex plans are generated and checked.
There is an initial consultation with the radiation oncologist. The oncologist conducts a history and examination and reviews all investigations. They also explain the aim and logistics of the radiotherapy, together with the risks and benefits of the treatment.
The next step is a planning scan appointment. This planning scan is performed on a conventional CT scanner connected to the radiotherapy planning computers( see figure 6).
The patient is placed in a comfortable reproducible treatment position and may be immobilised using aids such as a mask or stabilisation bags. Measurements are taken, clinical photographs may be taken, and small tattoo dots may be applied.
Based on this planning scan, the radiation oncologist determines and delineates the structures that need to be treated and those that need to be avoided( see figure 7). The radiation therapists then determine the best way to deliver the radiotherapy, using computers to optimise a plan. After this, the physicist reviews the plan and performs quality assurance.
External beam treatments are administered with the patient lying flat on a table under the linear accelerator, which rotates round them but does not touch them( see figure 8). Patients who receive brachytherapy may need hospital admission for the procedure.
Radiation safety is an important consideration when patients are receiving radiotherapy. Beyond ensuring the safe treatment of the patient, there are general principles that are applied to ensure a safe environment for the treating staff and the general public. This includes decreasing time of exposure to a radiation source, increasing distance from the source and using adequate shielding from radiation.
OUTCOMES
DIFFERENT cancer types have a range of outcomes, with the stage of the cancer a significant determinant of the outcome. The earlier the stage of disease, the greater the likelihood of cure. Disease that has metastasised is more difficult to cure with radiotherapy alone.
Early-stage prostate or breast cancer have very high cure rates. 5, 6 This is in stark contrast to primary brain tumours that tend to have lower cure rates. 7 Most haematological malignancies respond well to radiotherapy, with rapid clinical shrinkage of lesions. 8 Given high cure rates, particularly in Hodgkin lymphoma, there has been a move towards deintensification of treatment with both chemotherapy and radiotherapy. Deintensification of therapy also decreases the risk of long-term toxicities; this is of particular importance as haematological malignancies can affect younger people.
Follow-up appointments are an important component of a patient’ s care. Specific follow-up schedules will vary, depending on the tumour site treated. In the curative setting, follow-up aims to ensure there is no evidence of relapse of the cancer and to manage side effects, if present. In the palliative setting, follow-up allows for confirmation of whether the treatment has aided in symptom management.
SIDE EFFECTS
UNFORTUNATELY, the notion of radiotherapy has a negative connotation in some patients, possibly arising from experiences relayed from older and less accurate treatment planning, such as the 2D era.
With current modalities, many patients continue working throughout their treatment and may only notice minimal side effects; the latter is dependent on the treatment site and the concomitant use of other modalities.
The potential side effects of radiotherapy may be explained by radiobiology. Side effects are described as acute or late. The acute may develop towards the end of treatment, peaking shortly after treatment and then dissipating, while late side effects can occur months to years following the completion of radiotherapy.
Acutely responding tissue includes rapidly proliferating cells, such as skin and mucosal cells. This explains why patients may develop a skin or mucosal reaction towards the end of treatment. Late responding tissues include cells that are not rapidly proliferating, such as vascular or neuronal cells. This tissue may become scarred as a result of radiotherapy many months to years following treatment. Carcinogenesis is an important potential late effect of radiotherapy. The quantification of this risk is difficult as we cannot ethically irradiate humans and see if they develop a cancer. For this reason, an estimation is made from both retrospective and
Box 2. Factors considered before radiation therapy
Figure 5. MRI-linear accelerator.
• Patient:— Age:
• An older aged patient may not derive a large benefit from treatment because of a shortened life expectancy.
• In a younger patient, it may be preferable to avoid treatment with radiotherapy altogether to avoid the side effects of radiotherapy( mainly secondary malignancy risk – albeit low) if there is another option; for example, surgical resection.
— Comorbidities:
• A patient with multiple comorbidities may have a life-limiting condition that will compete with the benefit of radiotherapy.
• Rare radiosensitivity syndromes or conditions, such as inflammatory bowel disease, may increase the risk of toxicity from radiotherapy if the pelvic region is being treated.
— Medications:
• Some medications, such as methotrexate, are radiosensitisers; that is, these agents make tumour cells more sensitive to radiation therapy.
• These should be withheld before and during radiotherapy, where possible, to avoid excess toxicity.— Preference:
• A patient may prefer an organ preservation strategy rather than a surgical resection, or vice versa.
— Compliance:
• A non-compliant patient is not an ideal candidate for radiotherapy because of the need to remain still during treatments and to respond co-operatively with instructions from the radiation therapists.
— Treatment:
• Mode of delivery: is the tumour better suited to external beam radiotherapy or brachytherapy?
• Type of radiotherapy: if the tumour is deep seated, then photon therapy will be more beneficial than electron therapy.
• Concurrent treatment: systemic therapy given during radiotherapy may be beneficial for outcomes but may increase acute toxicity.
• Tumour:— Type: the tumour itself may be radiosensitive or radioresistant, which can determine the radiation dose prescribed.— Stage: the stage of the disease will determine the intent of the radiotherapy treatment.