Radiotherapy: what it is used for and what the effects are

By Cristiano Antonino On Sep 30, 2022

Radiotherapy is a branch of medicine that uses radiation (electromagnetic, similar to that used in X-rays, or body radiation, e.g. electrons) to treat diseases

Radiotherapy is currently used almost exclusively for the treatment of tumour diseases, but it is also used in certain non-tumour diseases

Along with surgery and chemotherapy, radiotherapy is one of the three ‘classic’ cancer treatments that still form the mainstays of cancer care today.

Of the three types of treatment, radiotherapy has been the second to be used since the beginning of the last century.

Radiotherapy is, like surgery, a loco-regional treatment, i.e. it only affects one part of the body, while chemotherapy is generally a systemic treatment, i.e. it affects the whole body.

The cell lesions caused by radiotherapy (both the curative ones on tumour cells and the collateral ones on normal cells) are immediate, but their ‘visible’ manifestation (cell death) may only be evident after some time.

The effectiveness of radiotherapy is related to:

to the total radiation dose
to its fractionation;
the sensitivity of the different tumour tissues to radiant energy.

What does radiotherapy consist of

Depending on the type, radiation has the ability to penetrate more or less deeply into human tissues (up to and through them completely, as is the case with X-rays for X-rays).

On their way through the human body, they release their energy to the cells they encounter, triggering chemical-physical reactions that cause cellular damage to the irradiated cells.

As with chemotherapy, all irradiated cells are damaged, possibly to the point of death, mainly those that multiply, i.e. both abnormal tumour cells and normal healthy cells.

The effectiveness of radiotherapy lies in the fact that the majority of tumour cells are unable to repair damage and die, while the majority of normal cells repair damage and survive.

How radiotherapy is administered

There are two main ways of administering radiotherapy: external beam radiotherapy and brachytherapy.

In external beam radiotherapy, a suitable device, placed at a certain distance from the body, produces and directs the radiation beam to a specific region of the body.

When this type of treatment is carried out, the patient absorbs the radiation without re-emitting it externally, so there is no danger to those around him (including children or pregnant women) and he can lead a regular relational life throughout the treatment.

Radiation treatment is delivered in doses, daily sessions, called fractions. In principle, the smaller the daily doses (hyperfractionation), the better the therapy is tolerated, but the higher the individual doses (hypofractionation), the more effective they are.

For each type of tumour and each site there are different protocols for total dose and fractionation in order to achieve maximum effectiveness with minimum side effects.

In brachytherapy, radioactive substances are introduced into the patient’s body, into the tumour or close to it.

These substances mainly emit radiation that only briefly penetrates the surrounding tissue (alpha radiation).

The radioactive substance is introduced by means of ‘needles’ that are placed at the site to be treated, or by oral or vascular injection, reaching the tumour for metabolic reasons (e.g. radioactive iodine in thyroid tumours) or simply following the local blood flow.

In this type of therapy, the radioactive substance remains in the patient’s body, which may emit a quantity, however small, of penetrating radiation (beta radiation).

Therefore, precautions must be taken, which may even involve isolating the patient for the period of treatment.

The treatment ends with the removal of the radioactive needles or the natural decay of the radioactive substances (cessation of radiation emission).

It must be emphasised that possible radiation damage is well known and the precautionary rules for operators, patients and cohabitants are precise, useful and very strict.

One should therefore have no worries about this if one follows the advice of radiation specialists.

The team of a radiotherapy centre consists of:

medical radiotherapist: who gives the indication for treatment, sets the treatment plan, and follows the patient with periodic visits both during treatment and afterwards;
medical physicist: who draws up the treatment plan and carries out periodic checks on the equipment;
radiotherapy technician: who carries out daily radiotherapy sessions on the doctor’s instructions;
radiotherapy nurse: with particular experience of the problems of patients undergoing radiotherapy treatment.

Side effects of radiotherapy

Over the years, with the improvement of knowledge about the biological effects of radiation, with the development of equipment that delivers radiation and with the refinement of delivery techniques, the frequency and severity of side effects of cancer radiotherapy has decreased enormously.

These effects are, however, since normal cells close to the tumour are also affected and damaged, inherent in radiation treatment even if they are predictable and partly controllable with specific medical therapies.

The side effects of radiotherapy are of two types:

Acute when they occur in the first few days of treatment and end within a short time of the end of treatment. They are usually due to inflammation caused by radiation;

late and often more severe, depending on the irradiated organs. They can also occur years later and are generally due to the death of cells and their replacement by scar tissue.

Because the effect of radiotherapy is permanent, it is not possible, with rare exceptions, to re-irradiate an area that has already been radio-treated.

This fact is an important limitation to the use of radiotherapy.

When and why radiotherapy is used

Like any other cancer treatment, radiotherapy of tumours can be used for two different purposes
curative treatment with the aim of curing the patient or, at any rate, giving him or her a longer life in good condition;
symptomatic treatment with the more limited aim of mainly improving the patient’s quality of life by controlling the symptoms of the disease.

Surgery and radiotherapy may be combined in the loco-regional treatment of tumours or their metastases:

exclusive radiotherapy: the tumour is very radiosensitive and can be destroyed with radiotherapy alone, or it is inoperable and symptomatic therapy is desired;
neo-adjuvant radiotherapy if the tumour is inoperable but could become so if radiotherapy (with possible addition of chemotherapy) proves effective, it could become operable, or, if the tumour is operable but if radiotherapy (with possible addition of chemotherapy) proves effective, the operation could become easier and more likely to be radical;
intra-operative radiotherapy – known as IORT – (i.e. administered during surgery). Used rarely and in only a few centres, it requires special equipment and its greater effectiveness compared to the usual treatment is unproven. It is in fact a post-operative therapy because it is administered at the end of surgery to destroy any residual tumour cells in the surgical field;
post-operative radiotherapy (i.e. administered after surgery);
adjuvant (precautionary) radiotherapy, when surgery has been radical, there is no visible tumour residue, but there is a risk that there are still viable tumour cells in or near the surgical field;
radiotherapy with curative character when surgery has not been radical, there are locally residual tumours, but these could be destroyed by radiation therapy;
pre-operative radiotherapy (i.e. administered prior to possible surgery).

The aim of research is to improve equipment and techniques to direct radiant energies as concentrated as possible into the tumour without irradiating surrounding healthy tissue

Added to this is the use of radio-sensitising substances, i.e. substances that penetrate the cells and amplify the damaging effect of radiation.

These substances, to be useful, should be concentrated more in tumour cells than in normal cells.

Finally, selective brachytherapy, binding a radioactive substance with local action to a ‘vehicle’ (mostly antibodies that selectively reach the tumour cells) that carries the substance into the tumour.

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