Radiotherapy

Indication

According to the type of the tumor, from his localization, his size, his extension and his stage, general state of the patient and symptoms associated, one distinguishes three situations very different in which one will use the radiotherapy with quite precise aims:

The curative radiotherapy

As its name indicates it, the objective is to irradiate all the cancer cells in order to involve control even the cure cancer. That implies the absence of remote lesions. It is indicated in approximately half of the irradiations. It can be used only or in partnership with the surgery or chemotherapy.

The amount necessary depends on the type and of the volume of the tumor, some being very Radiosensible S whereas others are Radiorésistant be. It should be taken care that the amount allowing tumoral control is lower than the amount of critical tolerance of the bodies, which implies a rigorous technique with the risk not to deliver a sufficient amount and to have a local repetition or contrary to delivering an excessive amount and to involve an side effect. The usual protocol delivers an amount of 10 Gy per week at a rate of 5 meetings of 2 Gy per day. The total amount varies according to the cases from 30 to 70 Gy.

The palliative radiotherapy

The objective is not here to cure cancer but to relieve the patient by light amounts, making it possible to attenuate the pain resulting from too advanced cancer to be neat.

She addresses herself to too advanced locally or metastatic cancers.

The treatment being palliative, it must be of short duration and not very aggressive, to involve less nuisances possible with the patient. For example, irradiation of the " type; Split-course" , allows to recover between 2 series of irradiations.

The symptomatic radiotherapy

Its objective is to relieve a particularly awkward symptom major for the patient. Its effectiveness is:

Antalgic: The antalgic effect of the irradiation is almost constant and appears quickly in a few days. It is often used in the pains of the osseous metastases. The disappearance of the pain appears as of the first meetings, after sometimes a painful recrudescence due to the induced radio ignition.

Hemostatic: In the case of the persistent hemorrhages that one sometimes finds in cancers of the rectum, bladder, ORL or gynaecological, some meetings of radiotherapy involve the draining and the stop of the bleeding.

Décompressive : In cancers with signs of compression medullary - which constitute an urgency, or radicular, the radiotherapy can be an effective cure, on the condition beginning it of dice the first signs of compression. It must be of short duration, often just some meetings in order to limit the vertebral irradiation. Moreover, the oedemas by venous or lymphatic compression are also well improved by the radiotherapy.

Application

According to the localization and the stage of the tumors, the radiotherapy can be used only, but it is generally combined with a surgical treatment and/or a Chimiothérapie and/or a Hormonothérapie.

The majority of the Cancer S can be treated by radiotherapy to a certain extent. This includes the breast cancers, of the prostate, the lung, the rectum etc

This therapy, most of the time, is applied to treat an area located around a tumor. The field of radiations covers often also the lymphatic network draining the tumor.

In order to reach the tumoral zone and his possible extensions without attacking surrounding healthy fabrics, one successively irradiates the target according to various angles, so that the exposure fields are superimposed on the area to treat. The maximum of radiation is then localized at the tumoral zone.

Before the development of the drugs immunosuppresseurs, this technique was used to prevent the undesirable immune reactions during transplantations of bodies.

Proportioning

The amount of radiations delivered in radiotherapy is measured in Gray (Gy). 1 Gray = 1 Joule/Kilogram. The doctor radiothérapeute prescribes an amount to be delivered in an area given (generally the tumor) as well as fractionation to use (amount by meeting). He defines the constraints of amount if necessary not to be exceeded in the neighbouring areas (bodies at the risks). The prescribed amount and its fractionation depend on the localization and the nature of the disease. Generally an amount from 45 to 80 Gy is delivered with the target by fraction of 2 Gy/jour (order of magnitude). The Sein for example is treated by amounts of 45-50 Gy and the tumors pulmonary by amounts higher than 65 Gy. The amount can be delivered by beams of Photon S or electron S of energy ranging between 1,25 MeV (bends with cobalt) and several MeV for the linear accelerators. More rarely the Neutron S, the Proton S, the Pawn S or of the Photon S of lower energy are also used. The Radiophysicien then proposes a planning of the treatment which will be validated then by the radiothérapeute. It is a question of establishing the number and the provision of the beams which will make it possible to deliver the amount with the target by limiting the amount delivered to healthy fabrics.

Here permissible maximum amounts of certain bodies: Spinal-cord: 45 Gy, Cerebral trunk: 54 Gy, Optical Chiasma: 54 Gy, Optical nerve: 60 Gy, Brain: 60 to 70 Gy, Parotid 40 to 60 Gy, Larynx: 60 to 64 Gy, Liver: 20 Gy

Diagrams of fractionation

Monitoring

As any treatment a monitoring is essential. It must be ensured:

of good the technical realization of the irradiation,
of good the tolerance of the patient, judged on the private clinic primarily, by supervising the appearance of side effects,
of good the effectiveness of the treatment, judged on the complementary private clinic and examinations.

Control technical requirements of the irradiation

the good performance of the generating of radiation is controlled by the engineers or the physicists of the service of radiotherapy; the periodic control of the amounts which it delivers is carried out by the physicists .

the good positioning of the patient and the beam is controlled by the Manipulateur in medical electroradiology and the Radiothérapeute at the time of the first meeting of location.

the time of irradiation, the delivered amounts and the collimations are programmed by the dosimetrists and physicists in co-operation with the radiothérapeute using computer tools.

good the installation of the patient on the table and the followed treatment is controlled with each meeting by the manipulator in medical electroradiology and, during the consultations, by the radiothérapeute .

Clinical monitoring of the patient

The monitoring of the patient throughout all radiotherapy is ensured by the doctor radiothérapeute and his Attending physician. The purpose of it is essential to make sure of good the tolerance by the patient and of good the effectiveness of the treatment.

During the first consultation, particularly long, the patient is informed of all the technical methods of the radiotherapy and the undesirable effects and secondaries to be supervised. He is weighed and of the hygiéno-dietetic councils are given. A psychological evaluation is made and a follow-up or a treatment is considered. A symptomatic treatment is also envisaged according to the cases - pain, anxiety, digestive disorders, slimming…

Then consultations of follow-up are carried out in a weekly way. The purpose of they are in particular

to support the patient on the psychological level in an adapted way,
to appreciate the clinical tolerance, on the general level - weight, tiredness, general state and on the locorégional plan - appearance of acute local complications,
to follow the evolution of the lesion, thanks to the private clinic and with the symptoms or thanks to biological or radiological complementary examinations,
to follow on the hygiéno-dietetics plan the patient.

Parfois the irradiation must be stopped in the event of major intolerance.

At the end of the treatment, the radiothérapeute writes a complete report in particular specifying the technique used, the delivered amounts, the side effects possibly met, the tolerance and the effectiveness. This report is addressed to the various doctors responsible for the patient.

Side effects

The side effects can be various and varied according to the localization of the irradiation . In all the cases, one distinguishes the acute toxicity from the late toxicity .

Acute toxicity gathers the consequences which are made feel in the few days after the treatment and up to 6 months afterwards. It touches especially the fabrics with fast renewal like the skin, the mucous membranes, osseous marrow. Late toxicity gathers the side effects which will appear between 6 months and 30 years after the end of the irradiation. It is irreversible and touches primarily fabrics of support, with development of a fibrosis.

Below, side effects according to the various sites:

Eyes:

opacification of the crystalline lens: cataract induced from 10 Gy
the retina is radio resistant (nonsensitive to the ionizing rays)
If the amount is higher than 50 Gy, risks necroses eye

On level ORL:

acute toxicity: mucite (irritation of the mucous membrane), épithélite, Agueusie
late toxicity: Xerostomia towards 30 to 40 Gy, necroses osseous, hypothyroïdie, dental risk

Hair:

Alopécie to 30 Gy, final to 40 Gy

Esophagus:

Œsophagite acute to 40 Gy, sténose late so more than 60 Gy

Lungs:

acute toxicity: radic pneumopathy (cough, asthenia, dyspnea, feverish state)
late toxicity: respiratory, variable insufficiency according to pulmonary volume irradiated

Heart:

acute toxicity: péricardite from 50 Gy
late toxicity: risk coronary

Internal:

acute toxicity: diarrhea, pains
late toxicity: radic hail if amount higher than 45 Gy

Reproductive organs:

final or temporary sterility possible according to the age from 10 to 12 Gy

Bladder:

acute toxicity: pollakiurie, mictionnelle burn
late toxicity: fibrosis of the bladder from 60 Gy

Kidneys:

impaired renal function

Skin:

the erythema appearing in the two weeks, follow-up of a Desquamation dries
the exsudative radiodermatitis, formed of Phlyctène S which can ooze
the acute radionécrose, painful Ulcération
late toxicity: the Atrophy, disorders of the pigmentation, Télangiectasie S, Sclerosis S.

In the event of serious undesirable effect, an overdose must be evoked.

How it goes

Implications

Kinds off radiation therapy

3-dimensional radiation therapy

Intensity-Modulated Therapy Radiation

Image Guided Therapy Radiation

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