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Utskriftsdato (21.11.2017)

Brachytherapy for oral cancer


Medical editor Jan Folkvard Evensen
Oncologist
Oslo University Hospital

General

Brachytherapy is a form of radiation therapy where one or more radioactive sources (iridium) are inserted close to or into the tumor .

Benefits compared to external radiation treatment

  • Problem with positioning of patient and organ movement is eliminated.
  • Allows increased dose to the target volume and thereby possible increase in curative potential.
  • Shorter treatment time
  • Saves normal tissue structures.

Disadvantages of brachytherapy

  • Invasive procedure with the need for anesthesia

To ensure the irradiation of possible microscopic cancer outside the tumor, brachytherapy is always given in combination with conformal (organ configured) external radiation therapy.

Indication

  • Boost treatment for cancer on the floor of the mouth, tongue/root of the tongue.

Goal

  • Eliminate tumor
  • Eliminate residual tumor if treatment is given postoperatively.

Definitions

Brachytherapy is differentiated by the rate of irradiation dose delivered to the tumor known as high-dose rate (HDR) and low-dose rate (LDR) brachytherapy. Theoretically, there is a great difference between these two methods. Most of our knowledge is centered around LDR brachytherapy. It has been problematic to convert this knowledge to HDR brachytherapy. For this conversion, mathematical models have been developed, which still are not adequately tested for head/neck cancer. The indications for HDR brachytherapy are therefore fewer than for LDR brachytherapy. 

Low-dose rate brachytherapy (LDR)

This is done by inserting radioactive rods/threads surgically into the patient. The rods remain for extended time intervals.

High-dose rate brachytherapy (HDR)

This is perfomed by moving a point-shaped radiation source through previously inserted plastic catheters (remote afterloading). The treatment is fractionated (one or two per day). Remote afterloading was introduced to reduce radiation exposure to technicians.


Preparation

The patient is evaluated preoperatively by an internist and anesthesiologist.

Insertion of plastic catheter .

While the patient is under general anesthesia, four parallel equidistant guide-needles are inserted centrally in the area at risk in the created rectangle.

The guide-needles are then replaced by plastic catheters for after loading. The closed ends of the plastic catheters are inserted close to the surface of the tongue. Under the chin, plastic tubes are attached with "snaps".

CT is taken with 1 mm thick slices. The target volume is drawn which is mostly in the volume within the limits of the catheters. 

A physicist will then prepare the dosage plan .


Implementation

A dosage of 2.5 Gy x 6 is given in 2 fractions daily. The total dose will vary from patient to patient.

After the last treatment, the tubes will be devided on the outside of the skin and removed from the tongue from inside the mouth.


Follow-up

The side effects will peak from 7-14 days after the last treatment.

Side effects may be as intense as for external radiation therapy, but are less extensive since the radiation field is smaller.