Some radiation techniques safer than others

In the first high-precision dosimetry study to compare five new radiotherapy techniques for breast cancer, Sunnybrook researchers find breast IMRT (intensity modulated radiation therapy) and virtual wedge significantly safer than an older technique of the metallic, physical wedge, for whole breast radiotherapy.

For partial breast radiotherapy, low energy source brachytherapy seed implants and 3D-CRT (conformal radiotherapy) appear safer than temporary 192Ir (Iridium) HDR (high-dose rate) brachytherapy.

Traditional radiotherapy use triangular-shaped blocks made from metallic material. The blocks serve to even out the radiation dose inside the breast during treatment. The blocks scatter the radiation, which is often absorbed in other parts of the body. Since 2000, in Ontario, the physical wedge technique has been replaced by the virtual wedge technique and eventually breast IMRT.

Both IMRT and virtual wedge techniques use computer-simulated fields and a motion of the radiation beam jaws, to better target therapy to the affected breast.

Since 2003, in the United States and Canada, selected patients have been offered treatment to part of the affected breast using the popular technique of HDR brachytherapy. The technique involves the temporary placement for a few minutes, twice a day and for five consecutive days, of a very intense and miniature source of 192Iridium inside a tube or balloon catheter implanted inside the surgical cavity. An alternate technique pioneered at Sunnybrook, involves the permanent insertion of low energy radioactive seeds under light sedation in a one-hour procedure.

"More patients are living longer, and with any therapy used, the goal is for us to reduce risk of complications from treatment itself to better ensure continued quality of life," says Dr. Jean-Philippe Pignol, lead investigator and radiation oncologist with the breast cancer care team at our Odette Cancer Centre.