IMRT reduces skin toxicity symptoms for breast cancer patients

There are various clinical benefits to using intensity-modulated radiation therapy (IMRT) rather than conventional radiation therapy after breast conservation surgery, according to a study published in the International Journal of Radiation Oncology, Biology, Physics.

The conventional whole-breast radiation therapy technique that has been the standard of care for the past 30 years delivers radiation to the breast from two opposing tangential fields. This technique spares normal tissue and is generally safe and effective, but it can result in inhomogeneous distribution of radiation dose due to breast contour variations. Wedges are often used to attenuate the beam to compensate for inhomogeneity.

IMRT offers a potentially more refined method for inhomogeneity compensation. It utilizes computer-controlled linear accelerators to deliver precise radiation doses that conform more exactly to the 3D shape of the tumor by controlling the intensity of the radiation beam in multiple small volumes.

Researchers at Fox Chase Cancer Center in Philadelphia confirmed IMRT's superiority in the largest study to date comparing the incidence and duration of skin inflammation between patients who received IMRT and those who received conventional radiation treatment.

Their findings were published in the July 1 issue of the International Journal of Radiation Oncology, Biology, Physics (2009, Vol. 74:3, pp. 689-694).

Breast cancer patients who received IMRT benefit from a more homogeneous dose distribution, lower radiation dose delivered to normal heart or lung tissue, low incidence of acute toxicity, and reduced incidence of subacute complications and undesirable cosmetic changes, compared with whole-breast radiation therapy. IMRT also reduces acute dermatitis, a condition that affects up to 50% of women receiving radiation therapy.

Lead author Dr. Gary Freedman, a radiation oncologist, led a team that evaluated the medical records of more than 800 women with stages 0, I, or II breast cancer who completed radiation therapy performed between 2001 and 2006 at Fox Chase. All 804 women received whole-breast radiation of 46-50 Gy, with or without regional nodal radiation, and a boost to the tumor bed of 10-18 Gy. The conventional technique using wedged tangents of radiation was given to 405 women, while 399 patients received IMRT.

The IMRT technique used at Fox Chase consisted of a combination of open and segmented tangential fields using volume-based inverse dose planning and step-and-shoot beam delivery. To make as valid a comparison as possible between the two groups, patient positioning, tangential beam orientation, and field sizes were kept the same when determining clinical target volume, according to Freedman.

Skin toxicity was evaluated on a weekly basis for each patient, as well as six weeks after treatment was completed. Patients who received IMRT had milder dermatitis, with 48% having grade 0/1 toxicity and 52% having grade 2/3. By comparison, 25% of patients who received conventional radiotherapy had grade 0/1 toxicity and 75% had grade 2/3.

IMRT also reduced the absolute number of weeks the patients experienced acute dermatitis, according to Freedman. Women treated with IMRT experienced grade 2 toxicity approximately one to two weeks later during their course of therapy, compared to women treated with the conventional technique, who spent the majority of treatment time with grade 2 dermatitis.

For both types of radiation therapy treatments, dermatitis increased in severity with breast size.

Percent of patients with grade 0/1 skin toxicity
Breast size IMRT Whole-breast RT
Small 70% 40%
Medium 59% 30%
Large 32% 10%

Percent of patients with grade 2/3 skin toxicity
Breast size IMRT Whole-breast RT
Small 30% 60%
Medium 41% 70%
Large 68% 90%

Freedman and colleagues believe that their study provides additional proof that there are observable benefits to moving beyond conventional radiation therapy for breast cancer treatment. They recommend further research so that a standard definition of breast IMRT can be formally adopted, noting that today many variations of IMRT are being used.

By Cynthia E. Keen
AuntMinnie.com staff writer
July 20, 2009

Related Reading

Breast intensity-modulated radiotherapy curbs acute skin reactions, May 27, 2008

Breast IMRT without the overspill, March 3, 2008

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