IMRT Allows Higher Radiation Therapy Dose for Breast Cancer

Women with breast cancer who receive higher doses of radiation with IMRT each day can reduce their treatment time by two weeks without increasing side effects, according to a study released today in the June 1 issue of the International Journal of Radiation Oncology*Biology*Physics, the official journal of the American Society for Therapeutic Radiology and Oncology.

Intensity modulated radiation therapy (IMRT) is a specialized form of radiation therapy that allows the radiation to be more exactly shaped to fit the tumor. With IMRT, the radiation beam can be broken up into many “beamlets,” and the intensity of each beamlet can be adjusted individually. In some cases, this may allow doctors to send a higher dose of radiation to the tumor, potentially increasing the chance of a cure.

In this particular study, IMRT was delivered with an additional concurrent “boost,” or high-dose radiation to the lumpectomy site where the tumor was removed. The standard boost is typically given after the four to five weeks of conventional radiation therapy and adds another one to two weeks to the treatment time. The boost in this study was given during the four weeks of whole breast irradiation to see if the increased dose would increase side effects. Some women who receive standard radiation therapy for breast cancer develop skin irritation as a side effect from the radiation’s effect. This side effect is similar to sunburn and usually heals on its own once treatment ends. Doctors believe that without the use of IMRT, the elevated level of radiation would not be tolerated by the patients.

Seventy-five women were treated in this Phase II study using IMRT for four weeks, as opposed to the traditional six to seven weeks. The women were treated with a slightly higher radiation dose to the entire breast while also delivering the boost to the original lumpectomy site of the breast. Though the dosage of radiation was increased, the daily treatments of radiation were at a well-tolerated level. Doctors graded the skin toxicity of each patient on a scale of Grade 0 (no skin toxicity present) to Grade 9 (severe toxicity). More than half of the women, 65 percent, had Grade 1 skin toxicity at the end of the four week treatment period, with 23 percent of the women reporting a skin toxicity of Grade 2. The other 12 percent had Grade 0 toxicity, meaning they showed no skin irritation. None of the patients had higher than Grade 3 toxicity.

In the short-term follow-up of six weeks, doctors found that the all toxicity levels had returned to normal, including the women who had Grade 2 skin toxicity.

This study demonstrated that in addition to safely increasing the daily dose to the whole breast during the four-week period, it is possible to deliver the “boost” concurrently, eliminating the extra two weeks and possibly sparing the women from more discomfort during the post-operative treatment.

“Earlier studies have proven without a doubt that six to seven weeks of radiation therapy after a lumpectomy cures most early-stage breast cancers. Now, we’re working to find ways to make the treatments easier for patients by reducing side effects or shortening the treatment. This study presents a good foundation of knowledge for the potential of IMRT for breast cancer,” said Gary Freedman, M.D., lead author of the study and a radiation oncologist at Fox Chase Cancer Center in Philadelphia. “With long-term follow up and further study, we can aim to condense the length of post-operative treatment for these women.”