Women with early-stage breast cancer are generally treated with breast-conserving surgery, or lumpectomy, which minimises the amount of breast tissue removed, followed by radiation therapy to the whole breast. Clinical studies have shown that this treatment approach is associated with a low risk of the cancer returning (recurrence) while maintaining the shape of the breast as much as possible. It provides an effective alternative approach to mastectomy, in which the breast is completely removed.
The problem with radiation therapy to the whole breast is that about one-third of women suffer acute side-effects to the skin where the radiation is concentrated. The top layers of the irradiated skin are broken down and the area becomes 'weepy' in a process referred to technically as 'moist desquamation.'
The complex, three-dimensional shape of the breast makes it difficult to deliver radiation at a uniform dose throughout the entire breast using conventional radiotherapy equipment. This results in radiation 'hot spots' that can cause skin damage. Wedges are used to try to protect narrower parts of the breast and various other approaches, such as creams, have been tried in efforts to reduce skin problems due to radiotherapy, but none have proved very effective.
Breast intensity-modulated radiation therapy uses a computerised planning system that calculates the dose of radiation delivered to each part of the breast allowing for changes in its shape. Essentially, it allows rapid blocking of the radiation beam in areas of the breast where the dose of radiation needs to be reduced to achieve more even dosing throughout the changing contours of the breast.
In the new study, Canadian researchers randomly assigned 358 women with early-stage breast cancer to intensity-modulated radiation therapy or to standard radiotherapy using wedges. They wanted to know if the new radiotherapy technique reduced acute skin reactions and the pain they cause and improved the women's quality of life.
Results in 331 women who completed the study showed that significantly fewer suffered moist desquamation during, or up to six weeks after, their radiation treatment with the new approach compared to those having traditional radiotherapy. Just under one in three women (31.2%) had the acute skin problem with intensity-modulation radiation therapy compared with nearly half (47.8%) of those undergoing standard treatment (P=0.002).
Using the new radiotherapy strategy did not significantly reduce pain or improve quality of life. The researchers thought this may have been because the measures they used for these factors were rather non-specific. However, their results showed that the occurrence of moist desquamation was significantly correlated with pain (P=0.002) and reduced quality of life (P=0.003).
The distribution of radiation dose within the breast was significantly improved with IMRT. Less than one-tenth (7.7%) of the volume of the breast received more than 105% of the prescribed radiation dose with the technique, compared to more than one-sixth (16.9%) with standard radiotherapy.
Commenting on the findings, the researchers, led by Jean-Philippe Pignol from the Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Canada, said: "To our knowledge, this the first multicentre randomised trial demonstrating a successful reduction in acute radiation skin toxicity using an improved radiation technique, breast IMRT."
"Our trial confirmed the dramatic improvement in the dose distribution homogeneity using breast IMRT, and demonstrated that it translated into a significant 17% absolute reduction in the frequency of moist desquamation."
They considered that their results supported breast IMRT being offered to patients receiving adjuvant breast radiotherapy instead of the standard wedge technique.
US-based breast radiation therapy specialists agreed. Writing in an accompanying editorial, Bruce Haffty (Cancer Institute of New Jersey, New Brunswick), Thomas Buchholz ( M.D. Anderson Cancer Center, Houston) and Beryl McCormick ( Memorial Sloan-Kettering Cancer Center, New York) said that the study "may have a significant impact on the practice of breast radiation." They recommended: "Most facilities that have the necessary planning equipment and technology available should strive for optimal homogeneity, which can be readily achieved with the techniques described."
The editorial writers cautioned that the improvement in treatment planning needed for IMRT is not reimbursed by all healthcare insurers in the US, with technical costs for IMRT treatment being about three times those for non-IMRT treatment. They hoped that these economic issues can be resolved "so that clinical applications of this exciting technology can continue to move forward."
A Multicenter randomized trial of breast intensity-modulated radiation therapy to reduce acute radiation dermatitis.
Pignol J-P et al.
Journal of Clinical Oncology, 10.1200/JCO.2007.15.2488
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