In Patients with Early Breast Cancer, Intensity-Modulated Radiotherapy Reduces Side Effects

The randomized trial findings were presented April 22, 2013, at the 2nd
Forum of the European Society for Radiotherapy and Oncology (ESTRO), held in Geneva (Switzerland). IMRT is an advanced, high-precision form of
radiotherapy that can deliver an even dose of radiation, thus reducing the cosmetic problems that can often occur after breast radiotherapy.

“We believe that this study, the largest prospective trial in the world to
test breast IMRT against standard two-dimensional radiotherapy, will be
practice-changing at an international level,” said Dr. Charlottes Coles, from Addenbrooke’s Hospital Oncology Center (Cambridge, UK) “Analyzing the results five years after treatment, we saw significant benefits in patients who had received IMRT.”

Researchers analyzed the radiotherapy treatment plans of 1,145 patients
with early breast cancer who had previously had breast-conserving surgery. The plans were screened to see if they would produce an uneven radiation dose with standard two-dimensional radiotherapy (2DRT). Seventy-one percent of the plans fell into this classification, and those patients were randomized between conventional 2DRT and IMRT. The 29% of patients whose plans would not produce an uneven dose were treated with standard 2DRT, but still followed up within the trial.

One of the objectives of external radiotherapy is to treat the target—in
this instance the whole breast—with an even dose distribution, i.e.,
within 95%–107% of the prescribed dose. Too low a dose can risk tumor recurrence, and too high a dose can cause undesirable side effects such as skin changes. The researchers tried to determine whether the effect of
using IMRT in those patients who would have received a dose greater than 107% to areas of their breast with 2DRT would translate into clinical benefit. IMRT planning uses results from scans to determine the dose intensity that will best treat the tumor, and therefore is more complex and time-consuming than 2DRT planning, so there was an important need to see a clear advantage to patients from the use of the procedure.

The only prior research looking at this was much smaller, and instead of
selecting all patients with doses greater than 107% and randomizing them, it only included women with larger breasts who are already known to be more likely to have regions of dose above the upper limit. “Our trial was more inclusive as all women were able to take part and we could quantify those who would receive an uneven dose,” said Dr. Coles. “We saw that fewer patients in the IMRT group developed skin telangiectasia, and the overall cosmetic effect in the breast was better,” she said. Although there was no significant difference between the two groups in breast edema, breast shrinkage, breast induration, and pigmentation alterations, the advantages of using IMRT in these patients were obvious. The researchers’ goal is to follow-up their research by studying the patients’ questionnaires to see whether IMRT has an influence on quality of life.

The trial has also contributed 1,000 blood samples to the UK translational
research RAPPER (Radiogenomics: Assessment of Polymorphisms for Predicting the Effects of Radiotherapy) study, which intends to eventually develop individualized radiotherapy plans based on the analysis of individual patients’ genetic composition.

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Addenbrooke’s Hospital Oncology Center