Intensity modulated radiotherapy reduces side effects in patients with early breast cancer

Geneva, Switzerland: Intensity modulated radiotherapy (IMRT) gives better results than standard radiotherapy in patients with early breast cancer, according to results from a randomised trial presented today (Sunday) to the 2nd Forum of the European Society for Radiotherapy and Oncology (ESTRO). 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 Centre, Cambridge, UK. "Analysing the results five years after treatment, we saw significant benefits in patients who had received IMRT."

The researchers analysed the radiotherapy treatment plans of 1145 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). A total of 71% of the plans fell into this category, and those patients were randomised between standard 2DRT and IMRT. The 29% of patients whose plans would not produce an uneven dose were treated with standard 2D RT, but still followed up within the trial.

One of the aims of external radiotherapy is to treat the target – in this case the whole breast – with an even dose distribution, i.e. within a range of 95% to 107% of the prescribed dose. Too low a dose can risk tumour recurrence, and too high a dose can cause undesirable side-effects such as skin changes.

"The problem with 2D breast radiotherapy is that the dose distribution is only recorded across the central part of the breast. Usually it meets the 95-107% constraints, but the shape of the breast changes, so if the same plan is looked at in 3D, then there may well be areas with overly high doses. By modulating the intensity of the radiation beam, IMRT can be used to correct for this and smooth out the dose," said Dr Coles.

The researchers set out to see whether the effect of using IMRT in those patients who would have received a dose greater than 107% to parts 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 tumour, 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 previous study looking at this was much smaller, and rather than picking out all patients with doses greater than 107% and randomising 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.