Women at a high risk of developing breast cancer will probably benefit from additional lymph node radiotherapy, Dr Philip Poortmans, from the Dr. Bernard Verbeeten Instituut, Tilburg, The Netherlands, and a member of the EORTC* Radiation Oncology Group, will say.
Initial findings from the 4,004-patient multi-centre study carried out by the EORTC radiotherapy and breast cancer groups (46 institutions from 13 countries) show that there is no evidence of increased toxicity to the heart at three years follow-up in patients who received additional lymph node radiotherapy.
Patients will be followed-up for many years to see whether specific lymph-node radiotherapy could lead to long-term damage of the heart or the lungs, side effects that are associated with breast cancer radiotherapy.
Dr Philip Poortmans, one of the trial co-ordinators, will tell delegates that the longer-term aim of the EORTC study is to see whether giving additional radiotherapy to the lymph nodes located behind the breast bone and above the collar bone (internal mammary and medial supraclavicular [IM-MS] lymph nodes) to patients with early operable breast cancer will improve overall survival.
“The first analysis of the primary endpoint, overall survival at 10 years, was planned to be performed in 2012. However, thanks to the actual survival estimate that is even higher than expected, this might have to be postponed until 2014,” Dr Poortmans will say.
“We are hopeful that we will see a survival benefit of at least five percent in patients at the time of the primary analysis,“ Dr Poortmans will say. “With a median follow-up of over seven years, 558 patients have died, so the estimated 10-year overall survival rate of 79%–83% is even above the anticipated range,” he added.
The majority of patients (76%) had breast-conserving surgery and the remainder had undergone complete removal of their breast (24%). All patients (99.4%) who had breast-conserving surgery received standard radiotherapy to the breast as well as a boost, and 73% of mastectomy treated patients received chest wall radiotherapy. Following this, patients were randomised to receive IM-MS lymph node radiotherapy or no further lymph node therapy.
Radiotherapy is usually given after breast cancer surgery to destroy any cancer cells that remain in the breast, chest wall, or underarm area, in order to reduce the risk of a local recurrence of cancer in that breast. But there is disagreement amongst cancer experts regarding the management of the internal mammary lymphnodes (lymph nodes located behind the breast bone) in patients with breast cancer. The question of whether specific internal mammary lymph node radiotherapy leads to improved survival in women with early breast cancer is currently being addressed by the EORTC radiotherapy and breast cancer groups.
Dr Poortmans said that the final overall survival data analysis will show if internal mammary lymphnode radiotherapy provides local control and improves overall survival in women with early breast cancer. “This is an important issue for radiotherapists and breast cancer patients alike, and we are eagerly awaiting the efficacy results from this trial,” he says.
*EORTC = European Organisation for Research and Treatment of Cancer
Institutions from the following countries participated in the trial: Belgium, Bosnia and Herzegovina, Chile, France, Germany, Israel, Italy, The Netherlands, Poland, Portugal, Spain, Switzerland and United Kingdom.
Sources of funding: National Cancer Institute (Bethesda, Maryland, USA) and Vlaamse Liga Tegen Kanker.
Abstract no: 6, Saturday 27 March, 11.00 hrs CET (Lecture Hall 1)