CHICAGO—After mastectomy, radiation treatment of the internal mammary lymph nodes does not improve the long-term survival rates of breast cancer patients, researchers report.
After 10 years, there was no difference in survival rates between women who underwent internal mammary chain radiation treatment (IMC-RT) and with those who did not, said Pascale Romestaing, MD, a radiation oncologist at Centre de Radiothérapie Mermoz in Lyon, France.
Some retrospective studies have shown that internal mammary chain radiation treatment is not effective, while others have shown that it is effective, she said in her talk here at the plenary session of the American Society for Radiation Oncology (ASTRO) Annual Meeting.
“Now, for the first time, we have a randomized controlled study that answers the important question of whether radiation treatment to the hard-to-treat internal mammary chain lymph nodes benefits patients,” she said.
The study involved 1,334 patients with newly diagnosed Stages I or II breast cancer that had spread to the axillary lymph nodes or whose original tumor was in an internal location in the breast area.
After mastectomy, all the patients received radiation to the chest wall and supraclavicular lymph nodes. Then, half were randomly assigned to specialized IMC-RT.
The primary end point of the trial was to define the impact of IMC-RT on the 10-year overall survival rate.
Over a median follow-up period of 8.6 years, 536 of the women died, 370 due to breast cancer.
The 10-year overall survival rate was 62.6% in the group of patients assigned to IMC-RT, compared with 59.4% in the group that was not assigned to IMC-RT, a difference that was not statistically significant, Dr. Romestaing said.
The researchers then performed three subgroup analyses, depending on whether the cancer had spread to lymph nodes; on the site of the original tumor; and on whether they underwent chemotherapy.
There was no significant difference in 10-year survival rates among the two arms in any of the three analyses, she said.
“Importantly, there was no excess of cardiac toxicity associated with IMC-RT after five years of follow-up—specifically, there were seven Grade 3–4 cardiac events in the arm that received IMC-RT vs five in the arm that did not.
The research received consistently high praise from other researchers. ASTRO 2009–2010 President Anthony L. Zietman, MD, the Jenot W. and William U. Shipley Professor of Radiation Oncology at Harvard Medical School, said that although IMC-RT was not associated with excess cardiac toxicity in this trial, “we run the risk of harming lung and heart muscle whenever we radiate lymph nodes inside the chest call.
“Thankfully, we can now leave these nodes alone.”
And ASTRO's Immediate Past President, Tim R. Williams, MD, a private practitioner at Boca Raton Community Hospital, agreed, “This answers a question we've had for a long time: If we don't have to radiate the internal mammary lymph nodes, we can spare the heart.”
Christopher U. Jones, MD, a radiation oncologist at Radiological Associates of Sacramento who also spoke at the Plenary Session, said that “after mastectomy, whether to radiate the internal mammary lymph nodes is always a concern. Now we have an answer: These women do not need additional radiation to these specialized cells.”
The findings, Dr. Zietman said, are in line “with many of the others we are hearing at this year's meeting. This is not a year of blockbusters with new techniques that will blow us all away. It's a year of introspection, where we are learning about areas where we can pull back, reducing the risk of side effects and making radiation treatment most convenient and cost-effective.”