News Author: Allison Gandey
CME Author: Désirée Lie, MD, MSEd
The long-term 10-year data are in and they show what many have been hoping — that boosting radiation to the breast prevents cancer recurrence. Boost doses have been standard for decades, but now clinicians have evidence to back what they have long suspected. The results were presented here at the American Society for Therapeutic Radiology and Oncology (ASTRO) 49th Annual Meeting.
"The study found that the largest benefits of the boost dose of radiation after standard breast-conserving treatment are seen in young women who have a higher risk for breast cancer recurrence to begin with," senior author Harry Bartelink, MD, PhD, from the Netherlands Cancer Institute at Antoni van Leeuwenhoek Hospital, in Amsterdam, said in a news release promoting the findings.
During an interview with Medscape Oncology, Shiv Khandelwal, MD, from the University of Virginia, in Charlottesville, called this an important study. "We've had a number of uncontrolled retrospective studies that suggested a benefit of boosting radiation, but there was never any prospectively conducted research," he said. "The study is very useful because it has changed this and it did show a benefit."
Early results from the randomized boost-vs-no-boost trial by the European Organization for Research and Treatment of Cancer were published in the New England Journal of Medicine (Bartelink H et al. N Engl J Med. 2001;345:1378-1387). Updated results were published in the August 1 issue of the Journal of Clinical Oncology (Bartelink H et al. J Clin Oncol. 2007;25:3259-3265).
Lead author Heather Jones, MD, from the Holzer Cancer Center for Cancer Care, in Gallipolis, Ohio, presenting at a plenary session, showed the impact of boost dose and margins on the local recurrence rate in breast-conserving therapy.
Is the Boost Too High at 16 Gy?
The investigators looked at more than 5300 breast cancer patients who had undergone complete excision. The median follow-up time was 10.8 years. Patients received external irradiation of 50 Gy and were randomized to receive either a boost of 16 Gy or no boost.
Speaking to Medscape Oncology, Dr. Khandelwal suggested that researchers have never offered a clear justification for why they selected a boost dose of 16 Gy, which is a little higher than most centers in the United States routinely use. Radiation of 50 Gy "to the whole breast is very standard, and I would say that it represents what most centers are doing, but 16 Gy for the boost seems a bit high; the problem with that is that this is the dose that has now been tested." He is concerned there will be pressure for clinicians to switch to a perhaps unnecessarily higher dose.
Presenting at the meeting, Dr. Jones said that a boost dose of 16 Gy reduced the local recurrence rate from 12% to 7% (hazard ratio, 0.59). She said that this relative reduction was similar in all age groups. But, she noted, severe fibrosis increased with the boost 1.6% compared with 4.4%.
The investigators also conducted a subset analysis of more than 1700 patients who participated in the completely or incompletely resected sections of the trials. All had a central pathology review by 1 expert, and local pathologists were asked to submit a set of representative slides. All patients had invasive tumor with or without accompanying ductal carcinoma in situ evaluated.
The researchers found that the largest risk factor for ipsilateral breast tumor recurrence was young age. They also found that a high grade of invasive tumor or ductal carcinoma in situ was a more significant risk factor than margin status.
"A boost dose of 16 Gy significantly improved local control in patients with complete excision," Dr. Jones told the meeting. "In the subgroup of patients with central pathology review, margin status was not associated with increased risk for local recurrence," she said. But, Dr. Jones pointed out, age and boost were independent factors associated with local control.
The researchers have disclosed no relevant financial relationships.
American Society for Therapeutic Radiology and Oncology 49th Annual Meeting: Plenary 4. Presented October 29, 2007.
http://www.medscape.com/viewarticle/565332?src=mp
