Older women who have had breast cancer surgery have a greater risk of the cancer returning if they delay their post-surgical radiation treatment, report Dana-Farber Cancer Institute scientists.
The study, which involved more than 18,000 women age 65 and older who had breast cancer, found that those who started radiation treatment more than six weeks after breast-conserving surgery were more likely to have a local recurrence than those whose radiation treatment started within six weeks of surgery.
The findings are being published online by the British Medical Journal.
Rinaa Punglia, MD, MPH, a radiation oncologist at Dana-Farber and Brigham and Women’s Hospital and the study’s lead author, said she and her colleagues conducted the research to address scientifically the debate about the “appropriate interval between surgery and radiation treatment, or radiotherapy, and its impact on treatment outcomes.”
Post-surgical radiotherapy is designed to destroy remaining cancer cells following the removal of a localized breast tumor. Punglia said four to six weeks after surgery is widely viewed as a safe interval for beginning radiotherapy, which typically is administered five days a week for six weeks.
The researchers reviewed Medicare database records of 18,050 women with early stage breast cancer to assess whether the timing of when radiotherapy started following surgery affected outcomes. These women were treated between 1991 and 2002 with lumpectomy and radiation, but not chemotherapy. Thirty percent of women began radiotherapy six or more weeks after surgery.
For the overall group, slightly more than 4 percent of the women experienced a local recurrence. The risk increased to about 5 percent, approximately a 19 percent jump, when the surgery-radiotherapy interval was longer than six weeks. The researchers found that there was no “threshold” at which the risk suddenly rose ? it increased incrementally day by day. “There isn’t a large difference between 43 days instead of 41,” commented Punglia. “The day-to-day risk increase is very small.”
Although the study focused on older women, the findings have implications for younger women.
The study’s other authors are Bridget Neville, MPH, and Jane Weeks, MD, MSc, of Dana-Farber; Craig Earle, MD, formerly of Dana-Farber and now of the Ontario Institute for Cancer Research, Toronto; and Akiko Saito, MD, PhD, formerly of Dana-Farber and now of Nagoya Medical Center, Japan.
Source: Dana-Farber Cancer Institute, USA