The study 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.
Rinaa Punglia, 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 tumour. Punglia said four to six weeks after surgery is widely viewed as a safe interval for beginning radiotherapy.
The researchers reviewed Medicare database records of 18,050 women age 65 and older 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 four percent of the women experienced a local recurrence. The risk increased to about five 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."
The study revealed more delays in areas such as the Northeast and fewer delays in the southern states. Waiting times were longer in cases involving African-American and low-income women, but the study did not pinpoint the exact source of the delay. "It could be factors such as access to care, the patients’ ability to navigate the healthcare system, or physician referrals," said Punglia. The findings may also have implications for younger women. "It's possible that the increased risk we identified in older women could be magnified in younger women, whose tumours are biologically different and tend to be more aggressive," said Punglia.
MEDICA.de; Source: Dana-Farber Cancer Institute