The study analysed data from 1,173 women in three clinical trials who had surgery for breast cancer, but no further treatment. The researchers found two relapse peaks: one at 18 months, and another five years. A closer analysis showed that 20 percent of premenopausal, node-positive patients relapsed within the first ten months after removal of the primary tumour.
The researchers, led by Michael Retsky, PhD, an investigator in the Vascular Biology Program at Children’s Hospital Boston, believe their observations may help to explain the so-called “mammography paradox” among women aged 40 - 49: a counterintuitive temporary excess in mortality for the screened population compared to controls.
Calculations based on their data predict that surgery-induced angiogenesis would accelerate disease by a median of two years and produce 0.11 early deaths per 1000 screened young women in the third year of screening.
Although the study did not look at biological mechanisms of relapse, primary tumours have been shown to secrete angiogenesis inhibitors, which naturally inhibit the growth of metastases, so surgery to remove the primary tumour might eliminate this inhibition. Alternatively, surgery might spur release of angiogenesis promoters through a wound-healing mechanism.
“Cancer outgrowth after surgery has been observed for over 100 years, and the mechanisms have not been fully identified,” comments Retsky. “Our analysis suggests that biology may be the underlying cause, rather than something going wrong during surgery. It also suggests that while most young women benefit from early detection of breast cancer, a small percentage will relapse and die early of metastatic disease. The paper suggests remedial steps that might prevent the sudden growth from occurring.”
MEDICA.de; Source: Children's Hospital Boston