Pathology grade predicts risk of local relapse

Young age and high-grade invasive tumours, but not margin status, are the most important risk factors for local relapse following breast-conserving therapy, research suggests. "The prognostic significance of the surgical margin status might be negated by margin directed tumour bed dose escalation," the researchers wrote in the Journal of Clinical Oncology. The EORTC Boost Versus No Boost Trial investigated the long-term impact of pathological characteristics on local relapse in over 16,000 women whose stage I or II invasive breast cancer had been treated with breast-conserving therapy and whole breast irradiation, with or without an extra boost dose of 16 Gy (with negative margins) or 10 to 26 Gy (with positive margins). On multivariate analysis, the presence of high-grade invasive ductal carcinoma (HR 1.67) and age younger than 50 years (HR 2.38) were associated with a significantly increased risk of local relapse. The additional boost dose of 16 Gy to the tumour bed significantly reduced the local relapse rate (P=.0006; HR 0.47). In patients with high grade invasive ductal carcinoma, the boost reduced the cumulative 10-year local relapse rate from 18.9% to 8.6%. In women younger than 50, the boost dose reduced the 10-year cumulative local relapse rate from 19.4% to 11.4%. The researchers said close or positive tumour margins status had no significant effect on local relapse, but this could be explained by the small number of patients with a positive margin involved in the study. While acknowledging the caveats associated with a subset analysis, the study authors said the results had important implications for clinical practice and may “guide in the decision which patients will benefit from a boost dose of 16 Gy. "Although this subgroup analysis did not find margins to be a prognostic factor for local recurrence, numerous studies have found it to be one of the strongest prognostic factors," a related editorial noted. "Surgical re-excision for positive margins should continue to be routinely performed," it concluded. J Clin Oncol 2009; published online before print....