Distribution of locoregional breast cancer recurrence in relation to postoperative radiation fields and biological subtypes.

Abstract

BACKGROUND\nand purpose: To investigate incidence and location of locoregional recurrence (LRR) in patients who have received postoperative locoregional radiotherapy (LRRT) for primary breast cancer. LRR-position in relation to applied radiotherapy and the primary tumours biological subtype were analysed with the aim to evaluate current target guidelines and RT techniques in relation to tumour biology.\n\n\nMATERIALS AND METHODS\nMedical records were reviewed for all patients who received postoperative LRRT for primary BC in southwestern Sweden from 2004-2008 (N=923). Patients with LRR as a first event were identified (N=57, distant failure and death were considered competing risks). CT images identifying LRR were used to compare LRR locations to postoperative LRRT fields. LRR risk and distribution were then related to the primary BC biological subtype and to current target guidelines.\n\n\nRESULTS\nCumulative LRR incidence after 10 years was 7.1% (95%CI 5.5-9.1). Fifty-seven of the 923 patients in the cohort developed LRR (30 local recurrences (LR), 30 regional recurrences (RR), of which 3 cases of simultaneous LR/RR). Most cases of LRR developed fully (56%) or partially (26%) within postoperatively irradiated areas. The most common location for out-of-field RR was cranial to RT fields in the supraclavicular fossa. Patients with an ER- (HR 4.6, p<0.001, 95%CI 2.5-8.4) or HER2+ (HR 2.4, p=0.007, 95%CI 1.3-4.7) primary BC presented higher risks of LRR compared to those with ER+ tumours. ER-/HER2+ tumours more frequently recurred in-field (68%) rather than marginal/out-of-field (32%). In addition, 75% of in-field recurrences derived from an ER-/HER+ tumour, compared to 45% of marginal/out-of-field recurrences. A complete pathological response in the axilla after neoadjuvant treatment was associated with a lower degree of LRR risk (p=0.022).\n\n\nCONCLUSION\nIncidence and locations of LRR seems to be related to the primary BC biological subtype. Individualized LRRT according to tumour biology may be applied to improve outcomes.