Impact of surgical delay beyond 8 weeks on tumor progression and lymph node involvement in early breast cancer: Insights from the KHRONOS Project.

Abstract

e12552 Background: Recent evidence highlights a potential negative impact of delaying surgery for early breast cancer (BC) beyond 8 weeks; however, the interplay between tumor biology and timing remains underexplored. This study investigates the role of surgical delay on tumor progression and lymph node (LN) involvement, emphasizing the biological heterogeneity of BC. Methods: This retrospective cohort study analyzed data from 924 early-stage BC patients (pts) (2015-2023). 267 pts underwent PAM50 testing to determine their intrinsic subtype. Patients had no initial radiological LN involvement and underwent primary surgery. Tumor progression and nodal status transition (N0 to N+) were analyzed based on surgical timing (≤ 8 weeks vs. > 8 weeks). Chi-square and ANOVA tests were employed to assess associations between clinicopathologic variables and outcomes. Results: 664 pts in our cohort (71.9%) underwent breast-conserving surgery, while 260 pts (28.1%) were treated with mastectomy. A total of 204 pts (22.08%) had a G3 tumor grade. The majority of tumors (784 pts; 84.89%) were smaller than 5 cm, as determined by mammography. Among the 267 pts who underwent the PAM50 test, 260 pts were classified within the luminal intrinsic subtype (141 pts as Luminal A and 120 pts as Luminal B). No significant differences were observed in tumor size progression or lymph node involvement between pts who underwent surgery within 8 weeks and those who experienced delays (p > 0.05). Subgroup analysis revealed that pts with G3 tumors had a higher likelihood of nodal progression when surgery was delayed (37.8% vs. 23.8%, p = 0.034). Additionally, the Luminal B subtype demonstrated increased nodal involvement associated with surgical delays (7,1% vs. 20,4%, p = 0.037). Conclusions: The subgroup of high-risk pts (G3) and luminal intrinsic subtype B may be associated with increased lymph node involvement following a surgical delay of > 8 weeks. These findings emphasize the importance of tumor biology in surgical prioritization and highlight the necessity for strategies to minimize delays in high-risk pts.