341P Impact of environmental temperature on clinical outcomes of early-stage breast cancer (BC)

Preclinical evidence using mouse model suggests that thermal/cold stress increases tumor growth by modulating the tumor microenvironment; however, the clinical relevance of temperature on BC outcomes is unknown. Studies show that residing in cold regions is associated with higher incidence of BC. We aim to study the impact of environmental temperature on the pathological complete response (pCR) and survival of early-stage BC patients (pts). A multi-institutional study was conducted within the Oncology Research Information Exchange Network. We analyzed the clinical and genomic data for early-stage BC pts from 12 centers in the United States from different environment zones (5 warm (W) and 7 cold (C)) (based on average annual regional temperature obtained from National Centers for Environmental Information). Cox regression was used to measure the association of climate and overall/relapse-free survival (OS/RFS) after adjusting for confounders. Out of the 1,304 early-stage BC pts, 271 pts received neoadjuvant chemotherapy (NAC) (186 W, 85 C). Higher clinical T- and N-stages were observed in pts from W compared to C regions (p<0.001). Pts residing in C regions had more comorbidities (57.6% vs 48%, p<0.001). Pts in W regions had higher pCR, though not statistically significant (8% vs 2.5%, p= 0.1). The OS (univariate (UV) HR= 0.48, 95% CI 0.27-0.64, p <0.001; multivariate (MV) aHR= 0.56, 95% CI 0.32 - 0.96, p= 0.03) and RFS (UV HR= 0.51, 95% CI 0.38 - 0.68, p<0.001; MV aHR= 0.52, 95% CI 0.36 - 0.75, p= 0.0005) were higher in pts from W compared to C regions (Table). The OS (aHR= 0.35, p= 0.02) and RFS (aHR= 0.49, p= 0.02) of pts who received NACT were also higher in W regions.Table: 341PRegions (n)5-yr OS (95% CI)Median OS (months) (95% CI)5-yr RFS (95% CI)Median RFS (95% CI)p-valueCold (782)83 (76-86) %157.7 (116.6-NR)69 (62-76) %108.4 (88.9-147.8)<0.001Warm (522)95 (92-97) %214.7 (205.3-NR)83 (79-87) %250.4 (129.9-250.4) Open table in a new tab Early-stage BC pts living in cold have worse OS and RFS compared to warm regions. Larger studies are warranted to validate these interesting findings and further research focusing on therapeutic strategies to abrogate this outcome disparity by temperature is needed.