Impact of environmental temperature on the survival outcomes of breast cancer: A SEER-based study

Experimental evidence in tumor-bearing mouse models shows that exposure to cool, that is, sub-thermoneutral environmental temperature is associated with a higher tumor growth rate and an immunosuppressive tumor immune microenvironment than seen at thermoneutral temperatures. However, the translational significance of these findings in humans is unclear. We hypothesized that breast cancer patients living in warmer climates will have better survival outcomes than patients living in colder climates.

A retrospective population-based analysis was conducted on 270,496 stage I-III breast cancer patients, who were retrieved from the Surveillance, Epidemiology and End Results (SEER) over the period from 1996 to 2017. The average annual temperature (AAT) was calculated based on city level data from the National Centers for Environmental Information.

A total of 270, 496 patients were analyzed. Temperature as assessed in quartiles. After adjusting for potential confounders, patients who lived in the 3rd and 4th quartile temperature regions with AAT 56.7-62.5°F (3rd quartile) and > 62.5°F (4th quartile) had a 7% increase in the OS compared to patients living at AAT < 48.5°F (1st quartile) (HR 0.93, 95% CI 0.90-0.95 and HR 0.93, 95% CI 0.91-0.96, respectively). For DSS, When comparing AAT quartiles, patients living with AAT in the range of 56.7-62.5°F and > 62.5°F demonstrated a 7% increase each in DSS after adjustment (HR 0.93, 95% CI 0.90-0.96 and HR 0.93, 95% CI 0.90-0.96).

Higher environmental temperatures are associated with significantly better OS and DSS in breast cancer patients. Future research is warranted to confirm this observation using large datasets to elucidate the underlying mechanisms and investigate novel therapeutic strategies to minimize this geographic disparity in clinical outcomes.