Disaggregating Asian American and Pacific Islander subgroups to evaluate disparities in breast cancer characteristics and outcomes.

1595 Background: When Asian American and Pacific Islander (AAPI) subgroups are aggregated under the labels “AAPI” or “Asian,” subgroup‐specific differences in breast cancer (BC) presentation and outcomes may be masked. Potential overlooked disparities among these diverse groups remain understudied. We analyzed BC characteristics and outcomes among regional AAPI subgroups. Methods: From the National Cancer Database (2009–2020), we identified patients diagnosed with stage I–IV BC, excluding patients missing race or stage. Multivariate logistic regression examined odds of advanced stage (III–IV), high‐grade histology, and triple-negative BC (TNBC) at diagnosis. Multivariate Cox regression assessed three-year overall survival (OS). Age, comorbidity index, diagnosis year, and zip code income quartile were analyzed to account for confounding. Results: Of 1,956,145 total patients, there were 61,731 pooled AAPI patients, comprised of East Asian (n=23,643), South Asian (n=13,642), Southeast Asian (n=19,000), and Pacific Islander (PI) (n=5,446) subgroups. Non‐Hispanic White (NHW) (n=1,639,814) served as the reference group. Compared to NHW, pooled AAPI had higher odds of advanced stage (adjusted odds ratio [aOR] 1.09; 95% CI 1.07–1.12; p<0.001) and high‐grade histology (aOR 1.21; 95% CI 1.17–1.25; p<0.001). There was no difference in odds of TNBC (0.98; 0.92–1.03; p=0.41). Despite this, AAPI had better three‐year OS (hazard ratio [HR] 0.79 (0.76–0.82; p<0.001). Compared to NHW, each AAPI subgroup had higher odds of high‐grade histology and better OS except for PIs, who had similar odds of both. South Asians and Southeast Asians had higher odds of advanced stage (aOR 1.27; 1.21–1.34; p<0.001 and 1.22; 1.17–1.27; p<0.001, respectively), while East Asians had lower odds (0.86; 0.83–0.90; p<0.001). South Asians showed increased odds of TNBC (aOR 1.11; 1.00–1.23; p=0.04), whereas Southeast Asians (0.82; 0.73–0.91; p<0.001) and PIs (0.81; 0.66–0.98; p=0.036) showed lower odds. Conclusions: Disaggregating AAPI subgroup data is necessary to understand disparities in BC among these heterogenous populations. Further studies are warranted to evaluate disparities in healthcare delivery and its efficacy in these subgroups. Breast cancer characteristics by AAPI and subgroup. Advanced Stage(aOR, 95% CI) High-Grade (aOR, 95% CI) TNBC (aOR, 95% CI) Three-Year OS (HR, 95% CI) NHW (Reference) 1.00 1.00 1.00 1.00 AAPI 1.09 (1.07–1.12)** 1.21 (1.17–1.25)** 0.98 (0.92–1.03) 0.79 (0.76–0.82)** East Asian 0.86 (0.83–0.90)** 1.12 (1.07–1.18)** 1.06 (0.97–1.15) 0.71 (0.67–0.75)** Southeast Asian 1.22 (1.17–1.27)** 1.30 (1.24–1.38)** 0.82 (0.73–0.91)** 0.84 (0.78–0.89)** South Asian 1.27 (1.21–1.34)** 1.28 (1.21–1.36)** 1.11 (1.00–1.23)* 0.75 (0.69–0.82)** PI 1.31 (1.21–1.42)** 1.10 (0.99–1.21) 0.81 (0.66–0.98)* 1.06 (0.96–1.18) *p-value <0.05. **p-value <0.001.