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SUPERIOR SURVIVAL OF SOUTH AND EAST ASIANS WITH COLORECTAL CARCINOMA IN THE UNITED STATES
Abhineet Uppal*1, Ramkishen Narayanan1, Shu-Ching Chang2, Trevan Fischer1, melanie Goldfarb1
1Surgical Oncology, John Wayne Cancer Institute, Santa Monica, CA; 2Clinical Services Research, Providence Health, Portland, OR
Background: In the UK, South Asians (SAs) with colorectal cancer (CRC) present at a younger age and are reported to have decreased survival compared to Non-Hispanic Whites (NHWs). There is no similar population-based study in the United States (US) in the era of modern chemotherapy regimens. Therefore, this study aims to explore any disparities in presentation, treatment, and survival among SAs and East Asians (EAs) compared to NHWs in the US.
Methods: Adult patients with Stage I-III colon (CC) and rectal (RC) adenocarcinoma diagnosed between 2004 and 2014 were identified in the National Cancer Database. Three ethnic cohorts were studied: SAs of Indian and Pakistani descent (CC: n=931; RC: n=376), EAs of Chinese, Japanese and Korean descent (CC: n=4,002; RC: n=1,310), and NHWs (CC: n=238,439; RC: n=74,869). Demographic, tumor, and treatment characteristics in SAs were compared individually to both EAs and WNHs. Cox proportional hazard analysis assessed the independent influence of ethnicity on overall survival (OS).
Results: SAs with CCs were more often male (CC: 56.2% vs 48.5%, p<0.001), and SAs with CRCs were younger (age<65) (CC: 57.8% vs 37.2%, p<0.001; RC: 71.3% vs 56.8%, p<0.001) compared to NHWs. SAs and EAs with CC had more left-sided tumors than NHWs (52.4% and 52.0% vs 38.4%, p<0.01). For both CC and RC, the distribution of T and N stages was similar in SAs and NHWs (p=NS), but SAs had fewer node-positive tumors than EAs (CC: 37.7% vs. 42.9%, p=0.02; RC: 22.1% vs 26.2%, p<0.05). However, SAs were more likely to receive chemotherapy for both Stage II and Stage III CCs (Stage II: 18.2% vs 12.3%, p<0.001; Stage III: 65.7% vs 52.9%, p<0.001). Systemic and radiotherapy for RC did not vary between ethnicities. For Stage III CC, SAs and EAs had a significantly greater 5-year OS compared to NHWs (SA 69.9%, EA 68.4% and NHW 57.7%, p<0.001). SAs, but not EAs, with Stage III RCs had significantly higher 5-year OS than NHWs (SA 81.5%, EA 66.6%, NHW 65.2%, p<0.001). These differences between ethnicities were also observed for Stage II CCs and RCs. After controlling for tumor stage, treatment, and demographics, both SA and EA ethnicity were strong independent predictors of improved OS in CC (SA: HR 0.68 [0.50-0.78]; EA: HR 0.70 [0.66-0.74]; p<0.001) and in RC (SA: HR 0.54 [0.41-0.70]; EA: HR 0.83 [0.75-0.91]; p<0.001).
Conclusion: CRC in the US presents at an earlier age in South Asians compared to Non-Hispanic Whites. However, in contrast to the UK, despite equivalent T and N stages at presentation, SAs in the US with non-metastatic colon cancer were more likely to receive systemic therapy. In addition, SAs with colon and rectal cancers, and EAs with colon cancers, had improved 5-year overall survival compared to NHWs. This suggests that both biology and environment may have significant impacts on survival in CRC, necessitating further research.
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