Clinical Scorecard: Geographic and Racial/Ethnic Variations in Second Primary Cancers Among Survivors of Stomach Cancer: A Comparative Analysis Between the United States and South Korea

At a Glance

Key Highlights

• Stomach cancer survival has improved significantly in the U.S. and South Korea, increasing SPC risk among survivors.
• SPC incidence varies by race/ethnicity and geography, with highest SPC proportions in White and Korean American patients in the U.S., and a lower proportion in South Korea.
• Disaggregated Asian subgroups reveal important differences in SPC risk and survival outcomes, underscoring the need for detailed racial/ethnic stratification.

Guideline-Based Recommendations

Diagnosis

• Define SPCs as non-stomach malignancies diagnosed at least 12 months after initial stomach cancer diagnosis to minimize misclassification.
• Exclude non-melanoma and basal cell skin cancers from SPC consideration due to low lethality.

Management

• Consider racial/ethnic and geographic variations when planning survivorship care and SPC surveillance.
• Account for initial cancer treatment factors, such as radiotherapy, which may influence SPC risk.

Monitoring & Follow-up

• Use cumulative incidence estimation methods (e.g., Aalen-Johansen estimator) accounting for competing mortality risks in SPC surveillance.
• Monitor survival outcomes post-SPC development using time-varying covariate models to avoid immortal time bias.

Risks

• Recognize that SPC risk is influenced by race/ethnicity, geographic location, tumor characteristics, and treatment modalities.
• High competing mortality in distant-stage stomach cancer patients limits SPC risk assessment; focus on localized and regional stages.

Patient & Prescribing Data

Stomach cancer survivors in the U.S. SEER-17 registries and South Korea CPLD database, excluding distant-stage and short-term survivors

Radiotherapy for initial stomach cancer may increase SPC risk; survival impact of SPC varies by race/ethnicity and Asian subgroups.

Clinical Best Practices

• Apply consistent inclusion/exclusion criteria across populations for SPC risk assessment to ensure comparability.
• Disaggregate Asian subgroups in clinical data to identify subgroup-specific SPC risks and outcomes.
• Incorporate competing risk methods in SPC incidence estimation to accurately reflect survivor risk.
• Adjust survival analyses for key prognostic factors and model SPC as a time-varying covariate to prevent bias.
• Explore individual- and system-level factors underlying racial/ethnic and geographic disparities in SPC incidence and survival.

References

• Global stomach cancer incidence and mortality statistics
• U.S. stomach cancer survival trends
• South Korea stomach cancer survival data
• SEER Program data
• Cancer Public Library Database (CPLD) South Korea