2121 - Trends in Neoadjuvant Radiation Therapy Utilization and Survival Outcomes for Locally Advanced Rectal Cancer in the Era of Total Neoadjuvant Therapy: A SEER Population-Based Analysis
Presenter(s)
J. Lasington1, L. S. Mathew Lasington2, and S. Umamaheshwaran3; 1New York Medical College at St. Mary's and St. Clare's, Denville, NJ, 2Rutger's University, East Hanover, NJ, 3Personio, Manhattan, NY
Purpose/Objective(s): Total neoadjuvant therapy (TNT) has transformed treatment for locally advanced rectal cancer (LARC). We characterized national trends in RT utilization patterns and survival outcomes across treatment eras using the SEER database
Materials/Methods: We identified 59,759 patients with Stage II/III rectal or rectosigmoid junction cancer (SEER, 2004-2022). Patients were classified by RT approach: neoadjuvant, adjuvant, or no RT. Three eras were defined: Pre-TNT (2004-2012), Transitional (2013-2017), and TNT (2018+). Overall Survival (OS) was evaluated by Kaplan-Meier analysis with log-rank testing. Multivariable Cox regression adjusted for age, sex, race/ethnicity, stage, chemotherapy, and treatment era. Racial disparities in neoadjuvant RT utilization were assessed across eras.
Results: Neoadjuvant RT increased from 29.3% (2004) to a peak of 52.6% (2018), while adjuvant RT declined from 27.0% to 5.6% (Chi-square trend p=6.62×10?³4). In the TNT era, neoadjuvant RT was used in 49.8% vs 38.3% Pre-TNT; adjuvant RT dropped from 18.3% to 7.3%. Median OS was 150 months (neoadjuvant), 136 (adjuvant), 95 (no RT) (all pairwise p<0.001). The TNT era was independently associated with improved survival (HR 0.78, 95% CI 0.74-0.81, p<0.005). After adjustment, adjuvant and no-RT showed equivalent outcomes to neoadjuvant RT, suggesting appropriate patient selection. NHB patients had lower neoadjuvant RT use (47.1% vs 49.8% TNT era) and worse survival (HR 1.36, p<0.005). NHAPI patients showed a survival advantage (HR 0.87, p<0.005). No-RT rates increased 2020-2022, potentially reflecting watch-and-wait strategies
Conclusion: Neoadjuvant RT has become the dominant approach for LARC with concurrent adjuvant RT decline, reflecting successful TNT adoption. The TNT era is associated with 22% survival improvement. Persistent racial disparities in RT utilization and survival highlight the need for equitable guideline-concordant care. The recent uptick in RT omission warrants monitoring as organ preservation strategies evolve.
RT Utilization Trends, Survival Outcomes, and Racial Disparities Across Treatment Eras (N=59,759)
HR - Hazard Ratio, NHB - Non-Hispanic Black, NHAPI - Non-Hispanic Asian/Pacific Islander| Category | Variable | Pre-TNT 2004-2012 | Transitional 2013-2017 | TNT Era >2018 | Neo RT | Adj RT | No RT | HR | p-value |
| RT Utilization | Neoadjuvant | 38.3% | 44.5% | 49.8% | - | - | - | - | - |
|
| Adjuvant | 18.3% | 11.1% | 7.3% | - | - | - | - | <10?³4 |
|
| No RT | 43.4% | 44.4% | 42.9% | - | - | - | - | - |
| Survival | Median OS (mo) | - | - | - | 150 | 136 | 95 | - | <0.001 |
| Cox MVA | TNT vs Pre era | - | - | - | - | - | - | 0.78 | <0.005 |
|
| Adj vs Neo RT | - | - | - | - | - | - | 1.00 | 0.90 |
| Disparities | NHB Neo RT% | 34.7% | - | 47.1% | - | - | - | 1.36 | <0.005 |
|
| NHAPI | - | - | - | - | - | - | 0.87 | <0.005 |
| Trend | Peak Neo RT | 29.3% | - | 52.6% | - | - | - | - | trend? |