3128 - Mortality And Equitability of Radiation Treatment in Locally Advanced Rectal Cancer: A Review from a National Cohort

J. W. Zweigle¹, A. Hebishy¹, S. Valasapalli¹, R. Mohamed¹, M. Muzaffar², and A. M. Burke¹; ¹Brody School of Medicine at East Carolina University, Greenville, NC, ²East Carolina University, Greenville, NC

Purpose/Objective(s): The treatment paradigm for locally advanced rectal cancer has evolved significantly over the last two decades regarding the timing (neoadjuvant vs. adjuvant) and even the necessity of radiation (RT) or surgery in the curative approach. While these paradigm shifts were evolving, the overall survival (OS) of patients with and without RT and the inclusion of minority populations in these shifts has not previously been well described. Materials/

Methods: A retrospective cohort study was performed using the NCI SEER database. Survival was calculated with statistical software using the Kaplan-Meier method and hazard ratios (HR) were calculated using the Cox-regression model with 95% confidence intervals (CI). Patients treated between 2000 – 2020 were included with the cause of death separating OS from cancer-specific survival (CSS). The 5-year survival after 2015 was unreliable and excluded. Patients were separated by whether they had received RT and by the timing of RT (neoadjuvant vs. adjuvant). Additionally, the patients were separated into ‘Non-Hispanic White’ (NHW) and ‘Other’. They were analyzed using a Chi-squared algorithm for an association between race and origin and receipt of RT. This same analysis was done on patients separated by race identified as ‘Black’ or ‘Not Black.’ These Chi-squared analyses were calculated for patients diagnosed before and after January 1, 2016.
Results: Of those diagnosed with stage II or III rectal cancer from 2000-2015 who received chemotherapy and surgical intervention with known survival times, the receipt of RT, specifically neoadjuvant RT, improved OS and CSS.

There was no evidence that NHW patients received RT at different rates from others. However, they did receive adjuvant RT at higher rates from 2000-2015 and neoadjuvant RT from 2016-2020. For Black patients, from 2000-2015 there was a trend towards lower rates of RT utilization and from 2016-2020 they were less likely to receive RT. Black race did not have a significant association with the timing of RT.
Conclusion: Stage II and III rectal cancer patients diagnosed from 2000-2015 who received chemotherapy, surgery, and RT, specifically, neoadjuvant RT had improved OS and CSS. Black patients were less likely to receive RT and, as the standard of care was changing towards total neoadjuvant RT after 2015, NHW patients were more likely than others to be treated with this regimen.

Abstract 3128 – Table 1

	HR (OS)	95% CI	HR (CSS)	95% CI	NHW ’00-’15 (%)	NHW ’16-’20 (%)	Black ’00-’15 (%)	Black ’16-’20 (%)
RT	0.734	0.691-0.779	0.743	0.693-0.796	70.7	64.1	7.7	7.7
p-value	<0.001	--	<0.001	--	0.768	0.105	0.085	0.007
X2 (phi)	--	--	--	--	0.087 (0.002)	2.632 (0.015)	2.975 (-0.010)	7.311 (-0.026)
No RT	--	--	--	--	70.9	66.3	8.6	9.8
Adjuvant	1.125	1.073-1.179	1.252	1.187-1.321	72.0	60.8	7.5	7.2
p-value	<0.001	--	<0.001	--	0.013	0.017	0.448	0.498
X2 (phi)	--	--	--	--	6.166 (-0.015)	5.703 (0.025)	0.575 (-0.005)	0.459 (-0.007)
Neoadjuvant	--	--	--	--	70.5	64.5	7.8	7.8