SSAT - SIXTEEN-YEAR NCDB OUTCOMES ANALYSIS OF PATIENTS WITH PANCREATIC DUCTAL ADENOCARCINOMA UNDERGOING NEOADJUVANT VERSUS ADJUVANT RADIATION

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SIXTEEN-YEAR NCDB OUTCOMES ANALYSIS OF PATIENTS WITH PANCREATIC DUCTAL ADENOCARCINOMA UNDERGOING NEOADJUVANT VERSUS ADJUVANT RADIATION
Anup Y. Parikh^*¹, Hadley D. Freeman¹, Liang Ji¹, Emanuel Eguia¹, Mark Reeves¹, Jukes Namm¹, Naveenraj L. Solomon¹, Aaron Saunders¹, Nephtali Gomez¹, Rhami Khorfan¹, Raja R. Narayan¹, Vicente Ramos-Santillan^1,2, David Caba Molina^1,2
¹Loma Linda University, Loma Linda, CA; ²Riverside University Health System, Moreno Valley, CA

Introduction
The optimal treatment sequence of radiotherapy (RT) and surgery in pancreatic ductal adenocarcinoma (PDAC) is widely debated. NCCN guidelines define resectability by local vascular invasion and not preoperative nodal staging. Neoadjuvant or adjuvant RT is generally utilized in patients at high-risk for recurrence, which may be variably influenced by biological or clinical characteristics of the patient such as age, since PDAC disproportionately affects the elderly. The aim of this study is to evaluate the possible impact of age and biological factors in treatment sequence of RT and surgery and the resultant outcomes.

Methods
A retrospective review of patients with PDAC only undergoing both RT and surgery was performed using the National Cancer Database (2004-2020). Survival analysis was completed using Cox proportional hazards model. Patients were stratified based on age: <60 years, 60-69 years, and >70 years.

Results
A total of 968 patients met inclusion criteria and were evenly distributed amongst age groups. The sequence of RT and surgery did not vary based on age, with RT mostly utilized in the adjuvant setting. Incomplete preoperative nodal stage reporting (cNx) was more common amongst all patients undergoing RT in the adjuvant vs. neoadjuvant setting irrespective of age (35.4% vs 3.85%, p <0.0001); cNx was independently associated with worse survival (HR 1.45, 95% CI 1.08-1.94). Those receiving adjuvant RT had a higher mortality (HR 1.55, 95% CI 1.27-1.91). Other factors associated with worse survival were age >70 (HR 1.46, 95% CI 1.21-1.75), cN+ (HR 1.29, 95% CI 1.06-1.59) and overlapping head/body disease or site NOS (HR 1.51, 95% CI 1.14-1.99). Patients aged <60 had the shortest time from diagnosis to radiation compared to the other age groups (p=0.0162) which was associated with lower mortality (HR 0.997, 95% CI 0.996-0.998).

Conclusions
RT was performed mostly in the adjuvant setting irrespective of age. Older patients received RT later in their disease and had worse survival. The rate of documentation of clinical nodal status varies between PDAC patients receiving either neoadjuvant versus adjuvant RT. This trend may reflect under-emphasis of preoperative nodal staging, which is not a criterion in the guidelines for determining resectability. Incomplete preoperative nodal stage reporting was associated with increased use of RT in the adjuvant setting, which in turn was associated with worse survival. Future studies should prospectively examine the importance of preoperative nodal staging in resectability determination.

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