Outcomes for patients with locally advanced pancreatic adenocarcinoma treated with stereotactic body radiation therapy versus conventionally fractionated radiation

Abstract

Background: As systemic therapy has improved for locally advanced pancreatic cancer (LAPC), efforts to improve local control with optimal radiotherapy may be critical. Although conventionally fractionated radiation therapy (CFRT) has more recently shown a limited role in LAPC, stereotactic body radiation therapy (SBRT) is an emerging approach with promising results. With no studies to date comparing SBRT with CFRT for LAPC, this study used the National Cancer Data Base (NCDB) to evaluate these 2 modalities.

Methods: With the NCDB, patients with American Joint Committee on Cancer cT2-4/N0-1/M0 adenocarcinoma of the pancreas diagnosed from 2004 to 2013 were analyzed. Radiation therapy delivered at ≤2 Gy was deemed CFRT, and radiation therapy delivered at ≥4 Gy per fraction was considered SBRT. Kaplan-Meier analysis, log-rank testing, and multivariate Cox proportional hazards regression were performed with overall survival (OS) as the primary outcome. Propensity score matching was used.

Results: Among 8450 patients, 7819 (92.5%) were treated with CFRT, and 631 (7.5%) underwent SBRT. Receipt of SBRT was associated with superior OS in the multivariate analysis (hazard ratio, 0.84; 95% confidence interval, 0.75-0.93; P < .001). With propensity score matching, 988 patients in all were matched, with 494 patients in each cohort. Within the propensity-matched cohorts, the median OS (13.9 vs 11.6 months) and the 2-year OS rate (21.7% vs 16.5%) were significantly higher with SBRT versus CFRT (P = .0014).

Conclusions: In this retrospective review using a large national database, SBRT was associated with superior OS in comparison with CFRT for LAPC, and these findings remained significant in a propensity-matched analysis. Further prospective studies investigating these hypothesis-generating results are warranted. Cancer 2017;123:3486-93. © 2017 American Cancer Society.

Keywords: intensity modulated radiation therapy (IMRT); pancreatic cancer; radiation therapy (RT); stereotactic body radiation therapy (SBRT).

Conflict of interest statement

CONFLICT OF INTEREST DISCLOSURES

The authors made no disclosures.

© 2017 American Cancer Society.

Figures

Figure 1

Patient Consolidated Standards of Reporting Trials diagram. AJCC indicates American Joint Committee on Cancer; CFRT, conventionally fractionated radiation therapy; NCDB, National Cancer Data Base; SBRT, stereotactic body radiation therapy.

Figure 2

Kaplan-Meier curves demonstrating overall survival for (A) unmatched cohorts and (B) propensity-matched cohorts. SBRT indicates stereotactic body radiation therapy.

Figure 3

Multivariate subgroup analyses of the effects of patient demographics, disease characteristics, and treatment details on overall survival with CFRT versus SBRT. CI indicates confidence interval; CFRT, conventionally fractionated radiation therapy; SBRT, stereotactic body radiation therapy.