Outcomes and Costs of SBRT vs. Conventional Treatments for Unresectable Pancreas Adenocarcinoma

Abstract

In elderly patients with unresectable pancreas cancer, identifying optimal treatment is difficult, due to combined challenges of an aggressive disease course along with toxicities of sustained chemotherapy and long conventional radiation treatment (RT) courses. We evaluated whether stereotactic body radiation treatment (SBRT) for unresectable pancreas cancer could offer less protracted time on RT and chemotherapy but still yield an acceptable survival, toxicity, and cost profile, compared with conventionally fractionated chemoradiation (CFRT) or chemotherapy (Chemo) alone. We evaluated 2,629 patients age >65 with unresected pancreatic adenocarcinoma in SEER- and Texas Cancer Registry-Medicare linked data from 2006-2013. Claims determined RT, chemotherapy, toxicities, and Medicare payment (Consumer Price Index adjusted to 2015 dollars). Treatment trends and associations with patient characteristics and gastrointestinal (GI) toxicities were tested using Pearson's Chi-square. Median survival was compared using the Kaplan-Meier method. Overall 51% of patients received RT plus chemotherapy vs 49% Chemo alone (91% gemcitabine-based). RT use declined over time (P=0.02), especially in 2013 to 43% of patients, contemporary with LAP-07 interim results presentation. However, among RT patients, SBRT use actually increased from 5% in 2006 to 10% in 2013 (P=0.04). SBRT was delivered with a median of 5 fractions (interquartile range [IQR] 3-5) and CFRT with 28 fractions (IQR 25-28). SBRT was used relatively more frequently in older patients vs CFRT or vs Chemo alone (P<0.001). Median unadjusted survival was 11.6 months for SBRT (95% CI 10.7-13.4), 12.2 months for CFRT (11.6-12.6), and 11.7 months for Chemo alone ≥6 cycles (11.2-12.7) (P>0.20). Median survival was limited, only 5.5 months (5.2-5.9) in patients who received ≤5 cycles Chemo alone (P<0.001). 10% of SBRT patients and 10% of CFRT patients underwent prolonged chemotherapy use >19 cycles vs 16% of Chemo alone patients (P<0.001). Frequency of gastric ulcer/bleed was 12% with SBRT (17% for 1-4 fractions and 8% for 5 fractions) vs 8% with CFRT vs 4% with Chemo alone (P<0.001). Duodenal ulcer/bleed was 15% with SBRT vs 13% with CFRT vs 4% with Chemo alone (P<0.001). Median total cost was $89,917 per SBRT patient, $80,611 per CFRT, $72,455 per Chemo alone ≥6 cycles, and $45,877 per Chemo alone ≤5 cycles. SBRT for unresectable pancreas cancer demonstrates promise as an emerging strategy, particularly in elderly patients who may poorly tolerate prolonged chemotherapy. SBRT could provide less protracted time on treatment without compromising survival compared with CFRT or Chemo alone, though with incrementally increased costs and local GI toxicity risks. Further optimizing techniques to decrease the GI risk profile could continue to enhance the value of SBRT in the future.