Long-Term outcomes of ablative stereotactic body radiation therapy for inoperable, non-metastatic pancreatic cancer.

Abstract

To evaluate long-term outcomes and tolerability of ablative 5-fraction stereotactic body radiation therapy (SBRT) administering a biologically effective dose (BED₁₀, α/β = 10) ≥ 100 Gy in patients with inoperable, non-metastatic pancreatic cancer (PC). We retrospectively reviewed a prospective registry of 88 patients with inoperable non-metastatic PC who underwent ablative 5-fraction SBRT using a CyberKnife with fiducial-based respiratory tracking between 2016 and 2020. The outcomes included overall survival (OS), progression-free survival (PFS), and treatment-related toxicity. The cohort included 55 men and 33 women (median age, 65 years; range, 36-84 years). At diagnosis, 29 patients were medically inoperable, and 59 had locally advanced PC (LAPC). SBRT was administered at 50 Gy/5 fractions in 82 patients and 55 Gy/5 fractions in 6 patients. The median gross tumor volume was 33.6  cm³ (range, 3.7-167.8). With a median follow-up of 64.0 months, the median OS (mOS) was 18.1 months (95 % confidence interval [CI], 16.6-27.1) from the time at diagnosis and 15.6 months (95 % CI, 14.1-23.4) from the start of SBRT. The 1-, 2-, and 3-year OS rates were 73.9 %, 39.8 %, and 26.1 % from diagnosis, and 64.0 %, 36.0 %, and 22.1 % from SBRT, respectively. The mOS from the time at diagnosis was 18.2 months (95 % CI, 17.0-37.1) for medically inoperable patients and 17.1 months (95 % CI, 15.9-28.9) for those with LAPC, with corresponding 1-, 2-, and 3-year OS rates of 86.2 %, 41.4 %, and 31.0 % vs. 67.8 %, 39.0 %, and 23.7 %, respectively. From the start of SBRT, corresponding mOS was 16.2 months (95 % CI, 15.0-35.9) for medically inoperable patients and 14.4 months (95 % CI, 11.0-23.7) for LAPC, with 1-, 2-, and 3-year OS rates of 75.9 %, 37.9 %, and 27.6 % vs. 57.6 %, 33.9 %, and 18.6 %, respectively. Grade 3 gastrointestinal bleeding occurred in four patients (4.5 %), with no grade ≥ 4 toxicities observed. Ablative 5-fraction SBRT with BED₁₀ ≥ 100  Gy results in favorable survival and acceptable toxicity in inoperable, non-metastatic PC.