Magnetic Resonance Guided Stereotactic Ablative Radiation Therapy Versus External Beam RT with Chemotherapy For Pancreatic Cancer: Single Institution Toxicity Analysis Of Patients Treated In An Urban Academic Center

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Conference Proceeding

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International Journal of Radiation Oncology Biology Physics


Purpose/Objective(s): Several academic institutions have investigated stereotactic MR guided adaptive radiation therapy (SMART) to safely dose escalate for locally advanced and borderline resectable pancreatic cancer with initial favorable toxicity and survival outcomes. However, it is not clear that this treatment is safe or effective in more challenging populations, such as in an urban academic center. The purpose of this abstract was to review outcomes immediately before and after implementing dose escalated MR guided adaptive radiation therapy for pancreatic cancer.

Materials/Methods: In this IRB approved analysis, we retrospectively reviewed 57 consecutive patients from 2017-2019 with locally advanced or borderline resectable pancreatic cancer who were treated with neoadjuvant radiation therapy. Initially all patients received standard fractionated chemoradiation (chemoRT) to a dose of 50.4 Gy in 28 fractions. In September 2018 our institutional treatment guidelines were changed to recommend SMART (50Gy in 5 fractions) for these patients. Toxicity outcomes evaluated were grade 3+ GI toxicity based on CTCAE v5.0 as well as unplanned hospital admissions, both at 90 and 180 days. Treatment differences were analyzed using two sample t-test and chi-square test. Overall survival was evaluated at 180 days, and by Kaplan-Meier and log-rank test and was calculated from first day of radiation therapy.

Results: 29 patients received chemoRT and 28 received SMART. Median follow up for the chemoRT group was 294 days and for SMART was 185 days. Groups did not have significant differences in age, performance status, stage, gender, CA 19-9, or neoadjuvant chemotherapy. Grade 3+ GI toxicity at 90 days was seen in 28% and 11% (p = 0.11) in the chemoRT and SMART groups, respectively. Types of toxicity were overall comparable with most being abdominal pain and duodenal bleeds. Hospital admissions at 90 days occurred in 38% and 21% of patients (p = 0.17) and at 180 days in 33% and 44% (p = 0.48). Surgical resection was achieved in 24% of chemoRT and 36% of SMART patients (p = 0.34). When evaluated using Kaplan-Meier and log-rank test there was a trend to overall survival benefit in the SMART group (p = 0.07). There was also a statistically significant 180-day survival improvement in SMART patients of 94% vs 70% in chemoRT patients (p = 0.046).

Conclusion: Dose escalated SMART for locally advanced and borderline pancreatic cancer does not cause significant increase in GI grade 3+ GI toxicity at 90 days or hospitalization at 90 or 180 days as compared to chemoRT. Dose escalated SMART appears to be both safe and effective in our urban population. OS in the chemoRT group was comparable to previous trials such as LAP07. There is a trend to OS improvement on Kaplan-Meier analysis in the SBRT group (p = 0.07), as well as statistically significant improvement in 180-day survival; which supports the ongoing multi-institutional SMART study (NCT03621644). Updated results to be presented at the meeting.





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