Incidence and patterns of locoregional failure following stereotactic body radiation therapy (SBRT) for pancreatic adenocarcinoma.

Publication date: Available online 3 July 2018
Source:Practical Radiation Oncology
Author(s): Michael J. Baine, Richard Sleightholm, Chi Lin
PurposeStereotactic body radiation therapy (SBRT) is increasingly utilized in the neoadjuvant and definitive settings for pancreatic adenocarcinoma. Risk of local and regional recurrence following this treatment remains largely unknown. Due to lack of elective nodal treatment and high fractional dose, we hypothesized that the incidence of regional out-of-field recurrence would predominate following SBRT.Methods and MaterialsElectronic medical records of all patients treated in our department with SBRT for pancreatic adenocarcinoma were retrospectively reviewed. Patients were separated into those who converted or did not convert to surgical resectability. Demographic, treatment, and outcome data were collected and analyzed. Recurrence was assessed based on RECIST 1.1 criteria. Treatment plans were reviewed to determine locations of failure with respect to treatment volume. Statistical comparisons were made using Mann-Whitney U testing for continuous variables and Chi-squared testing for dichotomous variables.ResultsData on 69 patients was available for analysis. Following treatment, 26.1% (18/69) of patients suffered in-field recurrence and 15.9% (11/69) of patients recurred regionally out-of-field. Median time to in-field and out-of-field failures were similar at 120.5 and 108.0 days, respectively (p=0.65). Of those who failed out-of-field, 36.4% (4/11) were without in-field failure prior to death. In-field failure rates were less in those who subsequently underwent surgical resection than in those who did not (9.1% (2/22) vs 34.0% (16/47), p=0.028), while out-of-field recurrence was unaffected by subsequent surgical resection (13.6% (3/22) vs 17.0% (8/47), p=0.720). All out-of-field failures occurred in areas receiving < 2600 cGy.ConclusionsThe incidence of out-of-field failure remains acceptable following SBRT for pancreatic adenocarcinoma. Despite the high BED allowed by SBRT in-field control remains problematic, continuing to signal relative radiation resistance associated with bulky disease.



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