Failure patterns and outcomes of dose escalation of stereotactic body radiotherapy for locally advanced pancreatic cancer: a multicenter cohort study.

OBJECTIVE

This study aims to compare recurrence patterns and outcomes of biologically effective dose (BED, α/β = 10) of 60-70 Gy with those of a BED >70 Gy for locally advanced pancreatic cancer (LAPC).

METHODS

Patients from three centers with a biopsy and a radiographically proven LAPC were retrospectively included and data were prospectively collected from June 2012 to June 2019. Radiotherapy was delivered by stereotactic body radiation therapy. Recurrences were categorized as in-field, marginal, and outside-the-field recurrence. Patients in two groups were required to receive abdominal enhanced contrast CT or MRI every 2-3 months and CA19-9 examinations every month during follow-up. Treatment-related toxicities were evaluated every month. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method.

RESULTS

After propensity score matching, there were 486 patients in each group. The median prescription dose of the two groups was 37 Gy/5-8 f (range: 36-40.8 Gy/5-8 f) and 42 Gy/5-8 f (range: 40-49.6 Gy/5-8 f), respectively. The median OS of patients with a BED >70 Gy and a BED 60-70 Gy was 20.3 months (95% CI: 19.1-21.5 months) and 18.2 months (95% CI: 17.8-18.6 months) respectively ( < 0.001). The median PFS of the two cohorts was 15.4 months (95% CI: 14.2-16.6 months) and 13.3 months (95% CI: 12.9-13.7 months) respectively ( < 0.001). A higher incidence of in-field and marginal recurrence was found in patients with BED of 60-70 Gy (in-field: 97/486 72/486,  = 0.034; marginal: 109/486 84/486,  = 0.044). However, more patients with BED >70 Gy had grade 2 or 3 acute (87/486 64/486,  = 0.042) and late gastrointestinal toxicities (77/486 55/486,  = 0.039) than those with BED of 60-70 Gy.

CONCLUSION

BED >70 Gy was found to have the best survival benefits along with a higher incidence of acute and late gastrointestinal toxicities. Therefore, a higher dose may be required in the case of patients' good tolerance.