Purpose To evaluate the influence of equivalent dose (EQD2) in clinical outcomes of patients with isolated locally recurrent tumors (ILRT), treated with salvage surgery and intra-operative electron beam radiation therapy (IOERT). Methods and materials We retrospectively reviewed 128 patients with non-metastatic ILRT of different tissues (soft tissue sarcomas, head and neck, uterine, and colorectal). Patients had received salvage surgery (R0/R1/R2) and IOERT. Previously not irradiated patients had received additional external beam radiation therapy (EBRT). Results IOERT was delivered at a median dose of 15 Gy (range, 5-25 Gy). Seventy-five patients (60.9%) received additional EBRT of 46 Gy. Median EQD2 of salvage program was 62 Gy and median EQD2 of exclusive IORT was 31.2 Gy. Median follow-up was 19.2 months (range: 1.3-220). Thirty-one patients (24.2%) developed severe (grade 3-5) complications. New locoregional recurrence was documented in 86 (67.2%) of the 123 cases. Five-year rates were 31% for locoregional control, 57% for distant metastasis-free and 31% for overall survival. On multivariate analysis, R0-1 vs. R2 resection (HR 2.2, 95 CI: 1.2-4.1) was statistically significant for locoregional recurrence and EQD2 ¿62 Gy for survival (HR 2.2, 95 CI: 1.1-4.1). Conclusions Surgical radicality (gross macroscopic resection) and radiation dose (EQD2 ¿62 Gy in radiation salvage program) are the dominant prognostic factors beside ILRT histology. Modest rates of long-term disease control are expected when both factors are fulfilled.