We hypothesize that intra-fractional motion monitoring with frequent kV imaging surveillance together with an appropriate intervention action level ensures adequate tumor dose to abdominal cancer patients with breathing amplitude restricted by compression who are treated with stereotactic body radiation therapy on a Linac. We retrospectively studied the treatment plans and intra-fractional images of 10 upper-abdominal cancer patients treated on a Linac with hypofractionated IMRT. For all patients, one or more radio-opaque markers were implanted near the tumor. Abdominal compression reduced respiratory marker motion below 6 mm as evaluated by fluoroscopy before each treatment. The PTV was defined by a 5 mm 3D expansion of the GTV. Intra-fractional kV radiographs were automatically acquired at 5-6 second intervals during beam delivery, triggered by the RPM system’s response to a motion phantom mounted above the patient. Planned marker positions are overlaid on each radiograph and displayed on the treatment console; therapists check compression and correct setup if persistent deviation from planned position is seen. kV images were retrospectively analyzed using in-house software to determine marker shifts from their planned positions. To estimate dosimetric effects, the MLC position at each control point is shifted according to the superior-inferior component of the fiducial trajectory, and the resulting dose to GTV and surrounding organs at risk (OAR) is reconstructed. The relationship between the degradation of GTV D95, dose to OAR, mean and maximal fiducial displacement is explored. The allowable mean and maximal marker motion excursion is determined to obey objectives such as GTV D95 degrades less than 5% and no OAR constraints are violated for this patient population. The marker motion excursion ranged from 2 to 6 mm on pre-treatment fluoroscopy, but from 2 to 23 mm on intra-fractional kV projections. The correlation between the two is 0.44. The weak correlation and bigger amplitude argue for intra-fractional motion monitoring and management. The relative difference between the planned GTV D95 and that reconstructed accounting for intra-fractional motion ranges from -8.8% to 4.4%, and averages -1.4%. Without additional intra-fractional intervention, the 5 mm margin around GTV resulted in 10% of fractions violating the objectives. However, the objectives can be met with tools to enforce marker-based action levels that limit mean marker motion to [-2mm 2mm] and maximal excursion to <12 mm. The combination of compression belt, intra-fractional kV imaging surveillance, and advanced intervention methods can ensure patients receive improved dose coverage.