BACKGROUND: The prognosis for patients with cervical or endometrial cancer has improved over the last decades. Thus, reducing therapy-related toxicity and impact on quality of life have become more and more important. With the development of new radiotherapy techniques like IMRT (Intensity-modulated radiotherapy) the incidence of acute and chronic toxicities has already been reduced. Nevertheless, rates of complications requiring medical treatment range from 0.7-8% according to literature. 7.7% of patients develop severe complications after 5 years with an increasing risk for complications of 0.3%/year. Particularly, the volume of the small and large bowel receiving low doses (15 Gy) has been shown to be a predictive factor for the development of higher bowel toxicity. With the introduction of proton therapy into clinical practice, there are new opportunities for optimization of organ at risk-sparing thus possibly reducing toxicity. METHODS/DESIGN: The APROVE study is a prospective single-center one-arm phase-II-study. Patients with cervical or endometrial cancer after surgical resection who have an indication for postoperative pelvic radiotherapy will be treated with proton therapy instead of the commonly used photon radiation. A total of 25 patients will be included in this trial. Patients will receive a dose of 45-50.4 GyE in 1.8 GyE fractions 5-6 times per week using active raster-scanning pencil beam proton radiation. Platinum-based chemotherapy can be administered if indicated. For treatment planning, rectum, sigma, large and small bowel, bladder and femoral heads are defined as organs at risk. The CTV is defined according to the RTOG consensus guidelines. DISCUSSION: The primary endpoint of the study is the evaluation of safety and treatment tolerability of pelvic radiation using protons defined as the lack of any CTC AE Grade 3 or 4 toxicity. Secondary endpoints are clinical symptoms and toxicity, quality of life and progression-free survival. The aim is to explore the potential of proton therapy as a new method for adjuvant pelvic radiotherapy to decrease the dose to the bowel, rectum and bladder thus reducing acute and chronic toxicity and improving quality of life. TRIAL REGISTRATION: Registered at https://clinicaltrials.gov , ClinicalTrials.gov Identifier: NCT03184350 , registered 09 June 2017, enrolment of the first participant 19 June 2017.