To answer this question, the considered standard of care after complete resection, namely observation with or without adjuvant systemic therapy, will be compared to a postoperative normofractionated stereotactic radiotherapy towards the resection cavity within an open label, randomized trial. The prescribed total dose will be 46 Gy in 2 Gy fractions of 36 Gy in 3 Gy fractions depending on the treatment volume.