Stereotactic radiotherapy is a standard treatment option for patients with stage I non-small cell lung cancer who are unfit for surgery or who are medically operable but refuse surgery. Comparable overall survival rates in operable patients are also supported by non-randomized single-institution and population based studies. Stereotactic radiotherapy has emerged as an alternative, effective and well tolerated in treating pulmonary oligometastases. The early detection of recurrence is important in the medically operable population for whom curative surgical salvage treatments are still available. A standardized definition of recurrence criteria becomes especially important in that context. In 2012, Huang et al. proposed a follow-up algorithm for these patients, whose different points are discussed in this publication.