Margriet Kwint

Chapter 8 154 ▶ Figure 1: Illustration of the oligometastatic disease classification system (A) De-novo oligometastatic disease. (B) Repeat oligometastatic disease. (C) Induced oligometastatic disease. In repeat and induced oligometastatic disease the primary tumor is assumed to be controlled by ongoing or previous treatment. Oligometastases are confirmed by imaging or biopsy to exclude simultaneous or secondary primary tumors. T0=at this current point of time. T-x=any previous point in time. (Figure from Guckenberger et al. (29) published with copyright permission of The Lancet Oncology) dian OS: 41 months versus 28 months). However, only 18% of the included patients had NSCLC. Therefore, the impressive OS might be an overestimation for NSCLC patients, due to the overall better prognosis of prostate, colorectal and breast cancer patients compared to NSCLC. The outcome of the SABR-COMET study prompted the initiation of the randomized phase III study SABR-COMET-10 (NCT03721341 ) (35). This study is at the moment enrolling patients to assess the impact of SABR in patients with 4-10 metastatic lesions. Randomization is stratified by two factors: histology (Group 1: prostate, breast, or renal; Group 2: all others), and type of pre- specified systemic therapy (Group 1: immunotherapy/targeted; Group 2: cytotoxic; Group 3: observation). Hopefully these results will contribute to answer the clinical relevant question if patients with ≥4 metastatic lesions are indicated and safe for ablative therapies (35). To conclude, consensus on the definition of oligometastatic disease is growing, but further research is necessary to investigate the association between the number of metastases, treatment options and overall survival in oligometastatic stage IV NSCLC patients.