Milea Timbergen

170 age at diagnosis of the AS group (available in twelve studies) ranged from 28 to 59 years. Twenty studies reported the number of primary and recurrent tumours included in their AS group (Table 2). In these studies, the majority of patients had a primary tumour with a median percentage of primary tumours of 100% (IQR: 68-100%). The remaining had a recurrent tumour. Based on the reported information, no distinction in numbers of patients needing shift to active treatment could be made between primary and recurrent tumours. Tumour response to active surveillance Fourteen out of twenty-five studies stated to use RECIST (either 1.0 or 1.1) 18 to objectively measure tumour response 2, 6, 8, 14, 23, 25, 29-33, 35, 36, 38 , however only a part of those studies actually reported the radiological response per treatment type in accordance with RECIST. Other studies used similar approaches describing the disease outcome as PD, SD, PR or CR. A total of 21 studies reported PD in 322 patients. The median percentage of PD reported in these studies was 20% (IQR: 13-35%). A total of eighteen studies reported SD in 382 patients. The median percentage of SD reported in these studies was 59% (IQR: 37-69%). Seventeen studies reported PR in 102 patients. The median percentage of PR reported in these studies was 19% (IQR: 3-23%). CR was reported sixteen studies in 34 patients. The median percentage of CR reported in these studies was 0% (IQR: 0-6%) (Table 3). Indications for start of treatment Table 3 . Overview of RECIST outcomes and shift to active treatment Number of studies reporting this variable Number of patients Median % of patients (IQR) reported in all studies RECIST outcomes Progressive disease 21 322 20% (13-35%) Stable disease 18 382 59% (37-69%) Partial response 17 102 19% (3-23%) Complete response 16 34 0% (0-6%) Active treatment Shifting to an active form treatment 20 402 29% (17-40%) Surgery 17 107 41% (11-62%) Systemic treatment 17 195 33% (0-52%) Local therapies a 16 4 0% (0%) Radiotherapy 16 18 0% (0-1%) Combination of therapies b 20 8 0% (0-3%) a radiofrequency, cryotherapy; b surgery + radiotherapy, systemic therapy + surgery 6