Milea Timbergen

177 the patients were unable to tolerate chemotherapy or radiotherapy 28 , had unresectable asymptomatic mesenteric masses 25 or had masses that were not life-threatening or at risk for mutilation 22 . Moreover, some studies selected patients based on tumour sites (e.g., breast desmoids 21, 23 ) or were interested in other study endpoints than the results of the AS approach (e.g., pregnancy status 2 , or imaging characteristics 24, 31 ). Another limitation is the relatively large number of studies included in this systematic review where there is potential cohort overlap (based on author names, affiliations and inclusion time period) 2, 9, 14&6, 10, 12, 21-23 . Despite these limitations, this systematic literature review was able to compile the available evidence for the use of the AS approach in adult DTF. Currently, the results of three prospective European studies evaluating the efficacy of AS in DTF are awaited. The French study (NCT01801176) and the Italian study (NCT02547831) which started in May 2012 and July 2013, respectively, both evaluate 3-year PFS 15, 16 . The Dutch study (NTR 4714) which started in May 2014, evaluates tumour progression at 5-years follow-up 17 . These three studies will provide further insights into the natural growth of DTF, the differences in growth behaviour between various tumour sites, tumour sizes, and β-catenin mutation types as well as the indications and considerations for the start of ‘active’ treatment. Conclusions Active surveillance is the mainstay of treatment for sporadic DTF. This systematic literature review underlined the ongoing trend of the AS approach and indicates that a minority of patients need shift to an active form of treatment avoiding overtreatment and minimising potential morbidity. Acknowledgements The authors would like to express their gratitude towards Maarten F.M. Engel and Sabrina Meertens-Gunput for their assistance with the systematic literature search. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Conflicts of interest Authors declare that there is no conflict of interest. 6