Mo'iad Alazzam, John Tidy, Raymond Osborne, Robert Coleman, Barry W Hancock, Theresa A Lawrie

Gestational trophoblastic neoplasia (GTN) is a highly curable group of pregnancy-related tumours; however, approximately 25% of GTN tumours will be resistant to, or will relapse after, initial chemotherapy. These resistant and relapsed lesions will require salvage chemotherapy with or without surgery. Various salvage regimens are used worldwide. It is unclear which regimens are the most effective and the least toxic. To determine which chemotherapy regimen/s for the treatment of resistant or relapsed GTN is/are the most effective and the least toxic. We searched the Cochrane Gynaecological Cancer Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 4), MEDLINE and EMBASE up to October 2011. In addition, we handsearched the relevant society conference proceedings and study reference lists. For the updated review, we searched Cochrane Group Specialised Register, CENTRAL, MEDLINE and EMBASE to 16 Novemeber 2015. In addition, we searched online clinical trial registries for ongoing trials. Only randomised controlled trials (RCTs) were included. We designed a data extraction form and planned to use random-effects methods in Review Manager 5.1 for meta-analyses. The search identified no RCTs; therefore we were unable to perform any meta-analyses. RCTs in GTN are scarce owing to the low prevalence of this disease and its highly chemosensitive nature. As chemotherapeutic agents may be associated with substantial side effects, the ideal treatment should achieve maximum efficacy with minimal side effects. For methotrexate-resistant or recurrent low-risk GTN, a common practice is to use sequential five-day dactinomycin, followed by MAC (methotrexate, dactinomycin, cyclophosphamide) or EMA/CO (etoposide, methotrexate, dactinomycin, cyclophosphamide, vinblastine) if further salvage therapy is required. However, five-day dactinomycin is associated with more side effects than pulsed dactinomycin, therefore an RCT comparing the relative efficacy and safety of these two regimens in the context of failed primary methotrexate treatment is desirable.For high-risk GTN, EMA/CO is the most commonly used first-line therapy, with platinum-etoposide combinations, particularly EMA/EP (etoposide, methotrexate, dactinomycin/etoposide, cisplatin), being favoured as salvage therapy. Alternatives, including TP/TE (paclitaxel, cisplatin/ paclitaxel, etoposide), BEP (bleomycin, etoposide, cisplatin), FAEV (floxuridine, dactinomycin, etoposide, vincristine) and FA (5-fluorouracil (5-FU), dactinomycin), may be as effective as EMA/EP and associated with fewer side effects; however, this is not clear from the available evidence and needs testing in well-designed RCTs. In the UK, an RCT comparing interventions for resistant/recurrent GTN will be very challenging owing to the small numbers of patients with this scenario. International multicentre collaboration is therefore needed to provide the high-quality evidence required to determine which salvage regimen/s have the best effectiveness-to-toxicity ratio in low- and high-risk disease. Future research should include economic evaluations and long-term surveillance for secondary neoplasms.