Prophylactic chemotherapy for hydatidiform mole to prevent gestational trophoblastic neoplasia

Background This is an update of the original Cochrane Review published in Cochrane Library, Issue 10, 2012. Hydatidiform mole (HM), also called a molar pregnancy, is characterised by an overgrowth of foetal chorionic tissue within the uterus. HMs may be partial (PM) or complete (CM) depending on their gross appearance, histopathology and karyotype. PMs usually have a triploid karyotype, derived from maternal and paternal origins, whereas CMs are diploid and have paternal origins only. Most women with HM can be cured by evacuation of retained products of conception (ERPC) and their fertility preserved. However, in some women the growth persists and develops into gestational trophoblastic neoplasia (GTN), a malignant form of the disease that requires treatment with chemotherapy. CMs have a higher rate of malignant transformation than PMs. It may be possible to reduce the risk of GTN in women with HM by administering prophylactic chemotherapy (P-Chem). However, P-Chem given before or after evacuation of HM to prevent malignant sequelae remains controversial, as the risks and benefits of this practice are unclear. Objectives To evaluate the effectiveness and safety of P-Chem to prevent GTN in women with a molar pregnancy. To investigate whether any subgroup of women with HM may benefit more from P-Chem than others. Search methods For the original review we performed electronic searches in the Cochrane Gynaecological Cancer Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 2, 2012), MEDLINE (1946 to February week 4, 2012) and Embase (1980 to 2012, week 9). We developed the search strategy using free text and MeSH. For this update we searched the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 5, 2017), MEDLINE (February 2012 to June week 1, 2017) and Embase (February 2012 to 2017, week 23). We also handsearched reference lists of relevant literature to identify additional studies and searched trial registries. Selection criteria We included randomised controlled trials (RCTs) of P-Chem for HM. Data collection and analysis Two review authors independently assessed studies for inclusion in the review and extracted data using a specifically designed data collection form. Meta-analyses were performed by pooling data from individual trials using Review Manager 5 (RevMan 5) software in line with standard methodological procedures expected by Cochrane methodology. Main results The searches identified 161 records; after de-duplication and title and abstract screening 90 full-text articles were retrieved. From these we included three RCTs with a combined total of 613 participants. One study compared prophylactic dactinomycin to no prophylaxis (60 participants); the other two studies compared prophylactic methotrexate to no prophylaxis (420 and 133 participants). All participants were diagnosed with CMs. We considered the latter two studies to be of poor methodological quality. P-Chem reduced the risk of GTN occurring in women following a CM (3 studies, 550 participants; risk ratio (RR) 0.37, 95% confidence interval (CI) 0.24 to 0.57; I-2 = 0%; P < 0.00001; low-quality evidence). However, owing to the poor quality (high risk of bias) of two of the included studies, we performed sensitivity analyses excluding these two studies. This left only one small study of high-risk women to contribute data for this primary outcome (59 participants; RR 0.28, 95% CI 0.10 to 0.73; P = 0.01); therefore we consider this evidence to be of low quality. The time to diagnosis was longer in the P-Chemgroup than the control group (2 studies, 33 participants; mean difference (MD) 28.72, 95% CI 13.19 to 44.24; P = 0.0003; low-quality evidence); and the P-Chem group required more courses to cure subsequent GTN (1 poor-quality study, 14 participants; MD 1.10, 95% CI 0.52 to 1.68; P = 0.0002; very low quality evidence). There were insufficient data to perform meta-analyses for toxicity, overall survival, drug resistance and reproductive outcomes. Authors' conclusions P-Chem may reduce the risk of progression to GTN in women with CMs who are at a high risk of malignant transformation; however, current evidence in favour of P-Chem is limited by the poor methodological quality and small size of the included studies. As P-Chem may increase drug resistance, delays treatment of GTN and may expose women toxic side effects, this practice cannot currently be recommended.