A Systematic Review and Meta-Analysis on the Survival of Cancer Patients Treated with a Fermented <b><i>Viscum album</i></b> L. Extract (Iscador): An Update of Findings

<b><i>Purpose:</i></b> We aimed at updating the evidence found in controlled studies addressing general and event-free survival of cancer patients treated with the fermented mistletoe extract Iscador. <b><i>Methods:</i></b> The databases Embase, PubMed, CAMbase, Scopus, AMED and Cochrane were searched for clinical studies on cancer patients treated with Iscador. Quality of studies and risk of bias were evaluated according to the Cochrane guidelines and the Newcastle Ottawa Scale. Outcome data were expressed as hazard ratios (HR) and the respective 95% confidence intervals (CI). Meta-analysis was carried out using a random-effects model. <b><i>Results:</i></b> Eighty-two controlled studies met the inclusion criteria, of which 32 with 55 strata provided data for extracting HR and CI. The overall HR was 0.59 (95% CI: [0.53; 0.65], <i>p</i> < 0.0001) in favour of Iscador treatment. Heterogeneity of study results was moderate (<i>I</i><sup>2</sup> = 50.9%; <i>p</i> < 0.0001, τ<sup>2</sup> = 0.053). Meta-regression did not reveal significant effects of sample size or study design. However, significant differences were found between cancer entities (<i>p</i> < 0.01), with most pronounced effects in cervical (HR = 0.43) and less pronounced effects in lung cancer (HR = 0.84). <b><i>Conclusions:</i></b> We found almost identical effects on cancer survival based on a broader database of higher quality. However, none of the studies was blinded and, therefore, there might be risk of performance bias. Implications for cancer survivors are as follows: findings indicate that adjuvant treatment of cancer patients with Iscador can be associated with a better survival.