Abstract: We identified two RCTs meeting our inclusion criteria. The two trials tested different comparisons. One RCT included 35 participants and compared PCV with 'eight drugs in one day' multidrug chemotherapy, which is a combination of drugs with different mechanisms of action. Median survival was 6 months for the PCV group and 6.5 months for the 'eight drugs in one day' group. Adverse event outcomes were not graded or quantified. Progression-free survival (PFS) and quality of life (QoL) were not described in the methods and were not an outcome of interest. The sample size in this study was small, which lead to insufficient statistical power to detect clinical differences. According to the GRADE approach we judged the quality of evidence to be low for survival outcome and very low for chemotherapy toxicity The second multi-institutional RCT included 447 participants and compared PCV with Temozolomide (TMZ). Participants were randomised into three arms to receive PCV, and two different regimens of TMZ in a 2:1:1 ratio at first recurrence. The trial reported a median overall survival of 6.7 months and 7.2 months for the PCV and TMZ group respectively. It reported a PFS of 3.6 months for the PCV group and 4.7 months for the TMZ group. There was no observed difference of effect on overall survival (hazard ratio (HR) 0.91, 95% CI 0.74 to 1.11; P = 0.35) or PFS (HR 0.89, 95% CI 0.73 to 1.08; P = 0.23) in participants receiving PCV or TMZ chemotherapy. The proportion of people with at least one grade 3 or 4 adverse event was not clinically important at 9.2% versus 12.2% in PCV and TMZ arms respectively. Mean QoL scores calculated at baseline, 12 weeks and 24 weeks was 51.9 versus 59.8 favouring TMZ (P = 0.04) which is statistically but not clinically significant and was less than the pre-defined 10 point change for moderate improvement. We judged the GRADE quality of evidence to be moderate for overall survival, PFS, and chemotherapy toxicity and low for QoL. Evidence is based on a single large trial analysis as the other trial was small, with inadequate power to detect survival difference. Chemotherapy-naive patients with HGG at first recurrence when treated with PCV or TMZ have similar survival and time-to-progression outcomes. Adverse events are similar and QoL scores are statistically but not clinically significant between TMZ and PCV. Further RCTs should be conducted with adequate power following CONSORT guidelines with emphasis on QoL outcomes.

Plain-language summary: In this review we found two randomised controlled trials which studied PCV in recurrent HGG patients. The comparator was Temozolomide (TMZ) in one and 'eight drugs in one day' multidrug chemotherapy in another. Results of the two trials were not combined because they compared PCV with different treatments. Conclusions should be drawn with caution as they are based on a single trial analysis as the other trial was too small and underpowered to detect significant difference. Adverse effects and QoL results are based on a single trial analysis. The proportion of participants experiencing severe adverse events with PCV was similar to TMZ. QoL scores were higher with TMZ but not clinically significant. We attributed moderate-grade quality of evidence for overall survival, progression-free survival, chemotherapy toxicity and low-grade evidence for QoL. Chemotherapy-naive patients with HGG at first recurrence when treated with PCV or TMZ have similar survival and time-to-progression outcomes. Adverse events are similar and QoL scores are statistically but not clinically important between TMZ and PCV. The results do not apply to our contemporary patients with recurrent HGG as most of them would receive chemotherapy after original diagnosis as standard care. Participants in this trial received only radiotherapy prior to recurrence. Molecular markers were not used in decision making, which is the standard of care now.