Management of Sporadic Renal Angiomyolipomas: A Systematic Review of Available Evidence to Guide Recommendations from the European Association of Urology Renal Cell Carcinoma Guidelines Panel

Abstract

Context: Little is known about the natural history of sporadic angiomyolipomas (AMLs); there is uncertainty regarding the indications of treatment and treatment options.

Objective: To evaluate the indications, effectiveness, harms, and follow-up of different management modalities for sporadic AML to provide guidance for clinical practice.

Evidence acquisition: A systematic review of the literature was undertaken, incorporating Medline, Embase, and the Cochrane Library (from 1 January 1990 to 30 June 2017), in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. No restriction on study design was imposed. Patients with sporadic AML were included. The main interventions included active surveillance, surgery (nephron-sparing surgery and radical nephrectomy), selective arterial embolisation, and percutaneous or laparoscopic thermal ablations (radiofrequency, microwaves, or cryoablation). The outcomes included indications for active treatment, AML growth rate, AML recurrence rate, risk of bleeding, post-treatment renal function, adverse events of treatments, and modalities of follow-up. Risk of bias assessment was performed using standard Cochrane methods.

Evidence synthesis: Among 2704 articles identified, 43 were eligible for inclusion (zero randomised controlled trials, nine nonrandomised comparative retrospective studies, and 34 single-arm case series). Most studies were retrospective and uncontrolled, and had a moderate to high risk of bias.

Conclusions: In active surveillance series, spontaneous bleeding was reported in 2% of patients and active treatment was undertaken in 5%. Active surveillance is the most chosen option in 48% of the cases, followed by surgery in 31% and selective arterial embolisation in 17% of the cases. Selective arterial embolisation appeared to reduce AML volume but required secondary treatment in 30% of the cases. Surgery (particularly nephron-sparing surgery) was the most effective treatment in terms of recurrence and need for secondary procedures. Thermal ablation was an infrequent option. The association between AML size and the risk of bleeding remained unclear; as such the traditional 4-cm cut-off should not per se trigger active treatment. In spite of the limitations and uncertainties relating to the evidence base, the findings may be used to guide and inform clinical practice, until more robust data emerge.

Patient summary: Sporadic angiomyolipoma (AML) is a benign tumour of the kidney consisting of a mixture of blood vessels, fat, and muscle. Large tumours may have a risk of spontaneous bleeding. However, the size beyond which these tumours need to be treated remains unclear. Most small AMLs can be monitored without any active treatment. For those who need treatment, options include surgical removal of the tumour or stopping its blood supply (selective embolisation). Surgery has a lower recurrence rate and lower need for a repeat surgical procedure.

Keywords: Active surveillance; Angiomyolipoma; Kidney; Nephron-sparing surgery; Selective arterial embolisation; Systematic review.