Active surveillance for renal angiomyolipoma: outcomes and factors predictive of delayed intervention

To present the outcomes of active surveillance (AS) for renal angiomyolipomas (AMLs) and to assess the clinical features predicting delayed intervention of this treatment option.

We retrospectively reviewed the outcomes of patients diagnosed with AMLs on computed tomography (CT) who were managed with AS at our institution. The AS protocol consisted of 6- and 12-month, then annual follow-up visits, each one including a physical examination and CT imaging. Discontinuation of AS was defined as the need or decision for an active procedure during the follow-up period. Causes of delayed intervention, as well as the type of active treatment (AT), were recorded. Clinical features at presentation of patients failing AS were compared with those who remained under AS at the time of the last follow-up. Predictive factors of delayed intervention were analysed using univariate and multivariate Cox regression models.

Overall, 130 patients were included in the analysis, of whom 102 (78.5%) were incidentally diagnosed, while 15 (11.5%) and 13 patients (10%) presented with flank pain and haematuria, respectively. After a mean (sd) follow-up of 49 (40) months, 17 patients (13%) discontinued AS and underwent AT. Patients who underwent delayed intervention were more likely to present with a higher body mass index, larger tumours and symptomatic disease. Angioembolization represented the first-line AT after AS (64.7%), whereas partial nephrectomy was adopted in 29.4% of patients. On the univariate analysis, risk factors for delayed intervention included tumour size ≥4 cm, symptoms at diagnosis, and history of concomitant or contralateral kidney disease. On the multivariate analysis, only tumour size and symptoms remained independently associated with discontinuation of AS.

Tumour size and symptoms at initial presentation were highly predictive of discontinuation of AS in the management of AMLs. Selective angioembolization was the first-line option used for AT after AS was discontinued.