Abstract
Purpose:
We review our single center experience in the management of renal angiomyolipoma (AML) in patients who were treated with active surveillance (AS) or invasive treatment protocols.
Patients and Methods:
A prospectively evaluated database was reviewed, and we identified 91 patients with the diagnosis of renal AML who presented between June 1985 and February 2009. Patient characteristics, clinical presentation, treatment modalities, and patient outcomes were evaluated. Patients on AS were analyzed for successful completion of the surveillance protocol considering age, symptomatic presentation, and tumor size as potential predictors of invasive treatment.
Results:
A total of 91 patients with AMLs were identified. The mean patient age was 57 years. Seventy-three (83.9%) patients presented incidentally, and 14 (16%) patients were symptomatic at presentation. Forty-five patients were treated with AS, 4 underwent embolization, and 38 patients had extirpative surgery. After a median follow-up of 54.8 months (range 0.2–211.7 mos), there was a mean growth rate of 0.088 cm/year in the group who were treated with AS. AS failed in three patients. Two patients had retroperitoneal bleeding during the observation period, and one patient manifested an expeditious growth rate of 0.7 cm/year and underwent a radical nephrectomy.
Conclusions:
AML is a renal tumor that usually exhibits a benign course. Surgical removal and embolization are the standard invasive treatment modalities. AS for AMLs is associated with a slow and consistent growth rate (0.088 cm/year), typically has minimal morbidity, and is a reasonable option in selected patients. Symptomatic presentation and size (>3 cm) are not predictive for necessitating an invasive procedure.
Introduction
We evaluated our single center experience in the management of renal angiomyolipoma regarding clinical presentation, patient characteristics, and treatment outcomes in an effort to assess the efficacy of contemporary management strategies.
Patients and Methods
We reviewed our prospectively established database and identified the records of 91 patients who had received a diagnosis of renal AML between June 1985 and February 2009. The clinical, radiographic, and pathologic data were extracted from the complete medical records. The data from patients with a history of tuberous sclerosis complex (TSC) are presented separately in the analysis.
Patients who were placed on an AS protocol were observed with annual follow-up imaging using CT or MRI. Tumor size was documented based on the maximal cross-sectional dimension, and the growth rate was calculated by comparing the change in cross-sectional diameter of the lesion with previous imaging. Age, symptomatic presentation, and size (>3 cm vs ≤3 cm) were evaluated using logistic regression to determine if an association existed between these variables and the need for an invasive procedure.
Results
A total of 91 patients were identified with 97 AMLs. Four (4.4%) of these patients had TSC and had six (6.2%) tumors. Eighty-seven (95.6%) patients with 91 sporadic tumors were identified. Among the patients with sporadic AML, the mean age at presentation was 57 years (range 32–86 y). There were 67 (77%) women and 20 (23%) men. Five (5.5%) patients had bilateral disease. Seventy-three (83.9%) patients presented with their tumor as an incidental finding. Among the 14 symptomatic patients, the most common presentation was pain in seven (50%) patients. The diagnosis of AML was made by CT in 90 (98.9%) and MRI in 1 (1.1%) of patients. Clinical follow-up was available for all patients with a median follow-up time of 39.1 months (range 1–212 mos).
Sporadic AML group
AS
A total of 45 patients with sporadic AMLs were placed on an AS protocol as a primary management strategy. In this group, the mean age was 59 years (range 40–75 y), and the mean tumor size was 1.7 cm (range 0.3–8.0 cm). The primary reason for AS was small tumor size (<4 cm) in 42 (93.3%) patients. Three (6.67%) patients were put on AS for significant comorbidities, because they were considered high-risk surgical candidates.
Radiographic follow-up for the observation group was available in 43 of 45 (95.6%) patients. After a median follow-up of 54.8 months (range 0.2–211.7 mos), the mean growth rate in this cohort was 0.088 cm/year (range 0–1.3 cm/year). Three failures occurred during AS. Two (4.2%) patients experienced retroperitoneal bleeding during the observation period necessitating embolization. The initial AML sizes at presentation were 3.5 cm and 5.5 cm, and the mean AS time for these two patients was 20.3 months. The third patient in whom observation failed manifested a growth rate of 0.7 cm/year and underwent a radical nephrectomy (central tumor) after an AS period of 17 months because of concerns for hemorrhage based on size.
Surgical extirpation
Thirty-eight surgical procedures were performed as primary treatment in the sporadic group. In this group, the mean age was 56.4 years (range 32–83 y), and the mean tumor size was 3.8 cm (range 0.7–13 cm). The indications for surgery included size larger than 4 cm in 9 (23.7%) patients, and suspicion for renal-cell carcinoma (fat not appreciated on preoperative imaging) in 29 (76.3%) patients. One (2.6%) patient underwent surgical removal (open partial nephrectomy) as a secondary procedure after embolization failed. The surgical procedures performed included 10 laparoscopic partial nephrectomies, 2 laparoscopic renal cryoablations, 1 laparoscopic radical nephrectomy, 10 open radical nephrectomies, and 15 open partial nephrectomies.
The mean follow-up time for the patients who were undergoing surgical treatment was 54.4 months. In this group, there were two (5%) complications: One patient experienced postoperative pneumonia, and one patient had a trocar site hernia. In the surgical group, there has been no documented recurrence, and all patients remain free of symptoms.
Selective embolization
Four patients with sporadic AMLs were treated with embolization. The mean age in the group was 48.2 years (range 20–74 y), and the mean tumor size was 9.5 cm (6–12 cm). Indications for embolization included bleeding in two (50%) patients and pain in two (50%) patients. The mean follow-up for the four patients who underwent embolization was 29.6 months (range 4.1–111 mos). One patient in whom embolization failed underwent an open partial nephrectomy. This patient presented initially with pain and a 12 cm AML. None of the patients needed repeated embolization.
Factors that predict intervention
Logistic regression analysis was performed to define metrics that are associated with an increased risk of intervention in sporadic AML patients. Advanced age, initial symptomatic presentation, and size >3 cm were not found to be significant factors in predicting the need for an invasive procedure at the 5% significance level. This is potentially because of the small number of failures causing the odds ratio and the variability thereof to lack predictability.
After stratifying the cohort by date of presentation (before vs after January 1, 2000) we found that 27.6% of incidentally detected masses were in patients who presented before 2000 and 72.4% who presented after January 1, 2000 (P = 0.76). In these patients who presented before 2000, 13 were treated with AS, 2 with selective embolization, and 6 with surgical removal. After 2000, there were 34 surgical extirpations with 26 (76.5%) nephron-sparing procedures (open or laparoscopic). Thirty-two patients were followed on AS and 4 patients were treated with selective embolization.
TSC group
Of the four patients with documented TSC, there were three women and 1 man. Two patients had bilateral disease. There were a total of six renal lesions in these four patients. The mean age at diagnosis was 43 years (range 20–70 y). Primary treatment modalities for the renal lesions (six) were AS in three (all tumors were <4 cm), extirpation in two (one open partial nephrectomy for a 4.5 cm AML, and one laparoscopic partial nephrectomy for a 3-cm mass that was suspicious for renal-cell carcinoma), and embolization in 1 patient. One patient who was undergoing AS for a 3.6 cm AML experienced a retroperitoneal bleed and needed embolization at 76 months.
Discussion
In our contemporary AML cohort, most patients presented incidentally and were found to have evidence of a renal mass on cross-sectional imaging. Previous series have demonstrated a symptomatic presentation in 21% to 100% of patients. 2 –5 Fourteen patients in our cohort were symptomatic with 7 (50%) presenting with pain and 7 (50%) presenting with gross hematuria. Nelson and Sanda 1 reported that flank pain was the most common presenting symptom in AML (41%) patients followed by a palpable mass and hematuria. 1
We observed that sporadic AML developed in the majority of patients, with four patients having an AML as part of TSC. Thirty-eight patients with a sporadic AML were treated with surgical removal. The most common indication (73.7%) was suspicion for malignancy based on preoperative imaging. Contemporary data support the concept of nephron sparing for the management of AML when possible. 6 –9 In the current study, there were a total of 38 surgical procedures performed with 32 (74.4%) being nephron sparing.
Four patients were initially treated with embolization. Embolization remains the least invasive intervention in the setting of acute hemorrhage. 1,10 The efficacy of embolization is difficult to assess in the absence of controlled studies, but series have reported a 14% to 80% incidence of reembolization with 14% to 24% of patients progressing to an operative intervention. 10 –15 One failure occurred after embolization in a patient with a 12-cm AML who presented initially with pain. Ultimately, the patient underwent a partial nephrectomy.
The majority of sporadic AML patients were placed initially on an AS protocol. Interest in the growth rate of small renal cortical neoplasms has generated debate in the literature regarding the appropriate protocol for AS. Rosales and colleagues 16 have demonstrated an annual growth rate of 0.34 cm in the largest AS series to date for renal tumors. At this time, the size limit necessitating intervention for an AML is unknown, because many patients are not observed until failure. In evaluating our AML population, however, there was a substantially slower growth rate of less than 1 mm per year (0.088cm/year), suggesting that AS is a valuable option for patients with an incidentally discovered AML. Successful application of observation protocols have been reported in other series with similar outcomes. 2,5,10,17
Three failures occurred in the AS cohort, necessitating intervention. Two patients experience retroperitioneal hemorrhage and needed selective embolization. One patient had a significant growth rate (0.7cm/year) and underwent a radical nephrectomy for a centrally located tumor. Patients with TSC have an increased likelihood of multifocal and bilateral disease compared with those with sporadic AMLs, and two patients in our series demonstrated bilateral tumors. TSC patients were also more likely to be younger and have larger AMLs necessitating invasive treatment. Two patients underwent partial nephrectomy and one needed embolization.
Factors to predict surgical intervention or embolization were evaluated using logistic regression. Age, symptomatic presentation, and size (>3 cm) were not significantly associated with an invasive procedure.
Finally, there have been significant changes in the presentation of AML over the past decade. In our cohort, 83.9% of patients presented with an incidental AML. When stratifying our patients by date of presentation (before vs after January 1, 2000), there was a trend toward an increase in the number of incidentally discovered AMLs over the past decade. This is consistent with the high incidence of small renal cortical neoplasms discovered incidentally because of the increased use of abdominal cross-sectional imaging.
Conclusions
AML is a benign renal tumor that usually presents as an incidentally. At this time, surgical removal and selective embolization are the standard interventions for AML. AS, however, is a less invasive option that may be applied in selected patients. A slow growth rate (0.088 cm/year) and an uncomplicated course of management make AS a reasonable approach for initial treatment. Symptomatic presentation and size do not seem to predict the need for intervention; however, with improved knowledge of the growth rate of AML, future studies should focus on size limitations for invasive intervention.
Footnotes
Disclosure Statement
No competing financial interests exist.