Patients with stromal enlargement of the prostate benefit the most from PAE, two-year STREAM trial data reveal

Prostate artery embolization (PAE)

Prostate artery embolization (PAE) is a good treatment option for patients with benign prostatic hyperplasia (BPH) with minimal complications, according to the 24-month results of the STREAM (Prostatic artery embolization for the treatment of benign prostatic hyperplasia) trial, which affirms the place of the minimally invasive procedure in interventional radiologists’ arsenal.

This MRI-based study looked to examine factors important in predicting successful PAE using MRI over a two-year follow-up period. The triallists report that while adenomatous BPH does particularly well in the short term when treated with PAE, stromal BPH demonstrates better results at two years. In addition, they conclude that patients with median lobe hypertrophy (MLH) do as well as those without MLH up to 24 months, and that initial prostate volume does not appear to be significant in predicting outcome at two years.

“This study has provided valuable information and allowed a better understanding of which glands respond and how they will respond to PAE,” Charles Tapping (Churchill Hospital, Oxford, UK) and co-authors write in Cardiovascular and Interventional Radiology (CVIR). “It also allows clinicians to provide more information to patients exploring treatment for their BPH. MLH responded as well as non-MLH BPH disease, suggesting this technique may be valuable in treating patients with MLH, especially if some of the other minimally invasive techniques are limited if significant MLH is present.”

STREAM trial data at two years proves the technical and clinical success of PAE

“PAE has established itself as one of the alternative minimally invasive treatments for BPH, and is now accepted as safe and effective,” Tapping et al write. They go on to say that while performing PAE can be technically challenging, with a significant learning curve to perform the technique successfully, it is important to ascertain factors that may aid in predicting which patients would benefit most from PAE. They note that this is a particular imperative for interventional radiologists as there are “a number of robust minimally invasive techniques to treat BPH, such as the Urolift system and water vapour thermal therapy (REZUM)”.

They therefore conducted a prospective cohort study of 50 patients with BPH who were treated with PAE at a single institution. Patients had moderate to severe symptoms of BPH refractory to medical management for at least six months prior to enrolment in STREAM. Patients were imaged with multiparametric MRI imaging pre-PAE, and at three months, 12 months, and 24 months post-procedure. Clinical success was measured with international prostate symptom score (IPSS), international index of erectile function (IIEF), and validated quality of life (QoL) EQ-5D-5L questionnaires.

The technical success rate was 96%—no prostate arteries could be identified intraprocedurally in two of the 50 patients. The study authors report only minor complications arising from PAE: two cases of acute urinary retention and one case of uncomplicated urinary tract infection. While these are positive data for PAE, the authors state that, “Unfortunately, as there was no comparison group or control group in this study, it is not possible to make direct comparisons between different minimally invasive methods for treating BPH.”

Clinical outcomes of the STREAM trial were also positive. The mean IPSS score dropped from a baseline score of 21.1 (range: 16–36) to 7.2 at 12 months, and 8.1 at 24 months. Meanwhile, results from the EQ-5D-5L quality of life questionnaire demonstrated an increased quality of life at three, 12, and 24 months post-procedure. Results from the IIEF showed no significant change in erectile function over the two-year study following PAE. The prostate volume as measured on MRI imaging was significantly reduced from baseline to three months post-PAE. There was then a non-significant volume reduction at 12 and 24 months when compared to baseline.

Greatest improvement in IPSS score seen in patients with adenomatous BPH

“An interesting analysis of the results showed that while adenomatous BPH had an initial greater reduction in their IPSS score, improvement in quality of life, and symptoms (at three and 12 months compared to stromal group), the stromal group had better results at 24 months,” Tapping and colleagues say.

“In fact”, they write, “there was a continued decline in IPSS score in the stromal group over the 24-month study period, with a slight increase in IPSS score in the adenomatous group from 12 to 24 months.”

While the stromal prostate gland volume decreased compared to baseline size at three, 12, and 24 months post-PAE, the adenomatous glands at first rapidly reduced in size, maintained this small volume out to 12 months, and then increased in size again, with a larger volume reported at 24 months.

Discussing this finding, the triallists say: “This adds to the previously perceived literature that suggests adenomatous BPH patients had a better outcome. Angiography of adenomatous masses within the prostate demonstrates that these are highly vascular structures and the more rapid reduction in symptoms and IPSS score can be accounted for by infarction of the adenoma and rapid reduction in pressure on the transition zone of the prostate. Moreover, the more gradual improvement in the stromal group corresponds to typically a less vascular pattern on angiography.”

Patients with median lobe hypertrophy do just as well post-PAE as those without median lobe hypertrophy

No significant difference in IPSS score was observed at any time point between the 19 patients with MLH and those without MLH, according to the STREAM trial findings.

“Typically,” Tapping and co-authors muse, “it has been considered that patients with MLH would not do as well with PAE. However, patients in this cohort did as well as those without MLH. PAE may therefore be a good option for patients with MLH that cannot have alternative minimally invasive forms of treatment for their BPH.”

In addition, there was no significant correlation between initial prostatic volume and the IPSS score at 12 and 24 months post-PAE (p=0.05), the authors note. While previous investigators have suggested that prostate size is associated with clinical success following PAE, Tapping et al consider that in their study, MRI provided extra detail of the internal prostate architecture, meaning that “factors such as adenomatous predominant and stromal dominant disease became more useful”.

They conclude that further studies are needed in order to determine who the most appropriate patients for each minimally invasive BPH treatment are, and to overcome the limitation imposed on this trial by its small sample size.


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