With widespread urological acceptance of prostate artery embolization (PAE) impending, Tiago Bilhim (Saint Louis Hospital, Lisbon, Portugal) calls for caution when selecting patients for the minimally invasive treatment of benign prostatic hyperplasia (BPH). In a recent commentary published in the Journal of Vascular and Interventional Radiology (JVIR; doi: 10.1016/j.jvir.2019.08.003), Bilhim says “It is important to better select patients before PAE to avoid clinical failures”, emphatically concluding: “Avoid pedunculated intravesical prostatic protrusions!”
The commentary was written following another article published in JVIR (doi: 10.1016/j.jvir.2019.07.035) in November 2019 by Simon Yu (Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, China) and collaborators, who reported that the thickness-to-height ratio of intravesical prostatic protrusions (IPPs) predicts the clinical outcome and morbidity of PAE for BPH.
Both the prospective, single centre study conducted by Yu et al and the subsequent commentary from Bilhim were carried out within the context of a dearth of information regarding the implications of the median lobe for patients with BPH. Defining the median lobe, Bilhim writes: “There are many different types of IPPs (intravesical prostatic protrusions) that may be due to median lobe overgrowth, but also from the central or transitional zone of the prostate, or even the anterior fibromuscular stroma. Usually, the terminology of ‘median lobe’ refers to the continued growth of the periurethral glands, leading to a well-demarcated expanding midline retrourethral tissue; thus, IPP connotes a broader reach, encompassing both the median lobes, as well as all IPP from other glandular zones of the prostate.”
According to Bilhim, a frequent question posed by physicians and patients alike is whether the median lobe is a contraindication for PAE. In praise of the study from Yu and colleagues in Hong Kong, Bilhim writes that “the present study sheds some light on this specific topic”. Indeed, the answer provided by Yu and his team is that not all median lobes are the same.
Yu and collaborators found that pedunculated IPPs, which are taller than they are wide, are indicative of poor outcomes after PAE. They postulate that this is due to a bladder outlet obstruction that “becomes more prominent after embolization, as the prostatic tissue gets softer and more mobile with ischaemia”. In their study, they evaluated 82 patients with an International Prostate Symptom Score (IPSS) ≥15 and a quality of life score ≥3, treated between June 2015 and December 2018 at their institution. IPPs were present in 57 of 82 patients (69.5%). They reported the presence of IPPs correlated with the occurrence of post-procedure complications (p=0.009), but not with suboptimal IPSS at 12 months (p=0.758). However, IPPs with a thickness-to-height ratio ≤1.3 did correlate with suboptimal IPSS at 12 months (p=0.025) and suboptimal quality of life at six months (p=0.025) and 12 months (p=0.008), as well as with the occurrence of post-procedure complications (p=0.009). They therefore concluded that while IPPs with a thickness-to-height ratio ≤1.3 predicted the occurrence of post-procedure complications with urinary obstruction up to 12 months after PAE, merely the presence of IPPs alone did not predict the clinical outcome.
This raises several questions about the median lobe, Bilhim argues: “What type of imaging classification can we use to assess it? What is the impact of the median lobe on the natural progression of disease in patients with BPH? Does the median lobe also limit the efficacy of other minimally invasive surgical techniques such as prostatic urethral lift (PUL) or water vapour thermal therapy? What do we know already about the effect of PAE for the median lobe? Can we target the median lobe during PAE? Is PAE effective when treating patients with BPH and a median lobe?”
Whilst seeking answers to these questions, Bilhim acknowledges that what Yu et al’s study does elucidate is that PAE can target the IPP, but it highlights that there are different clinical outcomes depending on the subtypes of IPP present. “Clearly,” Bilhim writes, “pedunculated IPPs with taller than wide protrusions into the bladder neck are poor candidates for PAE, with 34% of patients presenting worsening of bladder outlet obstruction symptoms, acute urinary retention, or failure to remove the bladder catheter, and 11% requiring bailout surgery after embolization. One would not want to end up as Stealers Wheel: ‘Here I am stuck in the middle with you’.”
However, he ends on a positive: “The good news is that these types of pedunculated IPPs have an overall reported prevalence of 10%, even though they were documented in 43% of patients from the study of Yu et al, which may be due to selection bias. The vast majority of IPPs are broad-based and respond well to PAE.”