Using MRI before biopsy: A divisive topic?

Emerging technologies trigger new approaches. But with the perceived benefits of novel discoveries come the expected criticisms and contrary viewpoints.

The issue of Magnetic Resonance Imaging (MRI) has prompted closer examination from both its adherents and critics during Thematic Session 11 which examined the question: “Is mpMRI-guided prostate biopsy the new standard?”

“The discussion is polarized now and the truth is somewhere in the middle,” said Prof. Mark Emberton (GB) who took the pro stance in a debate regarding multiparametric MRI (mpMRI). Emberton clashed with the contrary opinions of Dr. Christian Arsov (DE) who gave an equally persuasive argument to the need for a cautionary stance considering that MRI is a nascent technology with some flaws.

Currently, the standard of care is still systematic biopsies to diagnose prostate cancer. But with the incidence of infections and consequent impact on patient’s health, particularly the elderly or those with frail health, doctors require a procedure that would help them exclude biopsies or repeat procedures.

Emberton’s stance was insistent and unambiguous: “There is always a right time to adopt evidence, and the time is now. NOW.”

He enumerated several studies, including those which involved his contribution, to provide support to his views. One study led by V. Kasivisvanathan showed no difference in the detection of significant cancer (57% vs 62% p= 0.2). In the same study, it was also showed that fewer men were diagnosed with insignificant cancer with MRI-TB (9% vs 17%, p= 0.02).

He also cited the 2014 study by V. Panebianco which said none (0%) of the 130 men with a negative MRI had any Gleason pattern 4 identified on saturation biopsy. Another study that Emberton referred to was from January 2015 by M. Siddiqui which compared MRI/Ultrasound fusion-guided biopsy with ultra-sound guided biopsy in diagnosing prostate cancer (PCa).

Emberton, however, conceded there are still uncertainties. “Practice has not changed despite the growing evidence. Why is that? There are still questions such as: Do we need to biopsy a man with a negative MRI? Do random biopsies need to companion the targeted cores?,” said Emberton.

“MRI is the modern response to a man at risk. Location (of tumours) is achieving primacy and precise risk stratification is a requirement for a personalized approach to care. This does mean targeting to maximize precision,” were Emberton‘s concluding statements.

Arson, meanwhile, went straight to the core of the debate by putting to doubt the studies cited by Emberton.

“Systematic biopsies remain a standard and with good reason. We only have four randomized controlled studies that looked into MRI…and from these studies it was not shown that there was a distinct advantage in favour of MRI,” said Arsov while underscoring there was also a “strong, selection bias” in these studies in favour of MRI-targeted biopsy.

“The ideal diagnostic test in prostate cancer would be one that could identify clinically significant cancers in as few biopsy cores as possible, rule out clinically significant cancers and avoid detection of clinically insignificant cancers,” said Arsov. “Are mpMRI and MRI-targeted ready to fulfill all these conditions for all indications in prostate cancer?

Arsov argued that in the studies supporting the use of MRI, the definition of significant cancer was heterogenous and more remarkably there were different field strengths (1.5/3.0 Tesla), different sequences and scoring systems (trigger for MRI-targeted biopsy) used.

“In biopsy-naïve patients there is no evidence that MRI-targeted biopsy improves the detection of significant cancers,” he said.

He cited the recent study of C. Filson (Cancer 2016) which showed that a “negative” mpMRI misses cancers in up to 58% of cases with 35 to 40% of those having significant disease.

“The true negative predictive value of a negative mpMRI for significant cancers seems to be in a range of only 79% to 92%, which means that up to 21% with a negative mpMRI have significant cancers detected by TRUS biopsy only,” Arsov pointed out. And in the 2015 study (European Urology) conducted by J.D. Le, et al., Arsov said in patients with multifocal tumours, mpMRI did not recognize 23% of all index tumours, and 30% to 50% of intermediate/high-grade tumour foci.

“The vast majority of publications reporting very high accuracy for mpMRI and MRI-targeted biopsy come from high-volume academic centres of excellence. And there is also poor level of agreement for mpMRI reading between two of these institutions,” he noted.

To conclude his arguments, Arsov insisted: “The diagnostic accuracy of mpMRI and MRI-targeted biopsy is strongly dependent on the experience of the physician. Both should be restricted to high volume centres. Besides there is no evidence from an RCT that a MRI-targeted biopsy results to lower complication rates.