DRE Is Still a Prognostic Tool for Prostate Cancer

First-of-Its-Kind Analysis in Modern Era

Nick Mulcahy

July 31, 2019

In the modern era of advanced imaging and genomics testing, the digital rectal exam (DRE) is still an "important" and clinically relevant prognostic test for prostate cancer, conclude the authors of a new observational study.

The role of the DRE, which is a "historic" method of staging the disease, has been "uncertain" in recent years, acknowledge the investigators, led by Jenna Borkenhagen, MD, a radiation oncologist at the Medical College of Wisconsin in Milwaukee.

That's because of the availability of other prognostic tools such as the 4K Score, Decipher, and MRI, they say. Plus, no one has studied the question of DRE's usefulness in a more modern setting.

For a long time, the DRE served, along with a prostate-specific antigen (PSA) value and a Gleason score, as the bedrock for assessing prostate cancer prognosis, which influences treatment decisions.

The new observational, retrospective study shows that clinical stage classification via DRE is significantly prognostic in terms of overall survival among men with high-risk localized disease in a modern cohort (treated from 2004–2010) in a US database.

In short, the old tool still works in a contemporary setting.

"Digital rectal exam remains a valuable prognostic tool for prostate cancer patients," Borkenhagen told Medscape Medical News.

The study was published online in the July edition of the Journal of the National Comprehensive Cancer Network.

"The findings reaffirm that prostate cancer clinicians should be using DRE. I use it on all of my patients," said study senior author William Hall, MD, also from the Medical College of Wisconsin, in an interview with Medscape Medical News.

The findings reaffirm that prostate cancer clinicians should be using DRE. Dr William Hall

At New York University in New York City, all urologists perform a DRE during initial patient visits, said William Huang, MD, who was asked for comment.

"In patients with biopsy-proven prostate cancer, the ability to palpate a tumor with a finger provides an inexpensive prognostic tool," he told Medscape Medical News in an email.

However, DRE is "not high on the list" of such tools, which include PSA, Gleason grade, MRI, and genomic tests, said Huang.

The study authors point out that tumor (T) stage, which is established via DRE, is part of the NCCN risk stratification system for prostate cancer patients.

But, anecdotally, clinicians are moving away from the inexpensive physical exam (ie, DRE) and into more expensive high-tech tools to establish prognosis, Hall said.

NYU's Huang also observed that, as a screening test, the DRE has seen a drop in utilization as other more effective methods have emerged.

Borkenhagen and colleagues also acknowledge the obvious: DRE is "invasive and undesirable" to many patients.

Clinical T Staging Still Useful

For their study, the investigators identified a subset of 5291 men in the National Cancer Database with high-risk clinical T2N0M0 prostate cancer treated with external-beam radiotherapy and androgen deprivation therapies (ADT), with or without surgery in the latter part of the 2000s.

High-risk was defined as having any of the following clinical factors at diagnosis: Gleason score >7, PSA >20 ng/mL or clinical stage T3a-T4.

As expected, this group also had a high percentage of men with cT2 disease, which is determined by physical exam (ie, DRE). Hall explained that all of these men have organ-confined disease but are subclassified via DRE as cT2a, cT2b, and cT2c, based on the extent and location of their tumors, as detected by examination.

At a median follow-up of 5.4 years, the proportion of deaths in each subclass were 22.5% for cT2a, 25.7% for cT2b, and 29.8% for cT2c.

In multivariate analysis, the cT2a, cT2b, and cT2c subclassifications had prognostic significance, with increasing hazard ratios (HR) for death. Specifically, the values were 1.00 (reference) for cT2a; 1.25 for cT2b (P = .0046); and 1.43 for cT2c (P < .0001).

The findings were independent of other known prognostic variables such as age and insurance type.

Given that the DRE is such a subjective test, Hall was pleasantly surprised that the overall survival differences between the subclassification groups were spread out incrementally as might be expected with a more objective test, with the cT2c subset having the worst outcome.

In the clinic, the findings of a DRE — and the related T subclassification — may influence treatment decisions, Hall suggested. As an example, men with high-risk cT2c disease who undergo radiation therapy may want to consider longer durations of subsequent ADT, he said, although he pointed out that the study was not designed to assess this.

The new study sheds light on a matter of clinical uncertainty, emphasize the study authors. "Literature on the prognostic value of the cT2 subclassifications in a contemporary patient cohort is lacking," they write.

Lead author Borkenhagen acknowledged the new study's limitations, most notably that it is retrospective.

Still, any move away from the DRE is a lost opportunity, senior author Hall suggested: "This is an inexpensive, historic, time-tested physical exam the findings of which, in a modern cohort of men, hold prognostic significance with regard to overall survival."

The study was supported by the National Center for Research Resources and the National Center for Advancing Translational Sciences. The authors and Huang have disclosed no relevant financial relationships.

J Natl Comp Cancer Network. Published online July 2019. Full text

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