The Introduction of 3T multiparametric magnetic resonance imaging of the prostate to a peripheral hospital – clinical utility and cost savings

Introduction

Prostate cancer (PC) is the second most common cancer in men worldwide with an estimated 1.1 million cases diagnosed in 2012. The incidence of PC varies more than 25-fold worldwide with the highest rates in Australia and New Zealand. ¹ In Australia it is the most commonly diagnosed cancer in men with the second highest cancer-related death. ²

PC diagnosis is traditionally via systematic transrectal ultrasound-guided biopsy (TRUSGB) in men with an abnormal digital rectal examination (DRE) or elevated serum prostate-specific antigen (PSA). This method, however, has been associated with the over-diagnosis of many low-risk, clinically insignificant PCs and often failure to diagnosis clinically significant disease.^3,4 The risks of prostate biopsy and treatment of PC are well established, including sepsis, incontinence and sexual dysfunction.^5,6

Increasing use and improvement in 3-Tesla multiparametric magnetic resonance imaging (3T mpMRI) has provided an additional investigative modality in the workup of PC. 3T mpMRI has been shown to have high negative predictive values (NPVs) for clinically significant cancers, reducing the requirement for biopsy and increasing the detection rate.^7,8 3T mpMRI is an expensive resource; however, it has been previously suggested that it may have a cost-saving benefit and role in the active surveillance management pathway. ⁹

We aimed to assess the clinical utility and cost savings of 3T mpMRI prostate at a Queensland, Australia, hospital when compared to prostate biopsy as a first-line investigation.

Methods

Results

A total of 175 patients were identified who had an mpMRI prostate between January 2015 and January 2017.

Forty of the 175 patients had a previously known diagnosis of PC. Of these, 28 patients were on active surveillance with the mpMRI results leading to repeat prostate biopsy in six patients and three of these having an upgrade in their Gleason grade. Overall, eight patients moved to active treatment post-mpMRI.

Of the 175 patients, 135 were biopsy-naïve men undergoing primary investigation for PC. Based upon the mpMRI prostate, 52 patients progressed to prostate biopsy with the remaining 83 patients not proceeding to biopsy. Of the patients who had a prostate biopsy, 41 new diagnoses of PC were made: 11 patients with Gleason 6 disease and 30 patients with Gleason 7 or greater.

Treatment and management of the 41 patients with a new diagnosis of PC included 18 patients undergoing radical prostatectomy, four patients external-beam radiation therapy, one patient on androgen-deprivation therapy, 12 patients on active surveillance and six patients on watchful waiting.

Sixty-two biopsy-naïve men with Prostate Imaging Reporting and Data System (PI-RADS) 1 or 2 scoring on their mpMRI prostate were reviewed again in the outpatient department for follow-up PSA surveillance. Nine patients (14.5%) on repeat PSA testing had higher readings with four of these going on to prostate biopsy. Fifty per cent had a decrease in PSA on next testing while 35.5% were stable. Mean repeat PSA testing occurred at 4.3 months (standard deviation 2.1 months). One patient did not have a repeat PSA, moving interstate and undergoing a transurethral resection of the prostate for benign hypertrophy.

The cost to the hospital for an mpMRI prostate is $550 compared to $2800 for a TRUSGB. Other costs to consider include $850 for a day on a surgical ward, $6200 for a day in the intensive care unit and $240 for an outpatient appointment.

Given 175 patients underwent an mpMRI prostate, the total cost is $96,250. If these patients went to TRUSGB as first-line investigation the total cost would have been $490,000. Only 60 patients, however, went on to prostate biopsy. Therefore, over the two-year study period by utilising mpMRI prostate to reduce the number of patients undergoing TRUSGB, there has been a total saving of $225,750.

Discussion

The results of this study provide a novel insight into the utility of mpMRI at a hospital in Queensland. Several aspects of discussion have been identified, including the role of mpMRI prostate in primary investigation, active surveillance and cost savings.

TRUSGB has significant complications including sepsis, prostatitis, urinary retention, haematuria, haematospermia and anaesthetic risks. ⁶ Several studies have shown high NPV and PC detection rates using mpMRI for detecting clinically significant PC. ⁷ This is reiterated by MRI-guided biopsies detecting more clinically significant PC and less indolent disease than systematic TRUSGB. ⁸ There are, however, limited data relating to use of mpMRI as an initial triage test, with only positive mpMRI proceeding to biopsy. In a select group of patients this method has been utilised with close clinical surveillance.

We retrospectively assessed a group of biopsy-naïve men with PI-RADS 1 or 2 mpMRI scans who were followed up as clinical outpatients. A total of 85.5% of these patients on repeat PSA testing had either decreased or stable levels. By triaging investigation in this fashion, many men are saved biopsy with potentially significant morbidity and overtreatment. Close clinical surveillance and risk stratification should be employed as clinically significant PC can be present in negative mpMRI prostate.

Active surveillance is based around serial DRE, PSA testing and repeat biopsy. Rates of cancer upgrading and progression to active treatment of disease are between 6.7% and 11% per annum. ¹⁰ This is largely driven by repeat biopsy findings, PSA levels and patient choice. The role of mpMRI within this algorithm is yet to be established. Several studies have shown practical uses of mpMRI in assisting with targeted biopsy, assessing lesion size and providing reassurance with low PI-RADS scoring.^8,11,12 In our series all of these were utilised to assist with continuation on active surveillance, further biopsy or direct progression to active treatment.

Direct cost savings achieved from reducing the number of patients undergoing biopsy was $112,875 per annum. There are also significant indirect savings associated with hospital readmission rates post-TRUSGB. Roth et al. found that 3.66% of patients were readmitted to hospital post-TRUSGB within seven days for an average duration of four days and a mean cost of $7362 AUD. ¹³

Conclusion

Prostate mpMRI is a useful tool in the investigation and surveillance of PC. It can be effectively utilised to reduce the number of prostate biopsies and provide a significant overall cost benefit to the health care provider. As limited data are available on PSA triage and active surveillance via mpMRI, risk stratification and close clinical follow-up is required in these patient groups.