mpMRI Improves Initial Staging in Suspected Muscle-Invasive Bladder Cancer

Among patients with suspected MIBC, the incorporation of mpMRI for initial staging prior to TURBT was beneficial: © pikovit - stock.adobe.com

Among patients with suspected muscle-invasive bladder cancers (MIBCs), the incorporation of magnetic resonance imaging (mpMRI) for initial staging prior to transurethral resection of bladder tumor (TURBT) was beneficial, according to data from the BladderPath study, which was published in the Journal of Clinical Oncology. Researchers added that the mpMRI-directed pathway led to a 45-day reduction in TTCT for patients with MIBC.

The study, conducted between May 31, 2018, and Dec. 31, 2021, randomly assigned 143 patients to TURBT (72 patients) or initial mpMRI (71 patients); 36 of 39 participants with suspected MIBC underwent mpMRI. Overall, the median time to correct treatment (TTCT) for these participants was significantly shorter with initial mpMRI and there was no detriment for participants with non-MIBC.

“In conclusion, incorporating mpMRI ahead of TURBT into the standard pathway was beneficial for all patients with suspected MIBC. TURBT could be avoided in a proportion of these patients. This approach can improve decision making and accelerate time to treatment,” first study author Dr. Richard T. Bryan of the Bladder Cancer Research Centre, Department of Cancer and Genomic Sciences, University of Birmingham, in Birmingham, United Kingdom, and colleagues said of the research in the Journal of Clinical Oncology.

Based on current unmet needs in the treatment space, investigators aimed to determine whether patients with MIBC can be expedited to definitive treatment using flexible cystoscopic biopsy and mpMRI, with subsequent TURBT only if indicated. Specifically, the BladderPath study investigated whether multiparametric MRI after flexible cystoscopy and tumor biopsy could distinguish MIBC from NMIBC.

The randomized controlled BladderPath trial was conducted across 17 United Kingdom hospitals to assess the feasibility and impact of using mpMRI instead of TURBT for staging bladder cancer. Patients with suspected bladder cancer were eligible for the study and underwent flexible cystoscopy and upper tract imaging; eligible participants were randomly assigned to either a standard TURBT pathway or an mpMRI-based pathway. Those with probable NMIBC had TURBT versus those with possible MIBC who underwent mpMRI to determine the need for further biopsy or TURBT.

The primary outcome for the feasibility stage measured adherence to the mpMRI pathway, while the time-to-correct-treatment (TTCT) stage had a main outcome measure of how quickly patients received the appropriate treatment. Treatment for NMIBC was TURBT, whereas MIBC required systemic chemotherapy, radiotherapy, cystectomy or palliative care. Final diagnoses were confirmed through pathology or imaging. Overall, the main goals of the research were to streamline staging, reduce delays and improve treatment efficiency for MIBC.

Between May 31, 2018, and Dec. 31, 2021, 17 hospitals were included in the BladderPath trial, screening 638 patients and randomly assigning 143 to either the standard TURBT pathway (Pathway 1) or the mpMRI-based pathway (Pathway 2). After randomization, three participants were deemed ineligible, and seven withdrew from the study, including three individuals who did not have bladder cancer. Additionally, nine protocol deviations occurred across both pathways. The study maintained a balanced distribution of patient characteristics.

By the time of reporting, 91% of participants had received their respective treatments. Among the 13 who had not, reasons included early withdrawal, death or delays in confirming their diagnosis and receiving the correct therapy. Overall, 132 participants (92%) had a confirmed diagnosis of either NMIBC or MIBC. In total, 50 NMIBC cases were identified in Pathway 1 and 53 in Pathway 2, while 15 MIBC cases were found in Pathway 1 and 14 in Pathway 2.

In the feasibility stage of the investigation, 36 out of 39 participants (92%) in Pathway 2 who were identified as having possible MIBC successfully underwent mpMRI following randomization; however, three participants did not complete the imaging. Overall, 96% of participants adhered to their assigned pathway, with no significant difference between the two groups.

In the Time to Correct Treatment Stage, the primary outcome measured was the time to correct treatment (TTCT) for participants diagnosed with MIBC. Among 26 participants confirmed to have MIBC (14 in Pathway 1 and 12 in Pathway 2), 25 received the appropriate treatment, while one patient died 81 days post-randomization before treatment could be administered. The median TTCT for all MIBC patients was 77 days, with significantly shorter times observed in Pathway 2. Median TTCT for Pathway 1 was 98 days versus 53 days for Pathway 2.

For patients with probable NMIBC, all 58 confirmed cases (28 in Pathway 1 and 30 in Pathway 2) received TURBT as the correct treatment. The median TTCT for NMIBC patients was 16 days, with no significant difference between pathways. Pathway 1 had a median TTCT of 14 days, while Pathway 2 had a median TTCT of 17 days.

When analyzing all 143 randomly assigned participants, 131 (91.6%) received the correct treatment. Those who had not yet been treated were censored at their last known visit and included in the TTCT analysis. The median TTCT for all participants was 31 days, with Pathway 2 demonstrating a significantly shorter time. Pathway 1 had a median TTCT of 37 days, while Pathway 2 had a median TTCT of 25 days.

Furthermore, of the 17 patients in Pathway 2 diagnosed with MIBC via mpMRI, 8 (47%) still underwent TURBT. Reasons included tumor debulking before radical radiotherapy (four patients), concern about histologic variants (5 patients), presence of carcinoma in situ (one patient) and uncertainty about mpMRI findings (three patients). The investigators noted that some patients had multiple reasons for undergoing TURBT.

In the trial, the median follow-up period was 23.7 months for all participants, with 23.7 months for Pathway 1 and 24 months for Pathway 2. At the time of reporting, 47 participants had experienced recurrence, disease progression or a new primary tumor. Metastatic disease was detected in 13 participants, with a higher incidence in Pathway 1 (10 cases, 26%) compared with Pathway 2 (three cases, 10%). A total of 20 patients had died, with disease-related mortality reported in seven (70%) of Pathway 1 participants and three (30%) of Pathway 2 participants.

To conclude, investigators stated that, “We have demonstrated it is feasible and safe to omit TURBT after mpMRI for a proportion of patients visually assessed as MIBC at flexible cystoscopy. Importantly, mpMRI staging expedited definitive treatment [by over six weeks] for patients with MIBC. When all participants were analyzed, the faster TTCT for MIBC was achieved with no detriment to participants with NMIBC. This is impressive, given some participants with mpMRI-staged MIBC still underwent TURBT for histologic clarification.”

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Reference

"Randomized Comparison of Magnetic Resonance Imaging Versus Transurethral Resection for Staging New Bladder Cancers: Results From the Prospective BladderPath Trial," by Dr. Richard T. Bryan. Journal of Clinical Oncology.