PET-MUSE Study Shows Trend Toward Management Change of Patients With MIBC Undergoing PET

Standard computed tomography (CT) imaging is critical to making treatment decisions about the use of neoadjuvant chemotherapy (NAC) or local treatment with radical cystectomy (RC) or chemoradiation in patients with muscle-invasive bladder cancer (MIBC). However, CT imaging can underestimate the extent of disease.

The PET-MUSE study, which began in 2016, examined the impact of positron emission tomography (PET) imaging on MIBC staging. Researchers sought to determine if adding ¹⁸F-FDG PET/CT to baseline CT would change the type of treatment received by patients with MIBC. Their results are presented at the European Society for Medical Oncology Congress 2023.

Patients with newly diagnosed MIBC with predominant urothelial histology and no metastases on baseline CT were enrolled in the study from May 2016 to November 2021. They were randomized 2:1 to receive PET or no further imaging. The median follow-up was 2 years. The primary outcome was the proportion of patients who did not receive expected treatment, while secondary outcomes were disease-free survival (DFS) and overall survival (OS).

Of the 292 patients enrolled in the study, 194 received PET and 98 did not. In the PET arm, median patient age was 70 years (range, 43-90 years), 77% had T2 disease, 88% were node negative, 66% had planned RC, and 70% had planned NAC. In the no PET arm, median patient age was 68 years (range, 42-89 years), 77% had T2 disease, 87% were node negative, 69% had planned RC, and 64% had planned NAC. At PET scan, primary bladder tumor was seen in 86 (47%) patients, positive pelvic lymph nodes in 37 (20%), distant nodes in 32 (18%), and distant metastases in 13 (7%).

Expected treatment was received by 166 (86%) PET patients, while 21 (11%) did not receive expected treatment and 7 (4%) withdrew or died prior to receiving treatment. In the patients who did not receive PET, 90 (92%) received expected treatment, 4 (4%) did not, and 4 (4%) withdrew or died prior to treatment.

More PET patients were deemed palliative (18 [9.3%] vs 3 [3.1%]). Notably, over 60% of patients in both arms received NAC. PET patients were more likely to have a change in treatment (odds ratio, 2.89; 95% CI, 0.96-8.74; P=.06) compared with CT alone. No statistically significant difference was observed between arms for DFS (hazard ratio [HR], 0.78; 95% CI, 0.55-1.12) or OS (HR, 1.02; 95% CI, 0.66-1.56).

Overall, the PET-MUSE study demonstrated a trend toward a change in the management of patients undergoing PET, but it did not reach statistical significance.