Researchers behind an observational study of patients with muscle-invasive bladder cancer suggest that patients who are more likely to receive neoadjuvant versus adjuvant chemotherapy have increased overall survival (OS; Clin Genitourin Cancer. 2019 Dec 14. Epub ahead of print).

“We use observational methods to compare impact of perioperative chemotherapy timing (ie, neoadjuvant and adjuvant) on...OS...in muscle-invasive bladder cancer because there is no head-to-head randomized trial, and patient factors may influence decision-making,” explained Liam C. Macleod, MD, MPH, Department of Urology, University of Pittsburgh Medical Center, Pennsylvania, and colleagues.

Using SEER-Medicare data, Dr Macleod et al identified 1324 patients undergoing cystectomy for muscle-invasive bladder cancer receiving neoadjuvant (n = 676) or adjuvant (n = 666) chemotherapy.

The tendency to receive neoadjuvant chemotherapy was determined via gradient-boosted models. In addition, the inverse probability of treatment weighted survival curves was adjusted to accommodate 13 demographic, socioeconomic, temporal, and oncologic covariates, allowing for head-to-head group comparisons.

Follow-up lasted for a median of 23 months, and the average treatment effect of adjuvant versus neoadjuvant chemotherapy on OS was found to not be significant (hazard ratio [HR], 1.14; 95% CI, 0.99-1.31). Conversely, the average treatment effect was tied to a 33% increase in risk for mortality if patients given neoadjuvant therapy were given adjuvant therapy instead (HR, 1.33; 95% CI, 1.12-1.57).

“Significant treatment selection bias was noted in peri-cystectomy timing, which limits the ability to discriminate differential efficacy of these 2 approaches with observational data,” Dr Macleod and colleagues said.

“However, patients with higher propensity to receive neoadjuvant therapy were predicted to have increased OS with approach, in keeping with existing paradigms from trial data,” they concluded.—Hina Porcelli