Metastasis Profile and Survival Outcomes of Metastatic Non-Muscle Invasive Bladder Cancer: A National Cancer Database Analysis.

INTRODUCTION

Metastatic non-muscle invasive bladder cancer (mNMIBC) is a condition in which bladder cancer patients develop metastasis in the absence of muscle invasion. The nature of mNMIBC is understudied due to its recent increased recognition. The study aimed to analyze the baseline characteristics, metastatic patterns, and survival outcomes of this condition.

METHODS

A retrospective analysis of the National Cancer Database (NCDB) (2004-2021) was done to identify NMIBC patients who presented with distant metastasis at diagnosis, as defined in the NCDB. The patient characteristics, metastatic trends, and survival outcomes were analyzed. Multivariable logistic regression was performed to identify the variables associated with mNMIBC. Cox proportional hazards regression and Kaplan-Meier analysis were used to analyze the survival outcomes (overall survival).

RESULTS

Among the 537,674 patients diagnosed with NMIBC, 3982 (0.74%) patients had metastasis. The most common sites of metastasis were the bone (15.3%), followed by the lung (13.6%), liver (7.1%), and brain (0.9%). Furthermore, 15.1% of patients had multiple metastases. The median overall survival (OS) for mNMIBC was 6.54 months (95% Confidence Interval [CI]: 6.04-7.03). The OS was poorer among patients with metastasis to multiple sites (median OS: 3.55 months; 95% CI, 3.05-4.04) compared to those with metastasis to a single site. The best OS in isolated metastasis was seen in lung metastasis (median OS: 8.48 months; 95% CI, 6.68-10.27), and the worst OS was seen in liver metastasis (median OS: 3.70 months; 95% CI, 2.80-4.56). Older age, higher Charlson comorbidity score, and non-urothelial histology were associated with worse OS (P < .05).

CONCLUSION

mNMIBC is an uncommon condition with poor OS. Metastases to multiple sites have a poorer prognosis than metastases to a single site. Among the single-site metastases, the most common metastatic site was bone, and the best OS was seen in lung metastasis.