Impact of lymphovascular invasion and histological variants on BCG-treated high-grade NMIBC prognosis

Abstract

Purpose:

This study aimed to evaluate the impact of lymphovascular invasion (LVI) and histologic subtypes on prognosis following Bacillus Calmette-Guérin (BCG) therapy in high-grade non-muscle invasive bladder cancer (NMIBC).

Methods:

We retrospectively analyzed 245 patients who underwent transurethral resection of bladder tumor (TURBT) for high-grade Ta, T1, or carcinoma in situ (CIS) and received BCG therapy between January 2010 and December 2020. Effects of LVI and histologic subtypes on recurrence-free survival (RFS) and progression-free survival (PFS) were assessed using Kaplan-Meier and Cox regression analyses.

Results:

At median follow-up of 48.5 months, LVI was detected in 25.7% of patients and histologic subtypes in 36.3%. During follow-up, disease recurrence occurred in 98 patients (40.0%) and progression in 45 patients (18.4%). In multivariate analysis, LVI (HR: 2.28, 95% CI: 1.68–3.10, p < 0.001) and histologic subtypes ≥1% (HR: 1.95, 95% CI: 1.45–2.62, p < 0.001) were independent risk factors for recurrence. Similarly, LVI (HR: 2.85, 95% CI: 1.98–4.11, p < 0.001) and histologic subtypes ≥1% (HR: 2.34, 95% CI: 1.67–3.28, p < 0.001) were independent risk factors for progression. Patients with concurrent LVI and histologic subtypes demonstrated highest risk of progression (HR: 4.15, 95% CI: 2.85–6.05, p < 0.001) with 5-year PFS rate of 45.2%.

Conclusion:

In high-grade NMIBC patients receiving BCG therapy, LVI and histologic subtypes are strong independent risk factors for disease recurrence and progression. Patients with both factors have highest risk and may require more aggressive treatment strategies including consideration of early radical cystectomy. These findings support the importance of detailed pathological assessment in treatment selection for BCG-treated NMIBC patients.

Keywords

non-muscle invasive bladder cancer BCG therapy lymphovascular invasion histological variants prognosis recurrence progression

Introduction

Non-muscle invasive bladder cancer (NMIBC) accounts for approximately 75% of bladder tumors.¹ These tumors are typically confined to the bladder mucosa or submucosa, without evidence of invasion into the detrusor muscle layer.² Due to its high recurrence and progression risk, NMIBC presents a significant clinical challenge in urologic oncology, requiring long-term follow-up and personalized treatment strategies.³ It is more common in men than in women, and smoking and exposure to environmental carcinogens are the main etiological factors.^4,5

The standard treatment for NMIBC consists of transurethral resection of bladder tumor (TURBT) followed by intravesical therapy. Among these therapies, Bacillus Calmette-Guérin (BCG) immunotherapy is considered the gold standard for reducing recurrence and progression, particularly in high-risk patients.⁶ The efficacy of BCG was first demonstrated by Morales et al. and subsequently confirmed by randomized controlled trials.⁷ However, despite BCG therapy, approximately 30–40% of patients experience recurrence or progression, highlighting the biological heterogeneity of the disease and the need for additional prognostic factors.^8,9

In recent years, the importance of lymphovascular invasion (LVI) and histologic subtypes in determining prognosis in NMIBC has gained increasing recognition, particularly in the context of BCG immunotherapy.^10–12 LVI, defined as tumor cell invasion into vascular or lymphatic structures, has been identified as an independent adverse prognostic factor in T1 NMIBC patients receiving BCG therapy.¹³ Patients with LVI have demonstrated lower response rates to BCG therapy and significantly higher rates of recurrence and progression despite adequate immunotherapy.¹⁴ This finding has important implications for treatment selection and may influence decisions regarding immediate cystectomy versus BCG therapy in high-risk patients.

Similarly, histologic subtypes and differentiations (micropapillary, plasmacytoid, sarcomatoid, nested, squamous, glandular, trophoblastic differentiation etc.) contain cellular structures different from classic uroepithelial carcinoma and have been associated with poor BCG response and worse survival outcomes in NMIBC patients.¹⁵ The biological basis for reduced BCG efficacy in these variant histologies remains unclear, but may relate to altered immune microenvironment or differential expression of BCG response markers. Current evidence suggests that more aggressive treatment options, such as radical cystectomy, should be considered for patients with histologic subtypes, particularly when BCG therapy fails.¹⁶

Currently, risk classification and treatment planning for NMIBC patients utilize scoring models recommended by the European Association of Urology (EAU). The EAU NMIBC 2021 scoring model incorporates parameters such as tumor diameter, concomitant carcinoma in situ (CIS), LVI status, and tumor size, providing high accuracy in predicting progression risk.¹⁷ These models serve as important guides in personalizing treatment and follow-up strategies.

The literature contains conflicting results regarding the prognostic value of LVI and histologic subtypes in BCG-treated NMIBC patients. While some studies have demonstrated that these parameters play a critical role in determining BCG treatment response and disease course, others have reported limited prognostic value.^18–20 This controversy may be related to differences in study populations, BCG protocols, pathological assessment criteria, and follow-up durations. Therefore, more clearly establishing the effect of LVI and histologic subtypes on prognosis and BCG treatment response in NMIBC patients is of great importance for optimizing clinical decision-making processes and identifying patients who may benefit from alternative treatment strategies.

The rationale for studying LVI and histologic subtypes specifically in the BCG treatment setting is multifold. First, BCG therapy represents the standard of care for high-risk NMIBC, yet treatment failure rates remain substantial. Second, the biological mechanisms underlying BCG resistance may be related to the presence of LVI and variant histologies, which could alter the local immune microenvironment necessary for BCG efficacy. Third, identifying predictive factors for BCG failure could facilitate early identification of patients who might benefit from immediate radical cystectomy rather than delayed intervention after BCG failure.

The aim of this study was to evaluate the impact of LVI and histologic subtypes on prognosis following BCG therapy in high-grade NMIBC patients and to determine the contribution of these parameters to clinical practice in conjunction with current risk classification models. Specifically, we sought to assess whether these pathological features could serve as biomarkers for BCG treatment response and guide treatment selection in high-risk NMIBC patients.

Materials and methods

Study population and design

In this retrospective cohort study, we evaluated a total of 245 patients who underwent TURBT for high-grade Ta, T1 bladder cancer at our institution between January 2010 and December 2020. Demographic data, tumor characteristics (stage, multifocality, CIS, LVI, and histologic subtypes), BCG protocol administered, and follow-up outcomes were recorded in detail.

Inclusion criteria required completion of at least 5 of 6 induction BCG applications and at least 2 maintenance BCG applications at 3-month intervals. To ensure a homogeneous study population, comprehensive exclusion criteria were established. These criteria included low-grade tumors, muscle-invasive disease, concurrent upper urinary tract uroepithelial carcinoma, incomplete BCG therapy, previous pelvic radiation therapy, history of other malignancy within the past 5 years, and incomplete follow-up data.

All patients received the same BCG strain (TICE strain, Organon Teknika, Durham, NC, USA) intravesically for immunotherapy, starting 2 weeks after TURBT, with induction therapy consisting of weekly applications for 6 weeks, followed by maintenance therapy at 3, 6, 12, 18, 24, 30, and 36 months with 3-week applications. Weekly induction BCG therapy was administered for 6 weeks, with maintenance therapy given for at least 1 year in high-risk patients.

During follow-up, patients were monitored with cystoscopy and urine cytology every 3 months for the first 2 years and every 6 months thereafter. Upper urinary tract imaging (computed tomography or magnetic resonance urography) was performed annually or more frequently based on clinical necessity and indicators.

TURBT procedures were performed under spinal or general anesthesia using standard white light cystoscopy and a continuous-flow resectoscope. Complete tumor resection was performed, including the detrusor muscle layer to ensure accurate staging and reduce the risk of understaging. In high-risk cases, particularly T1 tumors, absence of detrusor muscle in the resection specimen, or incomplete initial resection, repeat TURBT was planned within 4–6 weeks.

TURBT specimens were meticulously re-evaluated by an expert uropathologist according to the 2022 World Health Organization (WHO) classification criteria.²¹ Pathological assessment was performed exclusively on the initial TURBT specimen to ensure standardized evaluation and avoid potential sampling bias from repeat procedures. All pathological evaluations included tumor stage, grade, presence of concomitant CIS, LVI status, and histologic subtypes and differentiations. LVI was defined as the presence of tumor cells in endothelium-lined spaces, and when visual assessment was ambiguous, immunohistochemical confirmation was performed using endothelial cell markers (CD31 and D2–40). Histological subtypes were classified as micropapillary, nested, plasmacytoid, and sarcomatoid. Additionally, squamous, glandular, and trophoblastic differentiations were also evaluated as separate categories. Tumors with histologic subtypes comprising 1% or more were considered clinically significant and included in the analyses.

The two primary endpoints of the study were recurrence-free survival (RFS) and progression-free survival (PFS). RFS was calculated from the date of complete TURBT to the date of histopathological confirmation of the first high-grade recurrence and measured treatment efficacy. PFS was followed until events such as stage progression (increase in T stage), regional lymph node involvement, distant metastasis, or bladder cancer-specific death. All procedures were meticulously conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. The study protocol was approved by the institutional ethics committee. Informed consent form was obtained from all individuals participating in the study.

Statistical analysis

The total sample size for the study was calculated as 128, considering similar studies in the literature and using the “G Power” power analysis calculation tool version 3.1. The collected data were comprehensively analyzed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA). Normal distribution of continuous variables was assessed using the Shapiro-Wilk test, and appropriate statistical methods were determined.

Missing data analysis was performed to assess the pattern and extent of missing values. Less than 5% of data was missing for any variable, and the pattern analysis indicated that data were missing completely at random (MCAR). For continuous variables with missing values, median imputation was used, while for categorical variables, the most frequent category imputation was applied. Sensitivity analyses were conducted using complete case analysis to ensure the robustness of results.

Continuous variables were presented as median and interquartile range (IQR) due to potential non-normal distribution. Categorical variables were reported as absolute numbers and percentages. Survival analyses were performed using the Kaplan-Meier method and log-rank test. Univariate and multivariate Cox proportional hazards models were constructed to identify independent predictors of RFS and PFS. Variables with p < 0.1 in univariate analysis were included in the multivariate model to control for confounding. The fundamental assumption of the Cox model, the proportional hazards assumption, was meticulously tested using Schoenfeld residuals. Statistical significance was set at p < 0.05, and all tests were two-sided.

Patient selection flow (CONSORT diagram)

Patient selection followed CONSORT (Consolidated Standards of Reporting Trials) guidelines for cohort studies (Figure 1). A total of 312 patients underwent TURBT for high-grade bladder cancer during the study period. Of these, 67 patients were excluded: 23 had muscle-invasive disease on final pathology, 15 had concurrent upper urinary tract uroepithelial carcinoma, 12 received incomplete BCG therapy (<5 induction doses), 8 had previous pelvic radiation therapy, 6 had other malignancy within 5 years, and 3 had incomplete follow-up data. The final study cohort comprised 245 patients who met all inclusion criteria and completed the planned BCG treatment protocol. During follow-up, 12 additional patients were excluded from the final analysis due to upstaging to muscle-invasive disease on re-TURBT, resulting in a final analytical cohort of 233 patients for progression analysis.

Results

In this study, key clinical parameters related to the tumor, as well as patients’ age, sex, body mass index (BMI), smoking status, family history, and comorbidities were evaluated; variables demonstrating statistically significant differences were specifically indicated. Following a comprehensive analysis, the median age of the 245 patients was determined to be 67 years (IQR: 58–75), with a notably high proportion of males (82.4%, n = 202). Upon examination of the initial tumor stage distribution, 68 patients (27.8%) were classified as Ta, 147 (60.0%) as T1, and 30 (12.2%) as CIS. Additionally, concomitant CIS was identified in 52 patients (21.2%). A detailed assessment of tumor characteristics revealed a median tumor size of 3.2 cm (IQR: 2.1–4.5), and the presence of multiple tumors at diagnosis was observed in 157 patients (64.1%) (Table 1).

Table 1.

Sociodemographic and clinical characteristics of the patients.

Characteristic	Value (n = 245)
Median age (IQR)	67 (58–75)
Male gender (%)	202 (82.4%)
Median BMI (IQR)	26.1 (23.8–28.7)
Smoking (%)	168 (68.6%)
Family history of bladder cancer (%)	19 (7.8%)
Presence of comorbidities (%)	112 (45.7%)
Initial stage
Ta	68 (27.8%)
T1	147 (60.0%)
CIS	30 (12.2%)
Concomitant CIS (%)	52 (21.2%)
Median tumor size (cm, IQR)	3.2 (2.1–4.5)
Multiple tumors (%)	157 (64.1%)
LVI positive, n (%)	63 (25.7%)
LVI confirmed by immunohistochemistry, n (%)	15 (6.1%)
Histologic subtypes and differentiation, n (%)	89 (36.3%)
Squamous differentiation	35 (14.3%)
Glandular differentiation	22 (9.0%)
Micropapillary subtype	15 (6.1%)

IQR: Interquartile range; BMI: Body mass index; CIS: Carcinoma in situ; LVI: Lymphovascular invasion.

In-depth histopathological examination showed that LVI was detected in 63 patients (25.7%); immunohistochemistry was used for confirmation in 15 (6.1%) of these cases. Histologic subtypes patterns were identified in 89 patients (36.3%) with the following distribution: squamous differentiation (n = 35, 14.3%), glandular differentiation (n = 22, 9.0%), micropapillary architecture (n = 15, 6.1%), nested pattern (n = 8, 3.3%), plasmacytoid morphology (n = 6, 2.4%), and sarcomatoid elements (n = 3, 1.2%) (Figure 2). In 79.8% (n = 71) of patients with histologic subtypes, at least 1% of the tumor contained variant components (Figure 3).

All patients were confirmed to have completed induction BCG therapy with a median of 5.8 (IQR: 5–6) applications. Maintenance therapy was administered to 218 patients (89.0%), of whom 167 (68.2%) successfully completed at least one year of maintenance therapy. As part of surgical management, re-TURBT was performed in 156 patients (63.7%), with stage progression observed in 12 (7.7%) who were excluded from the analysis (Table 2).

Table 2.

Surgical management and re-TURBT results.

Parameter	Value
Patients who underwent re-TURBT, n (%)	156 (63.7%)
Upstaging after re-TURBT, n (%)	12 (7.7%)
Patients excluded due to upstaging, n (%)	12 (7.7%)
Patients who completed induction BCG, median (IQR)	5.8 (5–6)
Patients who received maintenance therapy, n (%)	218 (89.0%)
Patients who completed ≥1 year of maintenance therapy, n (%)	167 (68.2%)

IQR: Interquartile range; TURBT: Transurethral resection of bladder tumor; BCG: Bacillus Calmette-Guérin

Long-term follow-up lasted a median of 48.5 months (IQR: 24–72), with disease recurrence detected in 98 patients (40.0%) and disease progression in 45 patients (18.4%). Survival analyses showed 2- and 5-year RFS rates of 68.2% and 52.4%, respectively, and PFS rates of 85.7% and 74.3%, respectively. Detailed analysis of progression patterns revealed progression to muscle-invasive disease in 62.2% (n = 28) of patients, lymph node metastasis in 26.7% (n = 12), and distant metastases in 11.1% (n = 5) (Figure 4).

Statistical analyses demonstrated that patients with LVI showed significantly worse outcomes compared to those without LVI, with HR: 2.45 (95% CI: 1.82–3.28, p < 0.001) for RFS and HR: 3.12 (95% CI: 2.24–4.35, p < 0.001) for PFS (Figure 5(a)). Detailed assessment of histologic subtypes showed that patients with ≥1% variant component were adversely affected, with RFS: HR 2.18 (95% CI: 1.65–2.89, p < 0.001) and PFS: HR 2.56 (95% CI: 1.88–3.49, p < 0.001) (Figure 5(b)).

Robust multivariate Cox regression analysis identified independent predictors of recurrence as LVI (HR: 2.28, 95% CI: 1.68–3.10, p < 0.001), histologic subtypes ≥1% (HR: 1.95, 95% CI: 1.45–2.62, p < 0.001), multifocal tumor (HR: 1.76, 95% CI: 1.28–2.42, p = 0.001), and concomitant CIS (HR: 1.89, 95% CI: 1.38–2.59, p < 0.001). Similarly, independent predictors of disease progression were LVI (HR: 2.85, 95% CI: 1.98–4.11, p < 0.001), histologic subtypes ≥1% (HR: 2.34, 95% CI: 1.67–3.28, p < 0.001), and concomitant CIS (HR: 2.12, 95% CI: 1.48–3.04, p < 0.001) (Table 3).

Table 3.

Multivariate cox regression analysis for recurrence and progression.

Variable	Recurrence HR [95% CI]	Recurrence p-value	Progression HR [95% CI]	Progression p-value
LVI	2.28 [1.68–3.10]	<0.001	2.85 [1.98–4.11]	<0.001
Histologic subtypes ≥1%	1.95 [1.45–2.62]	<0.001	2.34 [1.67–3.28]	<0.001
Multifocality	1.76 [1.28–2.42]	0.001	-	-
Concomitant CIS	1.89 [1.38–2.59]	<0.001	2.12 [1.48–3.04]	<0.001

LVI: Lymphovascular invasion; CIS: Carcinoma in situ.

Detailed subgroup analysis demonstrated that in patients with LVI and concurrent histologic subtypes, 5-year RFS and PFS rates were 28.6% and 45.2%, respectively (Figure 6). Advanced statistical models revealed that the combination of LVI and histologic subtypes ≥1% was most strongly associated with disease progression, with this combination carrying the highest risk ratio in multivariate analysis (HR: 4.15, 95% CI: 2.85–6.05, p < 0.001) (Table 4).

Table 4.

Combined risk analysis - LVI and histologic subtypes.

Risk Group	5-year RFS (%)	5-year PFS (%)	Progression HR [95% CI]	p-value
LVI (−) + histologic subtypes <1%	68.4	82.3	Reference	-
LVI (+) + histologic subtypes <1%	42.1	61.7	2.85 [1.98–4.11]	<0.001
LVI (−) + histologic subtypes ≥1%	45.8	68.9	2.34 [1.67–3.28]	<0.001
LVI (+) + histologic subtypes ≥1%	28.6	45.2	4.15 [2.85–6.05]	<0.001

LVI: Lymphovascular invasion.

Discussion

In this study, we comprehensively evaluated the impact of LVI and histologic subtypes on disease course in high-grade NMIBC patients. Our findings demonstrated that LVI and histologic subtypes are strong and independent prognostic factors for recurrence and progression in patients receiving BCG therapy. We found that the risk of disease progression was markedly increased in patients with both factors concurrently.

LVI is considered the first stage of tumor spread in NMIBC and represents a critical step for metastatic dissemination. In our study, the LVI rate was 25.7%, which is consistent with values reported in the literature. Cho et al. reported an LVI rate of 28% in T1 NMIBC patients.²² According to our findings, the presence of LVI is associated with a 2.28-fold increased risk for recurrence and a 2.85-fold increased risk for progression. These results parallel some studies in the literature.^23–25

Histologic subtypes is another important factor in NMIBC whose prognostic value has been increasingly recognized in recent years. In our study, the incidence of histological subtypes in NMIBC patients was determined as 36.3%. This rate is significantly higher than the prevalence of 19.5% reported by Shah et al. in bladder cancer cases.²⁶ In addition, in our series, the frequency of histological variant components being present in at least 1% of the tumor was determined as 79.8%, while the most common subtypes were squamous (14.3%) and glandular (9.0%) differentiation, respectively. These differences suggest that the higher incidence of histological subtypes in our study may be due to the characteristics of the patient population, developments in diagnostic methods, or differences in pathological evaluation criteria.

In our analysis, we grouped all histologic subtypes together based on several considerations. First, individual subtype sample sizes were insufficient for meaningful statistical analysis, with some subtypes having fewer than 10 cases. Second, previous studies have shown that most histologic subtypes, when present in ≥1% of the tumor, are associated with worse outcomes compared to pure urothelial carcinoma. Third, from a clinical perspective, the presence of any histologic subtype may influence treatment decisions regardless of the specific subtype. However, we acknowledge that different subtypes may have varying degrees of aggressiveness, with micropapillary and plasmacytoid variants generally considered more aggressive than squamous or glandular differentiation. Future studies with larger cohorts may benefit from subtype-specific analyses to better define individual risk profiles.

The literature contains conflicting results regarding the efficacy of treatment strategies in NMIBC cases with histologic subtypes. Shapur et al. reported that progression-free survival was lower in patients with histological subtypes despite BCG treatment.²⁷ In contrast, Yorozuwa et al. showed that BCG treatment improved progression-free survival in NMIBC patients with squamous or glandular differentiation.²⁸ Our study confirmed that histological subtypes were an independent adverse prognostic factor even in patients treated with BCG. In our study, we found that tumors containing 1% or more histologic subtypes were associated with a 1.95-fold increased risk for recurrence and a 2.34-fold increased risk for progression. One of the most important findings of our study is the markedly increased risk of progression in patients with concurrent LVI and histologic subtypes (HR: 4.15). The 5-year RFS and PFS rates in these patients were 28.6% and 45.2%, respectively. These results demonstrate the cumulative effect of multiple adverse prognostic factors in high-risk NMIBC cases, and studies focusing on this combination are limited in the current literature.

Current EAU guidelines have defined prognostic factor risk groups for NMIBC. In a meta-analysis by Sylvester et al., the 5-year progression rate in very high-risk patients was reported as 40%.²⁹ This rate is consistent with the progression rates we observed in our patient group with concurrent LVI and histologic subtypes. However, Lobo et al. reported that the EAU 2021 prognostic factor risk groups have limited capacity to predict progression in patients receiving BCG therapy and may overestimate progression risk.³⁰

The findings obtained in our study emphasize the prognostic importance of histopathological features, particularly in high-risk NMIBC patients receiving BCG therapy. In a multicenter study by Ferro et al., poor prognostic factors were shown to influence early cystectomy decisions in T1 high-grade tumors.³¹ Similarly, Gontero et al. reported that tumor size, concomitant CIS, and advanced age were associated with progression in T1G3 patients treated with BCG.³² Our study demonstrates that LVI and histologic subtypes are also critical prognostic markers in addition to these factors.

Standardization of LVI assessment is another important issue. In our study, all specimens were evaluated by an experienced uropathologist, and immunohistochemical confirmation was performed in doubtful cases. Berman et al. emphasized that standardizing LVI assessment is important for improving diagnostic and therapeutic strategies in bladder cancer management.³³

Among variant histologies, certain subtypes such as micropapillary and plasmacytoid are known to exhibit particularly aggressive behavior. National Comprehensive Cancer Network (NCCN) guidelines recommend early radical cystectomy in these highly aggressive variants.³⁴ In their meta-analysis evaluating outcomes after radical cystectomy in uroepithelial carcinoma with histologic subtypes, Mori et al. reported that histologic subtypes had a negative impact on survival.³⁵ However, in the review by Lobo et al., histologic subtypes were not found to significantly worsen survival compared to conventional uroepithelial carcinoma of the same stage.³⁰ These conflicting results emphasize the importance of tumor burden and tumor size.

Our study has several limitations. The retrospective design may present a disadvantage in terms of standardized measurements of the evaluated parameters. Additionally, some potential prognostic factors such as tumor substaging (T1a/T1b) were not included in the analysis. Kardoust Parizi et al. published a meta-analysis confirming the prognostic value of T1 substaging.³⁶

An important limitation to consider is potential selection bias in our cohort. High-grade T1 patients with variant histology or LVI may have been more likely to receive upfront radical cystectomy rather than BCG therapy, particularly in cases where these high-risk features were identified preoperatively or on initial pathology review. This selection bias could potentially underestimate the true prognostic impact of these factors, as the most aggressive cases may not have been included in our BCG-treated cohort. However, our institutional practice during the study period was to offer BCG therapy as first-line treatment for most high-grade T1 patients, with immediate cystectomy reserved primarily for those with extensive disease or patient preference. Nevertheless, this potential bias should be considered when interpreting our results and applying them to clinical practice.

Prospective studies with larger patient groups and multicenter studies are needed to confirm our results.

Most existing studies show an imbalance in tumor burden between histologic subtypes and conventional uroepithelial carcinoma. Most studies in the literature have not clearly specified criteria representing tumor burden, such as tumor size and multifocality. Additionally, the extent of histologic subtypes is a factor known to significantly affect prognosis. Therefore, when evaluating the prognostic role of histologic subtypes in NMIBC, it is important to consider factors such as tumor burden, extent of histologic subtypes, and treatment protocol.

Conclusion

In high-grade NMIBC patients receiving BCG immunotherapy, LVI and histologic subtypes are strong and independent risk factors for disease recurrence and progression, even in the setting of adequate BCG treatment. Patients with both factors concurrently have the highest risk of progression and may require more aggressive treatment strategies, including consideration of early radical cystectomy rather than delayed intervention after BCG failure. These pathological features may serve as important biomarkers for BCG treatment response and could be incorporated into clinical decision-making algorithms to optimize treatment selection. The findings support the importance of detailed pathological assessment in high-risk NMIBC patients and may assist in individualizing treatment strategies and improving risk classification beyond current prognostic models. Future studies should focus on developing and validating new prognostic models incorporating these risk factors specifically for BCG-treated patients, and investigating the biological mechanisms underlying BCG resistance in tumors with these high-risk features.

Footnotes

Acknowledgements

The authors thank the participating urologists for their expert evaluations and the pathology department at Mersin University Faculty of Medicine for their support in histopathological assessment and data analysis. We also acknowledge the contribution of the clinical staff involved in patient care and follow-up. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

ORCID iDs

Ali Nebioğlu

Mert Başaranoğlu

Murat Bozlu

Yasemin Yuyucu Karabulut

Ethics approval statement

This study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. The study protocol was approved by the Mersin University Clinical Research Ethics Committee (Approval No: 2025/551). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Patient consent statement

Informed consent was obtained from all individual participants included in the study. Given the retrospective nature of this study and the use of anonymized data, written informed consent was obtained according to institutional guidelines. All patient data were handled in accordance with applicable data protection regulations.

Author contributions

Ali Nebioğlu – Conceptualization; Methodology; Supervision; Writing – original draft.

Mert Başaranoğlu – Data curation; Formal analysis; Visualization; Writing – review & editing.

Murat Bozlu – Investigation; Resources; Project administration; Supervision.

Yasemin Yuyucu Karabulut – Funding acquisition; Validation; Writing – review & editing.

Funding

The authors declare that they have no financial or non-financial competing interests that might be perceived to influence the results and/or discussion reported in this paper. The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Disclosure of potential conflicts of interest

Data availability statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Due to privacy and ethical restrictions, raw data cannot be shared publicly but aggregated data supporting the conclusions of this article are included within the manuscript and its supplementary information files.

Clinical trial registration

This study does not involve a clinical trial and therefore does not require clinical trial registration. This is a retrospective observational cohort study analyzing existing patient data.

Permission to reproduce material from other sources

Not applicable. All materials presented in this manuscript are original work by the authors. No copyrighted material from other sources has been reproduced in this study.

Research involving human participants

This study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. The study protocol was approved by the Mersin University Clinical Research Ethics Committee (Approval No: * / ). All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee.

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