Dr. Bellmunt notes that the depth of lamina propria invasion is important in assessing patients that may benefit from an upfront cystectomy. Orsola et al.1 assessed treatment strategy according to substaging by depth of lamina propria invasion among 200 patients with T1 NMIBC. Patients with shallower lamina propria invasion (HGT1a) were followed without further surgery, whereas patients with HGT1b received a second TUR. There were 89 (44.5%) cases of T1a and 111 (55.5%) T1b NMIBC. At a median follow-up of 71 months, disease progression was observed in 31 (15.5%) of patients and on both univariable and multivariable analysis, substaging of T1 tumors (T1a: HR 0.30, 95% CI 0.12-0.81) predicted disease progression. As follows is the Kaplan-Meier curve for progression stratified by T1a and T1b disease:
A meta-analysis from Dr. Bellmunt’s group also looked at predictors of improving selection for early cystectomy among patients with high-grade T1 bladder cancer.2 In this analysis of 15,215 patients from 73 studies, they found that in the prognostic factor assessment (33 studies, n=8,880), the highest impact risk factor was depth of invasion (T1b/c) into the lamina propria (HR for progression 3.34, p<0.001; cancer-specific survival HR 2.02, p=0.001). Several other previously proposed factors also predicted progression and cancer-specific survival, including lymphovascular invasion, associated carcinoma in situ, nonuse of BCG, tumor size > 3 cm, and older age.
Dr. Bellmunt notes that progression of NMIBC to muscle-invasive bladder cancer is life-threatening and cannot be accurately predicted using clinical and pathologic risk factors. As such, biomarkers for stratifying patients to treatment and surveillance are greatly needed. Importantly, data from the TCGA is from muscle-invasive disease and Dr. Bellmunt cautions that we cannot extrapolate this date to patients with NMIBC. Furthermore, the majority of data in NMIBC is from low-grade tumors and there is a lack of reliable genomic predictors for disease recurrence and progression to MIBC.
Seminal work published in 2016 from Hedegaard and colleagues included comprehensive transcriptional analysis of 460 early-stage urothelial carcinomas and showed that NMIBC can be subgrouped into three major classes with basal- and luminal-like characteristics and different clinical outcomes.3 Analysis of transcript variants revealed frequent mutations in genes encoding proteins involved in chromatin organization and cytoskeletal functions. Furthermore, mutations in well-known cancer driver genes (for example TP53 and ERBB2) were primarily found in high-risk tumors, together with APOBEC-related mutational signatures. Josh Meeks and colleagues also reported their study assessing genomic characterization of high-risk non-muscle invasive bladder cancer, finding no difference in frequency of mutations of TP53, PIK3CA, or KMT2D between the primary tumors of progressors compared to non-progressors and metastatic tumors.4 However, there was an increased frequency of deletions of CDKN2A/B identified in tumors at progression (37%) compared to non-progressors (6%) (p = 0.10), and a significant decrease in total mutational burden associated with immunotherapy response comparing non-progressors (15 mutations/MB), progressors (10.1 mutations/MB), and metastatic tumors (5.1 mutations/MB; p = 0.02).
Recent work from Dr. Bellmunt’s group sought to identify genomic predictors of good outcome, recurrence, or progression in high-grade T1 NMIBC.5 This study assessed exome sequencing on 62 high-grade T1 and 15 matched normal tissue samples, studying somatic mutations, copy-number alterations, mutation load, and mutation signatures. DNA damage response gene mutations were associated with higher tumor mutational burden (p < 0.0001) and good outcomes (p = 0.003). Additionally, mutations in ERCC2 and BRCA2, as well as APOBEC-A and ERCC2 mutant tumors (COSMIC5) were also associated with good outcomes (p = 0.047; p = 0.0002). Mutations associated with TP53, ATM, ARID1A, AHR, and SMARCB1 were more frequent in patients with disease progression, as were focal copy-number gain in CCNE1 and CDKN2A deletion (p = 0.047; p = 0.06). Furthermore, there was a significant decrease in total mutational burden comparing non-progressors (9.6 mutations/MB), progressors (7.4 mutations/MB), and recurrent tumors (5.7 mutations/MB). MutSig2CV identified 17 genes significantly mutated in more than 10% of the samples:
- TP53 mutation was seen in 40% of samples (25/62) and rarely overlapped with MDM2amplifications
- TP53 pathway (TP53mutation or MDM2amplification) were exclusive with FGFR3 mutation or amplification or TSC1 mutations or deletions
- Seven of the 17 genes were CM or regulatory genes: KDM6A(24%), KMT2C(21%), KMT2D (27%), CREBBP(21%), EP300 (16%), ARID1A (11%), ASXL2 (13%)
- Cell cycle-related genes were the second most frequently altered set of genes including CDKN2A deletion (31%), RB1mutation (18%), and TP53mutations (40%)
- Other frequently altered pathway encompassed genes involved in the DNA-damage response and genomic regulation included ERCC2(16%), BRCA2(11%), STAG2 (13%), ATM (10%)
- The RAS/RTK/PI3K signaling pathway was also involved: FGFR3(13%), PIK3CA(13%), ERBB2 (15%), ERBB3(16%), RHOB (15%)
Taken together, the mutation frequency of the whole cohort was more similar to MIBC than the classical NMIBC studies. APOBEC-mediated mutagenesis was one of the major mutagenic sources in this cohort, but overall activity (46%) was lower than that in the TCGA MIBC cohort (~60%) and higher than that seen in low-grade NMIBC (35%). This may suggest a tendency of more prevalent APOBEC mutagenesis with disease progression. The following table summarizes Dr. Bellmunt’s findings of main genomic characteristics predicting outcome in high-grade T1 bladder cancer:
Dr. Bellmunt’s group has also recently published a study looking at transcriptomic analysis of micropapillary high grade T1 urothelial bladder cancer . There were 23 patients with micropapillary T1 disease and 64 conventional urothelial carcinoma patients (reference set) that underwent whole transcriptome RNA sequencing, looking at differentially expressed genes between these two cohorts. Over 3000 genes were differentially expressed in micropapillary T1 disease as compared with conventional high-grade T1 and a 26-gene signature was found to be characteristic of micropapillary T1 disease within high-grade T1. A set of three genes (CD36, FAPB3 and RAETE1) were significantly associated with time to progression: high expression of FABP3 and CD36 were associated with shorter time to progression (p = 0.045 and p = 0.08), as was low expression of RAET1E (p = 0.01). These results may help classify micropapillary T1 disease with high-risk of early progression, which may have implications for consideration of early cystectomy.
Dr. Bellmunt concluded his presentation by highlighting the proposed treatment algorithm based on main genomic characteristics predicting outcome in high-grade T1 bladder cancer:5
Presented by: Joaquim Bellmunt, MD, PhD, Beth Israel Deaconess Medical Center, Associate Professor, Medicine, Director, Bladder Cancer Program, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MAWritten by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, Twitter: @zklaassen_md during the 4th annual bladder cancer translational research meeting, co-sponsored by the American Urological Association (AUA) and the Johns Hopkins Greenberg Bladder Cancer Institute, March 4-6, 2021
- Orsola A, Werner L, de Torres I, et al. Reexamining treatment of high-grade T1 bladder cancer according to depth of lamina propria invasion: A prospective trial of 200 patients. Br J Cancer2015 Feb 3;112(3):468-474.
- Martin-Doyle W, Leow JL, Orsola A, et al. Improving Selection Criteria for Early Cystectomy in High-Grade T1 Bladder Cancer: A Meta-Analysis of 15,215 Patients.J Clin Oncol. 2016 Feb 20;33(6):643-650.
- Hedegaard J, Lamy P, Nordentoft I, et al. Comprehensive Transcriptional Analysis of Early-Stage Urothelial Carcinoma. Cancer Cell. 2016 Jul 11;30(1):27-42.
- Meeks JJ, Carneiro BA, Pai SG, et al. Genomic characterization of high-risk non-muscle invasive bladder cancer. Oncotarget. 2016 Nov 15;7(46):75176-75184.
- Bellmunt J, Kim J, Reardon B, et al. Genomic Predictors of Good Outcome, Recurrence, or Progression in High-Grade T1 Non-Muscle-Invasive Bladder Cancer. Cancer Res.2020 Oct 15;80(20):4476-4486.
- Bowden M, Nadal R, Zhou CW, et al. Transcriptomic analysis of micropapillary high grade T1 urothelial bladder cancer. Sci Rep. 2020 Nov 18;10(1):20135.