Histopathologic and Genetic Features of Mismatch Repair-Deficient High-Grade Prostate Cancer

AIMS

Mismatch repair (MMR) deficiency is commonly caused by functional inactivation of MLH1, PMS2, MSH2 or MSH6. The morphologic and molecular correlates of MMR deficiency have been extensively characterized in certain tumor types such as colorectal and endometrial adenocarcinoma. In contrast, the histologic and molecular features of MMR-deficient prostate cancer remain incompletely described. In this study, we evaluated 19 MMR-deficient prostate cancers, including 11 cases without prior systemic treatment.

METHODS AND RESULTS

All treatment-naïve cases (11/11, 100%) were Grade Group 4-5 and had predominant cribriform and/or solid growth patterns. Solid components (any amount) and tumor infiltrating lymphocytes were seen in 7/11 (64%) of these cases each. In 68 MMR-proficient Grade Group 5 prostate cancers, predominant cribriform or solid growth patterns, solid components (any amount) and tumor infiltrating lymphocytes were seen at significantly lower frequencies (31/68, 46%; 9/68, 13% and 6/62, 9%, respectively; p<0.001 for all comparisons). Molecular evaluation of 19 cases demonstrated that MMR-deficiency was secondary to functional loss of MSH2/MSH6 and MLH1/PMS2 in 15 cases (79%) and 4 cases (21%), respectively. Definite or likely germline mutations were present in 4 cases (4/19, 21%). TMPRSS2::ERG rearrangements were identified in 2 cases (2/19, 11%). Recurrent cancer-relevant somatic mutations included (but were not limited to) ATM, TP53, FOXA1, RB1, BRCA2 and PTEN.

CONCLUSIONS

MMR deficiency was most commonly secondary to inactivation of MSH2/MSH6 in this study. Importantly, MMR-deficient high-grade prostatic adenocarcinomas had morphologic features that might be useful to identify selected cases for MMR IHC.

Defining the current role of immune checkpoint inhibitors in the treatment of mismatch repair-deficient/microsatellite stability-high colorectal cancer and shedding light on future approaches

Introduction: Mismatch repair deficient (MMR-D)/microsatellite instability-high (MSI-H) colorectal cancer (CRC) carries unique biologic features including high tumor mutation burden, increased amount of mutation-associated neoantigen generation, and the presence of marked tumor-infiltrating lymphocytes. Immune checkpoint inhibitor (ICI) therapy has rapidly changed the treatment algorithm of MMR-D/MSI-H CRC.Areas covered: In this review article, we discuss the recent data regarding the use of ICIs in metastatic MMR-D/MSI-H CRC patients. We also elaborated on potential biomarkers of ICI response and innovative therapeutic approaches that may prevail resistance mechanisms for the treatment of MMR-D/MSI-H colorectal cancer.Expert opinion: Pembrolizumab was recently granted approval by the FDA as first-line therapy for metastatic MMR-D/MSI-H CRC based on the results of the Keynote 177 study. The combination of nivolumab and ipilimumab will also likely be a choice for the initial therapy of MMR-D/MSI-H CRC in the near future. More therapeutic modalities with novel immunomodulatory agents as well as targeted therapy directed to immune resistance pathways are needed. The novel approaches discussed in this review article will define potential treatment options for the management of MMR-D/MSI-H CRC patients who progress on first-line ICI therapy.

Mismatch repair deficiency and clinicopathological characteristics in endometrial carcinoma: a systematic review and meta-analysis

Background

Loss of mismatch repair (MMR) occurs frequently in endometrial carcinoma (EC) and is an important prognostic marker. However, the frequency of MMR deficiency (D-MMR) in EC remains inconclusive. This systematic review and meta-analysis addressed this inconsistency and evaluated related clinicopathology.

Methods

Electronic databases were searched for articles: PubMed, Science Direct, Web of Science, EMBASE, and the Wiley Online Library. Data were extracted from 25 EC studies of D-MMR to generate a clinical dataset of 7,459 patients. A random-effects model produced pooled estimates of D-MMR EC frequency with 95% confidence interval (CI) for meta-analysis.

Results

The overall pooled proportion of D-MMR was 24.477% (95% CI, 21.022 to 28.106) in EC. The Lynch syndrome subgroup had 22.907% pooled D-MMR (95% CI, 14.852 to 32.116). D-MMR was highest in type I EC (25.810) (95% CI, 22.503 to 29.261) compared to type II (13.736) (95% CI, 8.392 to 20.144). Pooled D-MMR was highest at EC stage and grades I–II (79.430% and 65.718%, respectively) and lowest in stages III–IV and grade III (20.168% and 21.529%). The pooled odd ratios comparing D-MMR to proficient MMR favored low-stage EC disease (1.565; 0.894 to 2.740), lymphovascular invasion (1.765; 1.293 to 2.409), and myometrial invasion >50% (1.271; 0.871 to 1.853).

Conclusions

Almost one-quarter of EC patients present with D-MMR tumors. The majority has less aggressive endometrioid histology. D-MMR presents at lower tumor stages compared to MMR-proficient cases in EC. However other metastatic parameters are comparatively higher in the D-MMR disease setting.

Precision medicine for metastatic colorectal cancer: an evolving era

Introduction: Metastatic colorectal cancer (CRC) remains a dilemma for cancer researchers with an increasing incidence in the younger patient population. Until the last decade, limited therapeutic options were available for metastatic CRC patients leading to relatively poor clinical outcomes.Areas covered: With advances in genome sequencing technology and reductions in the cost of next-generation sequencing, molecular profiling has become more accessible for cancer researchers and clinical investigators, which has furthered our understanding of the molecular behavior of CRC. This progress has recently translated into significant advances in molecular-based therapeutics and led to the development of new target-specific agents in metastatic CRC patients. In this review article, we extensively elaborate on genomic alterations seen in CRC patients including, but not limited to, EGFR, MMR, BRAF, HER2, NTRKs, FGFR, BRCA1/2, PALB2, POLE, and POLD1 genes, all of which are potentially actionable by either an FDA-approved agent or in a clinical trial setting.Expert opinion: We strongly recommend molecular profiling in metastatic CRC patients during the early course of their disease, as this may provide therapeutic and prognostic information that can guide clinicians to practice precision medicine. Patients with potentially actionable genes should be considered for targeting agents based on molecular alterations.