Analysis of the Prevalence of Microsatellite Instability in Prostate Cancer and Response to Immune Checkpoint Blockade

Practical Molecular Testing in a Clinical Genitourinary Service

CONTEXT.—

Molecular testing is increasingly playing a key role in the diagnosis, prognosis, and treatment of neoplasms of the genitourinary system.

OBJECTIVE.—

To provide a general overview of the clinically relevant molecular tests available for neoplasms of the genitourinary tract.

DATA SOURCES.—

Relevant medical literature indexed on PubMed.

CONCLUSIONS.—

Understanding of the molecular oncology of genitourinary neoplasms is rapidly advancing, and the pathologist must be aware of the practical implications of molecular testing. While many genomic abnormalities are not yet clinically relevant, there is an increasing library of ancillary tests that may guide diagnosis, prognosis, and/or treatment of many neoplasms. Recurrent genomic abnormalities have been identified in many types of renal cell carcinoma, and some types of renal cell carcinoma are specifically defined by the molecular abnormality. Two major routes of developing urothelial carcinoma have been molecularly described. Recurrent translocations involving ETS family genes are found in approximately half of prostate cancer cases. Testicular germ cell tumors typically harbor i(12p). Penile neoplasms are often high-risk human papillomavirus-driven cancers. Nonetheless, even as genitourinary neoplasms are increasingly better understood at the molecular level, further research with eventual clinical validation is needed for optimal diagnosis, prognosis, and treatment of aggressive malignancies in the genitourinary tract.

Pembrolizumab in men with heavily treated metastatic castrate-resistant prostate cancer

BACKGROUND

Pembrolizumab is approved for patients with metastatic, microsatellite instability (MSI)-high or mismatch repair-deficient (dMMR) solid tumors. However, very few men with prostate cancer were included in these initial studies.

METHODS

We performed a single institution retrospective review of men with metastatic castrate-resistant prostate cancer (mCRPC) who were treated with pembrolizumab. The primary objective was to describe the clinical efficacy of pembrolizumab associated with patient and genomic characteristics.

RESULTS

We identified 48 men who received ≥1 cycle of pembrolizumab for mCRPC. Of these, 94% (45/48) had ≥3 prior lines of therapy for mCRPC. Somatic tumor sequencing was available in 18/48 men (38%). We found that 17% (8/48) had a ≥50% confirmed PSA decline with pembrolizumab, and 8% (4/48) had a ≥90% PSA decline with durations of response ranging from 3.1 to 16.3 months. Two of these four men had mutations in LRP1b, one of whom also had MSH2 loss and was MSI-H and TMB-high. Despite prior progression on enzalutamide, 48% (23/48) of men were treated with concurrent enzalutamide. The median PSA progression-free-survival was 1.8 months (range 0.4-13.7 months), with 31% of patients remaining on pembrolizumab therapy and 54% of men remain alive with a median follow-up of 7.1 months.

CONCLUSIONS

In a heavily pretreated population of men with mCRPC, pembrolizumab was associated with a ≥50% PSA decline in 17% (8/48) of men, including a dramatic ≥90% PSA response in 8% (4/48), two of whom harbored pathogenic LRP1b mutations suggesting that LRP1b mutations may enrich for PD-1 inhibitor responsiveness in prostate cancer.

Cellular and Molecular Mechanisms Underlying Prostate Cancer Development: Therapeutic Implications

Prostate cancer is the most frequent nonskin cancer and second most common cause of cancer-related deaths in man. Prostate cancer is a clinically heterogeneous disease with many patients exhibiting an aggressive disease with progression, metastasis, and other patients showing an indolent disease with low tendency to progression. Three stages of development of human prostate tumors have been identified: intraepithelial neoplasia, adenocarcinoma androgen-dependent, and adenocarcinoma androgen-independent or castration-resistant. Advances in molecular technologies have provided a very rapid progress in our understanding of the genomic events responsible for the initial development and progression of prostate cancer. These studies have shown that prostate cancer genome displays a relatively low mutation rate compared with other cancers and few chromosomal loss or gains. The ensemble of these molecular studies has led to suggest the existence of two main molecular groups of prostate cancers: one characterized by the presence of ERG rearrangements (~50% of prostate cancers harbor recurrent gene fusions involving ETS transcription factors, fusing the 5' untranslated region of the androgen-regulated gene TMPRSS2 to nearly the coding sequence of the ETS family transcription factor ERG) and features of chemoplexy (complex gene rearrangements developing from a coordinated and simultaneous molecular event), and a second one characterized by the absence of ERG rearrangements and by the frequent mutations in the E3 ubiquitin ligase adapter SPOP and/or deletion of CDH1, a chromatin remodeling factor, and interchromosomal rearrangements and SPOP mutations are early events during prostate cancer development. During disease progression, genomic and epigenomic abnormalities accrued and converged on prostate cancer pathways, leading to a highly heterogeneous transcriptomic landscape, characterized by a hyperactive androgen receptor signaling axis.

Clinical utility of FoundationOne tissue molecular profiling in men with metastatic prostate cancer

PURPOSE

Targeted inhibitors and immunotherapy have entered the treatment landscape of metastatic prostate cancer. Genomic testing may uncover which patients benefit most from these therapies. We report the clinical utility and benefits of FoundationOne testing in men with advanced prostate cancer.

PATIENTS AND METHODS

We retrospectively identified all men with prostate cancer who received tissue FoundationOne testing at our institution between January 2010 and April 2017. Genomic alterations, treatment selection based on FoundationOne results, and clinical outcomes including response and duration of therapy following matched targeted therapy were analyzed.

RESULTS

A total of 77 men with metastatic prostate cancer were referred for FoundationOne testing; 59 (77%) had sufficient tumor tissue for testing. Of these, 22% (17/77) of men had a targetable mutation and 9% (7/77) of men received matched off-label targeted therapy. Overall, 5% (4/77) of patients derived clinical benefit. One patient with a BRCA2 loss had a complete response on olaparib (>27 months) and 3 patients (ATM substitution, PALB2 frameshift, CDK12 frameshift) had stable disease with olaparib (10.3, 18.7, and 7.8 months, respectively). Three patients (BRCA2 frameshift, PDL1 + PDL2 amplification, PMS2 missense) had progressive disease despite targeted therapy.

CONCLUSIONS

Tissue genomic testing can uncover patients who may benefit from targeted therapies such as poly(adenosine diphosphate-ribose) polymerase inhibitors or immunotherapy. In our limited single institution study, genomic testing led to clinical benefit in 5% of patients. Combined germline and circulating tumor DNA testing may be helpful to identify additional patients suitable for matched genomic therapies.

Lynch Syndrome in Urologic Malignancies - What Does the Urologist Need to Know?

Lynch Syndrome (LS) entails a defective DNA mismatch repair system, which is the postreplicative proofreading and editing system, ensuring our genome's integrity. LS predisposes to several cancers, most commonly colorectal and endometrial cancers. LS occurs in approximately 1 in 250-1000 people. LS is associated with urological malignancies with upper tract urothelial carcinoma the most common, although still clinically underestimated. Other urologic malignancies possibly associated with LS include bladder, prostate, testis, and renal cell carcinoma. Ascertaining their true prevalence in LS is mandatory for their and their relatives' diagnosis and treatment. Awareness regarding identifying patients at risk for LS through assessment of personal and familial oncologic history is critical among urologists.

Clinical implications of mismatch repair deficiency in prostate cancer

Immune checkpoint blockade holds great promise in the treatment of solid tumors but has not yet been approved for use in advanced prostate cancer. This is largely due to the relatively modest response in clinical trials in unselected patients and the lack of available biomarkers to predict clinical benefit. Germline and somatic mismatch repair (MMR) gene deficiencies are more prevalent than previously thought, especially in the metastatic setting, in patients with high-grade Gleason scores and in patients with variant histologies. An early signal suggests that patients with deficiency in MMR may respond well to immunotherapy. Both germline and somatic genetic testing are recommended, yet questions remain on the best modality for testing given lack of standardization and false-negative results in patients with complex genomic structural rearrangements. Expanded panels, such as next generation sequencing may increase the sensitivity without compromising specificity. Future studies are still needed to explore the relationships of hypermutation, tumor mutational burden, tumor-infiltrating lymphocytes and microsatellite instability-H status as predictors of response to immunotherapy. The drivers of variable response is largely unknown, and a more mature understanding of the mechanisms of resistance in deficiencies in MMR tumors may help to more precisely inform use of immunotherapy in prostate cancer.

PD-L1 instead of PD-1 status is associated with the clinical features in human primary prostate tumors

Immunotherapy targeting programmed cell death protein 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) has shown efficacy in a variety of solid tumors. However, prostate cancer has often been a non-responder to anti-PD-1/PD-L1 therapies. The objective of this study was to determine PD-1 and PD-L1 expression status and its correlation with clinical features of the patients. A total of 279 patients who underwent radical prostatectomy for prostate cancer were included in this study. PD-1 and PD-L1 expression in primary prostate tumors was detected using immunohistochemical staining. Analyses were made between PD-1/PD-L1 status and patients' age, ethnicity, body mass index (BMI), diabetes mellitus, tumor stage, lymph node metastasis, prostate-specific antigen (PSA), Gleason score, grade group, and survival. We found that 6.5 (standard deviation 14.3; range 0-161.6) tumor-infiltrating lymphocytes per high power field were positive for PD-1 staining and 50/279 (17.9%) tumors were positive for PD-L1 staining. PD-L1-positive tumors had significantly more PD-1-positive lymphocytes than PD-L1-negative tumors. The number of PD-1-positive lymphocytes was not correlated with any clinical features except that patients with diabetes had significantly less PD-1-positive lymphocytes than patients without diabetes. In contrast, more PD-L1-positive tumors were found in older patients (≥ 65 years), obese patients (BMI ≥ 30), and patients with advanced tumor stage, lymph node metastasis, and high Gleason score. Neither PD-1 nor PD-L1 status was correlated with ethnicity, PSA, or survival. Our findings suggest that PD-L1 instead of PD-1 status is associated with the clinical features in human primary prostate tumors.

Evolution of the Liquid Biopsy in Metastatic Prostate Cancer

We reviewed the literature for the biologic, prognostic, and predictive significance of circulating prostate cancer tumor cells (CTCs), and circulating tumor DNA in the blood of metastatic castration resistant prostate cancer patients. CTCs demonstrate robust prognostic value independent of PSA in predicting overall survival. The CTC androgen receptor variant receptor 7 phenotype predicts resistance to androgen receptor synthesis inhibitors and sensitivity to taxane based chemotherapy in metastatic castration resistant prostate cancer patients who are candidates for second line therapy. Research is rapidly pivoting toward circulating tumor DNA analysis because the approach is sensitive, prognostic, cost effective, and it can elucidate mechanisms of systemic therapy.

[Predictive biomarkers in oncologic uropathology]

BACKGROUND

Tumors of the genitourinary system are common. In recent years, our understanding of their molecular background and therefore the number of potential predictive biomarkers has massively increased.

OBJECTIVES

The aim of the current work is to give an overview of recent (molecular) developments and predictive biomarkers in urologic oncology and to give a perspective of what might become relevant in the future of the field.

MATERIAL AND METHODS

We considered the recent literature and study data and combined it with our own expertise in tumors of the urinary system, kidneys, and prostate.

RESULTS AND CONCLUSIONS

The molecular subtypes of muscle-invasive urothelial bladder cancer (MIBC) hold a predictive and prognostic significance and correlate with clinicopathological features. Immune therapy with checkpoint inhibitors (CPI) has a major role in urothelial carcinoma (UC), but also in renal cell carcinoma and a subgroup of prostate cancers. The first-line use in UC is restricted to PD-L1-"positive" cases (≥IC2/3, CPS ≥ 10). Further predictive markers are currently under evaluation, while the predictive significance of tumor mutational burden (TMB) is under debate. In addition to a subgroup of renal cell carcinomas, a subgroup of prostate carcinomas with alterations in the DNA repair system might benefit from a customized therapy approach (PARP inhibitors, platin-containing chemotherapy). The multitude of potentially therapy-relevant molecular alterations and related predictive biomarkers calls for the implementation of sophisticated molecular analyses in daily routine. This will lead to an even more rapid dynamic in the field of genitourinary pathology.

Targeting DNA Repair Defects for Precision Medicine in Prostate Cancer

PURPOSE OF REVIEW

Genomic studies of localized and metastatic prostate cancer have identified a high prevalence of clinically actionable alterations including mutations in DNA repair genes. In this manuscript, we review the current knowledge on DNA repair defects in prostate cancer and provide an overview of how these alterations can be targeted towards a personalized prostate cancer management.

RECENT FINDINGS

Twenty to 25% of metastatic prostate cancers harbor defects in DNA repair genes, most commonly in the homologous recombination genes. These defects confer increased sensitivity to platinum chemotherapy or poly (ADP-ribose) polymerase (PARP) inhibitors. Recent trials also support a synergistic effect of combining these therapies with androgen receptor-targeting agents. Identification of mismatch-repair defects could result in defining a prostate cancer population who may benefit from immune checkpoint inhibitors. These data have implications for family testing and early diagnosis, as many of these mutations are linked to inherited risk of prostate cancer. The DNA damage repair pathways are clinically relevant in prostate cancer, being a target for precision medicine; combination with standard-of-care androgen receptor (AR)-targeting agents may be synergistic.

Biological Evolution of Castration-resistant Prostate Cancer

CONTEXT

Recent studies focused on the molecular characterization of metastatic prostate cancer have identified genomic subsets and emerging resistance patterns. Detection of these alterations in patients has potential implications for therapy selection and prognostication.

OBJECTIVE

The primary objective is to review the current landscape of clinical and molecular biomarkers in advanced prostate cancer and understand how they may reflect underlying tumor biology. We also discuss how these features may potentially impact earlier stages of the disease.

EVIDENCE ACQUISITION

A literature search was performed of recent clinical biomarker/genomic studies focused on advanced metastatic prostate cancer as well as relevant preclinical studies investigating how these alterations influence therapy response or resistance.

EVIDENCE SYNTHESIS

Metastatic castration-resistant prostate cancer is commonly driven by androgen receptor signaling even after progression on potent hormonal agents, but other alterations may also be present or emerge during therapy resistance such as DNA repair gene aberrations or combined loss of tumor suppressor genes. Biological implications of these changes are context dependent, which may affect their detection and interpretation.

CONCLUSIONS

Molecular changes occur during prostate cancer progression and treatment resistance. Detection of genomic alterations has potential to influence therapy choice. Additional studies are warranted to elucidate the evolution of these changes and their impact in earlier stages of the disease.

PATIENT SUMMARY

We review the biology of advanced prostate cancer, and highlight opportunities and challenges for using biological or molecular assays to help guide individualized treatment decisions for patients.

Treatment of Advanced Prostate Cancer

The therapeutic landscape of prostate cancer has been transformed over the last decade by new therapeutics, advanced functional imaging, next-generation sequencing, and better use of existing therapies in early-stage disease. Until 2004, progression on androgen deprivation therapy for metastatic disease was treated with the addition of secondary hormonal manipulation; in the last decade, six systemic agents have been approved for the treatment of castration-resistant prostate cancer. We review clinical trials and survival benefit for these therapies and assess how the understanding of the disease shifted as these therapies were developed. We also discuss advances in noncastrate disease states, identification of biomarkers for prognosis and treatment selection, and opportunities in locoregional therapy to delay androgen deprivation therapy.

Germline and Somatic Defects in DNA Repair Pathways in Prostate Cancer

Recent studies have provided a better understanding of the molecular underpinnings of prostate cancer. Alterations in genes encoding for proteins involved in the different pathways in charge of preserving genomic integrity and repairing DNA damage are common in prostate cancer, particularly in late-stage disease. Generally, these alterations would confer a survival advantage for tumors, resulting in a more aggressive phenotype. However, DNA repair defects can also represent a vulnerability for tumors that can be exploited therapeutically, offering the possibility of precision medicine strategies. Moreover, many of these mutations are linked to hereditary risk for cancers; hence, identification of DNA repair mutations could also be relevant for cancer prevention and screening in healthy individuals, including relatives of prostate cancer patients. In this chapter, we summarize current knowledge about the prevalence of different DNA repair gene alterations across different stages of prostate cancer and review the clinical relevance of such events in terms of prognosis and treatment stratification.