Clinical and Genomic Characterization of Treatment-Emergent Small Cell Neuroendocrine

Prostate Carcinoma (t-SCNC)

Fabio Kater Oncologista da BP / GI e GU Cancer

Treatment-associated small cell/neuro-endocrine prostate cancer (t-SCNC) is emerging as a phenotype of resistance.

Classic Primary SCNCAndrogen Receptor (AR) null (no AR expression or signaling)Rare (<1% of all prostate cancers) Visceral metsLow PSA level despite bulky dzElevated neuro-endocrine markers (NSE, CGA) Usually not responsive to AR-targeted rxExplosive, virulent disease, with short survival

Drug Resistance in Advanced Prostate Cancer

t-SCNC: Unanswered Questions

How common is t-SCNC?Does it behave clinically as a primary SCNC?Is it genomically similar to primary SCNC?How does it develop? (Clonal selection? Lineage plasticity?)

Drug Resistance in Advanced Prostate Cancer

OUTLINE

1. Clinical characterization of t-SCNCA. Incidence in large consecutive seriesB. Clinical features

Sites of MetastasesPatient and Laboratory VariablesAR staining

C. Survival outcomes

SU2C/PCF West Coast Dream Team/PROMOTE Trials

Key Eligibility Criteria:

• Metastatic CRPC• Metastatic lesion amenable to

biopsy• Progressive disease by PCWG2

criteria

FFPE: Histology, targeted NGS (CLIA)Frozen: LCM RNAseq; WGS.

Adenocarcinoma

The Incidence of Treatment-associated SCNC is Higher Than Previously Appreciated (16% of all evaluable biopsies*)

Small cell/neuroendocrine

*In first 284 Evaluable Biopsies

Not Small Cell (N=239)Mixed Small Cell (N=13)Pure Small Cell (N=32)

Not small cell (84%)

t-SCNC (mixed + pure) 16%

Pure t-SCNC 11%Mixed

5%

Histologic Criteria Used for Defining t-SCNC

Independent review by three experienced pathologists (J Huang, G Thomas, L True)

If discrepancy in dx: consensus call review

If still discrepancy, called “indeterminate” ( < 10%)

OUTLINE

1. Clinical characterization of t-SCNCA. Incidence in large consecutive seriesB. Clinical features

Sites of MetastasesPatient and Laboratory VariablesAR staining

C. Survival outcomes

t – SCNC is a Distinct Clinical Entity

Compared to de novo small cell prostate cancer:

Prior History52% of t-SCNC pts had a Gleason Grade 7 or less at dxExtensive prior AR targeted rx:

Median duration of prior ADT = 3 yrs70% had prior treatment with abiraterone or enzalutamide

At time of t-SCNC Diagnosis (i.e. at time of Bx) Median serum PSA was > 50 ng/mL56% had bone/node only disease (i.e no visceral disease)

Aggarwal et al; JCO 8.2018

However: Clinical features cannot reliably distinguish t-SCNC from adenocarcinoma

Features that did not differ between t-SCNC patients and non- tSCNC patients:

Age, race/ethnicitySerum PSALDH, alkaline phosphatase, hemoglobinSerum neuroendocrine markersAnatomic site of metastases

Aggarwal et al; JCO 8.2018

Similar distribution of t-SCNC across sites of biopsy

Majority of liver

biopsies are NOT small

cell

Similar distribution of t-SCNC across sites of biopsy

t-SCNC fairly prevalent in node/bone

Similar distribution of t-SCNC across sites of biopsy

90%

10%

80%

20% t-SCNC retains nuclear Androgen Receptor (AR) expression as assessed by IHC

2+/3+ nuclear AR staining: 75% of t-SCNC samples87% of adenocarcinoma samples[P = 0.170]

Nuclear Androgen Receptor Histologic Expression

OUTLINE

1. Clinical characterization of t-SCNCA. Incidence in large consecutive seriesB. Clinical features

Sites of MetastasesPatient and Laboratory VariablesAR staining

C. Survival outcomes

t-SCNC on Biopsy is Associated with Shorter Overall Survival

Median OS by Histology

Adeno 44.5 m. t-SCNC 36.6 m.

P= 0.027

Aggarwal et al; JCO 8.2018

Outline

2. Molecular characterization of t-SCNCA. Is t-SCNC genomically distinct from adenocarcinoma? (That is, is

histology to be believed?)B. Targeted DNA sequencingC. RNA sequencing and transcriptional profiling/signatures

Combining Pathology Call with Gene Expression Cluster Identifies Very High-Risk Group

Median OS by Histology plus Transcriptional Profile

Others 41.7 mt-SCNC cluster 17.6 m

P= 0.009

Aggarwal et al; JCO 8.2018

Outline

2. Molecular characterization of t-SCNCA. Is t-SCNC genomically distinct from adenocarcinoma? (That is, is histology to be believed?)B. Targeted DNA sequencingC. RNA sequencing and transcriptional profiling/signatures

Mutational Profile of t-SCNC: Targeted NGS (CLIA)

Aggarwal et al; JCO 8.2018

AR amplification is common in t-SCNCAR copy number gain and/or activating mutations67% tSCNC vs 51% of non- tSCNC (P = 0.304)

Aggarwal et al; JCO 8.2018

Mutational Profile of t-SCNC: Targeted NGS (CLIA)

Aggarwal et al; JCO 8.2018

AR Genomic Amplification is Reflected in IHC…

Aggarwal et al; JCO 8.2018

But not in transcriptional activity

Avaliação da expressão do AR

80 pacientes estudados: 50 Adeno e 30 NeuroendocrinoPerda da amplificação do AR

Betran, Nat Med. 2016 Mar; 22(3): 298–305.

Mutational Profile: Targeted NGS

RB1 and TP53 loss of function is common

LOF variants in TP53 and/or RB183% of tSCNC vs 34% of non-tSCNC

Aggarwal et al; JCO 8.2018

RB1 Loss is Mirrored in Transcriptional Activity

Aggarwal et al; JCO 8.2018

A complexidade do mCRPC

The TCGA Research Network. Cell 2015:163(4):1011-25

N=333

Câncer de próstata primário

- 74% apresentam 1 dos 7 subtipos- Genes de fusão

- ERG- ETV1/4- FLI1

- Mutações - SPOP- FOXA1- IDH1

SPOP e FOXA1 – maiores níveis de transcritos do AR25% - lesões ativadoras do PI3K20% de dMMR de DNA

Mutações sequencias são pobremente descritas pois dependem do sítio metastático, como osso, que é difícil de estudar

A complexidade do mCRPC

Robbinson D et al. Cell 2015; 161(5):1215-28

• 150 metastáticos • Quase todos apresentavam 1 alteração

driver • 63% amplificação/mutação do receptor

andrôgeno• 23% defeitos de reparo de DNA• 8% mutações germinativas

A complexidade do mCRPC

Robbinson D et al. Cell 2015; 161(5):1215-28

• AR alterations: 63%• PI3K pathway: 49%• RAF kinases: 3%• CDK inhibitors: 7%• WNT pathway: 5%• DNA repair: 23%

DNA Repair mutations are present in t-SCNC

DNA Damage Repair (UCSF WGS series, n =101)

BRCA 2 10%BRCA1 1%ATM 6%CDK12 3%

Too few t-SCNC patients to know ifdistribution is similar.

Quigley et al Cell, 2018

Avaliação de genes de reparo de DNA

Presença de mutações e/ou perda do número de cópias em genes de reparo foi quase totalmente mutuamente exclusiva em t-SCNC ( 8% vs 40%, p= 0,035)

Outline

2. Molecular characterization of t-SCNCA. Is t-SCNC genomically distinct from adenocarcinoma? (That is, is histology to be believed?)B. Targeted DNA sequencingC. RNA sequencing and transcriptional profiling/signatures

Unsupervised transcriptional profiling identifies t-SCNC

t-SCNC Gene Expression Signature Accurately Predicts Histology

Aggarwal et al; JCO 8.2018

t-SCNC Gene Expression Signature Accurately Predicts Histology in independent data sets

Beltran 2016 neuroendocrine prostate cancer

International (East Coast) DT: • high grade prostatic adenocarcinoma

with neuro endocrine features.

Beltran et al, Nat med 2016Robinson et al, Cell 2015

Summary of Main Findings

• Treatment-emergent small cell neuroendocrine prostate cancer is strikingly prevalent and associated with poor outcomes

• Implication: Drug development in this subgroup is urgently needed

• Clinical features are distinct from de novo SCNC and don’t easily discriminate from adenocarcinoma

• Implication: Metastatic castration-resistant tumor biopsies should be considered in all patients with accessible lesion

• Transcriptional clustering is diagnostic and prognostic • Implication: Augmenting pathology calls with genomic/transcriptomic profiling likely to enhance clinical utility

• AR expression is retained but activity is lower• Implication: Co-targeting and restoring dependence on AR may be valid therapeutic approach

Conclusão• Necessidades terapêuticas do câncer de próstata neuroendócrino são

fortemente necessárias. Associada com piores resultados • Implicação: desenvolvimento de drogas para esse subgrupo urgentemente necessário

• Características clínicas são distintas do carcinoma neuroendócrino de novo e não são facilmente distintas do adenocarcinoma

• Implicação: biópsias de tumores metastáticos resistentes à castração deveriam ser consideradas em todos tumores acessíveis

• Cluster transcripcional é diagnóstico e prognóstico• Implicação: otimizar a discussão com patologista - determinação de perfis genômicos

transcriptômicos para aumentar a aplicabilidade clínica

• Expressão do Receptor androgênico é mantida, mas sua atividade é baixa• Implicação: restaurar a dependência do receptor androgênico pode ser uma abordagem

futura