Prostate cancer and neuroendocrine differentiation

PET radiotracers for whole-body in vivo molecular imaging of prostatic neuroendocrine malignancies

Prostatic neuroendocrine malignancies represent a spectrum of diseases. Treatment-induced neuroendocrine differentiation (tiNED) in hormonally treated adenocarcinoma has been the subject of a large amount of recent research. However, the identification of neuroendocrine features in treatment-naïve prostatic tumor raises a differential diagnosis between prostatic adenocarcinoma with de novo neuroendocrine differentiation (dNED) versus one of the primary prostatic neuroendocrine tumors (P-NETs) and carcinomas (P-NECs). While [18F]FDG is being used as the main PET radiotracer in oncologic imaging and reflects cellular glucose metabolism, other molecules labeled with positron-emitting isotopes, mainly somatostatin-analogues labeled with 68Ga and prostate-specific membrane antigen (PSMA)-ligands labeled with either 18F or 68Ga, are now routinely used in departments of nuclear medicine and molecular imaging, and may be advantageous in imaging prostatic neuroendocrine malignancies. Still, the selection of the preferred PET radiotracer in such cases might be challenging. In the current review, we summarize and discuss published data on these different entities from clinical, biological, and molecular imaging standpoints. Specifically, we review the roles that [18F]FDG, radiolabeled somatostatin-analogues, and radiolabeled PSMA-ligands play in these entities in order to provide the reader with practical recommendations regarding the preferred PET radiotracers for imaging each entity. In cases of tiNED, we conclude that PSMA expression may be low and that [18F]FDG or radiolabeled somatostatin-analogues should be preferred for imaging. In cases of prostatic adenocarcinoma with dNED, we present data that support the superiority of radiolabeled PSMA-ligands. In cases of primary neuroendocrine malignancies, the use of [18F]FDG for imaging high-grade P-NECs and radiolabeled somatostatin-analogues for imaging well-differentiated P-NETs is recommended. KEY POINTS: • The preferred PET radiotracer for imaging prostatic neuroendocrine malignancies depends on the specific clinical scenario and pathologic data. • When neuroendocrine features result from hormonal therapy for prostate cancer, PET-CT should be performed with [18F]FDG or radiolabeled somatostatin-analogue rather than with radiolabeled PSMA-ligand. • When neuroendocrine features are evident in newly diagnosed prostate cancer, differentiating adenocarcinoma from primary neuroendocrine malignancy is challenging but crucial for selection of PET radiotracer and for clinical management.

Serum chromogranin-A-based prognosis in metastatic castration-resistant prostate cancer

OBJECTIVE

To determine the prognostic value of serum chromogranin-A (CGA) in a two-cohort study of men with metastatic castrate resistant prostate cancer (mCRPC) and to compare with circulating tumor cells (CTCs)-based prognosis.

PATIENTS AND METHODS

A two-cohort-based evaluation for serum CGA for prognostication in CRPC stage was performed using a screening cohort of 256 men with mCRPC and an independent validation cohort of 92 men with mCRPC. In both cohorts, men receiving proton pump inhibitors and those with non-castrate levels of testosterone (>50 ng/dl) were excluded. Serum CGA was measured in a homogeneous automated immunofluorescent assay using time-resolved amplified cryptate emission. In the validation cohort, CTC enumeration was also performed using the FDA-cleared CELLSEARCH® CTC test. Cox proportional hazard regression models were used for prognostic association of serum CGA and CTC counts with overall survival.

RESULTS

In the screening cohort, 200 men were eligible for analysis. The median serum CGA was 100.3 ng/mL (interquartile range: 67-161.3) and 34/200 were above the reference range. In the subset of men with Gleason scores ≥ 8, elevated CGA was associated with shorter overall survival [hazard ratio (HR) 2.19, p = 0.017]. In the validation cohort for 71 men eligible for analysis, the median serum CGA was 90 ng/mL (interquartile range: 55-156) and 31/71 patients had an elevated CGA. 51% of patients had a Gleason score ≥ 8 and 66/71 patients had CTCs enumerated with 26/66 with a CTC count ≥ 5 per 7.5 ml blood sample (unfavorable). Both elevated serum CGA (HR: 1.91, p = 0.043) and unfavorable CTC counts (HR: 2.97, p = 0.0012) were adversely associated with overall survival and patients with ≥ 5 CTCs and elevated serum CGA had the shortest overall survival (HR: 3.76, p = 0.008).

CONCLUSION

Elevated serum CGA was negatively associated with OS in men with mCRPC. Serum CGA represents a prognostic biomarker that may complement CTC enumeration.

Neuroendocrine Tumors of the Prostate: Emerging Insights from Molecular Data and Updates to the 2016 World Health Organization Classification

Neuroendocrine neoplasms of the prostate represent a multifarious group of tumors that exist both in pure forms and associated with prostatic adenocarcinoma. Morphologically, neuroendocrine cells in prostate neoplasms can range from being indistinguishable from surrounding prostate adenocarcinoma cells to having high-grade neuroendocrine appearances similar to neuroendocrine malignancies of other organs. On the molecular level, neuroendocrine malignancies arising in the setting of prostate adenocarcinoma have been the subject of a large amount of recent research, most of which has supported the conclusion that neuroendocrine malignancy within the prostate develops as a transdifferentiation from prostate adenocarcinoma. There has not, however, been substantial investigation into rare, pure neuroendocrine malignancies and the possibility that these tumors may have a different cell of origin and molecular genesis. Here, we discuss the morphologic spectrum of malignant neuroendocrine prostate neoplasms and review the most recent molecular data on the subject of malignant neuroendocrine differentiation in prostatic adenocarcinoma. In reflection of the most recent data, we also discuss diagnostic classification of prostate neuroendocrine tumors with reference to the 2016 World Health Organization (WHO) classification. We discuss the reporting of these tumors, placing emphasis on the differentiation between pure and mixed neuroendocrine malignancies so that, in the least, they can be easily identified for the purposes of future clinical and laboratory-based investigation. Finally, we suggest a designation for an unclassifiable (or not otherwise specified) high-grade neuroendocrine prostate malignancy whose features do not easily place it into one of the WHO diagnostic entities.

Prognostic effect of neuroendocrine differentiation in prostate cancer: A critical review

BACKGROUND

The multiple pathways that are involved in neuroendocrine differentiation (NED) in prostate cancer (PCa) are poorly elucidated. Evidence suggests that several environmental triggers induce NED leading to the adaptation of PCa to its close environment to maintain cell proliferation. Nevertheless, there is conflicting evidence regarding the prognostic role of NED in PCa.

METHODS

In this review, we aimed to summarize all available data about NED and to assess the prognostic role of NED in disease progression and therapy resistance, and its role in routine clinical practice. This review was based on articles found through a PubMed literature search between 1993 and 2013. The study outcome measure was the effect of NED on oncologic outcomes at each PCa stage.

RESULTS

In total, 59 articles reporting on the effect of NED on oncologic outcomes have been selected. In clinical practice, immunostaining for NED markers could have interesting predictive value for assessing the oncologic outcomes in patients receiving androgen-deprivation therapy. Thus, patients with high NED burden may be candidates for more aggressive treatment strategies targeting NED pathways. Conversely, strong evidence is lacking concerning its potential independent prognostic value in hormone-naïve PCa.

CONCLUSIONS

Current published data are not sufficient to recommend the use of NE markers in routine practice, particularly at early PCa stage.

Proposed morphologic classification of prostate cancer with neuroendocrine differentiation

On July 31, 2013, the Prostate Cancer Foundation assembled a working committee on the molecular biology and pathologic classification of neuroendocrine (NE) differentiation in prostate cancer. New clinical and molecular data emerging from prostate cancers treated by contemporary androgen deprivation therapies, as well as primary lesions, have highlighted the need for refinement of diagnostic terminology to encompass the full spectrum of NE differentiation. The classification system consists of: Usual prostate adenocarcinoma with NE differentiation; 2) Adenocarcinoma with Paneth cell NE differentiation; 3) Carcinoid tumor; 4) Small cell carcinoma; 5) Large cell NE carcinoma; and 5) Mixed NE carcinoma - acinar adenocarcinoma. The article also highlights "prostate carcinoma with overlapping features of small cell carcinoma and acinar adenocarcinoma" and "castrate-resistant prostate cancer with small cell cancer-like clinical presentation". It is envisioned that specific criteria associated with the refined diagnostic terminology will lead to clinically relevant pathologic diagnoses that will stimulate further clinical and molecular investigation and identification of appropriate targeted therapies.

Small cell carcinoma of the prostate

Pure small-cell carcinoma (SCC) of the prostate is a rare entity and one of the most aggressive malignancies of the prostate. Histologically, prostatic SCCs of the prostate are part of a spectrum of anaplastic tumours of the prostate and are similar to SCCs of the lungs. In most cases, SCC of the prostate is associated with conventional prostatic adenocarcinoma. Both components of these mixed tumours frequently share molecular alterations such as ERG gene rearrangements or AURKA and MYCN amplifications, suggesting a common clonal origin. The clinical behaviour of small-cell prostate carcinomas is characterized by extensive local disease, visceral disease, and low PSA levels despite large metastatic burden. Commonly, the emergence of the SCC occurs in patients with high-grade adenocarcinoma who are often treated with androgen deprivation treatment (ADT). However, SCCs do not usually benefit from ADT. A biopsy of accessible lesions is strongly recommended to identify those with SCC pathological features, as management is undoubtedly affected by this finding. Chemotherapy is the standard approach for treating patients with either localized or advanced prostatic SCC. Despite the emergence of more-aggressive treatment modalities, the prognosis of men with prostatic SCC remains dismal.

Neuroendocrine differentiation does not have independent prognostic value in conservatively treated prostate cancer

In vitro studies have implicated neuroendocrine differentiation in the development of hormone resistant prostate cancer following administration of androgen blockers. Studies on clinical material are equivocal. We wished to understand the significance of neuroendocrine differentiation in our large and well-characterised cohort of clinically localised prostate cancer, treated conservatively. Immunohistochemical expression of chromogranin-A was assessed semi-quantitatively on tissue samples of 806 patients in a tissue microarray approach. The correlation of expression with 10-year prostate cancer survival was examined. Multivariate analysis including contemporary Gleason score was performed and sub-group analysis of early hormone treated patients was also undertaken. Chromogranin-A expression correlated with high Gleason score (χ(2) = 28.35, p < 0.001) and early prostate cancer death (HR = 1.61, 95 %CI = 1.15-2.27, p < 0.001). In univariate analysis, NE differentiation correlated significantly with outcome (HR = 1.61, 95 % CI 1.15-2.27, p < 0.001) However in multivariate analysis including Gleason score, chromogranin-A expression was not an independent predictor of survival (HR = 0.97, 95 %CI = 0.89-1.37, p = 0.87). Although chromogranin-A expression was higher in patients with early hormone therapy (χ(2) = 7.25, p = 0.007), there was no association with prostate cancer survival in this sub-group (p = 0.083). Determination of neuroendocrine differentiation does not appear to have any bearing on the outcome of prostatic carcinoma and does not add to the established prognostic model.

Prognostic significance of neuroendocrine expression in lymph node-positive prostate cancer

OBJECTIVES

To evaluate the expression of chromogranin A, a marker for neuroendocrine (NE) differentiation, in patients with lymph node-positive prostate cancer to determine its prognostic significance. NE cells are involved in cellular growth and differentiation in both normal and pathologic conditions of the prostate.

METHODS

We reviewed the data of 140 patients with lymph node-positive prostate adenocarcinoma treated with radical prostatectomy and pelvic lymphadenectomy. The median follow-up was 10.9 years (range 0.8 to 19.7). Immunohistochemical staining for chromogranin A was evaluated in areas of benign epithelium, primary prostate cancer, and lymph node metastasis. The association between chromogranin A expression and the clinical and pathologic factors (preoperative serum prostate-specific antigen and prostatectomy Gleason score and stage) and clinical outcomes, including overall and recurrence-free survival, was evaluated.

RESULTS

Staining was positive in 86% of benign areas, 61% of primary cancer specimens, and 12% of lymph node deposits. The preoperative serum prostate-specific antigen level and pathologic stage and grade of the primary tumor did not show any statistically significant correlation with NE staining in any of the areas. Only NE expression in the primary tumor was associated with clinical recurrence, with a 10-year recurrence-free survival rate for those with less than 5% staining of 67% compared with 35% for those with 5% staining or greater (P = 0.03). Furthermore, after adjusting for age, greater NE expression in the primary tumor (relative risk 2.15, P = 0.02) and lymph node deposit (relative risk 2.03, P = 0.03) was associated with poorer overall survival.

CONCLUSIONS

NE expression in the primary tumor and lymph node metastasis of patients with node-positive prostate cancer may provide additional prognostic stratification.

Effects of combined androgen blockade on bone metabolism and density in men with locally advanced prostate cancer

OBJECTIVE

To investigate whether combined androgen blockade (CAB) produces any adverse effects on bone metabolism and mineral density in patients with locally advanced prostate cancer.

MATERIALS AND METHODS

The study group consisted of 17 stage T4 prostate cancer patients treated with CAB and had no evidence of bone metastasis on bone scintigraphy. The mean duration of CAB and final total prostate specific antigen (PSA) level at the time of study were found at 28.5 +/- 15.9 (6-58) months and 0.39 +/- 0.5 (0.1-2) ngml, respectively. Twenty age and socioeconomically matched benign prostate hyperplasia (BPH) patients were taken as the control group. Both groups were compared with regard to lumbar bone mineral density (LBD), femur bone mineral density (FBD) and serum parameters of bone metabolism namely calcium (Ca), phosphate (P), magnesium (Mg) and alkaline phosphatase (ALP). Bone mineral density was measured with dual energy x-ray absorptiometry.

RESULTS

The mean FBD, LBD and serum Ca, P, Mg and ALP measurement of the patients treated with CAB were 0.85 +/- 0.1 g/cm2, 1.16 +/- 0.2 g/cm2, 9.1 +/- 0.3 mg/dl, 3.6 +/- 0.6 mg/dl, 1.95 +/- 0.14 mg/dl, 187.5 +/- 61 mg/dl, respectively. No significant difference was found between patients subjected to CAB and the age matched controls in any of the studied parameters namely age, FBD, LBD, Ca, Mg and ALP except serum phosphate. Serum phosphate levels were significantly (p = 0.001) higher in patients treated with CAB suggesting a minor effect of CAB on bone metabolism.

CONCLUSION

No convincing evidence was found about the detrimental effect of CAB on bone mineral density and metabolism in a highly selected group of patients with advanced prostate cancer without bone metastases.

Neuroendocrine expression in node positive prostate cancer: correlation with systemic progression and patient survival

PURPOSE

Neuroendocrine cells are ubiquitous but uncommon in benign and neoplastic prostate epithelium, and they are considered important for regulating cell growth and differentiation. The predictive value of neuroendocrine immunoreactivity for patient outcome after radical prostatectomy is uncertain. In this study we determined the expression of 2 important neuroendocrine markers, chromogranin and serotonin, in benign epithelium, primary prostate cancer and lymph node metastases, and correlated cellular expression with patient outcome.

MATERIALS AND METHODS

We studied 196 patients with node positive prostate adenocarcinoma who underwent bilateral pelvic lymphadenectomy and radical prostatectomy at Mayo Clinic between 1987 and 1992. Mean followup was 6.8 years (range 0.3 to 11). The cellular expression of chromogranin and serotonin in matched samples of benign tissue, primary prostate cancer and lymph node metastases from the same patients was evaluated by immunohistochemical staining using commercially available monoclonal antibodies. Results were correlated with patient age, pathological findings (Gleason score, DNA ploidy and cancer volume) and patient outcome, including clinical progression, cancer specific and all cause survival.

RESULTS

Chromogranin immunoreactivity was greater in benign prostatic epithelium and primary cancer cases (99% each) than in those of lymph node metastases (37.5%) (pairwise comparisons with metastases p <0.001). The mean incidence of immunoreactive cells in benign epithelium, primary cancer and metastases was 6% (median 5%), 6% (median 3%) and 2.2% (median 0%), respectively. Serotonin immunoreactivity was greatest in benign prostate epithelium cases (98.5%) with less in primary cancer (95%) and lymph node metastases (21.5%) (pairwise comparisons p <0.001). The mean incidence of immunoreactive cells in benign epithelium, primary cancer and metastases was 2.2% (median 3%), 2.4% (median 2%) and 0.4% (median 0%), respectively. Chromogranin expression was invariably greater than that of serotonin for all 3 diagnostic categories (p <0.0001). There was a marginally significant positive trend in the level of chromogranin expression in benign prostatic epithelium and systemic progression (p = 0.05) but no significant association with cancer specific or all cause survival (p >0.1). No significant association was observed of chromogranin expression in primary cancer or lymph node metastases with any patient outcomes (p >0.1). There was a significant association of the level of serotonin expression in benign prostatic epithelium with cancer specific survival (p = 0.03) but no significant association with systemic progression or all cause survival (p > 0.1). There were positive trends in the association of serotonin immunoreactivity in primary cancer with systemic progression (p = 0.09) and cancer specific survival (p = 0.05) but not with all cause survival (p >0.1). No significant association was observed of serotonin expression in lymph node metastases with any patient outcomes (p >0.1).

CONCLUSIONS

Benign prostatic epithelium and primary prostate cancer express a significantly greater number of chromogranin and serotonin immunoreactive cells than lymph node metastases, suggesting that decreased expression of neuroendocrine markers is involved in cancer progression. However, neuroendocrine expression was marginally useful for predicting the outcome in patients with node positive prostate cancer treated with radical prostatectomy.

A neuroendocrine/small cell prostate carcinoma xenograft-LuCaP 49

The late stages of progression of prostate carcinoma are typically characterized by an androgen-insensitive, rapidly proliferative state. Some late-stage tumors are composed predominantly of neuroendocrine cells. Virtually no animal models of a neuroendocrine/small cell variant of prostate carcinoma are available for experimental studies. We report a human neuroendocrine/small cell prostate carcinoma xenograft that was developed from a nodal metastasis of a human prostate carcinoma and that has been propagated as serial subcutaneous implants in severe combined immunodeficient mice for >4 years. Designated LuCaP 49, all tumor passages exhibit a neuroendocrine/small cell carcinoma phenotype-insensitivity to androgen deprivation, expression of neuroendocrine proteins, lack of expression of prostate-specific antigen or androgen receptor, and an unusually rapid growth (a doubling time of 6.5 days) for prostate cancer xenografts. Genetically this tumor exhibits loss of heterozygosity for the short arm of chromosome 8 and has a complex karyotype. This xenograft should prove to be useful in the investigation of mechanisms underlying the androgen-insensitive state of progressive prostate carcinoma.