Differential expression of somatostatin receptor (SSTR) subtypes across a spectrum of neuroendocrine neoplasms (NENs)

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Background: Targeted therapy of NENs based on the presence of SSTRs fills a unique niche in tumor biology and clinical treatment of patients with solid tumors. SSTRs have multiple isoforms and are collectively expressed in the majority of NENs. However, subtypes are still not routinely tested and thus not assessed for clinical decision-making, especially for patients meriting consideration of targeted radionucleotide therapy. Clarifying the landscape of SSTR subtypes using molecular techniques more sensitive than immunohistochemistry (IHC)-the standard of testing, and identifying associated genomic biomarkers that differ between them, will pave the way for more sophisticated decision-making in the future. Additionally, leveraging transcriptomics to better assess mitotic markers such as Ki-67 to assess tumor grade, would increase diagnostic accuracy. Here we provide initial validation across a spectrum of NENs. Methods:1595 NENs were analyzed using Next Generation Sequencing (592 gene panel, NextSeq), Whole Exome and Transcriptome Sequencing (NovaSeq), and IHC at Caris Life Sciences (Phoenix, AZ). Significance was determined using chi-square, Fisher-Exact or Mann-Whitney U and p-adjusted for multiple comparisons (q<0.05) where applicable. Results: In a subset of 492 NENs with accompanying tumor grading information, a median MKI67 (gene encoding Ki-67) TPM value of 2.27 for low-grade (LG-), and 38.7 for high-grade NENs (HG-NENs) was observed (q<0.05). Using ROC curve analysis, a threshold of MKI67 expression (13.4375 TPM) differentiated LG- from HG-NENs, with a true positive rate of 86.84%, a false positive rate of 11.9% and an AUC of 95% and was subsequently applied to the entire cohort to infer HG/LG. Compared to HG-NENs (n = 862), LG-NENs(n = 733) expressed higher levels of SSTR 1(3.5-fold),2 (2.9-fold) and 5 (1.67-fold) and lower levels of SSTR4 (0.28-fold)(q<0.05). Further, the expression of SSTRs 3 and 4 in HG-NEN (rs= 0.63) and SSTRs 1 and 2 in LG-NENs (rs= 0.64) were positively correlated. Overall, the prevalence of altered TP53, RB1, PIK3CA, APC, KRAS was higher and MEN1 was lower in HG-vs LG-NENs (q<0.05). For each SSTR subtype, we established high and low cohorts based on median expressions. In LG-NENs, increased alterations in TP53 and RB1 were associated with increased expression of SSTRs 1 and 2 and reduced expression of SSTRs 3 and 4. In HG-NENs, increased alterations in APC were associated with increased expression of SSTR 1 and 4 and reduced expression of SSTRs 3 and 5. Additional subtype- and grade-specific alterations were also observed. Conclusions: This study provides evidence that WTS and NGS can be leveraged to predict grade of NENs and define characteristic differences in the genomic landscape across SSTR subtypes in HG and LG NENs. Incorporating the molecular profiling of NENs can thus aid in advancing the development of more tailored therapeutic strategies.

Analysis of Differentially Expressed MicroRNAs and Circulating Tumor Cells as Predictive Biomarkers of Platinum Chemoresistance in Primary Ovarian Carcinomas: A Prospective Study

Lesson Learned.

Circulating tumor cells, microRNA markers, or other biomarkers merit examination as part of correlative scientific analyses in prospective clinical trials.

Background.

Platinum chemotherapy resistance occurs in approximately 25% of patients with ovarian carcinoma; however, no biomarkers of ovarian carcinoma chemoresistance have been validated. We performed a prospective trial designed to identify tumor‐based predictive biomarkers of platinum resistance.

Methods.

Tumor specimens were collected from 29 women with newly diagnosed histopathologically proven primary ovarian carcinoma. Of these, 23 women had specimens accessible for assessment and outcome data available regarding chemosensitive versus chemoresistance status via review of the medical record. Tumor slices were stained with antibodies against two microRNAs (miRNAs 29b and 199a) differentially expressed in chemoresistant ovarian cancer cell lines. Additionally, blood samples obtained at the time of diagnosis were analyzed for the presence of circulating tumor cells (CTCs).

Results.

The average age of the patients was 64 years, and 82.6% had high‐grade epithelial carcinomas. The baseline median CA‐125 was 464 (range 32–2,782). No statistically significant differences were observed in miR29b or 199a expression in platinum‐resistant/refractory versus platinum‐sensitive tumors. Furthermore, the presence of CTCs was not found to be statistically significantly predictive of eventual platinum resistance.

Conclusion.

Our analysis showed no differences in miR29b and 199a expression, and differences in baseline CTCs in women with newly diagnosed ovarian tumors were not statistically significant.

Tumor stroma proportion to predict platinum chemoresistance in primary ovarian carcinomas: A prospective study

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Background: Platinum chemotherapy resistance occurs in approximately 25% of patients with ovarian carcinoma and represents a major barrier to effective care of this patient population. To date there are no effective nor validate predictive biomarkers of chemoresistance of ovarian carcinomas. We performed a prospective trial designed to enroll patients with ovarian masses suspicious for ovarian cancer, with the goal of identifying tumor-based predictive biomarkers of platinum resistance. Methods: 60 women were enrolled on the study. Tumor specimens were collected from 49 of these women with newly diagnosed pelvic masses, of which 29 were found to have histopathologically proven primary ovarian carcinoma. Of these primary malignant cases, 24 had specimens accessible for assessment of tumor-stroma proportion and data available regarding chemosensitive vs chemoresistance status via review of the medical record using a UMN IRB-approved protocol. Tumor slices were stained with H&E and also for antibodies against two microRNAs (29b and 199a) differentially expressed in ovarian cancer cell lines. Tumor-stroma proportions were assessed by two experienced pathologists blinded to chemoresistance status, with <50% stroma scored as low proportion, >50% scored as high proportion. Results: The average age of assessed patients with malignant tumors was 62. 87.5% had high-grade epithelial carcinomas. Baseline median CA-125 was 416 (range 32-2782). 80% of ovarian cancer patients with chemoresistance had tumor stroma proportions >50%; 73.7% of cancer patients with chemosensitive tumors had proportions <50% (p-value: 0.047). Expression of miR29b or 199a did not significantly correlate with chemoresistance. Conclusions: Tumor-stroma proportion is a useful predictive biomarker of platinum chemoresistance. If validated in larger datasets, it would be a relatively inexpensive and helpful tool for tailoring treatment strategies and clinical decision-making in women with ovarian cancer.

Abstract P1-01-01: Systemic imaging fails to detect metastasis in early stage breast cancer

Background: Current NCCN guidelines for early stage breast cancer (Stage I and II) do not recommend routine systemic imaging in the absence of symptoms or abnormal labs suggestive of distant metastasis. This study aims to determine the frequency and appropriateness of these imaging studies performed, its impact on staging and the factors that influence physicians in ordering these imaging studies.

Methods: Patients with stage I and II breast cancer at initial presentation were retrospectively identified between years 2011-2015 from the tumor registry. Charts were reviewed to determine patients who got systemic imaging (CT scan, non-breast MRI, bone scan or PET scan) within 6 months of diagnosis. Provider notes and laboratory data were analyzed to establish the appropriateness of ordered imaging studies and if the imaging altered the stage. For each patient in the study, age at diagnosis, the grade of the breast tumor, hormonal receptor status and HER-2 status was documented. Statistical analysis was done using appropriate tests.

Results: A total of 1067 patient charts were screened, of which 882 were identified for inclusion in the study (544 stage I, 338 stage II). Amongst the cohort, 18.57% (101) of patients with stage I and 50.89% (172) of patients with stage II cancer received imaging studies within the first 6 months of diagnosis. Only 12.68% (69) of stage I patients and 18.24% (62) of stage II patients were judged appropriate for imaging based on symptoms and lab results suggesting metastasis. In the imaged cohort of Stage I patients, only 4.35% (3) of the appropriately imaged group and 13.33% (4) of the inappropriately imaged group had a change in stage. Similarly, in the Stage II cohort, only 4.84% (3) of the appropriately imaged group and 8.18% (9) of the inappropriately imaged group saw a change in state. The difference in stage change in the appropriately and inappropriately imaged groups was not statistically significant. (p = 0.11 for Stage I, p=0.41 for Stage II). Only 5.9% of Stage I and 2.9% of Stage II imaged patients changed to stage IV. Grade 1 patients were less likely to receive systemic imaging than grade 2 and 3 patients ((p &lt;0.001). Similarly, the difference in imaging rates ordered in patients with ER and/or PR negative status versus ER and PR positive status was significant (p=0.0004). Triple negative (p &lt;0.001) status and age≤ 50 years were statistically significant predictors of patients receiving imaging (p = 0.014). HER-2 status alone was not a significant predictor of getting imaged (p= 0.527).

Conclusions: We performed the first ever study to investigate a correlation between the appropriateness of ordered imaging studies in early stage breast cancer and its ability to detect a change in stage. Distant metastasis identification among stage I & II patients was extremely rare among both appropriately and inappropriately imaged groups. Our findings suggest a wide prevalence of inappropriately ordered imaging studies in Stage I and II breast cancer as well as limited utility for even appropriately ordered ones. Further, other factors such as grade of the tumor, ER/PR/HER2 status and age were found to be statistically significant predictors of whether patients received imaging studies.

Citation Format: Gaba AG, Kraft R, Stjern BK, Monu M, Gunderson MA, Hanish C, Samreen A, Paladugu G. Systemic imaging fails to detect metastasis in early stage breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-01-01.

Assessment of Circulating Tumor Cells as a Predictive Biomarker of Histology in Women With Suspected Ovarian Cancer

Background

The clinical assessment of circulating tumor cells (CTCs) as a blood-based biomarker is FDA-approved for use in breast, colorectal, and prostate cancers. The objective of this prospective clinical study was to determine whether pretreatment CTCs are a useful diagnostic biomarker in women with complex pelvic masses.

Methods

Whole blood was collected from 49 women with newly diagnosed pelvic masses. The presence of CTCs was compared between women with and without ovarian cancer histopathologic diagnosis after surgery using a Chi-squared test.

Results

CTCs were absent in those with benign disease (0/14), present in 17% (5/29) of patients with a histologic diagnosis of ovarian carcinoma, and present in 80% (4/5) of patients with ovarian metastases from other cancers (P = 0.001). All 5 women with ovarian cancer who had CTCs present presented stage III or IV of the disease (P = 0.13).

Conclusions

CTCs were more prevalent in patients with metastases to the ovary than in primary ovarian carcinomas.