Citations

100 Background: CRC is a common cancer world-wide, accounting for ̃10% of cancer cases and mortality. Treatment options are limited, and survival is poor for pts with advanced disease, particularly those with mKRAS. After failure of 1L treatment for mCRC, regardless of KRAS mutation status, the ORR for FOLFIRI-bev is 5-13%, with PFS 4-6 mos, and OS 10-12 mos. Onvansertib is a highly selective, ATP-competitive, orally bioavailable PLK1 inhibitor that is synergistic with irinotecan and with 5FU in xenograft models of mKRAS CRC. We present preliminary safety, efficacy, and biomarker data from an ongoing Ph1b/2 trial of onvansertib + FOLFIRI-bev in pts with mKRAS mCRC progressing after 1L treatment with fluoropyrimidine + oxaliplatin, +/- bev. Methods: Pts with mCRC with a KRAS mutation detected by a CLIA-certified lab were eligible. In the Ph1b portion of the study, onvansertib was given on a 3+3 dose escalation at 12, 15 or 18 mg/m2 on days 1-5 and 15-19 of each 28-day cycle in combination with FOLFIRI-bev. The MTD was 15 mg/m2 and was chosen as the RP2D. The primary endpoint for the Ph2 was ORR, and radiographic response was assessed every 8 wks per RECIST v1.1. Safety was evaluated continuously, and AEs were recorded using CTCAE v5.0. Baseline and post-treatment blood samples were collected for biomarker analyses, including mutant allele frequency (MAF) of the pt’s known KRAS mutation. Results: As of 16Sep2021, a total of 50 pts had been treated: 18 on the Ph1b and 32 on the Ph2, including 35 pts at the RP2D, and median follow up was 4.7 mos (range 0.4-18). Of the 50 pts, 26 remain on treatment, as do 24 of 35 RP2D pts. The combination was well-tolerated: fatigue, neutropenia, and nausea were the most common treatment-emergent adverse events (TEAE) and were generally low-grade. Neutropenia was managed by removing the 5FU bolus from subsequent cycles of FOLFIRI and adding growth factor. Of the 50 pts, 44 were evaluable for efficacy, including 31 of 35 RP2D pts. ORR was 36% for the total group (1CR and 15 PR in 44 pts) and 35% for the RP2D group (1 CR and 10 PR in 31 pts). First responses were seen between 2 and 6 months after the start of therapy. Responses were observed across different KRAS variants. Pts achieving a CR or PR showed the greatest decreases in plasma MAF after the first cycle of therapy. Of the 50 pts, 24 pts have discontinued for the following reasons: progressive disease (13), toxicity (4), patient decision (4), proceeding to potentially curative surgery or other localized therapy (3). Conclusions: The combination of onvansertib with FOLFIRI-bev was well tolerated: observed TEAEs have been generally low-grade and manageable. The combination has demonstrated a promising ORR in 2L treatment of mCRC pts harboring various KRAS mutations, and efficacy was correlated with early changes in plasma mKRAS. Updated safety, efficacy, and biomarker analyses will be presented. Clinical trial information: NCT03829410.

TPS155 Background: Chemotherapy in combination with targeted agents are standard-of-care options for patients for mCRC with response rates > 50% in first line. In the second line setting, efficacy of chemotherapy and targeted agents are much lower with response rates of 5% for FOLFIRI (5-fluorouracil, leucovorin, irinotecan) + bevacizumab (anti-VEGF). New treatment options are urgently needed in particular for the 50 % of patients harboring a KRAS mutation. PLK1 is a serine/threonine kinase, master regulator of the mitotic checkpoint and cell division. PLK1 is overexpressed in CRC and its overexpression is associated with poor prognostic. A genome wide RNAi screen identified PLK1 as a synthetic lethal target in KRAS mutant CRC cells, inducing cell cycle arrest and apoptosis upon inhibition. Onvansertib is an oral, highly selective PLK1 inhibitor that demonstrates single agent and synergistic activity with irinotecan and 5-FU in preclinical CRC models. Additionally, KRAS mutated versus wild-type cells showed higher sensitivity to onvansertib. PLK1 inhibition is a potential target in KRAS-mutated mCRC, and the combination of onvansertib + FOLFIRI + bevacizumab may provide a new second-line treatment option. Methods: The primary objective of this single-arm Phase 1b/2 study is to assess the safety and preliminary efficacy of onvansertib in combination with FOLFIRI and bevacizumab in the second line setting for KRAS-mutated mCRC patients. For the Phase 1b segment, a standard 3 + 3 dose-escalation design is used to determine the maximum tolerated dose or recommended phase 2 dose (RP2D) of onvansertib. As of September 15th 2020, the first two dose levels have been cleared for safety and the third is enrolling. Efficacy will be determined by objective response rate (ORR) according to RECIST v1.1 (primary endpoint), progression-free survival and reduction in KRAS allelic burden in liquid biopsies (secondary endpoints). Biomarker analyses include genomic profiling of circulating tumor DNA genomic to evaluate altered pathways that correlate with patient clinical response. Based on a one-sided one sample log-rank test with 10% Type I error, there will be at least 90% power to detect an improvement in ORR from 5% to 20% with 32 patients. Clinical trial information: NCT03829410.

Abstract Background: Chemotherapy in combination with targeted agents are standard-of-care options for patients for mCRC with response rates >50% in first line. In the second line setting, efficacy of chemotherapy and targeted agents are much lower with response rates of 5% for FOLFIRI (5-fluorouracil, leucovorin, irinotecan) + bevacizumab (anti-VEGF). New treatment options are urgently needed in particular for the 50 % of patients harboring a KRAS mutation. Polo-like kinase 1 (PLK1) is a serine/threonine kinase, master regulator of the mitotic checkpoint and cell division. PLK1 is overexpressed in CRC and its overexpression is associated with poor prognostic. A genome wide RNAi screen identified PLK1 as a synthetic lethal target in KRAS mutant CRC cells, inducing cell cycle arrest and apoptosis upon inhibition. Onvansertib is an oral, highly selective PLK1 inhibitor that demonstrates single agent and synergistic activity with irinotecan in preclinical CRC models. Additionally, KRAS mutated vs wild-type cells showed higher sensitivity to onvansertib. PLK1 inhibition is a potential target in KRAS-mutated mCRC and onvansertib + FOLFIRI + bevacizumab may provide a new second-line treatment option. Trial design: The primary objective of this single-arm Phase 1b/2 study is to assess the safety and preliminary efficacy of onvansertib in combination with FOLFIRI and bevacizumab in the second line setting for KRAS-mutated mCRC patients. For the Phase 1b segment, a standard 3 + 3 dose-escalation design is used to determine the maximum tolerated dose or recommended phase 2 dose (RP2D) of onvansertib. As of January 24th 2020, enrollment in the second dose level is ongoing. Efficacy will be determined by objective response rate (ORR) according to RECIST v1.1 (primary endpoint), progression-free survival and reduction in KRAS allelic burden in liquid biopsies (secondary endpoints). In the phase 2, based on a one-sided one sample log-rank test with 10% Type I error, there will be at least 90% power to detect an improvement in ORR from 5% to 20% with 26 patients. Exploratory endpoints include genomic studies of circulating tumor cells and ctDNA to evaluate altered pathways that correlate with patient response. Clinical trial identification NCT03829410. Citation Format: Afsaneh Barzi, Heinz-Josef Lenz, Errin Samuëlsz, Maya Ridinger, Mark Erlander, Tanios S. Bekaii-Saab, Daniel H. Ahn. A phase 1b/2 study of onvansertib (PCM-075) in combination with FOLFIRI and bevacizumab for second line treatment of patients with KRAS-mutated metastatic colorectal cancer (mCRC) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT235.

550 Background: Ductal carcinoma in situ (DCIS) is a heterogeneous group of non-invasive cancers with varying propensity for recurrence. There are no validated markers that identify patients at risk for invasive recurrence following lumpectomy. HOXB13/IL17BR (H/I) is expressed in both DCIS and invasive cancer (Ma Cancer Cell. 2004) and associated with recurrence in stage I cancer. A 5-gene molecular grade index (MGI) distinguishes outcome in grade II disease (Ma Clin Cancer Res. 2008). We sought to determine whether H/I or MGI was associated with invasive recurrence in resected DCIS. Methods: We identified patients at Mayo Rochester who underwent lumpectomy ± radiation for DCIS between 1988 and 2001 and performed a nested case/control study. Cases were patients with ipsilateral invasive recurrence, matched to controls based on age, surgery date, length of follow-up, and adjuvant radiation. DCIS was macrodissected from paraffin sections and RNA extracted to obtain H/I and MGI RT-PCR profiles. The association of H/I and MGI with case-control status was assessed with conditional logistic regression; results reported are odds ratios (OR) with 95% confidence intervals (CI). The association of H/I and MGI as continuous variables with nuclear grade (low, intermediate, high) was estimated with Spearman's rank correlation. Results: 427 patients underwent lumpectomy for DCIS, and 33 were identified as possible cases. Histologic review excluded 8 (non-sufficient tissue or DCIS recurrence without invasion). 25 cases were matched to 48 controls (2 controls for 23 cases, 1 control for 2 cases). Both H/I (r = 0.43, p = 0.0001) and MGI (r = 0.41, p = 0.0004) were significantly correlated with nuclear grade. Positive H/I was associated with trend towards higher recurrence (OR 1.9; p = 0.22) that was most pronounced in cases/controls (15/28) treated with lumpectomy alone (OR 3.3; CI: 0.8–13.2, p = 0.09). Similarly, positive MGI was associated with a trend towards higher recurrence risk in patients treated with surgery alone (OR 2.0; CI: 0.6–6.4, p = 0.27). Conclusions: These data suggest that both HOXB13/IL17BR and MGI can identify a subset of patients with surgically resected DCIS who are at risk for invasive recurrence. Further studies in larger cohorts are needed to confirm these findings. [Table: see text]

TPS4116 Background: Chemotherapy in combination with targeted agents are standard-of-care options for patients for mCRC with response rates >50% in first line. In the second line setting, efficacy of chemotherapy and targeted agents are much lower with response rates of 5% for FOLFIRI (5-fluorouracil, leucovorin, irinotecan) + bevacizumab (anti-VEGF). New treatment options are urgently needed in particular for the 50 % of patients harboring a KRAS mutation. PLK1 is a serine/threonine kinase, master regulator of the mitotic checkpoint and cell division. PLK1 is overexpressed in CRC and its overexpression is associated with poor prognostic. A genome wide RNAi screen identified PLK1 as a synthetic lethal target in KRAS mutant CRC cells, inducing cell cycle arrest and apoptosis upon inhibition. Onvansertib is an oral, highly selective PLK1 inhibitor that demonstrates single agent and synergistic activity with irinotecan in preclinical CRC models. Additionally, KRAS mutated vs wild-type cells showed higher sensitivity to onvansertib. PLK1 inhibition is a potential target in KRAS-mutated mCRC, and the combination of onvansertib + FOLFIRI + bevacizumab may provide a new second-line treatment option. Methods: The primary objective of this single-arm Phase 1b/2 study is to assess the safety and preliminary efficacy of onvansertib in combination with FOLFIRI and bevacizumab in the second line setting for KRAS-mutated mCRC patients. For the Phase 1b segment, a standard 3 + 3 dose-escalation design is used to determine the maximum tolerated dose or recommended phase 2 dose (RP2D) of onvansertib. As of January 24, 2020, enrollment in the second dose level is ongoing. Efficacy will be determined by objective response rate (ORR) according to RECIST v1.1 (primary endpoint), progression-free survival and reduction in KRAS allelic burden in liquid biopsies (secondary endpoints). In the phase 2, based on a one-sided one sample log-rank test with 10% Type I error, there will be at least 90% power to detect an improvement in ORR from 5% to 20% with 26 patients. Exploratory endpoints include genomic studies of circulating tumor cells and ctDNA to evaluate altered pathways that correlate with patient clinical response. Clinical trial information: NCT03829410 .

10588 Background: Accurate tumor classification is increasingly critical to individualized care as patient outcomes improve with use of targeted cancer therapies and predictive biomarkers. In metastatic cancers of uncertain or unknown origin, identification of a primary site remains equivocal in a significant number of cases. Gene expression signatures may improve accuracy and specificity of tumor classification, however, large-scale, blinded validation studies that demonstrate stable performance in metastatic and poorly differentiated cases are currently lacking. Methods: Seven hundred and ninety cases (51% female, 44% metastatic, 63% grade 2 and 3, 14% limited tissue specimens) representing 28 tumor types and 50 subtypes were processed and adjudicated between Mayo Clinic, UCLA and Massachusetts General Hospital. Blinded FFPE tumor sections were submitted and tested using a 92-gene RT-PCR assay (CancerTYPE ID, bioTheranostics Inc.). Molecular predictions were evaluated for concordance with the reference diagnosis; diagnostic accuracy between clinical subsets was compared. Results: The 92-gene assay demonstrated overall sensitivities of 87% for tumor classification and 82% for subtyping. Forty-seven (5.9%) cases were considered unclassifiable. Comparative analysis of performance between metastatic (n=329) and primary (n=414) tumors showed no statistically significant difference in accuracy (85% vs 88%, p=0.16). Similarly, no significant decreases in performance were observed across histological grades (p=0.58) and when comparing limited tissue to excisional biopsy specimens (p=0.16). Strong precision was demonstrated for accurate identification of a primary tumor in tissues biopsied from common metastatic sites, reported as positive predictive values of 100% for lung, brain and peritoneum, 92% for ovary and 80% for liver. Conclusions: Results from this multisite, blinded study validate the diagnostic accuracy of the 92-gene assay for classifying a diverse set of tumors, and support its clinical utility in the diagnosis of metastatic tumors to determine tissue of origin, and in the differential diagnosis of metastatic vs new primary disease.

2 Background: The MA.17 trial demonstrated that extended adjuvant endocrine therapy with letrozole after 5-y of tamoxifen markedly reduced the risk of recurrence in women with ER+ early stage breast cancer. This trial provides an opportunity to assess the ability of biomarkers to predict late recurrences in ER+ breast cancer. The Breast Cancer Index (BCI), a continuous risk index based on the combination of HOXB13:IL17BR (H:I) and the molecular grade index (MGI), estimates the individual risk of recurrence in ER+ breast cancer patients. In this study, the prognostic utility of BCI to predict late recurrences was examined. Methods: FFPE tumor blocks were collected from patients who experienced a breast cancer recurrence up to unblinding of MA.17. Controls were matched 2:1 for age, tumor size, nodal status and prior chemotherapy, and were disease free for longer than cases. All cases were reviewed for standard histopathology and evaluated using the real-time RT-PCR BCI assay. Results: Patient characteristics for the case-control study were similar to that from the overall study. Characteristics for cases (N=83) and controls (N=166) were not significantly different except for treatment. A higher percentage of controls compared to cases tended to be categorized as low risk by BCI (58% vs 43%), while a lower percentage of controls than cases tended to be categorized as high risk by BCI (34% vs 24%). In univariate analysis, treatment, BCI, H:I and HOXB13, but not tumor grade or MGI, were significant predictors of late recurrence. After adjusting for standard variables (age, tumor grade and treatment), BCI (OR 2.37; P=0.03), H:I (OR 2.55; P=0.04) and HOXB13 (OR 1.35; P=0.02) remained significant predictors of recurrence. HOXB13 expression at diagnosis predicted patient benefit from extended endocrine therapy with letrozole. Conclusions: In this case-controlled study, the data demonstrate that BCI is a significant predictor of late recurrences in ER+ patients following 5-y of tamoxifen. The prognostic performance of BCI to predict late recurrences was largely dependent on HOXB13 expression. The integration of H:I and MGI within BCI provides prognostic utility for both early and late recurrences.

Abstract Purpose: Accurate tumor classification is essential for cancer management as patient outcomes improve with use of site- and subtype-specific therapies. Current clinicopathologic evaluation is varied in approach, yet standardized diagnoses are critical for determining therapy. While gene expression–based cancer classifiers may potentially meet this need, imperative to determining their application to patient care is validation in rigorously designed studies. Here, we examined the performance of a 92-gene molecular classifier in a large multi-institution cohort. Experimental Design: Case selection incorporated specimens from more than 50 subtypes, including a range of tumor grades, metastatic and primary tumors, and limited tissue samples. Formalin-fixed, paraffin-embedded tumors passed pathologist-adjudicated review between three institutions. Tumor classification using a 92-gene quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay was conducted on blinded tumor sections from 790 cases and compared with adjudicated diagnoses. Results: The 92-gene assay showed overall sensitivities of 87% for tumor type [95% confidence interval (CI), 84–89] and 82% for subtype (95% CI, 79–85). Analyses of metastatic tumors, high-grade tumors, or cases with limited tissue showed no decrease in comparative performance (P = 0.16, 0.58, and 0.16). High specificity (96%–100%) was showed for ruling in a primary tumor in organs commonly harboring metastases. The assay incorrectly excluded the adjudicated diagnosis in 5% of cases. Conclusions: The 92-gene assay showed strong performance for accurate molecular classification of a diverse set of tumor histologies. Results support potential use of the assay as a standardized molecular adjunct to routine clinicopathologic evaluation for tumor classification and primary site diagnosis. Clin Cancer Res; 18(14); 3952–60. ©2012 AACR.

Abstract Background. Third generation aromatase inhibitors (AIs) have been shown to be superior to tamoxifen in multiple randomized clinical trials and become the new standard of treatment for postmenopausal women with early or advanced endocrine-sensitive breast cancer. It is thus important to identify biomarkers predicting resistance to AIs so that alternative therapeutic options can be employed. A two gene expression index, HOXB13:IL17BR, and HOXB13 in particular, has been shown to be a negative predictor of clinical benefit from tamoxifen. It is unclear whether HOXB13:IL17BR or HOXB13 is also predictive of AI therapy.Methods. We performed a retrospective analysis of a phase II randomized neoadjuvant study of everolimus+letrozole vs. placebo+letrozole in patients with estrogen receptor-positive breast cancer. Total RNA was extracted from frozen tissue biopsies taken either prior to treatment or after 15 days of treatment. HOXB13:IL13BR and a molecular grade index (MGI) were measured in 107 pre-treatment samples and 111 samples after 15 days of treatment. Antiproliferative response as defined by a ln[Ki767] <1 at day 15 in the samples analyzed was correlated with these gene expression indices.Results. In the placebo+letrozole treatment arm, the antiproliferative response rate was 30% (14/47). Using a pre-specified cutpoint of 0.06, the response rate was 40% for low HOXB13:IL17BR patients, compared to 12% for high HOXB13:IL17BR patients (p=0.05). In the everolimus+letrozole arm, the antiproliferative response rate in the samples analyzed was 55% (33/60), and the response rates for low and high HOXB13:Il17BR patients were 70% and 37% (p=0.02), respectively. When examined separately, high HOXB13 expression was significantly associated with nonresponse to therapy (everolimus+letrozole arm, p=0.02; placebo+letrozle arm, p=0.03), but IL17BR was not (everolimus+letrozole arm, p=0.6; placebo+letrozle arm, p=0.88). As expected, we observed a significant correlation between MGI and Ki67 staining (Spearman r=0.67, p<0.0001).Conclusions. High HOXB13:IL17BR index and high HOXB13 expression may identify a possible subset of patients with estrogen receptor-positive tumor that could be less responsive to aromatase inhibitors such as letrozole. Furthermore, use of MGI may enable rapid assessment of antiproliferative response by fine needle aspiration. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2120.

Abstract Abstract #57 Background: ABCSG 8 is the only prospective trial examining the value of switching patients (pts) to an aromatase inhibitor after tamoxifen (Tam) in which randomization occurred prior to therapy. This trial demonstrated that 2 years (yrs) of Tam followed by 3 yrs of anastrozole (TAM to A) was superior to 5 yrs of Tam (Jakesz SABC 2005). Tam is metabolically activated by CYP2D6 to endoxifen and pts with impaired CYP2D6 metabolism have a higher risk of recurrence (Goetz JCO 2005). The HOXB13/IL17BR (H/I) index (Ma Cancer Cell 2004) is associated with Tam resistance while a 5-gene molecular grade index (MGI) distinguishes outcome in grade II tumors. H/I and MGI are complementary prognostic factors that define low (low MGI), intermediate (low H/I, high MGI) and high risk groups (high H/I and MGI) (Ma Clin Cancer Res 2008). We sought to validate these biomarkers in ABCSG Trial 8, and hypothesized that they may predict the benefit of sequencing TAM to A versus Tam alone.
 Methods: From 1996-2004, ABCSG 8 randomized 3,901 pts with ER positive breast cancer. The primary endpoint was event-free survival. Assuming 40% of pts had reduced CYP2D6 metabolism, we designed a nested case control study in which 110 Tam treated cases matched to 2 controls would yield 80% power to detect a relative risk of 2.3 for pts with reduced CYP2D6 metabolism. Additionally, we sought to perform an exploratory analysis of the benefit of switching from Tam to A in pts with impaired vs non-impaired CYP2D6 metabolism. DNA and RNA derived from paraffin embedded sections were used to genotype for CYP2D6 and to obtain H/I and MGI RT-PCR profiles.
 Findings: Thus far, CYP2D6 genotyping is complete in 345 pts corresponding to 53 cases/106 controls (Tam) and 62 cases/124 controls (Tam to A). DNA and RNA yields were excellent with a CYP2D6 genotype call rate of >95%. CYP2D6 allele frequencies were as expected: *3 (.01), *4, (.23), *6 (.01), *10 (.02), *17 (.00), and *41 (.10). 44% of pts had reduced CYP2D6 metabolism (at least one CYP2D6 null allele or intermediate metabolizer) and 8% were CYP2D6 poor metabolizers. For H/I and MGI, 340 pts were profiled with 64%, 20% and 16% in the low, intermediate, and high risk groups, respectively. Tissue sectioning/genotyping for additional cases/controls is ongoing.
 Discussion: This is the first retrospective analysis of a large Tam versus Tam to A trial to evaluate the association between 1) CYP2D6, HOXB13/IL17BR, and MGI with TAM treatment outcome and 2) the predictive benefit of these biomarkers in pts randomized to switch from Tam to AI versus Tam alone. Final results will be presented at the meeting. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 57.