Wang, Wei‐Lien

PURPOSE Human epidermal growth factor receptor 2 (HER2), a transmembrane receptor with kinase activity involved in cell signaling through the RAS pathway, is expressed in osteosarcoma (OST). Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate with a HER2-targeting monoclonal antibody, trastuzumab, linked to a topoisomerase I inhibitor. We report results of a phase II study of T-DXd in adolescents and young adults with HER2-positive relapsed, unresectable OST (ClinicalTrials.gov identifier: NCT04616560 ). METHODS Patients age 12-39 years with relapsed, unresectable OST were eligible for centrally evaluated HER2 expression screening by immunohistochemistry. Patients with >10% of OST cells with cytoplasmic or membranous HER2 expression of any intensity were eligible to receive T-DXd at 5.4 mg/kg intravenously once every 3 weeks for up to 2 years. The study used a 9 + 15 Simon's optimal two-stage design with a primary end point of event-free survival at 24 weeks. RESULTS Fifty patients were screened for HER2, and 41 met the inclusion criteria of 10% of OST cells having membranous or cytoplasmic HER2 expression. Nine eligible patients, two younger than 18 years, were enrolled and received T-DXd. With a single patient having more than 24 weeks of stable disease (SD) of the nine planned in the first stage, this study did not meet criteria to progress to stage II. The estimated SD rate at 24 weeks is 11.1%. The median (range) number of cycles of therapy was 2 (2-12). Grade 3 and 4 possibly related adverse events occurred in three of nine patients and included nausea, vomiting, tumor hemorrhage, cytopenias (n = 3), wound infection, and hypertension. CONCLUSION T-DXd did not demonstrate sufficient activity to expand enrollment to the planned second stage in patients with OST. No new safety signals were observed.

Abstract Purpose: We recently reported a 17.5% objective RECIST 1.1 response rate in a phase II study of pembrolizumab in patients with advanced sarcoma (SARC028). The majority of responses occurred in undifferentiated pleomorphic sarcoma (UPS) and dedifferentiated liposarcoma (DDLPS). We sought to determine whether we can identify immune features that correlate with clinical outcomes from tumor tissues obtained pre- and on-treatment. Patients and Methods: Pretreatment (n = 78) and 8-week on-treatment (n = 68) tumor biopsies were stained for PD-L1 and multiplex immunofluorescence panels. The density of positive cells was quantified to determine associations with anti–PD-1 response. Results: Patients that responded to pembrolizumab were more likely to have higher densities of activated T cells (CD8+ CD3+ PD-1+) and increased percentage of tumor-associated macrophages (TAM) expressing PD-L1 pre-treatment compared with non-responders. Pre-treatment tumors from responders also exhibited higher densities of effector memory cytotoxic T cells and regulatory T cells compared with non-responders. In addition, higher density of cytotoxic tumor-infiltrating T cells at baseline correlated with a better progression-free survival (PFS). Conclusions: We show that quantitative assessments of CD8+ CD3+ PD-1+ T cells, percentage of TAMs expressing PD-L1, and other T-cell densities correlate with sarcoma response to pembrolizumab and improved PFS. Our findings support that multiple cell types present at the start of treatment may enhance tumor regression following anti–PD-1 therapy in specific advanced sarcomas. Efforts to confirm the activity of pembrolizumab in an expansion cohort of patients with UPS/DDLPS are underway.

Abstract Background: The methylthioadenosine phosphorylase (MTAP) gene encodes an essential enzyme for the salvage pathway of adenosine synthesis and is frequently lost in different types of cancer including urothelial bladder carcinoma. Therefore, MTAP-deficient tumors are theoretically very sensitive to anti-folate agents such as pemetrexed that can effectively block the de novo pathway of adenosine synthesis and as a result, create a state of synthetic lethality. We thus hypothesize that tumor MTAP gene deficiency is associated with response to pemetrexed therapy in bladder cancer. Methods: In this study, we investigated MTAP gene deficiency rates in the TCGA database and confirmed MTAP protein loss by immunohistochemistry using a tumor tissue microarray containing bladder tumor tissues from 151 patients. We then performed in vitro and in vivo studies using MTAP-proficient and MTAP-deficient human bladder cancer cell lines. Functional loss of MTAP was verified with mass spectrometry, which detects its substrate methylthioadenosine (MTA) levels. We also correlated these pre-clinical studies with clinical response data on patients with metastatic bladder cancer treated with pemetrexed. Results: We identified that 27.8% bladder cancer patients have MTAP protein deficiency, which is consistent with exome sequencing data from the TCGA database. In vitro data showed MTAP-deficient human bladder cancer cell lines were significantly more sensitive to pemetrexed, with IC50 at least 40 times lower than MTAP-proficient cell lines. Subsequent knockdown of the MTAP gene in MTAP-proficient cell lines increased sensitivities to pemetrexed treatment. Consistent with the in vitro data, pemetrexed significantly inhibited the growth of MTAP-deficient or knockdown xenograft tumors but not MTAP-proficient tumors. Furthermore, 4 of 4 (100%) patients with MTAP-deficient metastatic bladder cancer responded to pemetrexed treatment, whereas only 1 of 11 (9%) patients with MTAP-proficient metastatic bladder cancer responded to pemetrexed. Conclusion: Our data demonstrate that MTAP gene loss in urothelial bladder cancer leads to a metabolic state of synthetic lethality with pemetrexed therapy. Therefore, bladder tumor MTAP loss should be further investigated as a potential biomarker for selection of patients for anti-folate therapy. Citation Format: Jianfeng Chen, Omar Alhalabi, Guangchun Han, Wei-Lien Wang, Xin-Qiao Zhang, Jian H. Song, Lidia P. Lopez, Sumankalai Ramachandran, Anh G. Hoang, Tyrone Garnett, Matthew Campbell, Amishi Y. Shah, Jennifer Wang, Arlene O. Siefker-Radtke, Shi-Ming Tu, Mark Titus, Charles C. Guo, Gary E. Gallick, Eleni Efstathiou, William F. Benedict, Christopher J. Logothetis, Thai H. Ho, Linghua Wang, Jianjun Gao. MTAP gene deficiency creates vulnerability to anti-folate therapy in urothelial bladder carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 385.

4521 Background: The MTAP gene encodes an essential enzyme for the salvage pathway of nucleotide synthesis and is frequently deleted in UBC. Anti-folate agents such as pemetrexed can effectively inhibit the de novo pathway of nucleotide synthesis and as a result, create a synthetic lethality in MTAP deficient UBC. We hypothesize that MTAP gene loss correlates with enhanced response to pemetrexed in UBC. Methods: We investigated MTAP gene deletion rates in the TCGA database and determined MTAP protein loss rates by immunohistochemistry (IHC) using a UBC tissue microarray (TMA) from 151 patients (pts). We then performed in vitro and in vivo studies using MTAP proficient and MTAP deficient bladder cancer cell lines. At the clinical level, we performed a retrospective analysis based on MTAP status of pts treated with pemetrexed as 2nd line at our institution between 2014 and 2018. We are now enrolling pts in a single-arm, open-label, phase II clinical trial (NCT02693717) with pemetrexed in pts with MTAP deficient UBC. Results: Per our TCGA and TMA IHC analyses, MTAP deficiency rate was 25.9% and 27.8%, respectively. MTAP deficient UBC cell lines were at least 40 times more sensitive to pemetrexed than MTAP proficient lines. Knockdown of the MTAP gene increased apoptosis rate by pemetrexed from approximately 20% to 60%. Additionally, pemetrexed significantly inhibited the growth of MTAP deficient or knockdown xenograft tumors but not MTAP proficient tumors. Retrospective analysis of 12 pts using RECIST criteria indicated that all 4 MTAP deficient UBC pts responded to pemetrexed whereas only 1 of 8 (12.5%) MTAP proficient UBC pts responded. Of the 6 pts enrolled on the clinical trial, 3 (50%) had complete or partial response, 1 had stable disease, 1 was not evaluable and 1 had disease progression. Combined analysis of the entire experience demonstrates a higher response rate in MTAP deficient UBC (70%) as compared to MTAP proficient UBC (12.5%). Conclusions: Our preclinical and clinical data demonstrate that MTAP loss in UBC leads to a state of synthetic lethality when treated with pemetrexed and should be further investigated as a novel biomarker to predict response to anti-folate agents.

Abstract Background Spinal chordomas, a subtype of primary spinal column malignancies (PSCM), are rare tumors with poor prognosis, and we have limited understanding of the molecular drivers of neoplasia. Methods Study design was a retrospective review of prospectively collected data with cross-sectional survival. Archived paraffin embedded pathologic specimens were collected for 133 patients from 6 centers within Europe and North America between 1987 and 2012. Tumor DNA was extracted and the human telomerase reverse transcriptase (hTERT) promoter was sequenced. The hTERT mutational status was correlated with overall survival (OS) and time to first local recurrence. Results Ninety-two chordomas, 26 chondrosarcomas, 7 osteosarcomas, 3 Ewing’s sarcomas, and 5 other malignant spinal tumors were analyzed. Median OS following surgery was 5.8 years (95% CI: 4.6 to 6.9) and median time to first local recurrence was 3.9 years (95% CI: 2.5 to 6.7). Eight chordomas, 2 chondrosarcomas, 1 Ewing’s sarcoma, and 1 other malignant spinal tumor harbored either a C228T or C250T mutation in the hTERT promoter. In the overall cohort, all patients with hTERT mutation were alive at 10 years postoperative with a median OS of 5.1 years (95% CI: 4.5 to 6.6) (P = 0.03). hTERT promoter mutation was observed in 8.7% of spinal chordomas, and 100% of chordoma patients harboring the mutation were alive at 10 years postoperative compared with 67% patients without the mutation (P = 0.05). Conclusions We report for the first time that hTERT promoter mutations C228T and C250T are present in approximately 8.7% of spinal chordomas. The presence of hTERT mutations conferred a survival benefit and could potentially be a valuable positive prognostic molecular marker in spinal chordomas.

BackgroundAppropriate use criteria (AUC) provide physicians guidance in test selection, and can affect health care delivery, reimbursement policy and physician decision‐making.ObjectivesThe American Society of Dermatopathology, with input from the American Academy of Dermatology and the College of American Pathologists, sought to develop AUC in dermatopathology.MethodsThe RAND/UCLA appropriateness methodology, which combines evidence‐based medicine, clinical experience and expert judgment, was used to develop AUC in dermatopathology.ResultsWith the number of ratings predetermined at 3, AUC were developed for 211 clinical scenarios involving 12 ancillary studies. Consensus was reached for 188 (89%) clinical scenarios, with 93 (44%) considered “usually appropriate,” 52 (25%) “rarely appropriate” and 43 (20%) “uncertain appropriateness.”LimitationsThe methodology requires a focus on appropriateness without comparison between tests and irrespective of cost.ConclusionsThe ultimate decision of when to order specific test rests with the physician and is one where the expected benefit exceeds the negative consequences. This publication outlines the recommendations of appropriateness—AUC for 12 tests used in dermatopathology. Importantly, these recommendations may change considering new evidence. Results deemed “uncertain appropriateness” and where consensus was not reached may benefit from further research.

While superficial (cutaneous/subcutaneous) solitary fibrous tumor (SFT) have been described, definitive diagnosis is difficult due to overlapping features with other tumors. We describe the largest series to date of superficial SFT. For inclusion, SFT had to arise in dermis or subcutis. Twenty-six cases were identified. Patients ranged from 16 to 80 years (mean, 47 y) with a marked female predominance (19 F; 7 M). Tumors involved the head (11), thigh (7), back (3), shoulder (2), upper arm (1), ankle (1), and great toe (1). Mean size was 2.9 cm (range, 1.0 to 7.0 cm). The majority (n=19) had typical histologic features (cellular SFT) with irregular fascicles of spindled cells, staghorn-like blood vessels, and variable amounts of collagen. Necrosis was evident in 3 cases (all <25%). Mitotic activity ranged from 0 to 10 mitotic figures/10 high-power fields (mean, 2 mitotic figures/10 high-power fields). Seventeen of the 18 were positive for STAT6, whereas 21/22 expressed CD34. All were low risk (23/23) by proposed criteria (Demicco and colleagues), including 2 cases with malignant histology. Three could not be risk stratified due to lack of information on tumor size. Follow-up, available on 7 cases, showed no recurrence/metastasis (mean follow-up, 100 mo; range, 2 to 241 mo). Cutaneous SFT are more common in women and most often involve the head. They are usually low risk by proposed criteria and appear to behave in an indolent manner, though larger studies are needed to confirm this. Recognition that SFT may present as a superficial mass will avoid misclassification as other CD34-positive neoplasms that frequently arise in the skin and subcutaneous tissue.

Nodular fasciitis is a benign self‐limited myofibroblastic neoplasm, which usually involves the upper extremities and trunk of young patients. These tumors have been shown to harbor a translocation involving the MYH9 and USP6 genes, leading to overexpression of the latter. We report seven cases of nodular fasciitis with cutaneous presentations. All cases involved the dermis, with six involving the superficial subcutis, and one auricular tumor extending into cartilage. All cases showed USP6 rearrangement by fluorescence in situ hybridization; in two of three cases, the characteristic MYH9‐USP6 fusion was shown by RT‐PCR. All patients underwent conservative resection. Nodular fasciitis is an uncommon mesenchymal neoplasm that can occasionally present in superficial locations and is sometimes mistaken for a malignant process. Molecular testing can be useful to distinguish this entity from other cutaneous spindle cell tumors.

AimsEpithelioid haemangioendothelioma (EHE) is a malignant vascular neoplasm. Subsets have been characterized previously by translocations resulting in either WWTR1–CAMTA1 or YAP1–TFE3 fusion. We sought to develop molecular and immunohistochemical (IHC) assays to aid in the diagnosis and characterization of EHE.Methods and resultsFifty‐two formalin‐fixed, paraffin‐embedded (FFPE) cases diagnosed between 2002 and 2014 were retrieved from the pathology files of our institutions. Reverse transcription–polymerase chain reaction (RT–PCR) assays were optimized to detect WWTR1–CAMTA1 and YAP1–TFE3 fusion transcripts in FFPE tissue and transcription factor E3 (TFE3) protein accumulation was examined by immunohistochemistry (IHC). RNA was extracted from 33 adequate samples, with more recent cases providing a greater yield of high quality RNA. Fourteen of 18 informative cases were positive for WWTR1–CAMTA1 fusion transcripts, four of which showed higher‐grade cytological features termed by some as ‘malignant EHE’. Novel in‐frame fusion transcripts were identified in four cases by direct sequencing. IHC revealed variable nuclear TFE3 staining in six of 17 cases; three with patchy staining showed WWTR1–CAMTA1 fusion. One of 18 informative cases was positive for YAP1–TFE3 fusion and showed strong nuclear TFE3 staining by IHC.ConclusionsThis study confirms the high incidence of WWTR1–CAMTA1 and YAP1–TFE3 rearrangements in EHE and indicates that the staining pattern for TFE3 IHC is critical for specificity.