Clonal chromosomal abnormalities appearing in Philadelphia chromosome-negative metaphases during CML treatment.

Clonal chromosomal abnormalities in Philadelphia chromosome-negative (CCA/Ph-) metaphases emerge as patients with chronic phase chronic myeloid leukemia (CP-CML) are treated with tyrosine kinase inhibitors (TKIs). We assessed the characteristics and prognostic impact of 598 patients with CP-CML treated on clinical trials with various TKIs. CCA/Ph- occurred in 58 patients (10%); the most common were -Y in 25 (43%) and trisomy 8 in 7 patients (12%). Response to TKI therapy was similar for patients with CCA/Ph- and those without additional chromosomal abnormalities (ACAs). We further categorized CCA/Ph- into those in which -Y was the only clonal abnormality, and all others. We found that patients with non -Y CCA/Ph- had worse failure-free survival (FFS), event-free survival (EFS), transformation-free survival (TFS), and overall survival (OS) compared with those without ACAs with the following 5-year rates: FFS (52% vs 70%, P = .02), EFS (68% vs 86%, P = .02), TFS (76% vs 94%, P < .01), and OS (79% vs 94%, P = .03). In a multivariate analysis, non -Y CCA/Ph- increased the risk of transformation or death when baseline characteristics were considered with a hazard ratio of 2.81 (95% confidence interval, 1.15-6.89; P = .02). However, this prognostic impact was not statistically significant when achieving BCR-ABL <10% at 3 months was included in the analysis. In conclusion, non -Y CCA/Ph- are associated with decreased survival when emerging in patients with chronic-phase CML across various TKIs. This trial was registered at www.clinicaltrials.gov as #NCT00048672, #NCT00038649, and #NCT00050531 (imatinib); #NCT00254423 (dasatinib); #NCT00129740 (nilotinib); and NCT01570868 (ponatinib).

Atypical chronic myeloid leukemia is clinically distinct from unclassifiable myelodysplastic/myeloproliferative neoplasms.

Atypical chronic myeloid leukemia (aCML) is a rare subtype of myelodysplastic/myeloproliferative neoplasm (MDS/MPN) largely defined morphologically. It is, unclear, however, whether aCML-associated features are distinctive enough to allow its separation from unclassifiable MDS/MPN (MDS/MPN-U). To study these 2 rare entities, 134 patient archives were collected from 7 large medical centers, of which 65 (49%) cases were further classified as aCML and the remaining 69 (51%) as MDS/MPN-U. Distinctively, aCML was associated with many adverse features and an inferior overall survival (12.4 vs 21.8 months, P = .004) and AML-free survival (11.2 vs 18.9 months, P = .003). The aCML defining features of leukocytosis and circulating myeloid precursors, but not dysgranulopoiesis, were independent negative predictors. Other factors, such as lactate dehydrogenase, circulating myeloblasts, platelets, and cytogenetics could further stratify MDS/MPN-U but not aCML patient risks. aCML appeared to have more mutated RAS (7/20 [35%] vs 4/29 [14%]) and less JAK2p.V617F (3/42 [7%] vs 10/52 [19%]), but was not statistically significant. Somatic CSF3R T618I (0/54) and CALR (0/30) mutations were not detected either in aCML or MDS/MPN-U. In conclusion, within MDS/MPN, the World Health Organization 2008 criteria for aCML identify a subgroup of patients with features clearly distinct from MDS/MPN-U. The MDS/MPN-U category is heterogeneous, and patient risk can be further stratified by a number of clinicopathological parameters.

Primary intracranial soft tissue sarcomas in children, adolescents, and young adults: single institution experience and review of the literature.

There is a paucity of literature reporting the outcome of intracranial sarcomas (IS) in children, adolescents, and young adults (CAYA). A multimodal therapeutic approach is commonly used, with no well-established treatment consensus. We conducted a retrospective review of CAYA with IS, treated at our institution, to determine their clinical findings, treatments, and outcomes. Immunohistochemistry (PDGFRA and EGFR) and DNA sequencing were performed on 5 tumor samples. A literature review of IS was also conducted. We reviewed 13 patients (median age, 7 years) with a primary diagnosis of IS between 1990 and 2015. Diagnoses included unclassified sarcoma (n = 9), chondrosarcoma (n = 2), and rhabdomyosarcoma (n = 2). Five patients underwent upfront gross total resection (GTR) of the tumor. The 5-drug regimen (vincristine, doxorubicin, cyclophosphamide, etoposide, and ifosfamide) was the most common treatment used. Nine patients died due to progression or recurrence (n = 8) or secondary malignancy (n = 1). The median follow-up period of the 4 surviving patients was 1.69 years (range 1.44-5.17 years). The 5-year progression-free survival and overall survival rates were 21 and 44 %, respectively. BRAF, TP53, KRAS, KIT, ERBB2, MET, RET, ATM, and EGFR mutations were detected in 4 of the 5 tissue samples. All 5 samples were immunopositive for PDGFRA, and only 2 were positive for EGFR. IS remain a therapeutic challenge due to high progression and recurrence rates. Collaborative multi-institutional studies are warranted to delineate a treatment consensus and investigate tumor biology to improve the disease outcome.

TP53 overexpression is an independent adverse prognostic factor in de novo myelodysplastic syndromes with fibrosis.

Bone marrow (BM) fibrosis is associated with poor prognosis in patients with de novo myelodysplastic syndromes (MDS). TP53 mutations and TP53 (p53) overexpression in MDS are also associated with poor patient outcomes. The prevalence and significance of TP53 mutations and TP53 overexpression in MDS with fibrosis are unknown. We studied 67 patients with de novo MDS demonstrating moderate to severe reticulin fibrosis (MDS-F). Expression of TP53 was evaluated in BM core biopsy specimens using dual-colour CD34/TP53 immunohistochemistry with computer-assisted image analysis. Mutation analysis was performed using next-generation sequencing, or Sanger sequencing methods. TP53 mutations were present in 47·1% of cases. TP53 mutation was significantly associated with TP53 expression (P = 0·0294). High levels of TP53 expression (3 +  in ≥10% cells) were associated with higher BM blast counts (P = 0·0149); alterations of chromosomes 5 (P = 0·0009) or 7 (P = 0·0141); complex karyotype (P = 0·0002); high- and very-high risk IPSS-R groups (P = 0·009); and TP53 mutations (P = 0·0003). High TP53 expression independently predicted shorter overall survival (OS) by multivariate analysis (P = <0·001). Expression of TP53 by CD34-positive cells was associated with shorter OS and leukaemia-free survival (P = 0·0428). TP53 overexpression is a predictor of poor outcome in patients with MDS-F.

Improvement in clinical outcome of FLT3 ITD mutated acute myeloid leukemia patients over the last one and a half decade.

AML with FLT3 ITD mutations are associated with poor outcome. We reviewed outcomes of patients with FLT3 ITD mutated AML to investigate trends over time. We analyzed 224 AML patients (excluding patients with core binding factor and acute promyelocytic leukemia) referred to our institution between 2000 and 2014. Patients were divided into five cohorts by era: 2000-2002 (Era 1, n = 19), 2003-2005 (Era 2, n = 41), 2006-2008 (Era 3, n = 53), 2009-2011 (Era 4, n = 55), and 2012-2014 (Era 5, n = 56) to analyze differences in outcome. The baseline characteristics were not statistically different across Eras. The response rate (CR/CRp) from Era 1-5 was 68%, 49%, 72%, 73%, and 75%, respectively. The overall response rate (all Eras) with chemotherapy alone versus chemotherapy plus FLT3 inhibitor was 67% and 72.5%, respectively (P = 0.4). The median time to relapse was 6, 3.6, 7.9, 8.1 months and not reached from Eras 1 through 5, respectively (P = 0.001). The median OS has improved: 9.6, 7.6, 14.4, 15.7, and 17.8 month from Eras 1-5, respectively (P = <0.001). Stem cell transplant as a time-dependent variable, showed better OS in the univariate analysis (HR: 0.57, 95% CI: 0.39-0.84, P = 0.004) but did not retained its significance in multivariate analysis (HR: 0.75, 95% CI: 0.50-1.13, P = 0.16). Our data suggest improvement in outcome of FLT3 ITD mutated AML patients over the last 15 years. This is probably due to improvement in treatment strategies, including but not limited to integration of FLT3 inhibitors and increased use of SCT.

HCVAD plus imatinib or dasatinib in lymphoid blastic phase chronic myeloid leukemia.

BACKGROUND: Chronic myeloid leukemia (CML) may progress to blast phase (BP) at the rate of 1% to 1.5% per year. With the use of single-agent tyrosine kinase inhibitors, median overall survival ranges between 7 and 11 months. METHODS: The outcome was analyzed for 42 patients with lymphoid BP-CML who were treated with hyperfractionated cyclophosphamide, vincristine, Adriamycin, dexamethasone (HCVAD) plus imatinib or dasatinib. RESULTS: Complete hematological response was achieved in 90% of patients, complete cytogenetic remission in 58%, and complete molecular remission in 25%. Flow cytometry minimal residual disease negativity was achieved by 42% of evaluable patients after induction. Eighteen patients received allogeneic stem cell transplant (SCT) while in first complete hematological response. Median remission duration was 14 months and was longer among SCT recipients (P = .01) on multivariate analysis. Median overall survival was 17 months (range, 7-27 months) and was longer among SCT recipients (P < .001) and patients treated with dasatinib (P = .07) on multivariate analysis. Although a high rate of hematologic toxicity (100%) and infectious complications (59%) were observed, the related rate of treatment discontinuation was low (7% and 9%, respectively). CONCLUSIONS: HCVAD combined with tyrosine kinase inhibitors is an effective regimen for the management of BP-CML, particularly when followed by allogeneic SCT.

B acute lymphoblastic leukemia with t(14;19)(q32;p13.1) involving IGH/EPOR: a clinically aggressive subset of disease.

B acute lymphoblastic leukemia (B-ALL) with t(14;19)(q32;p13.1), in which IGH and EPOR are juxtaposed, has been reported rarely. We describe the clinicopathological features of six patients, three men and three women, with a median age of 39 years. Initial and follow-up bone marrow samples were examined from each patient. The clinical, morphologic, and immunophenotypic results were compared with data obtained from conventional cytogenetic analysis and by using home-brew fluorescence in situ hybridization (FISH) probes for IGH at 14q32 and EPOR at 19p13.1. The bone marrow specimens were hypercellular (median 90%; range 80-100%), with a median blast count of 90% (range 60-93%). Immunophenotypic analysis performed by flow cytometry demonstrated a stable, precursor B-cell immunophenotype. The t(14;19)(q32;p13.1) was present in all cases with morphologic evidence of disease. The translocation was stable and appeared morphologically subtle on conventional karyotypic analysis. Detection was facilitated using FISH, which confirmed IGH/EPOR rearrangement in all cases. All patients received aggressive multiagent chemotherapy as part of a variety of regimens. Four of six patients achieved an initial complete remission, but all relapsed. At last follow-up, five of six patients had died of disease (median survival, 12 months after diagnosis). We conclude that B-ALL associated with t(14;19)(q32;p13.1) is a distinctive form of disease that is associated with younger patient age and an aggressive clinical course.

Assessment at 6 months may be warranted for patients with chronic myeloid leukemia with no major cytogenetic response at 3 months.

Response to tyrosine kinase inhibitors at three months is a predictor for long-term outcome in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors. We analyzed 456 newly diagnosed chronic myeloid leukemia patients treated with tyrosine kinase inhibitors to determine their outcome based on their response at six months. Forty-four (10%) patients did not achieve major cytogenetic response at three months: 18 of 67 (27%) patients treated with imatinib 400; 18 of 196 (9%) with imatinib 800; and 8 of 193 (4%) with 2nd generation tyrosine kinase inhibitors. Among them, 19 (43%) achieved major cytogenetic response at six months and subsequently had an overall outcome similar to the patients who achieved a major cytogenetic response at three months. In conclusion, the response to tyrosine kinase inhibitors at three months is a static, one-time measure. Assessing the response at six months of patients with poor response at three months may provide a better predictor for long-term outcome.

Significance of deeper molecular responses in patients with chronic myeloid leukemia in early chronic phase treated with tyrosine kinase inhibitors.

Most patients with chronic myeloid leukemia (CML) in chronic phase (CP) treated with tyrosine kinase inhibitors (TKI) achieve complete cytogenetic response (CCyR). An increasing number of patients also achieve deep molecular responses (MR). We determined the frequency and significance of deep MR after TKI therapy for CML in CP. MR included: major molecular response (MMR), MR4, MR4.5, and undetectable transcripts (UND), i.e., BCR-ABL/ABL of ≤0.1, ≤0.01, ≤0.0032%, and undetectable transcripts, respectively. Four hundred eighty-three patients received imatinib 400 mg/day (IM400, 71, July 2000 to April 2001), imatinib 800 mg/day (IM800, 204, June 2001 to July 2005), nilotinib (106, July 2005 to date), or dasatinib (102, November 2005 to date). UND rates at 36 months were 18.1, 30.6, 29.2, and 28.6%, respectively. Patients achieving UND have superior transformation-free survival (TFS) and overall survival (OS) versus those obtaining ≤MMR, but not other MR levels. At the 18- and 24-month landmark analysis, patients achieving UND have no advantage in TFS and OS compared to those achieving a lesser degree of MR. Among patients achieving MR4.5, those who maintain it for ≥2 years (susMR4·5) have no additional benefit in TFS or OS. Most patients with early CP CML receiving TKI achieve MMR. BCR-ABL transcripts become undetectable in a significant fraction of them. Deeper MR at 18 or 24 months are not associated with a benefit in TFS or OS. Furthermore, achieving susMR4·5 does not appear to further reduce the risk of transformation or death.

Prognostic impact of RAS mutations in patients with myelodysplastic syndrome.

RAS is an oncogene frequently mutated in human cancer. RAS mutations have been reported in 10-15% of cases of acute myeloid leukemia (AML) but they appear to be less frequent among patients with myelodysplastic syndrome (MDS). The impact of RAS mutations in patients with MDS is unclear. We conducted a retrospective study in 1,067 patients with newly diagnosed MDS for whom RAS mutational analysis was available. Overall, 4% of patients carried mutant RAS alleles. Notably, FLT3 mutations, which were found in 2% of patients, were mutually exclusive with RAS mutations. Patients with RAS mutations had a higher white blood cell count as well as bone marrow blasts compared with patients carrying wild-type RAS. However, no differences were observed between both groups regarding the risk of AML transformation (9% vs. 7%) and overall survival (395 days vs. 500 days, P = 0.057). In summary, RAS mutations are infrequent in patients with MDS and do not appear to negatively impact their outcome.

FLT3 mutations in myelodysplastic syndrome and chronic myelomonocytic leukemia.

FMS-like tyrosine kinase III (FLT3) mutations occur in one-third of acute myeloid leukemia (AML) patients and predict poor outcome. The incidence and impact of FLT3 in myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) is unknown. We conducted a retrospective review to identify WHO MDS and CMML patients with FLT3 mutations at diagnosis. A total of 2,119 patients with MDS and 466 patients with CMML were evaluated at MD Anderson between 1997 and 2010. Of these, FLT3 mutation analysis was performed on 1,232 (58%) MDS and 302 (65%) CMML patients. FLT3 mutations were identified in 12 (0.95%) MDS patients: 9 (75%) had FLT3-ITD mutation and 3 had FLT3-tyrosine kinase domain (TKD) mutation. MDS patients with FLT3 mutations were younger (P = 0.02) and presented as RAEB (P = 0.03) more frequently. Median overall survival (OS) for FLT3-mutated MDS patients was 19.0 months versus 16.4 months for FLT3-nonmutated MDS patients (P = 0.08). FLT3 mutations were identified in 13 (4.3%) CMML patients: 8 had FLT3-ITD mutation and 5 had FLT3-TKD mutation. There were no significant differences in demographic and disease characteristics among CMML patients with and without FLT3 mutations. Median OS for FLT3-mutated CMML patients was 10.8 months versus 21.3 months for FLT3-nonmutated CMML patients (P = 0.12). FLT3 occurs in MDS and CMML at a lower frequency than AML and does not predict poor outcome.

Novel Clinical Tool to Estimate Risk of False-Negative KRAS Mutations in Circulating Tumor DNA Testing.

PURPOSE: In metastatic colorectal cancer, the detection of RAS mutations by circulating tumor DNA (ctDNA) has emerged as a valid and noninvasive alternative approach to determining RAS status. However, some RAS mutations may be missed, that is, false negatives can occur, possibly compromising important treatment decisions. We propose a statistical model to assess the probability of false negatives when performing ctDNA testing for RAS. METHODS: Cohorts of 172 subjects with tissue and multipanel ctDNA testing from MD Anderson Cancer Center and 146 subjects from Massachusetts General Hospital were collected. We developed a Bayesian model that uses observed frequencies of reference mutations (the maximum of APC and TP53) to provide information about the probability of KRAS false negatives. The model was alternatively trained on one cohort and tested on the other. All data were collected on Guardant assays. RESULTS: The model suggests that negative KRAS findings are believable when the maximum of APC and TP53 frequencies is at least 8% (corresponding posterior probability of false negative <5%). Validation studies demonstrated the ability of our tool to discriminate between false-negative and true-negative subjects. Simulations further confirmed the utility of the proposed approach. CONCLUSION: We suggest clinicians use the tool to more precisely quantify KRAS false-negative ctDNA results when at least one of the reference mutations (APC, TP53) is observed; usage may be especially important for subjects with a maximum reference frequency of <8%. Extension of the methodology to predict false negatives of other genes is possible. Additional reference genes can also be considered. Use of personal training data sets is supported. An open-source R Shiny application is available for public use.

Impact of numerical variation in FMS-like tyrosine kinase receptor 3 internal tandem duplications on clinical outcome in normal karyotype acute myelogenous leukemia.

BACKGROUND: The impact of single versus multiple fms-like tyrosine kinase receptor 3 internal tandem duplication (FLT3-ITD) mutations on the clinical outcome of patients with acute myelogenous leukemia has not been well studied, and particularly has not been investigated while simultaneously accounting for the quantitative mutation burden. METHODS: The authors conducted a multivariate analysis of overall survival, event-free survival, and complete remission duration, including numeric variation (single vs multiple) and quantitative mutant burden of FLT3-ITD as variables among other clinically relevant factors. RESULTS: An analysis of a cohort of 1043 patients with AML demonstrated that, among patients with normal-karyotype acute myelogenous leukemia and FLT3-ITD mutation, overall survival and event-free survival were not affected by the number of FLT3-ITD mutations, but complete remission duration was significantly longer in patients who had multiple FLT3-ITD mutations (median, 86 weeks vs 34 weeks; P = .03). CONCLUSIONS: The current results indicated that time-to-event analyses of patients with normal-karyotype acute myelogenous leukemia and FLT3-ITD mutation should take into account the number of mutations and the mutant burden, among other factors.

Clinical and proteomic characterization of acute myeloid leukemia with mutated RAS.

BACKGROUND: Activating mutations in RAS are frequently present in patients with acute myeloid leukemia (AML), but their overall prognostic impact is not clear. METHODS: A retrospective analysis was performed to establish the clinical characteristics of patients with RAS-mutated (RAS(mut) ) AML, to analyze their outcome by therapy, and to describe the proteomic profile of RAS(mut) compared with wild-type RAS (RAS(WT) ) AML. RESULTS: Of 609 patients with newly diagnosed AML, 11% had RAS(mut) . Compared with RAS(WT) , patients with RAS(mut) AML were younger (median age, 54 years vs 63 years; P = .001), had a higher white blood cell count (16K mm(-3) vs 4K mm(-3) ; P < 0.001) and bone marrow blast percentage (56% vs 42%; P = .01) at diagnosis, and were less likely to have an antecedent hematologic disorder (36% vs 50%; P = .03). The inv(16) karyotype was overrepresented in patients with RAS(mut) and the -5 and/or -7 karyotype was underrepresented. RAS mutations were found to have no prognostic impact on overall survival or disease-free survival overall or within cytogenetic subgroups. There was a suggestion that patients with RAS(mut) benefited from cytarabine (AraC)-based therapy. Proteomic analysis revealed simultaneous upregulation of the RAS-Raf-MAP kinase and phosphoinositide 3-kinase (PI3K) signaling pathways in patients with RAS(mut) . CONCLUSIONS: RAS mutations in AML may delineate a subset of patients who benefit from AraC-based therapy and who may be amenable to treatment with inhibitors of RAS and PI3K signaling pathways.

Activating internal tandem duplication mutations of the fms-like tyrosine kinase-3 (FLT3-ITD) at complete response and relapse in patients with acute myeloid leukemia.

FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutations are among the most frequent molecular aberrations in patients with acute myeloid leukemia. We retrospectively analyzed 324 patients with acute myeloid leukemia treated with front-line induction chemotherapy between October 2004 and March 2010. Fifty-six patients had FLT3-ITD mutation at diagnosis. Fifty-one (91%) patients with FLT3-ITD achieved complete remission. Thirteen patients had FLT3 analysis at complete remission. None had FLT3-ITD. Twenty-five (49%) patients with FLT3-ITD relapsed. Of these, 13 (52%) had FLT3-ITD at relapse (3 negative and 9 not done). Among the 201 patients without FLT3-ITD at diagnosis who achieved complete remission, 77 (38%) relapsed among whom 8 (10%) patients acquired FLT3-ITD clone. We conclude that FLT3-ITD mutations are unstable at follow up and may occur for the first time at relapse. Therefore, FLT3-ITD is not a reliable marker for minimal residual disease in acute myeloid leukemia.

Trichilemmomas show loss of PTEN in Cowden syndrome but only rarely in sporadic tumors.

BACKGROUND: Trichilemmoma (TL) can occur as a solitary sporadic lesion usually on the face or as multiple facial lesions almost invariably associated with Cowden syndrome (CS). CS is a multisystem disorder caused by a germline inactivating mutation in PTEN (10q23.31), a tumor suppressor gene. We sought to identify PTEN loss by immunohistochemistry (IHC) in sporadic and CS-associated TL to determine whether IHC is a useful tool to assess an individual for CS. METHODS: Six TL biopsies associated with CS and 33 biopsies without CS were retrieved. IHC for PTEN was performed. RESULTS were scored as positive (reactivity in TL cells) or negative (no reactivity in TL cells); normal squamous epithelium and vascular endothelium served as internal positive controls. RESULTS: Complete PTEN loss was noted in 5/6 (83%) CS-associated TL and 1/33 (3%) sporadic (non-CS) TL. CONCLUSION: Demonstration of complete PTEN loss in TL by IHC is strongly suggestive of association with CS, but retention of PTEN staining does not entirely exclude CS. Therefore, PTEN IHC in TLs may be helpful in screening TL for association with CS, but should be used in context with other established clinical criteria, and possibly germline PTEN genotyping to confirm a diagnosis of CS.

Clinical Testing for Mismatch Repair in Neoplasms Using Multiple Laboratory Methods.

Background: A deficiency in DNA mismatch repair function in neoplasms can be assessed by an immunohistochemical (IHC) analysis of the deficiency/loss of the mismatch repair proteins (dMMR) or by PCR-based methods to assess high microsatellite instability (MSI-H). In some cases, however, there is a discrepancy between the IHC and MSI analyses. Several studies have addressed the issue of discrepancy between IHC and MSI deficiency assessment, but there are limited studies that also incorporate genetic/epigenetic alterations. Methods: In this single-institution retrospective chart-review study, we reviewed 706 neoplasms assessed between 2015 and 2021. All eligible neoplasms were assessed by IHC testing, MSI analysis by PCR-based assay, and tumor-normal paired next-generation sequencing (NGS) analysis. Eighty percent of neoplasms with MLH1 protein loss had a concurrent MLH1 promoter methylation analysis. Mutation data for MMR genes, IHC, MSI analysis, and tumor histology were correlated with each other. Results: Fifty-eight (8.2%) of 706 neoplasms had MSI-H by PCR and/or dMMR by IHC. Of the 706 analyzed neoplasms, 688 neoplasms (98%) had concordant results: MSI-H/dMMR (n = 44), microsatellite-stable (MSS)/proficient MMR (pMMR) (n = 625), and MSI-Low (L)/pMMR (n = 19). Of the remaining 18 neoplasms, 9 had a major discordance: MSS/loss of MSH2 and MSH6 (n = 3), MSS/loss of MSH6 (n = 2), MSS/Loss of MLH1 and PMS2 (n = 1), and MSI-High/pMMR (n = 3). In total, 57% of cases with dMMR and 61% of cases with MSI-H had a null mutation of an MMR gene mutation (or methylation of the MLH1 promoter), whereas this figure was 1% for neoplasms with a normal IHC or MSI pattern (p < 0.001). Among 9 cases with major discordance between MSI and IHC, only 3 cases (33%) had an underlying genetic/epigenetic etiology, whereas 37 (76%) of 49 cases with MSI-H and/or dMMR and without major discordance had an underlying genetic abnormality (p = 0.02). Discussion: For most neoplasms, IHC and PCR-based MSI testing results are concordant. In addition, an underlying genetic abnormality (a null mutation of an MMR gene or MLH1 promoter methylation) was attributable to dMMR and/or MSI-H findings. For neoplasms with major discordance in IHC and MSI testing, the addition and integration of NGS results and MLH1 promoter methylation analyses can be beneficial for resolving borderline cases, thereby facilitating patient management.

Bintrafusp alfa, an anti-PD-L1:TGF-ß trap fusion protein, in patients with ctDNA-positive, liver-limited metastatic colorectal cancer.

Background: Identification of circulating tumor DNA (ctDNA) following curative intent therapies is a surrogate for microscopic residual disease for patients with metastatic colorectal cancer (mCRC). Preclinically, in micrometastatic microsatellite stable (MSS) CRC, increased TGF-ß signaling results in exclusion of anti-tumor cytotoxic T cells from the tumor microenvironment. Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domain of the TGF-ßRII receptor ("TGF-ß trap") and anti-PD-L1 antibody. Methods: Patients with liver-limited, MSS mCRC and with detected ctDNA after complete resection of all known tumors and standard-of-care therapy were treated with 1200 mg of BA intravenously every 14 days for six doses. The primary endpoint was ctDNA clearance. Radiographic characteristics at recurrence were compared using independent t-tests to historical data from a similar cohort of patients with liver-limited mCRC who underwent observation. Results: Only 4 of 15 planned patients received BA before the study was stopped early for loss of equipoise. There was no grade ≥3 AE. None of the patients cleared ctDNA. All patients developed radiographic recurrence by the first planned restaging. Although not detectable at prior to treatment, TGFß3 was found in circulation in all patients at cycle 2 day 1. Compared to a historical cohort, patients administered BA developed more metastases (15 versus 2, p=0.005) and greater tumor volumes (9 cm vs 2 cm, p=0.05). Conclusions: Treatment with BA in patients with ctDNA-detected, liver-limited mCRC did not clear ctDNA and was associated with large-volume recurrence, highlighting the potential context-specific complexity of dual TGF-ß and PD-L1 inhibition.