Routbort, Mark J.

AbstractBackgroundBlood involvement by mycosis fungoides (MF)/Sézary syndrome (SS) influences prognosis and therapeutic decisions. MF/SS blood stage is currently determined by absolute CD4 + CD26− or CD4 + CD7‐cell counts, which quantification method may overestimate MF/SS by including CD26− or CD7− normal CD4+ T‐cells, or underestimate disease burden when MF/SS cells show incomplete loss of CD26 and/or CD7. Recently, through the standardization effort led by the International Clinical Cytometry Society (ICCS), recommendation was made to quantify MF/SS by enumerating immunophenotypically aberrant CD4+ T‐cells, rather than CD26− or CD7− in isolation.MethodsWe compared these two quantitation methods in 309 MF/SS patients who had blood samples analyzed by flow cytometry immunophenotyping (FCI) over a 1‐year period.ResultsUsing the European Organization of Research and Treatment of Cancer (EORTC)/International Society for Cutaneous Lymphomas (ISCL) criteria, 221 (71.5%) patients had a blood stage corresponding to B0, 57 (18.4%) to B1, and 31 (10%) to B2. By FCI analysis, a total of 62 patients (20.0%) were found positive for MF/SS. Among EORTC B0 patients, 11/221 (5%) were positive by FCI (false negatives), and among EORTC Stage B1 patients, 35/57 (61%) were negative by FCI (false positives). Regarding patients positive for MF/SS cells by FCI, there was an overall excellent correlation (r = .999, p < .001) between the EORTC/ISCL method and FCI method; however, four (6.5%) patients would have an altered B stage between B0 and B1.ConclusionThe MF/SS cell quantification method using immunophenotypic aberrancies, as recommended by the ICCS, allows to distinguish MF/SS cells from background benign T‐cells and enables for more accurate staging, especially among patients currently being considered to have B0 and B1 stage diseases.

e13681 Background: Cell-free tumor DNA or circulating tumor DNA tests are increasingly used in clinical care to detect somatic mutations from solid tumors. However, data on laboratory performance characteristics using standardized samples is limited. Methods: Well-characterized reference materials were used for the College of American Pathologists (CAP) cell-free tumor DNA proficiency testing surveys, which consisted of stabilized DNA fragmented to simulate cell-free DNA in a synthetic plasma matrix. For the 2018A, 2018B, 2019A and 2019B surveys, laboratories tested for hotspot mutations (single and dinucleotide sequence changes) in EGFR, BRAF, KRAS, NRAS, and IDH1 at variant allele fractions ranging from 0.1% - 1.0%. As per CAP proficiency testing standards, results were scored according to the known mutation(s) engineered at designated variant allele fractions in each PT sample. Nine laboratories were excluded from analysis because they provided incomplete results. Statistical significance was calculated using a multivariate logistic regression model. Results: In 2018 and 2019, 101 laboratories submitted survey results for at least one proficiency testing mailing. There were 5088 total proficiency testing responses for EGFR, BRAF, KRAS, NRAS, and IDH1 mutations across 12 different samples. For the 3585 responses submitted for BRAF, KRAS, NRAS, and IDH1, sensitivity ranged from 94.6 – 100%, while specificity exceeded 99%. There were no significant differences in performance between analytical methodologies for BRAF, KRAS, NRAS, and IDH1 mutations. Performance characteristics for EGFR mutations among the 1503 responses showed a combined sensitivity of 87.1% and specificity of 98.7%. For laboratories detecting mutations in EGFR, next-generation sequencing methods exhibited a sensitivity (true positivity) of 95.7% while the sensitivity of non-NGS methods was lower at 81.7% ( P= 0.02). Conclusions: These findings demonstrate high sensitivity and specificity for clinical laboratories performing cell-free tumor DNA tests. For EGFR mutations, NGS outperformed non-NGS methods. These data suggest excellent overall agreement among laboratories performing clinical cell-free tumor DNA tests. Further investigation across variant allele fractions and additional variant types is warranted.

Key Points The ClinGen MM-VCEP has specified RUNX1-specific curation rules to address gene function, gene-specific domains, and phenotypic criteria. RUNX1-specific criteria resulted in a reduction in CONF and VUS variants by 33%, emphasizing the need for expert variant curation.

AbstractObjectivesIn the 2008 World Health Organization classification, cases of acute myeloid leukemia (AML) and myelodysplastic syndrome that arise after chemotherapy or radiation therapy for a primary neoplasm are considered together as therapy-related myeloid neoplasms (TR-MNs). This concept, however, is not universally accepted since there are confounding variables in attributing myeloid neoplasms to earlier therapies.MethodsCases in session 6 of the 2013 Workshop of the Society for Hematopathology/European Association for Haematopathology illustrated myeloid neoplasms thought likely to be TR-MNs, and discussed the differences and biologic similarities with de novo myeloid neoplasms.ResultsWe reviewed data showing that diagnosis of TR-MN alters patient outcome only in specific subsets. The session also included examples of therapy-related AML with recurrent genetic abnormalities, such as t(15;17), inv(16), and t(8;21), and reports were highlighted showing that patients with these neoplasms have clinical outcomes similar to patients with their de novo counterparts.ConclusionsThe study of TR-MNs will likely provide insight into the pathogenesis of de novo myeloid disease and may explain why some patients with cancer develop TR-MN and evidently have a higher genetic susceptibility, whereas most patients treated with the same agents do not. These studies will also result in critical reappraisal of current concepts related to TR-MNs.