Behdad, Amir

3036 Background: The presence of HER2 expressing (HER2+) circulating tumor cells (CTCs) occurs often in metastatic breast cancer (MBC) patients (pts). We have previously showed that the ratio among CTCs expressing high level of HER2 and the total number of HER2+ CTCs (circulating HER2 ratio, cHer2 ratio) has a prognostic role in MBC patients. Here we further investigate the role of the cHER2 ratio in the process of metastatic spread. Methods: Under IRB-approved study we prospectively analyzed blood samples of patients with MBC enrolled before starting a new line of therapy. Samples were collected from pts treated at Northwestern University (Chicago, IL) between 2016 and 2020. CTCs were enumerated through CellSearch (Menarini Silicon Biosystems, Bologna, Italy) and characterized for HER2 expression using the CellSearch CXC Kit. HER2+ CTCs were divided in 3 different categories (1+,2+,3+) leaning on fluorescence intensity. Pts with <5 CTCs (stage IV indolent) were excluded from the analysis. The cHER2 ratio, defined as the sum of 2+ CTCs and 3+ CTCs divided by the total number of HER2+ CTCs, was used to split the remaining pts in 2 different cohorts: cHER2 ratio high (> 0.75) (cHER2high) and cHER2 ratio low (≤0.75) (cHER2low). The frequency of each metastatic site (i.e. liver, lung, central nervous system, bone, lymph nodes, skin/soft tissue, serosa) and the total number of different sites involved (1-7, ≤2 and >2 sites) were compared among the two sub-populations and analyzed through Fisher exact test. Results: Out of 98 pts enrolled, 77 were classified as cHER2low and 21 as cHER2high. We observed a higher frequency of oligometastatic pts (≤2 sites involved) in the cHER2high cohort (16, 76%), compared to only 29 (37%) in the cHER2low (p<0.005). Moreover, the cHER2 ratio was associated with a tropism toward specific sites of disease spread with higher incidence of liver, lung and lymph nodes metastases in the cHER2low cohort (p<0.05). No other statistical associations were observed in respect of specific organ tropism. The frequency of involvement for each metastatic site among the two cohorts are reported in the table. Conclusions: Measuring CTCs enumeration and HER2 expression we identified two cohorts, cHER2high and cHER2low, associated with distinct patterns of metastatic spread. The cHER2low pts were correlated to multiple sites of metastatic involvement, with particular tropism toward liver, lung and lymph nodes. These results confirm the prognostic role of the cHER2 ratio, suggesting a peculiar biological meaning of the HER2+ 1+ CTCs.[Table: see text]

AbstractAggressive morphologic variants of mantle cell lymphoma (MCL), including blastoid and pleomorphic (B/P‐MCL), are rare and associated with poor clinical outcomes. The genomic landscape of these variants remains incompletely explored. In this multi‐institutional study, we describe recurrent mutations and novel genomic copy number alterations (CNAs) in B/P‐MCL, using next generation sequencing and SNP‐array. Chromothripsis, a recently described phenomenon of massive chromosomal rearrangements, was identified in eight of 13 (62%) B/P MCL cases, and a high degree of genomic complexity with frequent copy number gains and losses was also seen. In contrast, a comparative cohort of nine cases of conventional MCL (C‐MCL) showed no chromothripsis and less complexity. Twelve of 13 (92%) B/P‐MCL cases showed loss of CDKN2A/B (6 biallelic and 6 monoallelic losses); while only one C‐MCL showed monoallelic CDKN2A/B loss. In B/P‐MCL, TP53 was the most commonly mutated gene, with mutations present in eight cases (62%), six of which showed concurrent loss of chromosome 17p. Of the eight cases with chromothripsis, six (85%) harbored TP53 mutations. Other recurrent mutations in B/P‐MCL included ATM (7, 53%), CCND1 (5, 38%), NOTCH1 (2, 18%), NOTCH2, and BIRC3 (each in 3, 23%). Here, we describe high genomic instability associated with chromothripsis and a high frequency of CDKN2A/B and TP53 alterations in the aggressive variants of MCL. The nonrandom chromothripsis events observed in B/P‐MCL may be an indicator of clinically aggressive MCL. In addition, frequent CDKN2A deletion and high genomic instability may provide potential targets for alternative treatment.