Clinical Importance of Clonal Hematopoiesis in Metastatic Gastrointestinal Tract Cancers

Key Points Question To what extent is clonal hematopoiesis (CH) associated with treatment response and toxicity among patients with metastatic cancer who receive chemotherapy or immune checkpoint blockade? Findings In this cohort study of 633 patients with metastatic esophagogastric and colorectal cancers, one-third of patients had CH, and half of these alterations were present in putative CH driver genes (CH-PD). The presence of CH and CH-PD were not associated with differences in progression-free survival, baseline leukocyte counts, or increased need for granulocyte colony-stimulating factor support. Meaning Detection of CH or CH-PD does not appear to be associated with progression-free survival during chemotherapy or immune checkpoint blockade, nor with leukocyte recovery, suggesting limited utility of CH in solid tumor clinical decision-making.


Introduction
Clonal hematopoiesis (CH) represents nonrandom clonal selection of bone marrow-derived cells identified by somatic alterations in certain genes.4][5] Presence of CH has been associated with the development of therapy-related myeloid neoplasms, increased risk of coronary heart disease and stroke, and inferior survival among patients with cancer. 3,6Preclinical evidence suggests that CH in hematopoietic stem cells (HSCs) induces a dysregulated inflammatory response as evidenced by altered inflammatory signaling, [7][8][9][10][11] cytokine expression, 8,[12][13][14] and HSC differentiation. 15wever, the clinical implications of these acquired leukocyte alterations in solid tumor therapy remain poorly understood, with conflicting trends in overall survival among patients with CH. 3,16 In the context of the widespread use of immune checkpoint blockade (ICB) and the central role that HSC-derived lymphocytes play in mediating antitumor responses, 17,18 we studied the association between CH and therapeutic efficacy and hematologic toxicity.We therefore retrospectively assessed the association of CH with progression-free survival (PFS) and overall survival (OS) in patients with metastatic colorectal (CRC) and esophagogastric (EGC) cancers who were undergoing treatment with first-line chemotherapy or immunotherapy.

Patients and Data
This retrospective cohort study included patients diagnosed with CRC or EGC between January 1, 2006, and December 31, 2020, at Memorial Sloan Kettering Cancer Center (MSKCC) who underwent sequencing of tumor and normal blood buffy coat samples using Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT), 19 and who had available clinical and genomic data.All patients provided written informed consent to an institutional prospective tumor sequencing protocol, 20 21 We defined MSI-high (MSI-H) as having absence of mismatch repair immunohistochemical expression, with MSIsensor scores of at least 10 21,22 ; for MSI-indeterminant samples (by MSIsensor), a multiple instance MSI score 23 of at least 10 was used.
Baseline hematologic parameters were included for patients who had undergone a complete blood cell count with differential at MSKCC within 7 days prior to first-line chemotherapy initiation.
Similarly, receipt of filgrastim or pegfilgrastim was retrieved from the electronic medical record for patients who received their first-line systemic therapy at MSKCC.The proportion of cycles of doublet (ie, FOLFOX [leucovorin (folinic acid), fluorouracil, and oxaliplatin], FOLFIRI [leucovorin (folinic acid), fluorouracil, and irinotecan]) or triplet (FLOT [fluorouracil, leucovorin (folinic acid), oxaliplatin, and docetaxel]) chemotherapy cycles requiring filgrastim or pegfilgrastim was calculated to account for variable chemotherapy intensity and duration, as well as differences in the number of doses of filgrastim vs longer-acting pegfilgrastim that would be utilized per cycle.

CH Identification
Blood

Study Outcomes
We calculated OS and PFS from the date of treatment start until the date of death (for OS) or until first treatment-related progression or death (for PFS), whichever occurred first.Patients who finished treatment without progression and continued to other definitive treatments (surgery, radiotherapy, or sought treatment elsewhere) were censored at their last date of evaluation, and the remaining patients who did not experience an event of interest for PFS were censored at their last contact date.For PFS analyses, first-line treatment was defined as first chemotherapy-containing treatment after stage IV cancer diagnosis.Patients who received ICB (without concurrent chemotherapy) as the first-line treatment were assessed for PFS only in the ICB cohort, not in the first-line chemotherapy cohort.For ICB PFS analyses, patients treated with ICB and concurrent chemotherapy were excluded from analysis to ensure homogeneous treatment populations (eTable 1 in Supplement 1).

Statistical Analysis
All survival analyses were performed separately among the EGC and CRC cohorts based on the type of treatment received (first-line systemic therapy vs ICB).Baseline characteristics were compared between the presence of CH and CH-PD using the Wilcoxon rank sum test for continuous covariates and χ 2 test for categorical variables.Fisher exact test was used for subgroups with numbers less than 5.We estimated OS and PFS using Kaplan-Meier methods and compared the presence of CH and CH-PD using a log-rank test.A Cox proportional hazards regression model was used to examine the association between CH-PD status and other baseline characteristics listed above with OS and PFS.
Age at diagnosis and TAB were used as continuous variables in the models.Multivariable Cox proportional hazards regression was constructed for patients in the EGC-first-line systemic therapy cohort to evaluate the independent association between CH-PD and OS.Adjustment was made by

Results
Of We then evaluated the immune-modulating potential of CH by assessing the association between CH and ICB outcomes.Upon univariable analysis, there was no significant difference in PFS when stratified by presence of CH (eFigure 1E-F in Supplement 1) or CH-PD (Figure 2C-D) among patients in both the EGC and CRC cohorts receiving ICB therapy, while MSI-H status was associated with improved PFS for the EGC (HR, 0.30 [95% CI, 0.14-0.62];P = .001)and CRC (HR, 0.22 [95% CI, 0.13-0.38];P < .001)cohorts, as would be expected (eFigure 4A-B in Supplement 1).
Many patients with EGC and CRC require dose reductions in their doublet and triplet chemotherapy and/or granulocyte colony-stimulating factor (G-CSF) support to continue therapy.
Therefore, we next sought to evaluate the association of CH and CH-PD presence with baseline We then assessed whether the presence of CH and CH-PD was associated with the need for G-CSF support during first-line systemic therapy, specifically the proportion of platinum-or irinotecan-containing cycles that required G-CSF support.Presence of CH was not associated with significant differences in the proportion of cycles requiring G-CSF support in either cohort.Among patients with CRC, those with CH-PD required fewer chemotherapy cycles with G-CSF support (median proportion of first-line chemotherapy cycles requiring G-CSF: 0.11 [IQR, 0-0.33] vs 0 [IQR, 0-0.06];P = .007),while for patients with EGC, there was no difference in G-CSF support based on CH-PD presence (eFigure 6A-B in Supplement 1).However, we noted that in the CRC cohort, no patients with CH-PD received triplet chemotherapy, likely related to their older age at diagnosis, compared with patients without CH-PD, of whom 15 (7.3%) received triplet chemotherapy, which may explain why patients without CH-PD appeared to require more G-CSF support.

Discussion
In this cohort study, while CH-PD was associated with reduced OS among patients with metastatic

Figure 1 .
Figure 1.Characteristics of Clonal Hematopoiesis (CH) and CH Alterations Annotated as Likely Putative Drivers (CH-PD) in Patients With Metastatic Esophagogastric Cancer (EGC) and Colorectal Cancer (CRC)

JAMA Network Open | Genetics and Genomics
and this study was approved by the MSKCC institutional review board.This report followed the Strengthening the Reporting of Observational Studies in MSH2, and MSH6), were extracted from the institutional databases and clinical records by 3 abstractors (B.H.D., S.S., and S.B.M.) with random secondary cross-validation.Because of potential differences in CH based on race or ethnicity, patients' self-reported race and ethnicity were collected from the electronic medical record.Variant calls were obtained from MSK-IMPACT testing, as were JAMA Network Open.2023;6(2):e2254221.doi:10.1001/jamanetworkopen.2022.54221(Reprinted) February 2, 2023 2/12 Downloaded From: https://jamanetwork.com/ on 09/15/2023 extrapolated tumor purity, alteration count, tumor alteration burden (TAB), and microsatellite instability (MSI) sensor score.

Table 1 .
Demographic and Clinical Characteristics of the EGC and CRC Groups leukocyte count and composition prior to initiating first-line doublet or triplet chemotherapy.There was no significant difference in white blood cell count, absolute neutrophil count, absolute lymphocyte count, or neutrophil-to-lymphocyte ratio between patients with or without CH or CH-PD before initiating first-line systemic therapy, suggesting that CH did not impair hematopoiesis (eFigure 5A-H in Supplement 1).

on 09/15/2023 trial
16C, CH and CH-PD were not associated with PFS in patients receiving first-line systemic therapy or ICB.Previous pancancer studies 3 suggested inferior OS for patients with CH-PD, but these analyses failed to account for phenotypes with outlying therapeutic benefit (ERBB2, MSI-H, etc) or cancer stage at diagnosis.By including patients with earlier-stage cancer, their results may drastically overestimate survival in the recurrent or de novo stage IV setting.In contrast, a CRC-specific evaluation of patients treated with first-line FOLFIRI plus cetuximab or bevacizumab in the FIRE-3 Figure 2. Survival Outcomes for Patients With Clonal Hematopoiesis (CH) Alterations Annotated as Likely Putative Drivers (CH-PD)16suggested that patients with CH, in particular DNMT3A alterations, actually had an improved OS but no differences in PFS in this treatment setting.Our study corroborates these findings with lack of difference based on CH status across multiple first-line systemic therapies in EGC and CRC, while also demonstrating this with ICB.This finding may reflect inadequate exposure or lead time from CH-accelerating agents (smoking, radiotherapy, chemotherapy) to CH development in patients with limited life expectancy.However, our findings, particularly in EGC, suggest that CH may primarily reflect older patients with more comorbidities, and thus inferior prognosis due to Downloaded From: https://jamanetwork.com/

Table 2 .
Univariable and Multivariable Analysis of CH-PD and OS Among Patients With Metastatic EGC Using a Cox Proportional Hazards Regression Model