Minimal Residual Disease Status Research Articles

Utility of surgically documented minimal residual disease as a therapeutic target and early surrogate of frontline treatment outcomes in ovarian cancer.

5549 Background: Cure rates for patients with advanced stage ovarian cancer have not changed over the last four decades likely due to inability to eradicate residual cancer cells after frontline therapy. Identifying clinically undetectable minimal residual disease (MRD) after frontline therapy by second look laparoscopy (SLL) has potential to a) uncover mechanisms of chemoresistance, b) identify MRD-specific therapeutic targets, and c) allow for earlier intervention with investigational therapies. The objective of this study is to describe the initial safety and feasibility of SLL and illustrate clinical pathologic correlates. Methods: This IRB-approved observational, single-center study includes patients with epithelial high-grade ovarian cancer with complete CA-125 and radiologic response after frontline treatment who underwent SLL from 4/2017-12/2022. Patients were subsequently offered standard of care or investigational maintenance therapy options based on homologous recombination deficiency (HRD) and MRD status. Summary statistics described the study population, chi-square tests compared categorical variables, and progression free survival (PFS) based on MRD status was estimated using Kaplan-Meier method and compared using log rank test. Results: 64 patients underwent SLL with a median of 8 biopsies (range 1-16). The majority of patients had stage III-IV disease (89%), and high-grade serous histology (89%). Approximately half (52%) of patients underwent neoadjuvant chemotherapy (NACT) with interval tumor reductive surgery (TRS). MRD was present in 28 patients (44%), and the presence of MRD was associated with a worse PFS (HR 3.1, 95% CI 1.5-6.3; 9.2 vs 24.6 months; P=0.002). MRD was more frequent among NACT recipients compared to those who underwent primary TRS (61% vs 26%, P=0.005), those with HRD negative tumors (63% vs 22%, P=0.003), and those with R1 versus R0 resections (71% vs 35%, P=0.012). Of patients with MRD, 20 patients (71%) received bevacizumab until progression as part of a clinical trial (NCT02884648), 3 (11%) received bevacizumab off trial, 4 (14%) received a PARP inhibitor (all HRD positive) and 1 received other therapy. There was one (1.6%) intraoperative complication requiring conversion to laparotomy. Conclusions: SLL is feasible, overall safe, and detected MRD in 44% of ovarian cancer patients who were in radiologic and CA-125 remission after frontline therapy. MRD rates were higher in patients who received NACT and HRD negative patients, and PFS was significantly longer in patients without residual disease. MRD rate by SLL may have utility as an early surrogate for efficacy in trials evaluating novel frontline investigational therapies. Knowledge of MRD status in this patient population enables interventional, observational, and translational investigations, as well as personalized prognostic counseling.

Ultra-sensitive baseline-informed MRD assay to predict prognosis outcomes in patients with resectable hepatocellular carcinoma.

e16228 Background: The detection of minimal residual disease (MRD) has been shown to be a potential biomarker for the prognosis and post-surgery treatment of resectable hepatocellular carcinoma (HCC). However, the application of MRD in HCC has been limited by the traditional requirement of carrying out MRD over 30 days post-surgery, which is often incompatible with the time window for adjuvant treatment decisions. Additionally, MRD results may be impacted by post-surgery imbalances if assayed too soon after surgery. Methods: This retrospective study enrolled 255 early-stage HCC patients who received surgical resections and had complete information on relapse and survival. Matched tumor and normal tissue samples were collected at the time of surgery and plasma samples were collected as early as 7 days post-surgery. An ultra-sensitive, baseline-informed MRD assay (PredicineBEACON) was used to evaluate the correlation between peri-surgical MRD status and prognosis outcomes. Somatic mutations were identified through PredicineWES+ whole exon sequencing, and up to 50 somatic mutations were selected for the design of a patient-specific capture panel, in addition to a fixed panel of 500 actionable variants. Results: The study has completed MRD tests for 58 patients, of which 8 were called MRD positive with ≥0.005% tumor fractions. The tumor fraction proportion of MRD-positive patients ranged from 0.008% to 5.653% (median 0.315%). The relapse-free survival (RFS) and overall survival (OS) were correlated with MRD status: the median RFS of MRD-positive patients was 13.9 months compared to not reached after 44.4 months for MRD-negative patients (p = 0.1), and the median OS of MRD-positive patients was 27.2 months compared to not reached after 55.5 months for MRD-negative patients (p = 0.03). Conclusions: Our results demonstrate the feasibility of using an ultra-sensitive, baseline-informed MRD assay to detect strong correlations between MRD status and prognosis outcomes in peri-surgical plasma samples collected as early as 7 days post-surgery in resectable HCC patients. This study highlights the clinical utility of MRD testing in peri-surgical settings.

Baseline and early post-infusion biomarkers associated with optimal response to idecabtagene vicleucel (ide-cel) in the KarMMa-3 study of triple-class–exposed (TCE) relapsed and refractory multiple myeloma (RRMM).

8031 Background: Ide-cel, a B-cell maturation antigen (BCMA) chimeric antigen receptor T cell therapy, significantly improved median progression-free survival (mPFS) and overall response rate (ORR) vs standard regimens (SRs) in patients (pts) with TCE RRMM in the KarMMa-3 study (NCT03651128; Rodríguez-Otero et al. NEJM 2023). Previous analyses in KarMMa (Munshi et al. NEJM 2021) of pts with later-line (4L+) TCE RRMM identified low baseline (BL) levels and complete clearance of soluble BCMA (sBCMA, a measure of tumor burden) and early minimal residual disease (MRD) negativity as correlates of durable response to ide-cel. The current analysis explored the association between biomarkers and efficacy or severity of inflammatory adverse events of ide-cel in KarMMa-3. Methods: sBCMA levels were measured in blood samples collected from pts in KarMMa-3 at BL and regular intervals from treatment (tx) initiation until confirmed progression. MRD status was assessed in bone marrow aspirate (clonoSeq; 10-5 sensitivity) at 6 and 12 mo post infusion and reported in all pts, regardless of response. Biomarker analyses were based on pts who received ide-cel or ≥1 dose of SR. Post hoc analyses assessed correlations between biomarkers and efficacy endpoints or cytokine release syndrome (CRS) and investigator-identified neurotoxicity (iiNT); associations of interest were identified using a ranked sum test and nominal P value < 0.05. Results: Lower BL sBCMA levels were associated with higher ORR ( < partial response [PR] vs ≥PR) in both tx arms (ide-cel, P= 0.0223; SR, P= 0.0395), indicating this may be agnostic of the BCMA-directed modality. Lower BL sBCMA was also associated with higher complete response (CR) rate ( < CR vs ≥CR) in the ide-cel arm ( P= 0.0038). Additionally, lower BL sBCMA levels in the ide-cel arm were associated with lower grade (gr) of CRS (gr 0–1 vs 2 vs ≥3; P= 0.0022) and iiNT (gr 0–1 vs ≥2; P= 0.0113); however, overlapping ranges may limit predictive utility. Further analyses will be presented. In the ide-cel arm, landmark mPFS was longer in pts with undetectable versus detectable sBCMA at 2 mo post infusion (16.3 vs 5.2 mo; HR, 0.26) or at 6 mo (16.8 vs 9.6 mo; HR, 0.62). Furthermore, landmark mPFS was also longer in pts with MRD negativity versus pts with positive/indeterminate MRD status at 6 mo (17.2 vs 5.8 mo; HR, 0.288) or at 12 mo (13.8 vs 4.6 mo; HR, 0.121). Conclusions: BL sBCMA levels correlated with response and CRS and iiNT grade in the ide-cel arm of KarMMa-3, potentially reinforcing the importance of management of BL tumor burden for optimal response to ide-cel. Early clearance of sBCMA at 2 mo, sustained clearance of sBCMA at 6 mo, and MRD negativity at 6 or 12 mo, regardless of clinical response, may be useful biomarkers for identifying pts likely to achieve a complete and durable response to ide-cel. Clinical trial information: NCT03651128 .

MRD assay to evaluate recurrence and response via a tumor-informed assessment: MARIA-Breast observational trial.

TPS622 Background: The recognition that cancers release nucleic acids into the peripheral circulation of the patient has enabled a new paradigm for disease detection and surveillance. Detectable ctDNA in patients with solid tumors has been associated with disease prognosis pre-treatment, assessing response to therapy in the form of minimal residual disease (MRD), and monitoring for recurrence after curative intent treatment. Utilizing patient-specific genomic mutation profiling of an individual’s cancer from a tissue sample, in conjunction with the patient’s germline DNA, to create a personalized sequencing panel to then systematically analyze for a subset of these genetic mutations from ctDNA in blood is a strategy that has high sensitivity in detection of MRD. Studies have shown that pretreatment levels of ctDNA using this approach are a potential early indicator of disease recurrence after surgery, that ctDNA clearance may be an early predictor of favorable outcomes and have been shown to correlate with pathologic complete response (Forde et al. N Engl J Med. 2022, PMID:35403841), and that this approach has high sensitivity in its ability to detect recurrence for patients in advance of the current standard of care (Abbosh et al. Cancer Res (2020) 80 (16_Supplement): CT023). Methods: This is a multi-site, prospective, observational trial in the United States of 200 patients with early stage breast cancer undergoing curative intent treatment, who have FFPE tissue available from resection sufficient for a patient-specific bespoke MRD assay who are willing to provide serial whole blood specimens for ctDNA analysis. Participants are asked to provide study specimens prior to initial treatment intervention, after curative intent surgical resection, during adjuvant therapy (as applicable) and pre-recurrence follow-up. ctDNA will be analyzed with an NGS-based, tumor-informed MRD assay that identifies somatic mutations from DNA obtained from the patient’s tumor tissue, subtracts germline variants via NGS-based analysis of the patients germline DNA, and detects a selected set of between 18-50 tumor-specific ctDNA in their blood. All primary tumor specimens will undergo full exome sequencing using the Personalized Cancer Monitoring (PCM) assay. Impact of results of this CLIA-approved MRD assay on clinical decision making will be captured. The primary objective is to assess the ability of MRD to predict post-treatment recurrence. Further objectives are to correlate MRD status with pathologic complete response, determine the lead time to detection of recurrence compared to standard of care, and the association of MRD status with overall survival. Active enrollment started in March, 2022. Clinical trial information: NCT05219734 .

An ultra-sensitive amplicon-based NGS assay for MRD detection.

e13634 Background: Detection of the minimal residual disease (MRD) has proven a promising noninvasive approach for monitoring the tumor remissions and relapses after surgical resection or other therapies. However, circulating tumor DNA (ctDNA) after surgery in the early-stage cancers can be at very low levels, which makes the MRD detection quite challengeable if the plasma sample only contains a few ctDNA copies. In the clinical practice, an ultra-sensitive and tumor-informed multiplexing variant detection system is required for postsurgical cancer surveillance. Methods: In this study we developed an ultra-sensitive amplicon-based NGS approach, namely UMIamp, to provide a personalized and tumor-informed strategy for MRD detection using plasma sample. Firstly, up to 16 clonal somatic variants can be obtained by whole exome sequencing (WES) of the tumor tissue samples. Then optimized primers were designed to uniformly cover the target DNA regions and those target regions were efficiently enriched by linear amplification. With randomly unique molecular identifiers (UMI) attached to DNA templates and ultra-deep NGS sequencing, the somatic target mutations with very low frequency can be identified using a customized bioinformatic pipeline. To validate the performance of the limit of detection (LOD), the reference standard samples were diluted to the allele frequencies of 0.02%, 0.01%, 0.005% and 0.002%, respectively. Each sample contained 14 single nucleotide variants (SNVs). The sensitivity and specificity were calculated based the mutations called. Results: Single site level sensitivity and specificity were 75% and 100% with the allele frequency of 0.02%, while they were 70.73% and 95.08% with the allele frequency of 0.01%. The results showed UMIamp was very sensitive and was able to detect 2 copies from 60ng cfDNA sample at 0.01% mutation level. Even at the 0.005% and 0.002% allele frequency levels there were less than two copies in 60ng cfDNA, UMIamp still achieved single site sensitivities of 24.18% and 23.07%, respectively. In the MRD clinical practice, sample level sensitivity was important to evaluate the detection capability based on more gene mutations. When combined the 14 variants as a unified indicator to detect the sample level MRD status, the positive rates at the VAFs of 0.02%, 0.01%, 0.005% and 0.002% were all 100%, which demonstrated the LOD of UMIamp approach can reach to as low as 0.002%. Such sensitivity will be adequate for post-surgical early-stage cancer surveillance. Conclusions: We developed an ultra-sensitive amplicon-based NGS approach which can effectively detect MRD status at the allele frequency of 0.002%. The developed approach can be applied in a personalized, tumor-informed MRD detection settings in post-surgical early-stage cancers.

Circulating tumor DNA-based molecular residual disease detection for the monitoring of high-grade serous ovarian cancer.

e17600 Background: The current standard treatment of epithelial ovarian cancer includes surgery and platinum-based chemotherapy. Most of the patients are sensitive, but still over 70% of patients have recurrence or disease progression. Post-operative circulating tumor DNA (ctDNA)-based minimal residual disease (MRD) test can be a potential biomarker for monitoring the disease. Methods: Stage II-IV high-grade serous ovarian cancer (HGSOC) patients were recruited in this study. Tumor tissues were collected for whole exome sequencing (WES; 300x). Germline mutations were excluded by paired white blood cell test. Proprietary algorithm was used to select 30-40 single nucleotide variants (SNV) for each patient. Blood samples were collected at diagnosis, after surgery, after chemotherapy, and during adjuvant treatment, and MRD was detected by multiplex polymerase chain reaction (PCR)-based sequencing (100,000x) using the customized panel. Results: At the time of analysis, WES was performed in 20 patients, of which 11 of them harbored HRR pathway-related mutations, including 5 BRCA1, 4 BRCA2, 1 ATM, and 1 FANCL. 7 patients had completed MRD monitoring for 3 times (pre-surgery, post-surgery, and post-chemotherapy). 71.4% (5/7) of patients were positive for MRD at baseline, with a median variant allelic frequency (VAF) of 2.79%. The VAF at baseline was positively associated with CA125 level at baseline (Pearson R = 0.937，p = 0.002). 2 patients were positive for MRD after surgery (VAF = 0.09% and 0.04%). One of them presented with multiple diverse lesions and the CA125 level returned normal after surgery and 8 cycles of chemotherapy. Another patient had an abnormal CA125 level of 1597 U/ml after surgery. All the 7 patients were negative for MRD after completion of chemotherapy. Follow-up is ongoing. Conclusions: We preliminary proved the feasibility of dynamic monitoring with MRD in epithelial ovarian cancer patients. Over 70% of HGSOC patients were MRD-positive at baseline. The MRD status was generally consistent with the clinical status of the patients. The performance of MRD in predicting recurrence of HGSOC is still under investigation. Clinical trial information: NCT05027828 .

Association of myeloid-derived suppressor cells with hematopoietic recovery after high-dose chemotherapy in multiple myeloma

Myeloid-derived suppressor cells (MDSCs) play an important role in the immune response regulation in many pathologies, primarily in malignant tumors, but their role in the hematopoietic stem cell engraftment and the hematopoietic recovery after high-dose chemotherapy and autologous stem cell transplantation remains practically unexplored. This study is aimed at studying the correlation between the number of MDSC subpopulations and blood parameters at the stage of hematopoietic recovery after high-dose chemotherapy and autologous hematopoietic stem cell transplantation in patients with multiple myeloma (MM). Circulating MDSCs were assessed at the stage of leukopenia recovery (absolute leukocyte count in peripheral blood (PB) > 1 x 109/L) by flow cytometry. The number of transplanted CD34+CD45+ hematopoietic stem cells was 4.38 x 106/kg (IQR (3.1—5.6) x 106/kg). The duration of recovery from leukopenia varied from 8 to 18 days (Me 12 days). The number of MDSCs at the engraftment was not associated with the number of CD34+ cells/kg in the graft. The relative number of monocytic MDSCs (M-MDSCs, CD14+HLA-DRlow/-) directly correlated with the number of monocytes at the stage of recovery from leukopenia (R = 0.417, p = 0.002). Granulocytic MDSCs (PMN-MDSCs, Lin-HLA-DR-CD33+CD66b+) were characterized by an inverse correlation with the number of monocytes (R = -0.493, p = 0.0003) while the association with the absolute number of neutrophils was weak (R = 0.273, p = 0.048). The number of lymphocytes at the stage of recovery from leukopenia had an inverse correlation with PMN-MDSCs (R = -0.347, p = 0.014) and did not correlate with M-MDSCs. When analyzing the duration of leukopenia, an inverse correlation with this indicator was revealed for the percentage and absolute number of M-MDSCs (R = -0.347, p = 0.018 and R = -0.469, p = 0.0008, respectively). Multiple regression analysis showed dependence of the lymphopenia duration on the proportion of circulating M-MDSCs (p = 0.014) and the number of transplanted CD34+ cells/kg (p = 0.032). According to the data of multivariate analysis of variance, the number of transplanted CD34+ cells/kg and the number of M-MDSCs were significant factors for the duration of leukopenia. At the same time, such clinical parameters as the depth of response and minimal residual disease status before high-dose chemotherapy and hematopoietic stem cell transplantation, as well as the MM stage, did not affect the duration of hematopoietic recovery. Thus, the obtained results indicate the association of a higher number of M-MDSCs with a shorter duration of leukopenia after high-dose chemotherapy with autologous stem cell transplantation and indicate a positive role of M-MDSCs in hematopoietic recovery in the early post-transplant period in patients with MM.

LINKER-MM1 study: Linvoseltamab (REGN5458) in patients with relapsed/refractory multiple myeloma.

8006 Background: Linvoseltamab is a BCMA×CD3 bispecific antibody with encouraging efficacy and a manageable safety profile in patients (pts) with relapsed/refractory multiple myeloma (RRMM) (Bumma et al. ASH 2022). Two Phase (Ph) 2 full dose cohorts (50 mg and 200 mg) in the LINKER-MM1 (NCT03761108) trial were studied to optimize dose selection. Methods: Ph 2 enrolled adults with MM who progressed on/after ≥3 lines of therapy (LoT) including a proteasome inhibitor (PI), an immunomodulatory drug (IMiD), and an anti-CD38 antibody (Ab), or were at least triple class (IMiD/PI/anti-CD38 Ab) refractory. A protocol amendment permitted pts who progressed during 4–12 wks on 50 mg to dose escalate to 200 mg. Primary endpoint was objective response rate (ORR). Key secondary endpoints included duration of response (DoR) and minimal residual disease status. Results: As of 1 Sept 2022, 252 pts have enrolled (Ph 1: 73; Ph 2: 179 [200 mg: 75; 50 mg: 104]). Median age was 66 yrs (range 37–90), 12% had extramedullary plasmacytomas, 12% high-risk cytogenetics, 37% bone marrow plasma cell percentage (BMPC) ≥50%. Median soluble BCMA concentration (sBCMA) was 0.43 mg/L (range 0–10.2), median prior LoT: 5 (range 1–16), and 81% were ≥triple class refractory. Numerically higher efficacy was observed with 200mg, including in high disease burden subgroups; ORR was 64% (200 mg cohort; n = 58, includes 12 Ph 1 pts) and 50% (50 mg cohort; n = 104). Subgroup analyses showed higher ORR in the 200 mg cohort versus 50 mg for sBCMA ≥0.4 mg/L (52% vs 37%), BMPC > 67% (64% vs 35%) and revised ISS stage III (71% vs 27%). Median DoR was not reached for both cohorts (median follow-up: 2.3 months [200 mg], 4.7 months [50 mg]). Probability of maintaining response at 6 months was 89% (200 mg) and 85% (50 mg). Eight pts dose escalated from 50 to 200 mg; 6 (75%) achieved a response. Treatment-emergent adverse events (TEAEs) occurred in 95% (Grade [Gr] ≥3: 66%) of pts in the 200 mg cohort (n = 87, includes 12 Ph 1 pts) and 100% (Gr ≥3: 80%) in the 50 mg cohort. The most common TEAEs were cytokine release syndrome (200 mg: 37% [Gr 3: 1%]; 50 mg: 53% [Gr 3: 2%]), fatigue (200 mg: 32% [Gr ≥3: 0]; 50 mg: 33% [Gr ≥3: 0]) and anemia (200 mg: 28% [Gr ≥3: 24%]; 50 mg: 40% [Gr ≥3: 36%]). Grade ≥3 ICANS occurred in 2 pts (2%) in the 200 mg cohort and 1 pt (1%) in the 50 mg cohort. TEAEs leading to treatment discontinuation occurred in 7% (200 mg cohort) and 8% (50 mg cohort) of pts. Infections occurred in 43% (Gr ≥3: 26%) in the 200 mg cohort and 59% (Gr ≥3: 31%) in the 50 mg cohort. Conclusions: Linvoseltamab 200 mg showed better efficacy compared with 50 mg, including in pts with high disease burden. The 200 mg dose had consistent efficacy across high-risk subgroups and induced responses in pts who progressed on 50 mg. Safety was consistent across Ph 2 doses. The recommended linvoseltamab dose for further development is 200 mg. Updated data with longer follow-up and complete enrollment of the 200 mg cohort will be presented at the meeting. Clinical trial information: NCT03761108 .

Clinical validation of next-generation sequencing-based clonality assays for minimal residual disease tracking in multiple myeloma.

e20037 Background: The prognosis of multiple myeloma (MM) patients is dependent on minimal residual disease (MRD) status after treatment. Multicolor flow cytometry (MFC) as a clinical MRD evaluation method has certain limitations regarding sample requirement, sensitivity and specificity. Next-generation sequencing (NGS)-based B cell receptor (BCR) clonality assessment has an edge in lymphoid clone MRD detection, with easier sample preparation and higher sensitivity. NGS-based BCR clonality assays were performed to evaluate curative effect and track MRD of MM patients, and its performance in testing samples with limited DNA contents was explored. Methods: In this retrospective study, newly diagnosed or relapsed MM patients with paired sample collected before and after initial treatment were included, and OriMIRACLE L NGS assay were used for BCR clonality detection in genomic DNA (gDNA) extracted from clinical residual marrow smear samples. The quantitative accuracy of NGS was compared to MFC. The concordance of MRD between MFC, NGS and clinical response assessment were analyzed. Results: From December 2016 to April 2022, 29 patients were included with a median age of 65 years old. The gDNA input of the sample collected before treatment was 100.0 ng, and the median DNA content of the sample collected after treatment was 1673.4 ±594.8 ng. The quantitative results of NGS and MFC were consistent in samples with a frequency of cancer cells of above 1x10-4 among all nucleated cells. BCR clonality detection in 23 newly diagnosed and 6 relapsed cases showed a 100% sensitivity at diagnosis. For post-treatment monitoring, patients with positive MRD by both MFC and NGS (n = 18), the MRD results were consistent with clinical response assessment. One of the patients achieved complete response (CR), while the remaining patients were unable to achieved CR. The CR patient was relapsed after 134 days. The clinical responses of 11 cases with negative MRD by MFC and positive MRD by NGS were reviewed. There were 7 cases with CR, 3 cases with very good partial response or partial response, and one case with stable disease. Among those CR patients, except for one patient who was lost to follow-up, 4 patients who underwent continuous treatment were still CR and 2 patients who had treatment discontinued recurred at 67 and 134 days. Conclusions: OriMIRACLE L NGS assay showed the higher sensitivity and specificity of MRD evaluation than MFC. For patients with negative MRD by MFS and positive MRD by NGS, recurrence might occur in case of treatment discontinuation. It is recommended to consider carefully that whether maintenance treatment is required in such cases.

Prognostic value of month 1 bone marrow and PET MRD status in CAR-T therapy for myeloma.

8024 Background: Minimal residual disease (MRD) is prognostic for survival in multiple myeloma (MM). MRD is usually assessed in the bone marrow (BM) by flow cytometry or NGS. MRD by FDG PET/CT provides a global representation of the tumor burden, including response assessment of extramedullary disease. We examined MRD status in MM pts using both BM and PET/CT at Mayo Clinic. Methods: Medical records were reviewed retrospectively for MM pts who received CAR-T between 4/2018 and 12/2022. All PET/CT scans were assessed by radiologists. BM MRD was assessed by flow cytometry with a sensitivity of 10-5. Progression-free survival (PFS) and overall survival (OS) were analyzed by Kaplan-Meier method. Results: Among the 157 CAR-T pts, including 89 pts who received FDA-approved CAR-T, median age was 63 years, 59% (92/157) were males, 42% (66/157) had high risk cytogenetics with median of 5 prior lines of therapy, 36% (57/157) had plasmacytoma. Incidence of CRS was 83%, 5% grade ≥ 3 CRS. Incidence of ICANS was 19%, 4% grade ≥ 3 ICANS. CR/sCR rate was 37%. One hundred and thirty-seven pts (87%) had evaluable BM at month (mo) 1, 85% (117/137) were BM MRDneg at mo 1. Baseline demographics were comparable between the two groups except age, % BM plasma cells and use of bridging therapy. Among the MRDneg pts, CR/sCR rate was 44% (51/117) and 95% (111/117) had sFLC below normal. At median follow-up of 13.8 months, median PFS among pts with BM MRDneg at 1 mo was 12 mo (95% CI: 11, 30) vs 3 mo (95%CI: 2, 7) for BM MRDpos (p<0.001). Median OS among pts with BM MRDneg at 1 mo was 34 mo (95% CI: 24, NR) vs 22 mo (95%CI: 7, NA) for BM MRDpos (p<0.01). At month 1, 112 pts had both BM and PET/CT assessments available, 64/112(57%) were both BM MRDneg/PET MRDneg, 38/112 (34%) were MRDneg for either BM or PET and 10/112 (9%) were positive for both BM and PET (MRDpos/PET MRDpos). Baseline demographics except age were comparable between the 2 groups (Table). Rate of conversion from MRDpos to MRDneg was low. Rate of sustained BM and PET MRDneg at mo 12 was 44% (8/18). The median PFS and OS for BM MRDneg/PET MRDneg was significantly longer as compared to others (Table). Conclusions: Achieving FLC below normal, BM MRDneg and PET MRDneg at 1 month, regardless of IMWG response at that time, is prognostic for both PFS and OS in MM pts receiving CAR-T. Failure to achieve any of these confers poor prognosis. [Table: see text]

Dynamic ctDNA to inform the precise management of resected NSCLC: LUNGCA-2 study.

8528 Background: Circulating tumor DNA (ctDNA) has been reported to be valuable for minimal residual disease (MRD) detection, but there is a lack of studies comprehensively assessing whether dynamic ctDNA monitoring can inform whole-course precise postoperative cancer management. In the present study (LUNGCA-2), we analyzed data obtained from longitudinal ctDNA monitoring of stage I-III NSCLC patients in the LUNGCA cohort, and sought to assess the use of dynamic ctDNA monitoring for precise whole-course postoperative management of NSCLC patients. Methods: All eligible NSCLC patients underwent curative-intent surgery and subsequently received adjuvant therapies when indicated by clinical practice guidelines for NSCLC. The clinical follow-up was scheduled to be every 3-6 months mainly involving CT and/or MRI. Fresh frozen or paraffin-embedded tissues of primary tumors were collected intraoperatively for baseline somatic mutation profiling. Blood samples were collected before surgery, at 3 days and 1 month after surgery, and then every 3-6 months at clinical visits up to 3 years postoperatively. 233 patients with a total of 2123 plasma samples were ultimately included in the longitudinal ctDNA analysis in the current study. NGS assays were performed with a custom-designed panel that covered 769 cancer-related genes via the MinerVA platform (Genecast Biotechnology Co., Ltd). Results: Among the cohort, 166 patients harboring targetable mutations in the primary tumor tissue, 15 were preadjuvant ctDNA positive, and among them, only 25% patients treated with adjuvant TKI therapy experienced relapse during follow-up, and patients received ACT or no adjuvant therapy had a relapse rate of 100%. TKI treatment tended to improve RFS compared with no treatment (HR 0.1, P = 0.025), but ACT failed to improve RFS (HR 1.1, P = 0.834). Among all 82 patients receiving adjuvant therapy, the pre- and post-adjuvant therapy postoperative ctDNA status with a negative-negative or positive-negative pattern had similar and favorable RFS ( P = 0.545) but that patients with a positive-positive or negative-positive pattern had significantly inferior RFS than those with a negative-negative pattern (both P < 0.001). For recurrence monitoring, posttreatment ctDNA MRD status had a positive predictive value of 100% and a negative predictive value of 91.8%, and the sensitivity of MRD detection was affected by the organ of relapse. Among positive ctDNA MRD patients, faster increase of ctDNA concentration correlated with more imminent clinical relapse. The median lead time from ctDNA detection to radiological relapse was 273 days. Moreover, ctDNA negativity after relapse was associated with favorable survival. Conclusions: These findings highlight the clinical significance of ctDNA dynamics for the precise whole-course postsurgical management of NSCLC patients.

The use of minimal residual disease in thoracic oncology: Gaps between promises and the on-the-ground reality of daily practice.

The assessment of minimal residual disease (MRD) from blood samples of patients with resected non-small cell lung carcinoma (NSCLC) is promising and opens up many opportunities for the optimisation of patient care in daily practice. Notably, this includes the potential for escalation or de-escalation of adjuvant therapies. Thus, the evaluation of MRD status can directly contribute to an increase in the overall survival of early stage NSCLC patients and/or limit therapeutic but also "financial" toxicity. Therefore, several clinical trials recently evaluated MRD in early stage NSCLC by integrating and retrospectively comparing the results of MRD assessments. In this context, there is an urgent need to close the gap between clinical research and the use of the evaluation of MRD in routine daily practice. Further action needs to be taken, particularly in evaluating the pertinence of the detection of MRD in prospective interventional clinical studies. This may be done in part by comparing different parameters, such as the techniques used, the different time points and the cutoffs of MRD assessments. This article investigates the assessment of MRD in non-small cell lung cancers, with a special focus on the issues associated with the various assays and the limitations of using circulating free DNA analyses for MRD assessment in early stage lung cancer. Recommendations and tips for the optimisation of MRD evaluation in non-small cell lung cancers are provided.

Molecular genetic and cytofluorimetric prognostic factors in the development of acute myeloid leukemia relapse in children after allogeneic hematopoietic stem cell transplantation

Relapse of acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains one of the main causes of reduced long-term survival. Modern methods for predicting the risk of AML relapse after allo-HSCT take into account the data on the pre-transplant level of minimal residual disease (MRD) determined by flow cytometry and molecular biological studies of recurrent genetic abnormalities, which are currently widespread in clinical practice. Recent studies of the expression of genes characteristic of leukemic stem cells (LSCs) have shown prognostic significance for children with AML in relation to treatment response and the risk of relapse. The study of LSC persistence in order to predict the risk of recurrence after allo-HSCT in children with AML in addition to standard MRD detection methods may be of great importance. The aim of the work was to evaluate the impact of MRD status, both using classic methods and taking into account the genes characteristic of LSC, on the results of allo-HSCT in children with AML. The study was approved by the Independent Ethics Committee and the Scientific Council of the I.P. Pavlov First Saint Petersburg State Medical University of Ministry of Healthcare of the Russian Federation. To assess MRD using standard diagnostic methods, we analyzed the data of 95 children with AML in their 1st–2nd remission (cohort 1). MRD status was negative in 67 (70.6 %) patients; in 28 (29.4 %) children, MRD status was positive according to molecular genetic studies and / or immunophenotyping results. For pre-transplant evaluation of the expression of genes characteristic of LSC, we investigated bone marrow samples of 50 patients (cohort 2) using real-time polymerase chain reaction. The DNMT3B, GPR56, CD34, SOCS2, SPINK2, FAM30A, and ABL genes were studied by real-time polymerase chain reaction, followed by calculation of the pLSC6 value using the formula: DNMT3b × 0.189 + GPR56 × 0.054 + CD34 × 0.0171 + SOCS2 × 0.141 + SPINK2 × 0.109 + FAM30A × 0.0516. At the time of allo-HSCT, 37 (74 %) children with AML were in their 1st or 2nd remission of the disease, 13 (26 %) were out of the 1st–2nd remission. With a median follow-up of 5 years in the group of patients with a positive MRD status, determined by standard methods (cohort 1), overall survival (OS) was 67.9 % vs 73.1 % for patients with a negative MRD status (p = 0.83). The cumulative incidence of relapse was 50 % and 22 %, respectively; p = 0.012. When assessing the level of expression of genes characteristic of LSC (cohort 2), a pLSC6 level was above the median in 18/37 (49 %) patients. The results of linear regression showed that the pre-transplant level of expression of genes characteristic of LSC was not associated with the number of blasts/MRD (odds ratio 1.002; 95 % confidence interval 0.979–1.025). One-year OS rates did not differ significantly in children in the 1st–2nd remission of AML, depending on pLSC6 level: 84.2% in patients with low pLSC6 and 72.2 % – with high pLSC6 (p = 0.4), event-free survival in the corresponding groups – 68.4 % and 61.1 %, respectively (p = 0.34). The cumulative incidence of early relapse after allo-HSCT in the group of AML patients with a high pLSC6 score was significantly higher than in children with a low pLSC6 score before allo-HSCT (22 % and 0 %, respectively; p = 0.03). MRD does not have a statistically significant effect on OS. However, MRD positivity before allo-HSCT increases cumulative incidence of relapse. The level of expression of genes characteristic of LSC, determined before allo-HSCT, showed a prognostic significance in relation to the development of early AML relapse after allo-HSCT.

A long-term follow-up of observation in treatment-free remission in patients with chronic myeloid leukemia

Introduction. The option of observation without therapy with tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) patients is already included in Russian and international clinical guidelines. Evaluation of long-term follow-up results of treatment free remission (TFR) in CML patients is relevant for the introduction of this approach into routine clinical practice. Aim — to demonstrate the outcomes in a long-term follow-up of CML patients who discontinued TKI therapy in the RU-SKI trial. Patients and methods. The prospective study included 98 CML patients with TKI therapy duration ≥ 3 years and a deep molecular response (DMR, BCR::ABL1 ≤ 0.01 %) duration ≥ 2 years. TKI therapy was resumed with the loss of a major MR (MMR, BCR::ABL1 > 0,1 %). Results. Median time of follow-up after TKI discontinuation was 64 months (range of 51–86 months). Survival without MMR loss at 3 and 5 years after TKI discontinuation was 51 % (CI 41–61 %) and 46 % (CI 36–57 %) respectively. From 3 to 5 years of follow-up without therapy, the loss of MMR occurred in 2 (4 %) patients. There was no MMR loss observed after 5 years of follow-up. In patients with first and second treatment discontinuation, survival without MMR loss was 50 % versus 12,5 %(р = 0,039). All 50 patients with molecular relapses regained MMR and MR4 after TKI therapy resumption. BCR::ABL1 level fluctuations 0,01–0,1 % were in 62 % (n = 29) patients, who were in TFR at the time of analysis. Loss of MR4 was observed in 38 (42 %) from 90 patients with first TKI discontinuation. Survival without MMR loss from MO4 loss was 24 % at 5 years after TKI discontinuation. Loss of MO4 in the first 3 months after TKI cessation was associated with a high probability of further MMR loss (8 % versus 54 % in patients with loss of MO4 for > 3 months, p = 0.00015). Conclusion. The low frequency of late relapses (4 % after 3 years of follow-up) and the possibility of long-term persistence of minimal residual disease (MRD) after discontinuation of therapy determine the need to optimize the timing of molecular monitoring, taking into account the MRD status of patients.

Minimal residual disease status improved the response evaluation in patients with Waldenström's macroglobulinemia.

Minimal residual disease (MRD) has been recognized as an important prognostic factor of survival in patients with hematological malignancies. However, the prognostic value of MRD in Waldenström macroglobulinemia (WM) remains unexplored. We analyzed 108 newly diagnosed WM patients receiving systematic therapy and assessed for MRD by multiparameter flow cytometry (MFC) using bone marrow samples. Of the total patients, 34 (31.5%) achieved undetectable MRD (uMRD). A hemoglobin level of >115 g/L (P=0.03), a serum albumin level of >35 g/L (P=0.01), a β2-MG level of ≤3 mg/L (P=0.03), and a low-risk International Prognostic Scoring System for WM (IPSSWM) stage (P<0.01) were associated with a higher rate of uMRD. Improvements in monoclonal immunoglobulin (P<0.01) and hemoglobin (P=0.03) levels were more evident in uMRD patients compared with that in MRD-positive patients. The 3-year progression-free survival (PFS) was better in uMRD patients compared with that in MRD-positive patients (96.2% vs. 52.8%; P=0.0012). Landmark analysis also showed that uMRD patients had better PFS compared with MRD-positive patients after 6 and 12 months. Patients who achieved partial response (PR) and uMRD had a 3-year PFS of 100%, which was significantly higher than that of patients with MRD-positive PR (62.6%, P=0.029). Multivariate analysis showed that MRD positivity was an independent factor of PFS (HR: 2.55, P=0.03). Moreover, the combination of the 6th International Workshop on WM assessment (IWWM-6 Criteria) and MRD assessment had a higher 3-year AUC compared with the IWWM-6 criteria alone (0.71 vs. 0.67). MRD status assessed by MFC is an independent prognostic factor for PFS in patients with WM, and its determination could improve the precision of response evaluation, especially in patients who achieved PR.

Treatment Strategy for Ultra-High-Risk Multiple Myelomas with Chromosomal Aberrations Considering Minimal Residual Disease Status and Bone Marrow Microenvironment.

Despite the development of anti-myeloma therapeutics, such as proteasome inhibitors, immunomodulatory drugs, anti-CD38 monoclonal antibodies, and autologous stem cell transplantation (ASCT), multiple myeloma remains incurable. A trial treatment combining four drugs-daratumumab, carfilzomib, lenalidomide, and dexamethasone-followed by ASCT frequently results in minimal residual disease (MRD) negativity and prevents progressive disease in patients with standard- and high-risk cytogenetics; however, it is insufficient to overcome the poor outcomes in patients with ultra-high-risk chromosomal aberration (UHRCA). In fact, MRD status in autografts can predict clinical outcomes after ASCT. Therefore, the current treatment strategy might be insufficient to overcome the negative impact of UHRCA in patients with MRD positivity after the four-drug induction therapy. High-risk myeloma cells lead to poor clinical outcomes not only by aggressive myeloma behavior but also via the generation of a poor bone marrow microenvironment. Meanwhile, the immune microenvironment effectively suppresses myeloma cells with a low frequency of high-risk cytogenetic abnormalities in early-stage myeloma compared to late-stage myeloma. Therefore, early intervention might be key to improving clinical outcomes in myeloma patients. The purpose of this review is to improve clinical outcomes in patients with UHRCA by considering MRD assessment results and improvement of the microenvironment.

Transcriptomic profiles and 5-year results from the randomized CLL14 study of venetoclax plus obinutuzumab versus chlorambucil plus obinutuzumab in chronic lymphocytic leukemia

Data on long-term outcomes and biological drivers associated with depth of remission after BCL2 inhibition by venetoclax in the treatment of chronic lymphocytic leukemia (CLL) are limited. In this open-label parallel-group phase-3 study, 432 patients with previously untreated CLL were randomized (1:1) to receive either 1-year venetoclax-obinutuzumab (Ven-Obi, 216 patients) or chlorambucil-Obi (Clb-Obi, 216 patients) therapy (NCT02242942). The primary endpoint was investigator-assessed progression-free survival (PFS); secondary endpoints included minimal residual disease (MRD) and overall survival. RNA sequencing of CD19-enriched blood was conducted for exploratory post-hoc analyses. After a median follow-up of 65.4 months, PFS is significantly superior for Ven-Obi compared to Clb-Obi (Hazard ratio [HR] 0.35 [95% CI 0.26–0.46], p < 0.0001). At 5 years after randomization, the estimated PFS rate is 62.6% after Ven-Obi and 27.0% after Clb-Obi. In both arms, MRD status at the end of therapy is associated with longer PFS. MRD + ( ≥ 10−4) status is associated with increased expression of multi-drug resistance gene ABCB1 (MDR1), whereas MRD6 (< 10−6) is associated with BCL2L11 (BIM) expression. Inflammatory response pathways are enriched in MRD+ patient solely in the Ven-Obi arm. These data indicate sustained long-term efficacy of fixed-duration Ven-Obi in patients with previously untreated CLL. The distinct transcriptomic profile of MRD+ status suggests possible biological vulnerabilities.

Abstract CT166: Similar outcomes regardless of post-randomization treatment with ibrutinib or ibrutinib + venetoclax in the phase 2 CAPTIVATE study of first-line ibrutinib + venetoclax in CLL

Abstract Background: CAPTIVATE (NCT02910583) is a multicenter phase 2 study of first-line ibrutinib (Ibr) + venetoclax (Ven) in CLL. In the Minimal Residual Disease (MRD) cohort, pts underwent randomization to subsequent treatment based on MRD status after completing Ibr + Ven (Wierda et al, J Clin Oncol 2021). Here, 4-yr follow-up (3-yr post-randomization) outcomes are reported for MRD cohort pts randomized to continued Ibr or Ibr + Ven. Methods: 164 pts aged &amp;lt;70 yr with previously untreated CLL received 3 cycles of Ibr then 12 cycles of Ibr + Ven (Ibr 420 mg/d; Ven ramp-up to 400 mg/d); a 13th cycle occurred concurrent with MRD assessment. Pts not meeting criteria for Confirmed undetectable MRD (uMRD Not Confirmed) were randomized to open-label Ibr (n=31) or Ibr + Ven (n=32; 1 additional yr of Ibr + Ven then Ibr alone). Pts with Confirmed uMRD were randomized 1:1 to double-blind placebo or Ibr (n=86). Results: In uMRD Not Confirmed pts, median time on study was 48 mo; post-randomization median follow-up was 33 mo. Improvements in overall best uMRD rates from pre-randomization were: +3% (to 48%) with Ibr and +25% (to 72%) with Ibr + Ven in peripheral blood, and +10% (to 42%) with Ibr and +38% (to 69%) with Ibr + Ven in bone marrow. uMRD rates over time are in the Table. Improvements in complete response (CR) rates were similar with Ibr (+29%) and Ibr + Ven (+28%). 4-yr progression-free survival (PFS) rates were 93% in both arms; 4-yr overall survival (OS) rates were 97% (Ibr) and 100% (Ibr + Ven) and consistent with Confirmed uMRD arms (Allan et al, ASH 2022). Adverse events (AEs) generally decreased over time post-randomization (Table) except for hypertension. In this 4th yr of follow-up (25-36 mo post-randomization), atrial fibrillation was rare (n=1/arm); no AEs led to drug discontinuation in either arm. With continued Ibr, outcomes in uMRD Not Confirmed pts were similar to those in Confirmed uMRD pts: median time on study, 56 mo; post-randomization median follow-up, 42 mo; CR rate, 81%; 4-yr PFS, 95%; 4-yr OS, 98%. Conclusion: In pts without Confirmed uMRD after Ibr + Ven, continued Ibr + Ven improved uMRD rates; PFS and OS were similarly high with continued Ibr or Ibr + Ven (≥97%). AE rates generally decreased over time in both arms. Outcomes with continued Ibr were not impacted by pre-randomization Confirmed uMRD status. Table. uMRD rates and prevalence of AEs over time in uMRD Not Confirmed pts Ibr + Ven then Ibr Ibr + Ven then Ibr + Ven uMRD rate at selected timepoints in evaluable pts, n/N (%) End of Pre-Rnd 12 cycles Post-Rnd 36 cycles Post-Rnd End of Pre-Rnd 12 cycles Post-Rnd 36 cycles Post-Rnd Peripheral blood 13/31 (42) 10/31 (32) 7/31 (23) 9/32 (28) 19/30 (63) 11/31 (35) Bone marrow 10/31 (32) 9/30 (30) Not done 10/31 (32) 18/31 (58) Not done Prevalence of AEs of clinical interest, n (%)a First 16 cycles, n=31 1-12 mo, n=31 25-36 mo, n=27 First 16 cycles, n=32 1-12 mo, n=32 25-36 mo, n=25 Grade ≥3 AEs Hypertension 2 (6) 1 (3) 0 2 (6) 0 0 Atrial fibrillation 1 (3) 0 0 0 1 (3) 0 Diarrhea 2 (6) 0 0 2 (6) 1 (3) 0 Neutropenia 10 (32) 2 (6) 0 10 (31) 2 (6) 0 Infections/infestations 6 (19) 0 2 (7) 2 (6) 2 (6) 1 (4) Hemorrhage 0 0 0 0 1 (3) 0 Any-grade AEs Hypertension 5 (16) 5 (16) 6 (22) 5 (16) 4 (13) 5 (20) Atrial fibrillation 3 (10) 2 (6) 1 (4) 0 2 (6) 1 (4) aAEs were assessed at every visit pre-Rnd and every 3 cycles post-Rnd. Rnd, randomization. Citation Format: Tanya Siddiqi, Constantine S. Tam, William G. Wierda, Paolo Ghia, Thomas J. Kipps, Alessandra Tedeschi, Eva Gonzalez-Barca, Edith Szafer-Glusman, Cathy Zhou, Lynne D. Neumayr, John N. Allan. Similar outcomes regardless of post-randomization treatment with ibrutinib or ibrutinib + venetoclax in the phase 2 CAPTIVATE study of first-line ibrutinib + venetoclax in CLL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT166.

Prognostic value of early bone marrow MRD status in CAR-T therapy for myeloma

Bone marrow (BM) assessment of minimal residual disease (MRD) is prognostic for survival in multiple myeloma (MM). BM is still hypocellular at month 1 post CAR-T, thus the value of MRD negative (MRDneg) status at this timepoint is unclear. We examined the impact of month 1 BM MRD status in MM patients who received CART at Mayo Clinic between 8/2016 and 6/2021. Among 60 patients, 78% were BM-MRDneg at month 1; and 85% (40/47) of these patients also had decreased to less than normal level of both involved and uninvolved free light chain (FLC < NL). Patients who achieved CR/sCR had higher rates of month 1 BM-MRDneg and FLC < NL. The rate of sustained BM-MRDneg was 40% (19/47). Rate of conversion from MRDpos to MRDneg was 5%(1/20). At month 1, 38%(18/47) of the BM-MRDneg were hypocellular. Recovery to normal cellularity was observed in 50%(7/14) with a median time to normalization at 12 months (range: 3–Not reached). Compared to Month 1 BM-MRDpos patients, patients who were BM-MRDneg had longer PFS irrespective of BM cellularity [PFS: 2.9 months (95% CI, 1.2-NR) vs. 17.5 months (95% CI, 10.4-NR), p < 0.0001]. Month 1 BM-MRDneg and FLC below normal were associated with prolonged survival. Our data support the continued evaluation of BM early post-CART infusion as a prognostic tool.

Abstract 3375: Ultrasensitive ctDNA minimal residual disease monitoring in early NSCLC with PhasED-Seq

Abstract Background: Circulating tumor DNA (ctDNA) minimal residual disease (MRD) detection is a promising approach for personalization of adjuvant therapy in non-small cell lung cancer (NSCLC). First generation ctDNA MRD assays that employ tumor-informed approaches to track single nucleotide variants (SNVs) have limits of detection (LOD95) of ~1E-4 and have high positive predictive values for recurrence. However, they have suboptimal clinical sensitivity, with false negative results at the completion of therapy in most patients who will ultimately recur. PhasED-Seq is a novel ctDNA MRD method that tracks multiple “phased” variants (PVs) within individual DNA fragments with a LOD95 ~100-fold better than first generation assays. Here we report PhasED-Seq ctDNA MRD results for the first prospective cohort of early stage NSCLC patients. Methods: Tumor tissues (n=46), PBMCs (n=46) and plasma samples (n=169) from 46 Stage I-III NSCLC patients treated with curative intent were prospectively collected at Memorial Sloan Kettering Cancer Center. All patients underwent resection and received neoadjuvant +/- adjuvant therapy (n=14), adjuvant therapy only (n=17), or neither (n=15). Samples were analyzed in Foresight Diagnostics' CLIA laboratory (Aurora, CO) using personalized PhasED-Seq. Briefly, PVs were identified via whole genome sequencing of tumors and matched blood germline DNA. Custom capture panels targeting PVs were synthesized and used to assess MRD status in pre-, on- and post-treatment plasma samples. Detection of ctDNA MRD was assessed at a post-treatment landmark, defined as the first post-therapy sample or when not available the last post-surgical sample taken during therapy. To enable comparisons, the same plasma samples were analyzed using an SNV-based ctDNA MRD approach. Results: PVs were identified in tumor tissue from all 46 patients. Across all plasma samples PhasED-Seq achieved a median LOD95 of 1.3E-6 and as low as 2.5E-7. Of 74 plasma samples with detectable ctDNA, 38 (51%) contained concentrations below 1E-4 and the lowest level of ctDNA MRD detected was 1.7E-7. For post-treatment landmark samples (n=45), the median time from end of therapy was 2 months. Cancer recurred in all patients (n=10) with detectable MRD at the landmark. Furthermore, PhasED-Seq better stratified freedom from recurrence (log-rank p=3E-8, Cox HR=10.8) than the SNV-based approach (log-rank p=0.08, Cox HR=2.5) and detected MRD at the landmark in more patients who ultimately recurred (56% vs 28%). PhasED-Seq also achieved longer lead times, including detecting MRD in 66% of samples collected 12 to 24 months prior to recurrence versus only 33% using SNV-based monitoring. Conclusion: PhasED-Seq achieves ctDNA detection below 1 part per million and appears to be significantly more sensitive than SNV-based MRD monitoring. These results suggest that PhasED-Seq is a promising approach for use in risk adapted trials in early stage NSCLC. Citation Format: James M. Isbell, Bob T. Li, Pedram Razavi, Jorge Reis-Filo, Si-Yang Liu, Pier Selenica, Prasad Adusumilli, Matthew Bott, David R. Jones, Valerie W. Rusch, Smita Sihag, Darren J. Buonocore, Justin Jee, Emily Lebow, Daniel Gomez, Andreas Rimner, Fernando C. Santini, Charles M. Rudin, Jordan E. Eichholz, Andres Martinez, Daphne Alerte, Gregory J. Hogan, Andre Schultz, Ronald P. Schuyler, Alanna Roff, Dustin Hite, Jacob J. Chabon, David M. Kurtz, Ash A. Alizadeh, Maximilian Diehn. Ultrasensitive ctDNA minimal residual disease monitoring in early NSCLC with PhasED-Seq [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3375.