HER2-positive Metastatic Colorectal Cancer Research Articles

Trastuzumab deruxtecan in HER2-positive metastatic colorectal cancer: less is more?

Trastuzumab deruxtecan in HER2-positive metastatic colorectal cancer: less is more?

Efficacy of Pyrotinib With/Without Trastuzumab in Treatment-Refractory, HER2-Positive Metastatic Colorectal Cancer: Result From a Prospective Observational Study

BackgroundHuman epidermal growth factor receptor 2 (HER2) is a promising therapeutic target in metastatic colorectal cancer (mCRC). This study was to evaluate the efficacy and safety of pyrotinib alone or pyrotinib with trastuzumab in patients with HER2-positive mCRC. Patients and MethodsIn this prospective observational study, patients with HER2 positive, Ras Sarcoma Viral Oncogene Homolog (RAS) wild type mCRC who received at least one standard treatment of palliative chemotherapy were enrolled. Patients were treated with oral pyrotinib alone or pyrotinib with trastuzumab. The primary endpoint was progression free survival (PFS), and the secondary endpoints were overall survival (OS), confirmed objective response rate (ORR), and safety. This trial is registered with chitcr.org, number ChiCTR2100046381. ResultsFrom February 15, 2021, to January 10, 2023, 32 patients were enrolled in this study. Twenty (62.5%) patients were treated with pyrotinib, while 12 (37.5%) received pyrotinib and trastuzumab. As of June 24, 2023, with a median follow-up of 11.0 months, the median PFS was 5.7 months (95%CI 4.5-10.2), while OS was not evaluable (NE), ORR and disease control rate (DCR were 34.4% and 87.5%. Patients’ PFS in the pyrotinib plus trastuzumab subgroup and pyrotinib monotherapy group were 8.6 and 5.5 months, OS was not evaluable (NE) and 10.9 months, ORR was 50.0% and 25.0%, respectively. Most treatment-related adverse events (TRAEs) were grade 1-2, diarrhea was the most frequent TRAE (81.3%, 26/32). Grade 3 TRAEs occurred in 11 patients: 9 for diarrhea, 1 for nausea, and 1 for oral mucositis. ConclusionPyrotinib with or without trastuzumab showed promising anti-tumor activity and acceptable toxicities in treatment-refractory, HER2-positive mCRC.

PRESSING Need of Precision Care in HER2-Positive Colorectal Cancer: The ELEPHANT in the Room.

Although dual HER2 inhibition has shown promising clinical activity in patients with RAS wild-type HER2-positive metastatic colorectal cancer, predictive biomarkers of response/resistance are less well characterized. Activating HER2/RTK/MAPK genomic alterations appears to blunt the clinical benefit of dual anti-HER2 therapy and may hold a potential albeit partial role in patient selection. See related article by Randon et al., p. 436.

A Meta-Analysis to Assess the Efficacy of HER2-Targeted Treatment Regimens in HER2-Positive Metastatic Colorectal Cancer (mCRC).

Recent trials provide evidence that HER2 is a potential new target for patients with colorectal cancer. While HER2-positive tumors do not show a very encouraging response to anti-HER2-positive agents like trastuzumab alone, promising results have been observed when combined with other synergistically acting tyrosine kinase inhibitors (TKIs). Our meta-analysis was conducted following the Cochrane Handbook and written following the PRISMA guidelines. The protocol was registered on PROSPERO with the registration number CRD42022338935. After a comprehensive search for relevant articles, 14 CTs were identified and uploaded to Rayyan, and six trials were ultimately selected for inclusion. The meta-analysis revealed that a median of three prior lines of therapy was used before enrolling in the six trials comprising 238 patients with HER2-positive metastatic colorectal cancer (mCRC). The pooled objective response rate (ORR) and disease control rate (DCR) were 31.33% (95% confidence interval [CI] 24.27-38.39) and 74.37% (95% CI 64.57-84.17), respectively. The pooled weighted progression-free survival (PFS) was 6.2 months. The pooled ORR and DCR meta-analysis indicate a significant response to HER2-targeted therapy in this patient in HER2-positive mCRC. Additionally, a pooled PFS of 6.2 months suggests that HER2-targeted treatment regimens are associated with a meaningful improvement in survival outcomes in this population.

Impact of Anti-EGFR Therapies on HER2-Positive Metastatic Colorectal Cancer: A Systematic Literature Review and Meta-Analysis of Clinical Outcomes.

HER2 overexpression/amplification in patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC) may be associated with resistance to standard-of-care anti-EGFR therapies. Given the lack of comprehensive investigations into this association, we assessed the prognostic or predictive effect of HER2 amplification/overexpression on anti-EGFR treatment outcomes. A systematic review of MEDLINE, Embase, and Cochrane Library (2001-2021) identified studies evaluating progression-free survival (PFS), overall response rate (ORR), and overall survival (OS) in HER2-positive vs. HER2-negative patients with RAS WT mCRC who received anti-EGFR treatments and whose HER2 status was known. Meta-analyses of proportions (ORR) and hazard ratios (PFS, OS) were performed using random-effect models with pre-specified sensitivity analyses. Five high-quality retrospective cohort studies were included in the meta-analyses representing 594 patients with mCRC. All patients received anti-EGFR treatment, either as monotherapy or in combination with chemotherapy. Meta-analysis of PFS demonstrated a 2.84-fold higher risk of death or progression (95% CI, 1.44-5.60) in patients with HER2-positive (vs. HER2-negative) RAS WT mCRC treated with anti-EGFR regimens. The odds of response to anti-EGFR treatment were 2-fold higher in HER2-negative vs. HER2-positive (odds ratio, 1.96 [95% CI, 1.10-3.48]). Differences in OS were not statistically significant. Sensitivity analyses confirmed the robustness of the base-case estimates. While this study could not account for all confounding factors, in patients with RAS WT mCRC who received anti-EGFR therapy, HER2 overexpression/amplification was associated with worse PFS and ORR and may therefore predict poorer outcomes. HER2 testing is important to inform treatment decisions and could optimize outcomes for patients.

Tucatinib plus trastuzumab for chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer (MOUNTAINEER): a multicentre, open-label, phase 2 study

HER2 is an actionable target in metastatic colorectal cancer. We assessed the activity of tucatinib plus trastuzumab in patients with chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer. MOUNTAINEER is a global, open-label, phase 2 study that enrolled patients aged 18 years and older with chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer at 34 sites (clinics and hospitals) in five countries (Belgium, France, Italy, Spain, and the USA). Initially, the study was designed as a single-cohort study, which was expanded following an interim analysis to include more patients. Initially, patients were given tucatinib (300 mg orally twice daily) plus intravenous trastuzumab (8 mg/kg as an initial loading dose, then 6 mg/kg every 21 days; cohort A) for the duration of treatment (until progression), and after expansion, patients were randomly assigned (4:3), using an interactive web response system and stratified by primary tumour location, to either tucatinib plus trastuzumab (cohort B) or tucatinib monotherapy (cohort C). The primary endpoint was confirmed objective response rate per blinded independent central review (BICR) for cohorts A and B combined and was assessed in patients in the full analysis set (ie, patients with HER2-positive disease who received at least one dose of study treatment). Safety was assessed in all patients who received at least one dose of study treatment. This trial is registered with ClinicalTrials.gov, NCT03043313, and is ongoing. Between Aug 8, 2017, and Sept 22, 2021, 117 patients were enrolled (45 in cohort A, 41 in cohort B, and 31 in cohort C), of whom 114 patients had locally assessed HER2-positive disease and received treatment (45 in cohort A, 39 in cohort B, and 30 in cohort C; full analysis set), and 116 patients received at least one dose of study treatment (45 in cohort A, 41 in cohort B, and 30 in cohort C; safety population). In the full analysis set, median age was 56·0 years (IQR 47-64), 66 (58%) were male, 48 (42%) were female, 88 (77%) were White, and six (5%) were Black or African American. As of data cutoff (March 28, 2022), in 84 patients from cohorts A and B in the full analysis set, the confirmed objective response rate per BICR was 38·1% (95% CI 27·7-49·3; three patients had a complete response and 29 had a partial response). In cohorts A and B, the most common adverse event was diarrhoea (55 [64%] of 86), the most common grade 3 or worse adverse event was hypertension (six [7%] of 86), and three (3%) patients had tucatinib-related serious adverse events (acute kidney injury, colitis, and fatigue). In cohort C, the most common adverse event was diarrhoea (ten [33%] of 30), the most common grade 3 or worse adverse events were increased alanine aminotransferase and aspartate aminotransferase (both two [7%]), and one (3%) patient had a tucatinib-related serious adverse event (overdose). No deaths were attributed to adverse events. All deaths in treated patients were due to disease progression. Tucatinib plus trastuzumab had clinically meaningful anti-tumour activity and favourable tolerability. This treatment is the first US Food and Drug Administration-approved anti-HER2 regimen for metastatic colorectal cancer and is an important new treatment option for chemotherapy-refractory HER2-positive metastatic colorectal cancer. Seagen and Merck & Co.

A systematic review to assess the efficacy of HER2-targeted treatment regimens in HER2-positive metastatic colorectal cancer (mCRC).

166 Background: Recently, there has been a breakthrough in the treatment and disease control of HER-2 positive mCRC using Trastuzumab (TRA) +Tyrosine Kinase inhibitor (TKI) regimens and regimens with trastuzumab based antibody drug conjugates (ADCs). Methods: A total of 14 randomized controlled trials and single arm clinical trials were collected from PubMed, Cochrane library, and Embase. 7 trials were excluded for being duplicate, irrelevant or because of lack of response from the trial researchers. Data from the remaining 7 articles was extracted either from the full publication or from researchers for undergoing studies. Trials using similar drug combinations were added up and results were reported cumulatively. Results: The data demonstrate an ORR of 30% or greater with the ADC, TRA deruxtecan or TRA+Tucatinib regimen with the Tucatinib combination being the most efficacious (38.10%), followed closely by the Deruxtecan ADC (36.99%). Promising disease control rate (DCR) was observed with all the combinations with TRA-Ematasin + Pertuzumab leading the charts (77.40%). TRA-Lapatinib provided the longest PFS (16.75 months) followed by TRA-Tucatinib (8.2 months) (Table). Most common treatment related adverse events (AEs) were fatigue, nausea, vomiting, diarrhea and dermatitis. More nausea/vomiting reported with TRA-deruxtecan (64.4%), while more diarrhea reported with TRA-lapatinib (81%) and TRA-tucatinib (52.3%). Dermatitis was reported mostly with TRA-lapatinib (44%) and TRA-tucatinib (17.4%). Conclusions: Our analysis shows that combination treatment with TRA-Deruxtecan and TRA-tucatinib are associated with the highest ORR and DCR in HER2+ mCRC. Long term data are needed to define clinical efficacious based on survival endpoints.[Table: see text]

Trajectory for the Regulatory Approval of a Combination of Pertuzumab Plus Trastuzumab for Pre-treated HER2-positive Metastatic Colorectal Cancer Using Real-world Data

Utilizing real-world data (RWD) for effective clinical implementation is becoming more and more appealing as the cost of drug development rises, especially for patients with rare diseases and rare molecular subtypes for whom conducting randomized controlled trials is challenging. If a regulatory approval methodology based on RWD as an external control group can be established, drug development for rarer fractions can be accelerated by lowering costs and time, as well as reducing physical and emotional burdens on both patients and healthcare professionals. Since 2017, we have been prospectively collecting the clinical data of standard therapies in patients with rare molecular fractions under the SCRUM-Japan Registry platform, which is a qualified registry utilized as external control data for regulatory submission. Based on the results of the phase II TRIUMPH study (UMIN000027887) and the extracted data from the SCRUM-Japan Registry, the pharmaceutical company submitted an application for pertuzumab and trastuzumab in patients with HER2-positive metastatic colorectal cancer in April 2021. Pertuzumab and trastuzumab were approved as expanded indications on March 28, 2022, as 6 cases out of 14 extracted from the SCRUM-Japan Registry were classified and utilized as “evaluation material” under the review process of the Pharmaceuticals and Medical Devices Agency (PMDA). Through the TRIUMPH study and the SCRUM-Japan Registry, we have paved the way for regulatory approval of RWD in Japan. In future, we must define the steps for constructing regulatory-grade registries and the method/process for utilizing RWD by accumulating case experiences.

1705P HER2 intratumoral genetic and non-genetic heterogeneity in metastatic colorectal cancer

HER2-positive metastatic colorectal cancer (mCRC) is a distinct subtype for which HER2-targeted therapy is established. HER2 intratumoral heterogeneity (ITH), containing two types of heterogeneity–genetic heterogeneity (GH, a mixture of HER2 positive and negative tumor cells) and non-genetic heterogeneity (NGH, a mixture of HER2 positive tumor cells and amplified HER2 gene tumor cells without HER2 protein expression)– is a predictor of response to HER2-targeted treatment in breast cancer (BC). Here, using samples with mCRC, we evaluated the diagnostic accuracy of the Gene-Protein Assay (GPA), an assay assessing HER2 ITH by a combined HER2 immunohistochemistry (IHC) and bright-field HER2 in situ hybridization (ISH) on the same tissue section, and the frequency of HER2 ITH and heterogeneous patterns.

376P Impact of anti-EGFR therapies on HER2-positive metastatic colorectal cancer (HER2+ mCRC): A systematic literature review and meta-analysis of clinical outcomes

HER2 overexpression/amplification in patients with RAS wild-type (WT) mCRC may be associated with resistance to standard of care anti-EGFR therapies. However, there are no meta-analyses investigating this association. Our objective was to assess the predictive effect of HER2 amplification/overexpression on anti-EGFR treatment outcomes.

361P Tucatinib plus trastuzumab in patients (Pts) with HER2-positive metastatic colorectal cancer (mCRC): Patient-reported outcomes (PROs) from ph II study MOUNTAINEER

HER2 amplification/overexpression (HER2-positive [HER2+]) is reported in ∼3-5% of all pts with mCRC. Treatment strategies for mCRC focus on prolonging survival, delaying tumor progression, and maintaining health-related quality of life (HRQoL). Tucatinib (TUC) is a highly selective, HER2-directed, tyrosine kinase inhibitor. Results from the MOUNTAINEER (NCT03043313) study demonstrated that dual HER2 inhibition with TUC and trastuzumab (T) in pts with HER2+ RAS WT mCRC is well tolerated with durable clinical benefit. Here we report the impact of TUC + T on HRQoL in pts from MOUNTAINEER. MOUNTAINEER is a global, multi-center, open-label, phase 2 trial that enrolled pts with HER2+ RAS WT mCRC previously treated with fluoropyrimidine, oxaliplatin, irinotecan, and anti-VEGF mAb. Overall, 117 pts were enrolled or randomized to receive TUC + T (cohorts A [n=45] and B [n=41]) or TUC monotherapy (cohort C [n=31]). HRQoL was assessed with EQ-5D-5L and EORTC QLQ-C30 for cohorts B and C. Cohort A was not assessed for HRQoL. Questionnaires were administered at predose on Cycle 1 Day 1 (C1 D1), C1 D8, C1 D15, then every D1 of C2-4 and every 3 following cycles until end of treatment. HRQoL data for cohorts B and C were analyzed using descriptive statistics. Thirty-seven pts in cohort B and 28 pts in cohort C had ≥1 dose of study treatment and completed baseline and at least 1 follow-up HRQoL assessment. For both cohorts, the mean changes from baseline during the treatment period for EORTC QLQ-C30 generally remained stable across all scales, including global health status/QoL and functional domains. Descriptive analyses showed some fluctuations in observed individual domain scores; however, global health status/QoL remained stable over time. EQ-5D-5L VAS scores also remained similar over time. HRQoL was maintained for pts treated with TUC + T or TUC monotherapy throughout the treatment period. These results, together with the primary efficacy and safety data from MOUNTAINEER, further support the overall tolerability profile of TUC + T and suggest this regimen may be an important treatment option for pts with HER2+ mCRC.

HER2 status is positively associated with vessel invasion of colorectal cancer: a retrospective large cohort study

PurposeHER2-positive colorectal cancer was drawn increasing attention in recent years. Accumulating evidence showed HER2-positive metastatic colorectal cancer could benefit from HER2-targeted therapy. While HER2 expression and the relationship between HER2 status and clinicopathological characteristics of overall colorectal cancer remains largely unknown. The aim of this study was to evaluate HER2 expression in colorectal cancer and compare the clinicopathological features between HER2-positive and HER2-negative colorectal cancer.MethodsWe retrospectively analyzed 3910 primary colorectal cancer patients treated in our institution from January 2016 to December 2019. Medical records and pathology reports after surgery were collected to provide information about HER2 status and other clinicopathological characteristics.ResultsWe identified 3347 HER2-negative and 79 HER2-positive colorectal cancer patients in our cohort. The chi-square test showed that vessel invasion was significantly more common in HER2-positive colorectal cancer patients. Crude analysis showed HER2 positive was associated with vessel invasion in colorectal cancer [OR and 95% CI 0.534 (0.341, 0.835), p = 0.006]. After adjusting for N stage, a significant association was still observed between HER2 status and vessel invasion in colorectal cancer [OR and 95% CI 0.550 (0.322, 0.941), p = 0.029]. Survival analysis showed that there was no significant difference in 3-year overall survival rate between HER2 positive and HER2 negative group (p = 0.603).ConclusionOur findings indicate that the rate of HER2 positivity in colorectal cancer was relatively low, and HER2 status was strongly associated with vessel invasion while having no significant influence on the 3-year overall survival rate in colorectal cancer patients.

Dual HER2 Targeted Therapy With Pyrotinib and Trastuzumab in Refractory HER2 Positive Metastatic Colorectal Cancer: A Result From HER2-FUSCC-G Study

BackgroundDual-HER2 targeted therapy has led to a promising antitumor effect in HER2 positive cancers including gastrointestinal cancer. The present data focus on patients with HER2 positive colorectal cancer who received pyrotinib and trastuzumab after failure to standard second-line treatment. MethodsPatients diagnosed of HER2 positive refractory or metastatic colorectal cancer were enrolled to receive trastuzumab in combination with pyrotinib as third-line and beyond therapy. Trastuzumab was given as a loading dose at 8 mg/kg followed by 6mg/kg once every 3 weeks, and oral pyrotinib as 400 mg per day until progression. ORR was set as the primary endpoint. PFS and OS were set as a secondary endpoints. This trial is registered with Clinical Trial.gov, NCT04960943, and is ongoing. ResultsBetween February 2020 to December 2021, 16 patients including 14 with RAS wild-type status were enrolled in this cohort. ORR was 50.0% in the overall population, and 57.1% in RAS wild-type patients. At a median follow-up of 11.2 months, median PFS and OS were 7.53 and 16.8 months, respectively. The RAS/BRAF wild-type patients had prolonged survival (PFS: 7.53 vs. 1.63 months, P = .02; OS: NR vs.4.13 months, P = .001) compared with RAS/BRAF mutant patients. The most common treatment-emergent adverse event (TEAE) reported is diarrhea. Five (31.3%) patients reported grade 3 TEAEs, and no death was reported. ConclusionsTrastuzumab in combination with pyrotinib demonstrated encouraging antitumor activity that translated to prolonged survival benefit in HER2 positive refractory or mCRC patients who are RAS wild-type with acceptable tolerance.

Clinicopathological features of HER2 positive metastatic colorectal cancer and survival analysis of anti-HER2 treatment

BackgroundWe aimed to investigate response and prognostic factors in patients with human epidermal growth factor receptor 2 (HER2) positive metastatic colorectal cancer (mCRC) and compare the curative effect on patients who received different therapy regimens (including chemotherapy and chemotherapy combined with targeted drugs).MethodsWe retrospectively analyzed all HER2 positive mCRC patients treated at Peking University Cancer Hospital between September 2011 and February 2021. We divided 63 HER2 positive mCRC into group A and group B according to the use of trastuzumab or not. Besides, we assigned four subgroups according to the first-line therapies of KRAS/NRAS/BRAF WT patients. The Kaplan–Meier estimator was used to calculate PFS and OS. Univariable analysis and Cox proportional hazards models were used to analyze the association between clinicopathological features and survival outcomes.ResultsAmong 63 patients, 54 (85.7%) were KRAS/NRAS/BRAF wild-type (WT). Univariate analysis showed that the male sex, primary lesions in the right colon, simultaneous metastasis, and unresectable primary lesions were significant risk factors for poor survival of HER2 positive mCRC (P < 0.05). Using Cox proportional hazards models, we found that the two factors of gender and resection of primary lesions were independent prognostic factors (P < 0.05). The median PFS and median OS of HER2-positive patients with mCRC who received first-line treatment were 8.4 months [95% confidence interval (CI): 5.0–11.7] and 48.2 months (95% CI: 23.5–72.8), respectively. The log-rank test revealed a significant difference in median OS survival between group A and group B (χ2 = 5.852, P = 0.016), and the two groups were divided according to the use or absence of trastuzumab treatment. In KRAS/NRAS/BRAF WT patients, there was a significant difference in median PFS and median OS between the fourth group patients (chemotherapy plus trastuzumab) and each of the other three groups (P < 0.05).ConclusionsThe two factors of gender and resection for primary lesion may be independent prognostic factors of advanced HER2 positive colorectal cancer patients. For patients with HER2-positive mCRC, patients in the chemotherapy combined with trastuzumab group have better efficacy than those without trastuzumab.

Anti-HER2 therapy with pyrotinib and trastuzumab in refractory HER2-positive metastatic colorectal cancer: A preliminary report from HER2-FUSCC-G study.

97 Background: Dual-targeted HER2 therapy has led to a promising antitumor effect in HER2 positive metastatic colorectal cancer. The current study was aimed to evaluate the therapeutic efficacy of pyrotinib and trastuzumab in patients with HER2 positive colorectal cancer. Methods: HER2-FUSCC-G is an ongoing, open-label, non-randomised, phase 2a study. Patients in this subset were diagnosed as HER2 positive metastatic colorectal cancer refractory to standard chemotherapies. All the enrolled patients were treated with a loading dose of trastuzumab at 8 mg/kg followed by 6mg/kg once every three weeks, and oral pyrotinib at 400 mg per day until progression. ORR was set as the primary endpoint. Estimates of PFS (progression free survival) and OS (overall survival) were obtained with the Kaplan-Meier method and compared with log-rank test. Results: Between January 2020 to June 2021, 11 patients were enrolled in this study. The ORR was 45.5% in whole population, and 55.6% in RAS wild-type patients. At a median follow-up of 17.73 months, median PFS and OS were 7.80 and 14.97 months, respectively. The KRAS wild-type group of patients had prolonged survival (PFS: 9.97 vs. 7.73 months, P = 0.19; OS: 20.67 vs. 12.43 months, P = 0.021) compared with KRAS mutant group. Nine of 11 (81.8%) patients reported≥1 grade treatment-emergent adverse events (TATEs), while 4 (36.4%) patients reported grade 3/4 TATEs. Conclusions: The combination of trastuzumab and pyrotinib showed a promising anti-tumor response and prolonged long-term survival benefit in RAS wild-type and HER2 positive mCRC with acceptable tolerance. Clinical trial information: NCT04960943.

Trastuzumab combined with irinotecan in patients with HER2-positive metastatic colorectal cancer: A phase II multicenter single-arm study and exploratory biomarker analysis.

301 Background: HER2 overexpression has proven to be an effective treatment target in several malignancies. Trastuzumab plus chemotherapy showed favorable clinical efficacy and safety in HER2-positive gastric cancer and breast cancers. In this study, we aimed to evaluate the antitumor activity of trastuzumab plus irinotecan in pretreated patients with HER2-postive unresectable metastatic CRC and explore biomarkers for response and resistance to this treatment. Methods: mCRC patients with confirmed HER2 positivity (defined as IHC3+ or IHC2+/FISH+ on archival tissue) and wild-type RAS gene that progressed after ≥ 1 prior systemic treatment were enrolled in this phase II clinical trial. Patients received trastuzumab (6mg/kg q3w) plus irinotecan (120mg/m2, d1,8 q3w) for the first six cycles and trastuzumab (6mg/kg q3w) as maintenance treatment sequentially. Primary end point is objective response rate (ORR) and secondary endpoints are progression-free survival (PFS) and safety. Pretreatment tumor tissue, plasma at baseline and after disease progression were collected and analysed using a customized NGS panel covering 733 cancer-related genes in a CAP/CLIA-approved laboratory (3DMed). Results: Between June 2019 and December 2020, 21 HER2 positive patients were enrolled, with median age 55(30-67). At data cutoff (August 1, 2021), six (28.6%) of 21 patients achieved a partial response, and 12 (57.1%) patients had stable disease. The median progression-free survival was 4.3 months (95% CI, 2.65 to 5.95 months). Treatment-related adverse events of grade 3 or 4 occurred in 9.5% of patients, with the most common being neutropenia. No treatment-related death was reported. HER2 3+ expression and higher tumor tissue HER2 copy number were associated with durable response (p for PFS = 0.09 and 0.019, respectively). Two patients with KRAS amplification and one patient with BRAF amplification and fusion mutation at baseline all experienced primary resistance. In the after-progression plasma samples, heterogeneous and complicated genomic alterations potentially contribute to the acquired resistance were observed, with RAS/MAPK pathway (n = 4), cyclin/CDK-RB-E2F pathway (n = 4), PI3K/AKT/mTOR pathway (n = 3), and HER2 gene (n = 1) involved. Intriguingly, except for the SNV, copy number variation and gene fusion may represent an important resistance mechanism of HER2 targeted therapy. Conclusions: Trastuzumab plus irinotecan showed promising efficacy and well tolerated safety profile in HER2-positive mCRC. This combination therapy might present a feasible option for patients with HER2-positive unresectable metastatic colorectal adenocarcinoma. ctDNA sequencing provides novel insights into genomic alteration underlying HER2 targeted therapy in HER2-positive mCRC. Clinical trial information: NCT03185988.

446P Bayesian monitoring of lapatinib (L) plus trastuzumab (T) treatment of HER2 positive metastatic colorectal cancer (mCRC): An observational cohort study

HER2 positivity is found in 3-5% of mCRC. The phase II HERACLES-A trial showed that dual anti-HER2 therapy with T + L has 30% response rate (RR) in HER2+ RAS wt mCRC after failure of standard care (Sartore-Bianchi 2016). These data led to inclusion of T+ L among recommended treatments by NCCN and other guidelines, but still lack confirmation by large trials comparing treatments. The latter, especially for this uncommon subset of mCRC, would require efforts unbearable in the setting of independent clinical research.

PD-1 MOUNTAINEER: Open-label, phase 2 study of tucatinib combined with trastuzumab for HER2-positive metastatic colorectal cancer (SGNTUC-017, trial in progress)

The clinical benefit of approved therapies in patients (pts) with metastatic colorectal cancer (mCRC) who progress on first- and second-line chemotherapy (FOLFOX and FOLFIRI) is limited. In pts with chemotherapy-refractory RAS wild type mCRC, antibodies targeting EGFR offer a monotherapy response rate of approximately 20% and a progression-free survival (PFS) of 4 months (Price 2014). HER2 is a validated target in gastric and breast cancers, with HER2 amplification occurring in ∼3–5% of pts with mCRC.

Dual-targeted therapy with pyrotinib and trastuzumab for HER2-positive advanced colorectal cancer: Preliminary results from a multicenter phase 2 trial.

e15554 Background: HER2 is an emerging treatment target for colorectal cancer (CRC). Previous phase 2 trials have demonstrated the promising antitumor activity of dual HER2 inhibition with trastuzumab plus lapatinib or pertuzumab in HER2-positive metastatic CRC. Pyrotinib, a novel irreversible HER2/EGFR dual tyrosine kinase inhibitor, has been approved for breast cancer in 2018 in China. The antitumor effect of pyrotinib was also shown in other solid tumors, such as lung cancer and gastric cancer. The randomized phase 3 PHOEBE trial proved that the efficacy of pyrotinib was better than lapatinib when in combination with capecitabine in HER2-positive local relapsed or metastatic breast cancer. We reported preliminary results of pyrotinib plus trastuzumab in patients with HER2-positive advanced CRC from an ongoing multicenter phase 2 trial (NCT04380012). Methods: Patients with confirmed recurrent/metastatic CRC, HER2-positive disease, and ECOG performance status 0-2, received oral pyrotinib 400 mg once a day plus intravenous trastuzumab 8 mg/kg loading dose followed by 6 mg/kg once every 3 weeks. The primary endpoint was objective response rate (ORR), as assessed according to the Response Evaluation Criteria In Solid Tumors version 1.1. The data cutoff date was December 24, 2020. Results: From December 2019 to November 2020, a total of 11 patients were enrolled. The median age was 57 (range, 44-70) years and 73% (8/11) of patients were male. The number of prior therapy lines was 0, 1, and ≥2 in 1 (9%), 2 (18%), and 8 (73%) patients, respectively. One (9%) patient only showed HER2 overexpression, 7 (64%) showed HER2 amplification and overexpression, and 3 (27%) showed HER2 mutation and overexpression. The detection of co-mutations showed that 5 (45%) patients had KRAS mutations, 1 (9%) had NRAS mutation, and none had BRAF mutation. Three patients achieved partial response, with an ORR of 27% (3/11) in the total population, 50% (3/6) in KRAS wild-type patients, and 60% (3/5) in patients with wild type of both KRAS and NRAS, respectively. The disease control rate was 45% (5/11). The most common (occurring in at least 2 patients) grade ≥3 adverse event was diarrhea (73% [8/11]). Dose interruption owing to diarrhea occurred in 7 (64%) patients, and 5 (45%) patients reduced the dose to 320 mg due to diarrhea. No treatment-related death was observed. Conclusions: Pyrotinib combined with trastuzumab showed promising ORR with acceptable safety in patients with HER2-positive advanced CRC, suggesting a potential treatment option, especially in those without co-mutations. Clinical trial information: NCT04380012.

Trastuzumab deruxtecan: heralding biomarker-directed therapy in metastatic colorectal cancer.

Biomarker-directed therapy is increasingly being used to treat metastatic colorectal cancer, including using RAS mutational status to select patients for EGFR antibodies use, mismatch repair deficiency to select patients for treatment with PD-1 and CTLA-4 antibodies, and, more recently, BRAF mutational status to select for treatment with encorafenib plus cetuximab. Trastuzumab deruxtecan (DS-8201) in patients with HER2-expressing metastatic colorectal cancer (DESTINY-CRC01): a multicentre, open-label, phase 2 trialTrastuzumab deruxtecan showed promising and durable activity in HER2-positive metastatic colorectal cancer refractory to standard treatment, with a safety profile consistent with that reported in previous trastuzumab deruxtecan trials. Interstitial lung disease and pneumonitis are important risks requiring careful monitoring and prompt intervention. Full-Text PDF