Curative resection via right hemicolectomy and regional lymph node dissection for colonic adenomatous polyposis of unknown etiology with adenocarcinomas localized in the right side of the colon: a case report.

BACKGROUND: APC and MUTYH are both well-known colorectal polyposis causative genes. However, 30-50% of colorectal adenomatous polyposis cases are classified as colonic adenomatous polyposis of unknown etiology and lack identifiable pathogenic variants. Although guidelines recommend total proctocolectomy for colonic adenomatous polyposis of unknown etiology with over 100 adenomas, evidence is lacking. This study presents a unique case of localized colonic adenomatous polyposis of unknown etiology with multiple adenocarcinomas, treated with hemicolectomy and regional lymph node dissection. CASE PRESENTATION: The patient was a 72-year-old woman whose colonoscopy revealed numerous polyps and two adenocarcinomas localized in the right side of the colon, with no lesions in the left side. The patient had no family history of polyposis or colorectal cancer. No extracolonic lesions, enlarged lymph nodes, or distant metastases were found. Considering the patient's age and lesion localization, laparoscopic right hemicolectomy with regional lymph node dissection was performed. Histopathological diagnosis revealed three adenocarcinoma lesions with no lymph node metastasis. The most advanced pathological stage was T2N0M0 Stage I (UICC 8th edition). The patient was alive 5 years postoperatively, without recurrence of cancer or polyposis in the remaining colon and rectum. To diagnose hereditary colorectal cancer/polyposis, a germline multigene panel testing for APC, EPCAM, MBD4, MLH1, MLH3, MSH2, MSH3, MSH6, MUTYH, NTHL1, PMS2, POLD1, POLE, and TP53 was performed using DNA extracted from blood samples: however, no pathogenic variant was detected. Therefore, the patient was diagnosed with colonic adenomatous polyposis of unknown etiology. CONCLUSIONS: In this rare case, colonic adenomatous polyposis of unknown etiology, with numerous adenomatous polyps and multiple adenocarcinomas localized in the right side of the colon, was successfully treated with right hemicolectomy and regional lymph node dissection. Despite genetic analysis, no causative germline variants were identified. Segmental colectomy according to the distribution of polyps might be a curative approach.

Incidence and molecular characteristics of deficient mismatch repair conditions across nine different tumors and identification of germline variants involved in Lynch-like syndrome.

BACKGROUND: Based on molecular characteristics, deficient DNA mismatch repair (dMMR) solid tumors are largely divided into three categories: somatically MLH1-hypermethylated tumors, Lynch syndrome (LS)-associated tumors, and Lynch-like syndrome (LLS)-associated tumors. The incidence of each of these conditions and the corresponding pathogenic genes related to LLS remain elusive. METHODS: We identified dMMR tumors in 3609 tumors from 9 different solid organs, including colorectal cancer, gastric cancer, small-bowel cancer, endometrial cancer, ovarian cancer, upper urinary tract cancer, urinary bladder cancer, prostate cancer, and sebaceous tumor, and comprehensively summarized the characterization of dMMR tumors. Characterization of dMMR tumors were performed as loss of at least one of MMR proteins (MLH1, MSH2, MSH6, and PMS2), by immunohistochemistry, followed by MLH1 promotor methylation analysis and genetic testing for MMR genes where appropriate. Somatic variant analysis of MMR genes and whole exome sequencing (WES) were performed in patients with LLS. RESULTS: In total, the incidence of dMMR tumors was 5.9% (24/3609). The incidence of dMMR tumors and the proportion of the three categorized dMMR tumors varied considerably with different tumor types. One to three likely pathogenic/pathogenic somatic MMR gene variants were detected in 15 out of the 16 available LLS tumors. One patient each from 12 patients who gave consent to WES demonstrated non-MMR germline variants affect function (POLQ or BRCA1). CONCLUSIONS: Our data regarding the LS to LLS ratio would be useful for genetic counseling in patients who are suspected to have LS, though the genetic backgrounds for the pathogenesis of LLS need further investigation.

ctDNA improves prognostic prediction in relapsed/refractory MM receiving ixazomib, lenalidomide, and dexamethasone.

It remains elusive how driver mutations, including those detected in circulating tumor DNA (ctDNA), affect prognosis in relapsed/refractory multiple myeloma (RRMM). Here we performed targeted-capture sequencing using bone marrow plasma cells (BMPC) and ctDNA of 261 RRMM cases uniformly treated with ixazomib, lenalidomide, and dexamethasone in a multicenter, prospective, observational study. We detected 24 and 47 recurrently mutated genes in BMPC and ctDNA, respectively. In addition to clonal hematopoiesis-associated mutations, varying proportion of driver mutations, particularly TP53 mutations (59.2% of mutated cases), were present in only ctDNA, suggesting their subclonal origin. In univariable analyses, ctDNA mutations of KRAS, TP53, DIS3, BRAF, NRAS, and ATM were associated with worse progression-free survival (PFS). BMPC mutations of TP53 and KRAS were associated with inferior PFS, while KRAS mutations were prognostically relevant only when detected in both BMPC and ctDNA. A total number of ctDNA mutations in the six relevant genes was a strong prognostic predictor (2-year PFS rates: 57.3%, 22.7%, and 0% for 0, 1, and ≥ 2 mutations, respectively) and independent of clinical factors and plasma DNA concentration. Using the number of ctDNA mutations, plasma DNA concentration, and clinical factors, we developed a prognostic index (ctRRMM-PI), classifying patients into three categories with 2-year PFS rates of 57.9%, 28.6%, and 0%. Serial analysis of ctDNA mutations in 94 cases revealed that TP53 and KRAS mutations frequently emerge after therapy. Thus, we clarify the genetic characteristics and clonal architecture of ctDNA mutations and demonstrate their superiority over BMPC mutations for prognostic prediction in RRMM.

Risk of metachronous colorectal cancer after surgical resection of index rectal cancer in Lynch syndrome: a multicenter retrospective study in Japan.

PURPOSE: This study evaluated the risk of metachronous colorectal cancer (CRC) after resection of index (first) rectal cancer in patients with Lynch syndrome (LS). METHODS: Clinicopathological data of patients with genetically proven LS were retrospectively analyzed in this multicenter Japanese study. The cumulative incidence of metachronous CRC and the overall survival were compared between patients with index rectal cancer (rectal group) and those with index colon cancer (colon group). RESULTS: The median age at index CRC surgery was lower in the rectal group than in the colon group (37 vs. 46 years old, P = 0.01). The cumulative 5-, 10-, and 20-year incidences of metachronous CRC were 3.5%, 13.9%, and 21.1%, respectively, in the rectal cancer group and 14.9%, 22.0%, and 57.9%, respectively, in the colon cancer group (P = 0.02). The overall survival curves were not significantly different between two groups (P = 0.23). CONCLUSION: This is the first report from an East Asian country to report the risk of metachronous CRC after resection of index rectal cancer in patients with LS. Despite this study having several limitations, we cannot recommend extended resection, such as total proctocolectomy, for index rectal cancer as a standard surgical treatment in patients with LS.

Treatment-related neuroendocrine prostate cancer with BRCA2 germline mutation treated with olaparib.

Introduction: The efficacy of olaparib for treatment-related neuroendocrine prostate cancer is unknown. Here, we report a case of treatment-related neuroendocrine prostate cancer with a BRCA2 mutation that was treated with olaparib with 1-year efficacy. Case presentation: A 75-year-old man initially diagnosed with prostate adenocarcinoma developed treatment-related neuroendocrine prostate cancer after 10-year androgen deprivation therapy. Despite the initial temporary effects of etoposide and carboplatin, the patient experienced prostate bed tumor recurrence 1 year after chemotherapy cessation. FoundationOne® detected a BRCA2 gene mutation, and olaparib was initiated after repeating one chemotherapy course using the same chemotherapeutic agents. The patient received olaparib with sustained tumor regression for 1 year without severe side effects. Conclusion: Olaparib may be the treatment of choice for treatment-related neuroendocrine prostate cancer in patients with BRCA mutations.

Baseline ctDNA gene alterations as a biomarker of survival after panitumumab and chemotherapy in metastatic colorectal cancer.

Certain genetic alterations and right-sided primary tumor location are associated with resistance to anti-epidermal growth factor (EGFR) treatment in metastatic colorectal cancer (mCRC). The phase 3 PARADIGM trial (n = 802) demonstrated longer overall survival with first-line anti-EGFR (panitumumab) versus antivascular endothelial growth factor (bevacizumab) plus modified FOLFOX6 in patients with RAS wild-type mCRC with left-sided primary tumors. This prespecified exploratory biomarker analysis of PARADIGM (n = 733) evaluated the association between circulating tumor DNA (ctDNA) gene alterations and efficacy outcomes, focusing on a broad panel of gene alterations associated with resistance to EGFR inhibition, including KRAS, NRAS, PTEN and extracellular domain EGFR mutations, HER2 and MET amplifications, and ALK, RET and NTRK1 fusions. Overall survival was prolonged with panitumumab plus modified FOLFOX6 versus bevacizumab plus modified FOLFOX6 in patients with ctDNA that lacked gene alterations in the panel (that is, negative hyperselected; median in the overall population: 40.7 versus 34.4 months; hazard ratio, 0.76; 95% confidence interval, 0.62-0.92) but was similar or inferior with panitumumab in patients with ctDNA that contained any gene alteration in the panel (19.2 versus 22.2 months; hazard ratio, 1.13; 95% confidence interval, 0.83-1.53), regardless of tumor sidedness. Negative hyperselection using ctDNA may guide optimal treatment selection in patients with mCRC. ClinicalTrials.gov registrations: NCT02394834 and NCT02394795 .

A prospective, multicenter, observational study of ixazomib plus lenalidomide-dexamethasone in patients with relapsed/refractory multiple myeloma in Japan.

Real-world studies permit inclusion of a more diverse patient population and provide more information on the effectiveness of treatments used in routine clinical practice. This prospective, multicenter, observational study investigated the effectiveness and safety of ixazomib plus lenalidomide and dexamethasone (IRd) in 295 patients with relapsed/refractory multiple myeloma (RRMM) in routine clinical practice in Japan. Patients had a median age of 74 years, 80.0% were aged ≥ 65 years, 42.0% had received ≥ 3 lines of prior treatment, and 28.5% were "frail" according to the International Myeloma Working Group frailty score. After a median follow-up of 25.0 months, median progression-free survival (PFS) was 15.3 (95% CI 12.4-19.5) months, while median overall survival was not reached. The overall response rate was 53.9%, and 31.5% of patients had a very good partial response or better. In the subgroup analysis, median PFS was better in patients with 1 versus 2 or ≥ 3 lines of prior treatment (29.0 vs 19.2 or 6.9 months) and paraprotein versus clinical relapse (16.0 vs 7.9 months), but median PFS was not notably affected by frailty score or age group. Dose adjustment was more frequent among patients aged > 75 years, especially early after IRd treatment initiation. Treatment-emergent adverse events (TEAEs) of any grade occurred in 84.4% of patients and 24.7% of patients discontinued treatment due to TEAEs; no new safety concerns were found. These findings suggest that oral IRd triplet regimen is an effective and tolerable treatment option for RRMM patients in real-world settings outside of clinical trials.ClinicalTrials.gov identifier: NCT03433001; Date of registration: 14 February 2018.

[A Case of Transverse Colon Cancer Associated with Lynch Syndrome with Excellent Response to Pembrolizumab].

A 47-year-old woman diagnosed with transverse colon cancer with liver, peritoneal, and lymph node metastases was admitted. Modified FOLFOX6(mFOLFOX6)regimen was given as a first line chemotherapy and was followed by pembrolizumab after 1 cycle of the mFOLFOX6, because microsatellite instability(MSI)test of the tumor showed high-frequency MSI. Because of the transverse colon obstruction after 2 cycles of pembrolizumab, she underwent right hemicolectomy. Histological examination of the resected specimen revealed no residual tumor cells in the primary tumor and reginal lymph nodes. Immunohistochemistry for mismatch repair proteins(IHC-MMR)showed loss of MSH2 and MSH6 expression. Genetic test identified a MSH2 pathogenic variant leading to the diagnosis of Lynch syndrome. The present case shows the importance of MSI test or IHC-MMR before the treatment of metastatic colorectal cancer.

Usefulness of genotyping APC gene for individualizing management of patients with familial adenomatous polyposis.

BACKGROUND: Colorectal polyp burden is crucial for the management of patients with familial adenomatous polyposis (FAP). However, accurate evaluation of polyp burden is difficult to standardize. This study aimed to examine the possible utility of genotype-oriented management of colorectal neoplasms in patients with FAP. METHODS: Clinicopathological data from genetically proven patients with FAP was analyzed using the database of a nationwide retrospective Japanese multicenter study. The cumulative incidence of CRC was evaluated between different genotype groups. Genotype-1 were defined as germline variants on attenuated FAP-associated regions (codons 1-177, alternative splice site of exon 10 (codon 312), 1581-2843) and Genotype-2 as the other variants. Weibull and Joinpoint analyses were performed to determine the annual percentage changes in CRC risk. RESULTS: Overall, 69 men and 102 women were included. Forty-eight patients underwent colorectal resection for the first CRC, and five patients underwent resection for first cancer in the remnant anorectal segment after prophylactic surgery. The 70-year cumulative incidence of CRC in all patients was 59.3%. Patients with Genotype-1 (n = 23) demonstrated a lower risk of CRC stages II-IV than those with Genotype-2 (n = 148, P = 0.04). The risk of stage II-IV CRC was estimated to increase markedly at the age of 49 years in the Genotype-1 patients and 34 years in the Genotype-2 patients, respectively. CONCLUSIONS: Different interventional strategies based on genotypes may be proposed for the clinical management of patients with FAP. This policy needs to be validated in further prospective studies focusing on long-term endoscopic intervention and optimal age at prophylactic (procto)colectomy.

Concordance between microsatellite instability testing and immunohistochemistry for mismatch repair proteins and efficient screening of mismatch repair deficient gastric cancer.

Microsatellite instability (MSI) testing, an established technique that has gained prominence in recent years for its predictive potential regarding the efficacy of immune checkpoint inhibitors, is used to evaluate DNA mismatch repair (MMR) deficiency (dMMR). As with other methods, the immunohistochemistry (IHC) of MMR proteins is also widely adopted. Although both techniques have been validated, their concordance rate remains unknown, particularly regarding non-colorectal cancer. Therefore, the aim of the present study was to explore and elucidate their concordance in the context of gastric cancer (GC). A total of 489 surgically resected primary GC tissues were analyzed to compare the results yielded by the MSI test and those from IHC. Of 488 GC cases, 56 (11.5%) exhibited a loss of MMR proteins, whereas 52 (10.7%) were classified as high-frequency MSI (MSI-H). The concordance rate between these two categories was 99.2%. The microsatellite markers BAT26 and MONO27 demonstrated 100% sensitivity and 99.5% specificity in detecting dMMR GC. In addition, histopathological analysis revealed that MSI-H was more prevalent in GCs exhibiting coexisting Tub2 and Por1 subtypes. However, four discordant cases were observed. All four cases were microsatellite-stable cases but exhibited loss of MLH1 protein expression with hypermethylation of the MLH1 promoter. The results of the present study highlight that while there is a strong concordance between MSI and IHC testing results for determining dMMR status, IHC testing may offer superior efficacy in detecting dMMR.

Risk of metachronous colorectal cancer after colectomy for first colon cancer in Lynch syndrome: multicenter retrospective study in Japan.

BACKGROUND: We evaluated the risk of metachronous colorectal cancer (mCRC) and explored the optimal extent of colectomy in patients with Lynch syndrome (LS) and first colon cancer (fCC) in Japan, where the extent of colectomy for colon cancer (CC) is shorter than that in Western countries. METHODS: The clinicopathologic and survival data of patients with LS who developed CC were collected from a nationwide database and analyzed retrospectively. The cumulative incidence of mCRC after actual segmental colectomy was compared with that of mCRC when more extensive colectomy was assumed. RESULTS: There were 142 eligible patients (65 female). The median age at fCC surgery was 46.5 (range: 14-80) years. The cumulative incidence of 5-, 10-, and 20-year mCRC rate was 13.4%, 20.8%, and 53.6%, respectively. The incidence was higher in the left-sided group (splenic flexure to rectosigmoid colon, n = 54) than in the right-sided group (cecum to transvers colon, n = 88) (66.3% vs. 45.3% in 20 years, P < 0.01). Assuming that all patients would have undergone hemicolectomy or total colectomy, the estimated mCRC risk was 41.5% and 9.4% (P < 0.01, vs. actual procedures), respectively. The 20-year overall survival rate of all the patients was 83.3% without difference by fCC sidedness (P = 0.38). CONCLUSIONS: To reduce the incidence of mCRC, patients with genetically diagnosed LS and fCC, preferentially located in the left-sided colon, may need to undergo more extended colectomy than that usually performed in Japan. However, such extended colectomy should be counterbalanced with favorable overall survival and actual risk of mCRC development.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of immunotherapy in patients with DNA mismatch repair deficient (dMMR) tumors, third edition.

BACKGROUND: Clinical trials have reported the efficacy of immune checkpoint inhibitors in the treatment of mismatch repair-deficient (dMMR) advanced solid tumors. The accumulated evidence of tumor agnostic agent has been made since PD-1 inhibitor was approved and used in clinical practice. Therefore, we have revised the guideline "Japan Society of Clinical Oncology provisional clinical opinion for the diagnosis and use of immunotherapy in patients with deficient DNA mismatch repair tumors, cooperated by Japanese Society of Medical Oncology, First Edition". METHODS: Clinical questions regarding medical care were formulated for patients with dMMR advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by Japan Society of Clinical Oncology (JSCO), Japanese Society of Medical Oncology (JSMO), and Japanese society of pediatric hematology/oncology (JSPHO) voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO and the public comments among all societies' members were done. RESULTS: The current guideline describes two clinical questions and eight recommendations for whom, when, and how MMR status should be tested. CONCLUSION: In this guideline, the committee proposed eight recommendations for performing MMR testing properly to select patients who are likely to benefit from immunotherapy.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of immunotherapy in patients with high tumor mutational burden tumors.

The development of novel antitumor agents and accompanying biomarkers has improved survival across several tumor types. Previously, we developed recommendations for tumor-agnostic treatments in patients with solid tumors with DNA mismatch repair deficient or neurotrophic receptor tyrosine kinase fusions. Recently, immune checkpoint inhibitors have shown efficacy in patient with tumor mutation burden-high (TMB-H) solid tumors and have been established as a third tumor-agnostic agent, making it necessary to develop the guideline prioritized for these patients. Clinical questions regarding medical care were formulated for patients with TMB-H advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by Japan Society of Clinical Oncology (JSCO), Japanese Society of Medical Oncology (JSMO), and Japanese society of pediatric hematology/oncology (JSPHO) voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO, and the public comments among all societies' members was done. The current guideline describes three clinical questions and seven recommendations for whom, when, and how TMB should be tested, and what is recommended for patients with TMB-H advanced solid tumors. In this guideline, the committee proposed seven recommendations for performing TMB testing properly to select patients who are likely to benefit from immunotherapy.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of tropomyosin receptor kinase inhibitors in adult and pediatric patients with neurotrophic receptor tyrosine kinase fusion-positive advanced solid tumors.

BACKGROUND: Clinical trials have reported the efficacy of tropomyosin receptor kinase (TRK) inhibitors against neurotrophic receptor tyrosine kinase (NTRK) fusion gene-positive advanced solid tumors. The accumulated evidence of tumor-agnostic agent has made since TRK inhibitors were approved and used in clinical practice. Therefore, we have revised the 'Japan Society of Clinical Oncology (JSCO)/Japanese Society of Medical Oncology (JSMO)-led clinical recommendations on the diagnosis and use of tropomyosin receptor kinase inhibitors in adult and pediatric patients with neurotrophic receptor tyrosine kinase fusion-positive advanced solid tumors, cooperated by the Japanese Society of Pediatric Hematology/Oncology (JSPHO)'. METHODS: Clinical questions regarding medical care were formulated for patients with NTRK fusion-positive advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by JSCO, JSMO, and JSPHO voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO, and the public comments among all societies' members was done. RESULTS: The current guideline describes 3 clinical questions and 14 recommendations for whom, when, and how NTRK fusion should be tested, and what is recommended for patients with NTRK fusion-positive advanced solid tumors. CONCLUSION: The committee proposed 14 recommendations for performing NTRK testing properly to select patients who are likely to benefit from TRK inhibitors.

Panitumumab vs Bevacizumab Added to Standard First-line Chemotherapy and Overall Survival Among Patients With RAS Wild-type, Left-Sided Metastatic Colorectal Cancer: A Randomized Clinical Trial.

Importance: For patients with RAS wild-type metastatic colorectal cancer, adding anti-epidermal growth factor receptor (anti-EGFR) or anti-vascular endothelial growth factor (anti-VEGF) monoclonal antibodies to first-line doublet chemotherapy is routine, but the optimal targeted therapy has not been defined. Objective: To evaluate the effect of adding panitumumab (an anti-EGFR monoclonal antibody) vs bevacizumab (an anti-VEGF monoclonal antibody) to standard first-line chemotherapy for treatment of RAS wild-type, left-sided, metastatic colorectal cancer. Design, Setting, and Participants: Randomized, open-label, phase 3 clinical trial at 197 sites in Japan in May 2015-January 2022 among 823 patients with chemotherapy-naive RAS wild-type, unresectable metastatic colorectal cancer (final follow-up, January 14, 2022). Interventions: Panitumumab (n = 411) or bevacizumab (n = 412) plus modified fluorouracil, l-leucovorin, and oxaliplatin (mFOLFOX6) every 14 days. Main Outcomes and Measures: The primary end point, overall survival, was tested first in participants with left-sided tumors, then in the overall population. Secondary end points were progression-free survival, response rate, duration of response, and curative (defined as R0 status) resection rate. Results: In the as-treated population (n = 802; median age, 66 years; 282 [35.2%] women), 604 (75.3%) had left-sided tumors. Median follow-up was 61 months. Median overall survival was 37.9 months with panitumumab vs 34.3 months with bevacizumab in participants with left-sided tumors (hazard ratio [HR] for death, 0.82; 95.798% CI, 0.68-0.99; P = .03) and 36.2 vs 31.3 months, respectively, in the overall population (HR, 0.84; 95% CI, 0.72-0.98; P = .03). Median progression-free survival for panitumumab vs bevacizumab was 13.1 vs 11.9 months, respectively, for those with left-sided tumors (HR, 1.00; 95% CI, 0.83-1.20) and 12.2 vs 11.4 months overall (HR, 1.05; 95% CI, 0.90-1.24). Response rates with panitumumab vs bevacizumab were 80.2% vs 68.6%, respectively, for left-sided tumors (difference, 11.2%; 95% CI, 4.4%-17.9%) and 74.9% vs 67.3% overall (difference, 7.7%; 95% CI, 1.5%-13.8%). Median duration of response with panitumumab vs bevacizumab was 13.1 vs 11.2 months for left-sided tumors (HR, 0.86; 95% CI, 0.70-1.10) and 11.9 vs 10.7 months overall (HR, 0.89; 95% CI, 0.74-1.06). Curative resection rates with panitumumab vs bevacizumab were 18.3% vs 11.6% for left-sided tumors; (difference, 6.6%; 95% CI, 1.0%-12.3%) and 16.5% vs 10.9% overall (difference, 5.6%; 95% CI, 1.0%-10.3%). Common treatment-emergent adverse events were acneiform rash (panitumumab: 74.8%; bevacizumab: 3.2%), peripheral sensory neuropathy (panitumumab: 70.8%; bevacizumab: 73.7%), and stomatitis (panitumumab: 61.6%; bevacizumab: 40.5%). Conclusions and Relevance: Among patients with RAS wild-type metastatic colorectal cancer, adding panitumumab, compared with bevacizumab, to standard first-line chemotherapy significantly improved overall survival in those with left-sided tumors and in the overall population. Trial Registration: ClinicalTrials.gov Identifier: NCT02394795.

Regulation of MEK inhibitor selumetinib sensitivity by AKT phosphorylation in the novel BRAF L525R mutant.

BACKGROUND: Oncogenic mutations in BRAF genes are found in approximately 5-10% of colorectal cancers. The majority of BRAF mutations are located within exons 11-15 of the catalytic kinase domains, with BRAF V600E accounting for more than 80% of the observed BRAF mutations. Sensitivity to BRAF- and mitogen-activated protein kinase (MEK) inhibitors varies depending on BRAF mutations and tumor cell types. Previously, we newly identified, BRAF L525R-mutation, in the activation segment of the kinase in colorectal cancer patient. Here, we characterized the function of the BRAF L525R mutation. METHODS: HEK293 cells harboring a BRAF mutation (V600E or L525R) were first characterized and then treated with cetuximab, dabrafenib, and selumetinib. Cell viability was measured using WST-1 assay and the expression of proteins involved in the extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) signaling pathways was evaluated using western blot analysis. RESULTS: The MEK inhibitor selumetinib effectively inhibited cell proliferation and ERK phosphorylation in BRAF L525R cells but not in BRAF V600E cells. Further studies revealed that AKT phosphorylation was reduced by selumetinib in BRAF L525R cells but not in BRAF V600E cells or selumetinib-resistant BRAF L525R cells. Moreover, the AKT inhibitor overcame the selumetinib resistance. CONCLUSIONS: We established a model system harboring BRAF L525R using HEK293 cells. BRAF L525R constitutively activated ERK. AKT phosphorylation caused sensitivity and resistance to selumetinib. Our results suggest that a comprehensive network analysis may provide insights to identify effective therapies.

Diagnostic and therapeutic challenges of glioblastoma as an initial malignancy of constitutional mismatch repair deficiency (CMMRD): two case reports and a literature review.

BACKGROUND: Constitutional mismatch repair deficiency (CMMRD) results from a biallelic germline pathogenic variant in a mismatch repair (MMR) gene. The most common CMMRD-associated malignancies are brain tumors; an accurate diagnosis is challenging when a malignant brain tumor is the only tumor at presentation. We describe two cases of glioblastoma as the initial CMMRD malignancy and discuss current diagnostic and therapeutic challenges. CASE PRESENTATION: Two children with brain tumors without remarkable family history had biallelic pathogenic germline variants in PMS2. Patient 1: A 6-year-old girl presented biallelic PMS2 germline pathogenic variants. Glioblastomas at the left frontal lobe and right temporal lobe were resistant to immune-checkpoint inhibitor, temozolomide, and bevacizumab. Patient 2: A 10-year-old boy presented biallelic PMS2 germline variants. His glioblastoma with primitive neuroectodermal tumor-like features responded to chemoradiotherapy, but he developed advanced colon cancer and acute lymphocytic leukemia. In both patients, only a monoallelic PMS2 germline variant was detected by conventional gene tests. PMS2 immunohistochemistry showed lack of staining at both the tumors and normal tissue as vascular endothelial cells. Further gene tests revealed large genomic deletion including the entire PMS2 gene, confirming biallelic PMS2 germline variants. CONCLUSION: Conventional multi-gene panel tests are insufficient for detecting large deletions of MMR genes, resulting in misdiagnoses of CMMRD as Lynch syndrome. PMS2 variants have low cancer penetrance; family histories may thus be absent. Long-range gene analyses or immunohistochemical staining of MMR proteins in normal tissue should be considered for pediatric brain tumors with a single allele MMR variant when CMMRD is suspected.

Clinical utility of Todai OncoPanel in the setting of approved comprehensive cancer genomic profiling tests in Japan.

Comprehensive cancer genome profiling (CGP) has been nationally reimbursed in Japan since June 2019. Less than 10% of the patients have been reported to undergo recommended treatment. Todai OncoPanel (TOP) is a dual DNA-RNA panel as well as a paired tumor-normal matched test. Two hundred patients underwent TOP as part of Advanced Medical Care B with approval from the Ministry of Health, Labour and Welfare between September 2018 and December 2019. Tests were carried out in patients with cancers without standard treatment or when patients had already undergone standard treatment. Data from DNA and RNA panels were analyzed in 198 and 191 patients, respectively. The percentage of patients who were given therapeutic or diagnostic recommendations was 61% (120/198). One hundred and four samples (53%) harbored gene alterations that were detected with the DNA panel and had potential treatment implications, and 14 samples (7%) had a high tumor mutational burden. Twenty-two samples (11.1%) harbored 30 fusion transcripts or MET exon 14 skipping that were detected by the RNA panel. Of those 30 transcripts, 6 had treatment implications and 4 had diagnostic implications. Thirteen patients (7%) were found to have pathogenic or likely pathogenic germline variants and genetic counseling was recommended. Overall, 12 patients (6%) received recommended treatment. In summary, patients benefited from both TOP DNA and RNA panels while following the same indication as the approved CGP tests. (UMIN000033647).

Clinical and genetic diagnosis of Cowden syndrome: A case report of a rare PTEN germline variant and diverse clinical presentation.

INTRODUCTION: Cowden syndrome is a rare autosomal dominant disease characterized by the development of hamartomas and increased risks of other tumors, including breast, thyroid, and uterine cancers. Most patients with Cowden syndrome show mutations of the phosphatase and tensin homolog (PTEN) gene on chromosome 10; however, some patients with mutations do not show clinical symptoms, while patients with clinical symptoms may not have detectable PTEN mutations. CASE PRESENTATION: A 39-year-old woman with macrocephaly had previously been diagnosed with Cowden syndrome at another hospital, when she presented with the onset of breast cancer. A wide variety of complications were detected, including cerebellar tumors treated by resection, hydrocephalus, and multiple polyps in the stomach and large intestine. She was further diagnosed with adult-onset Lhermitte-Duclos disease as a complication of Cowden syndrome. She subsequently developed a dural arteriovenous fistula treated by transvenous embolization. After transfer to our hospital, she developed adenomatous goiter treated by resection, recurrent breast cancer treated with hormonal therapy, and multifocal oral mucosal papillomatosis. Her older sister had previously been diagnosed with Cowden syndrome and her father was undiagnosed but had macrocephaly, hydrocephalus, and multifocal oral mucosal papillomatosis, suggestive of Cowden syndrome. After consultation with a genetic specialist, analysis of the PTEN gene showed a rare but likely pathogenic germline c.801 + 2T>A variant located at the splice donor site of intron 7. The patient's clinical diagnosis of Cowden syndrome was accordingly confirmed by the genetic findings. Appropriate surveillance procedures were put in place to detect any further tumors. CONCLUSIONS: The clinical symptoms of Cowden syndrome do not always correlate with the genetic results. However, recent improvements in genetic testing suggest the importance of diagnosing this disease using both clinical and genetic approaches, in collaboration with genetic experts, to ensure an accurate diagnosis and appropriate surveillance for malignant tumors.

Two Cases of Thymic Cancer in Patients with Lynch Syndrome.

We herein report two cases of thymic cancer with Lynch syndrome showing a high frequency of microsatellite instability and loss of mismatch repair protein expression without MLH1 promoter hyper-methylation. In Case 1, a 71-year-old man had a pathogenic germline variant in MLH1 and underwent tumor resection. No relapse has been reported thus far. In Case 2, a 43-year-old man underwent genetic testing that also showed a pathogenic germline variant in MLH1. Since these two cases had MLH variants, we suspect a possible association between thymic cancer with Lynch syndrome and germline pathogenic variants in MLH1.