Rapid disease progression in a patient with mismatch repair-deficient and cortisol secreting adrenocortical carcinoma treated with pembrolizumab

A novel lynch syndrome kindred with hereditary adrenal cortical carcinoma

BACKGROUND

Adrenal cortical carcinoma (ACC) is an extremely rare malignancy, and advanced ACC carries a very poor prognosis. Early detection is critical since early-stage disease can be cured with surgical resection. ACC can be seen in Lynch syndrome; this case and review of the literature provide insight as to the potential biological origin of this malignancy. Clinicians should be aware of this association and the potential impact on cancer screening in these kindreds.

CASE PRESENTATION

We describe a novel kindred with hereditary adrenal cortical carcinoma and the Muir- Torre syndrome, a phenotypic variant of Lynch syndrome that includes sebaceous neoplasms and visceral malignancies. We report a 59-year-old Caucasian man with an MSH2 deletion who was diagnosed with metastatic adrenal cortical carcinoma. The patient's brother also had a history of adrenal cortical carcinoma. The patient's cancer initially responded to immunotherapy with pembrolizumab. Somatic genetic testing performed on a tumor biopsy did not identify the germline MSH2 deletion.

CONCLUSIONS

A review of the literature identifies an association between germline MSH2 mutations and ACC, suggesting a potential biological basis for carcinogenesis. This case highlights the importance of ACC screening for patients with Lynch Syndrome and a family history of adrenal cortical carcinoma due to the high mortality from this malignancy. This case also highlights the importance of separate germline and somatic testing for patients with a concerning personal or family history of cancers.

Etoposide, cisplatin, and sintilimab combined with anlotinib in successful treatment of adrenocortical carcinoma with lung metastasis: a case report

Background

Adrenocortical carcinoma (ACC) is a rare malignant tumor that occurs in the adrenal cortex. It has a high degree of malignancy and comparatively poor overall prognosis. Surgery is the standard curative therapy for localized ACC patients. The combination regimen of etoposide, doxorubicin, cisplatin (EDP) plus mitotane has been considered as the standardized chemotherapy regimen for advanced ACC. However, new effective regimens are emerging for specific conditions in metastatic ACC.

Case presentation

We report a case of a 66-year-old man diagnosed with metastatic ACC who had a large left adrenal mass (110 mm × 87 mm) and multiple metastases in both lungs. The patient was treated with EP and sintilimab for six cycles; anlotinib was introduced after the third cycle. Follow-ups after the second to fourth cycles found significantly reduced lung metastases with all imaging examinations indicating partial response (PR) status. The patient received maintenance therapy thereafter with sintilimab plus anlotinib. Until recently, the patient's lung metastases and the left adrenal gland area mass (39mm × 29mm) have disappeared, and no disease progression has been observed. The progression-free survival of this patient has been extended to approximately 31 months, in sharp contrast to a median survival time of 12 months for majority of advanced ACC. The main adverse events during treatment were appetite loss and grade I myelosuppression and revealed only grade I hypertension and grade I hypothyroidism.

Conclusion

This case highlights the remarkable response of our patient's ACC to treatment with a novel combination of EP and sintilimab combined with anlotinib. Our findings suggest a safe and more effective combination therapeutic option for patients with adrenocortical carcinoma.

Current prospects of hereditary adrenal tumors: towards better clinical management

Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies. Regarding hereditary tumors, some patients with ACC are associated with with Li-Fraumeni syndrome (LFS), and those with PPGL with multiple endocrine neoplasia type 2. Recent studies have expanded this spectrum to include other types of hereditary tumors, such as Lynch syndrome or familial adenomatous polyposis. Individuals harboring germline TP53 pathogenic variants that cause LFS have heterogeneous phenotypes depending on the respective variant type. As an example, R337H variant found in Brazilian is known as low penetrant. While 50-80% of pediatric ACC patients harbored a LFS, such a strong causal relationship is not observed in adult patients, which suggests different pathophysiologies between the two populations. As for PPGL, because multiple driver genes, such as succinate dehydrogenase (SDH)-related genes, RET, NF1, and VHL have been identified, universal multi-gene germline panel testing is warranted as a comprehensive and cost-effective approach. PPGL pathogenesis is divided into three molecular pathways (pseudohypoxia, Wnt signaling, and kinase signaling), and this classification is expected to result in personalized medicine based on genomic profiles. It remains unknown whether clinical characteristics differ between cases derived from genetic predisposition syndromes and sporadic cases, or whether the surveillance strategy should be changed depending on the genetic background or whether it should be uniform. Close cooperation among medical genomics experts, endocrinologists, oncologists, and early investigators is indispensable for improving the clinical management for multifaceted ACC and PPGL.

The Efficacy and Safety of Immune Checkpoint Inhibitors in Adrenocortical Carcinoma: A Systematic Review and Meta-Analysis

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of different malignancies. However, their efficacy in advanced adrenocortical carcinoma (ACC) remains uncertain. Thus, we conducted a systematic review and meta-analysis to summarize the efficacy and tolerability of ICIs in patients with advanced ACC. We searched PubMed, Scopus, and CENTRAL for studies that used ICIs in ACC. Studies with more than five patients were included in the meta-analysis of the objective response rate (ORR), disease control rate (DCR), overall survival (OS), progression-free survival (PFS), and grade 3/4 adverse events. Twenty studies with 23 treatment arms and 250 patients were included. Single-agent anti-PD1 or anti-PD-L1 treatment was utilized in 13 treatment arms, whereas an anti-PD1 or anti-PD-L1 and anti-CTLA4 combination was used in 4 treatment arms. Other anti-PD1- or anti-PD-L1-based combinations were used in five treatment arms. The ORR was 14% (95% CI = 10-19%, I2 = 0%), and the DCR was 43% (95% CI = 37-50%, I2 = 13%). The combination anti-PD1- or anti-PD-L1-based treatment strategies did not correlate with higher responses compared with monotherapy. The median OS was 13.9 months (95% CI = 7.85-23.05), and the median PFS was 2.8 months (95% CI = 1.8-5.4). ICIs have a modest efficacy in advanced ACC but a good OS. Further studies are needed to investigate predictive biomarkers for ICI response and to compare ICI-based strategies with the current standard of care.

Pathogenic Insights into DNA Mismatch Repair (MMR) Genes-Proteins and Microsatellite Instability: Focus on Adrenocortical Carcinoma and Beyond

DNA damage repair pathways, including mismatch repair (MMR) genes, are prone to carcinoma development in certain patients. The assessment of the MMR system is widely recognized as part of strategies concerning solid tumors (defective MMR cancers), especially MMR proteins (through immunohistochemistry), and molecular assays for microsatellite instability (MSI). We aim to highlight the status of MMR genes-proteins (including MSI) in the relationship with ACC (adrenocortical carcinoma) according to current knowledge. This is a narrative review. We included PubMed-accessed, full-length English papers published between January 2012 and March 2023. We searched studies on ACC patients for whom MMR status was assessed, respectively subjects harboring MMR germline mutations, namely Lynch syndrome (LS), who were diagnosed with ACC. MMR system assessments in ACCs involve a low level of statistical evidence. Generally, there are two main types of endocrine insights: 1. the role of MMR status as a prognostic marker in different endocrine malignancies (including ACC)-which is the topic of the present work, and 2. establishing the indication of immune checkpoint inhibitors (ICPIs) in selective, mostly highly aggressive, non-responsive to standard care forms upon MMR evaluation (which belongs to the larger chapter of immunotherapy in ACCs). Our one-decade, sample-case study (which, to our knowledge, it is the most comprehensive of its kind) identified 11 original articles (from 1 patient to 634 subjects per study diagnosed with either ACC or LS). We identified four studies published in 2013 and 2020 and two in 2021, three cohorts and two retrospective studies (the publication from 2013 includes a retrospective and a cohort distinct section). Among these four studies, patients already confirmed to have LS (N = 643, respective 135) were found to be associated with ACC (N = 3, respective 2), resulting in a prevalence of 0.0046%, with a respective of 1.4% being confirmed (despite not having a large amount of similar data outside these two studies). Studies on ACC patients (N = 364, respective 36 pediatric individuals, and 94 subjects with ACC) showed that 13.7% had different MMR gene anomalies, with a respective of 8.57% (non-germline mutations), while 3.2% had MMR germline mutations (N = 3/94 cases). Two case series included one family, with a respective four persons with LS, and each article introduced one case with LS-ACC. Another five case reports (between 2018 and 2021) revealed an additional five subjects (one case per paper) diagnosed with LS and ACC (female to male ratio of 4 to 1; aged between 44 and 68). Interesting genetic testing involved children with TP53-positive ACC and further MMR anomalies or an MSH2 gene-positive subject with LS with a concurrent germline RET mutation. The first report of LS-ACC referred for PD-1 blockade was published in 2018. Nevertheless, the use of ICPI in ACCs (as similarly seen in metastatic pheochromocytoma) is still limited. Pan-cancer and multi-omics analysis in adults with ACC, in order to classify the candidates for immunotherapy, had heterogeneous results, and integrating an MMR system in this larger and challenging picture is still an open issue. Whether individuals diagnosed with LS should undergo surveillance for ACC has not yet been proven. An assessment of tumor-related MMR/MSI status in ACC might be helpful. Further algorithms for diagnostics and therapy, also taking into consideration innovative biomarkers as MMR-MSI, are necessary.

Management of adrenocortical carcinoma: are we making progress?

Adrenocortical carcinoma (ACC) is a rare malignancy characterized by aggressive biology and potential endocrine activity. Surgery can offer cure for localized disease but more than half of patients relapse and primary unresectable or metastasized disease is frequent. Prognosis of metastatic ACC is still limited, with less than 15% of patients alive at 5 years. Recent advances in understanding the molecular profile of ACC underline the high complexity of this disease, which is characterized by limited drugable molecular targets as well as by a complex interplay between a yet scarcely understood microenvironment and potential endocrine activity. Particularly steroid-excess further complicates therapeutic concepts such as immunotherapy, which have markedly improved outcome in other disease entities. To date, mitotane remains the only approved drug for adjuvant and palliative care in ACC. Standard chemotherapy-based protocols with cisplatin, doxorubicin and etoposide offer only marginal improvement in long-term outcome and the number of clinical trials conducted is low due to the rarity of the disease. In the current review, we summarize principles of oncological management for ACC from localized to advanced disease and discuss novel therapeutic strategies, including targeted therapies such as tyrosine kinase inhibitors and antibodies, immunotherapy with a focus on checkpoint inhibitors, individualized treatment concepts based on molecular characterization by next generation sequencing methods, the role of theranostics and evolvement of adjuvant therapy.

An Update on Immune Checkpoint Therapy for the Treatment of Lynch Syndrome

During the recent years, immune checkpoint-based therapy has proven highly effective in microsatellite instable (MSI) solid tumors irrespective of organ site. MSI tumors are associated with a defective mismatch repair (MMR) system and a highly immune-infiltrative tumor microenvironment—both characteristics of Lynch syndrome. Lynch syndrome is a multi-tumor syndrome that not only confers a high risk of colorectal and endometrial cancer but also cancer in, eg the upper urinary tract, ovaries, and small bowel. Since the genetic predisposition for Lynch syndrome are pathogenic variants in one of the four MMR genes, MLH1, MSH2, MSH6 or PMS2, most of the Lynch syndrome cancers show MMR deficiency, MSI, and activation of the immune response system. Hence, Lynch syndrome cancer patients may be optimal candidates for immune checkpoint-based therapies. However, molecular differences have been described between sporadic MSI tumors (developed due to MLH1 promoter hypermethylation) and Lynch syndrome tumors, which may result in different treatment responses. Furthermore, the response profile of the rare Lynch syndrome cases may be masked by the more frequent cases of sporadic MSI tumors in large clinical trials. With this review, we systematically collected response data on Lynch syndrome patients treated with FDA- and EMA-approved immune checkpoint-based drugs (pembrolizumab, atezolizumab, durvalumab, avelumab, ipilimumab, and nivolumab) to elucidate the objective response rate and progression-free survival of cancer in Lynch syndrome patients. Herein, we report Lynch syndrome-related objective response rates between 46 and 71% for colorectal cancer and 14–100% for noncolorectal cancer in unselected cohorts as well as an overview of the Lynch syndrome case reports. To date, no difference in the response rates has been reported between Lynch syndrome and sporadic MSI cancer patients.

Advanced Adrenocortical Carcinoma: Current Perspectives on Medical Treatment

Adrenocortical carcinoma (ACC) is a rare and aggressive malignancy. For stage I and II tumors, surgery is a curative option, but even in these cases recurrence is frequent. Practical guidelines advocate a combination of mitotane with etoposide, doxorubicin, and cisplatin as first-line therapy for metastatic adrenocortical carcinoma. However, this scheme presents limited efficacy and high toxicity. The use of Immune Checkpoint Inhibitors (ICI) and multi-Tyrosine Kinase Inhibitors (mTKI) has modified the approach of multiple malignancies. The expectation of their applicability on advanced adrenocortical carcinoma is high but the role of these new therapies persists unclear. This article provides a short summary of last years' findings targeting outcomes, limitations, and adverse effects of these new therapeutic approaches. The results of recent trials and case series pointed pembrolizumab as the most promising drug among these new therapies. It is the most often used ICI and the one presenting the best results with less related adverse effects when in comparison to the standard treatment with mitotane. Hereafter, the identification of specific molecular biomarkers or immune profiles associated with ICI or mTKI good response will facilitate the selection of candidates for these therapies. So far, microsatellite instability and Lynch Syndrome related germline mutations are suggested as predictive biomarkers of good response. Contrarywise, cortisol secretion has been associated with more aggressive ACC tumors and potentially poor responses to immunotherapy.

Tumor Microenvironment in Adrenocortical Carcinoma: Barrier to Immunotherapy Success?

Adrenocortical carcinoma is a rare malignancy with aggressive behavior, with up to 40% of patients presenting with metastases at the time of diagnosis. Both conventional chemotherapeutic regimens and novel immunotherapeutic agents, many of which are currently being tested in ongoing clinical trials, have yielded modest results so far, bringing the need for a deeper understanding of adrenal cancer behavior to the forefront. In the recent years, the tumor microenvironment has emerged as a major determinant of cancer response to immunotherapy and an increasing number of studies on other solid tumors have focused on manipulating the microenvironment in the favor of the host and discovering new potential target molecules. In the present review we aim to explore the characteristics of adrenocortical cancer's microenvironment, highlighting the mechanisms of immune evasion responsible for the modest immunotherapeutic results, and identify novel potential strategies.

The role of immune checkpoint inhibitor therapy in advanced adrenocortical carcinoma revisited: review of literature

PURPOSE

Adrenocortical carcinoma (ACC) is a rare disease with few therapeutic options. There is an urgency of new effective therapeutic options for these patients. The role of immune checkpoint inhibitors (ICI) in advanced ACC patients is still unclear.

METHODS

We conducted a MEDLINE search using the following string: adrenocortical carcinoma and immunotherapy or checkpoint inhibitors.

RESULTS

We found four case series comprising 10 patients, and four prospective studies totaling 115 patients. The response rate (RR) in the group of 10 patients was 1 complete response, 3 partial response (PR), 4 stable disease (SD), and 2 progressive disease (PD). The median progression-free survival (mPFS) ranged from 2 to 31 months and the median overall survival (mOS) ranged from 4.3 to 31 months. The results in the 115 patients from prospective trials was variable, the PR ranged from 6 to 23%, the SD ranged from 18 to 50% and overall disease control rate ranged from 30 to 64%. The mPFS reported varied from 1.8 to 2.6 months while the mOS varied from 10.6 to 24.9 months. There were five patients with sustained response for more than 24 months. The most common treatment-related adverse event (TRAE) was the increase in liver enzymes. No treatment-related deaths were reported. Better results in terms of RR and survival were observed in studies that used pembrolizumab. No predictive biomarker of response was found up to now.

CONCLUSION

ICI, mainly pembrolizumab, is a potential therapeutic option, which is safe and associated with prolonged OS benefit, in selected patients with advanced ACC.

CAUTION ADVISED USING COMBINATION KETOCONAZOLE AND PD-1 INHIBITORS

Objective

Immune checkpoint inhibitors are approved to treat multiple cancers. We report life-threatening hepatic failure in 2 consecutive patients with Cushing syndrome that were treated with ketoconazole (KTZ) in combination with 2 different programmed cell death protein 1 (PD-1) inhibitors, Nivolumab and Pembrolizumab.

Methods

The first patient suffered from corticotroph pituitary carcinoma and the second from metastatic adrenal cortical carcinoma. They were both treated with KTZ for tumor-associated hypercortisolism.

Results

Hepatic function was normal on KTZ prior to initiation of PD-1 inhibitors, after which they rapidly developed severe hepatic dysfunction. In both cases, liver biopsy was consistent with drug-induced hepatic injury. Liver function fully recovered on discontinuing KTZ and the PD-1 inhibitors along with methylprednisone therapy.

Conclusion

Antifungal azole therapy is commonly used in oncology patients who may be co-treated with PD-1 inhibitors. Although the specific combination of KTZ and PD-1 inhibitors to treat Cushing syndrome may be relatively uncommon, we recommend careful monitoring of hepatic function using a combination PD-1 inhibitors and azole antifungal agents, especially KTZ, due to the potential of life-threatening hepatic failure.

Molecular genomic profiling of adrenocortical cancers in clinical practice

BACKGROUND

At presentation, 21% to 49% of patients with adrenocortical cancer have metastases. Standard chemotherapy has a 23% response rate. We assessed whether next generation sequencing could elucidate additional treatment options in refractory adrenocortical cancer.

METHODS

Retrospective analysis using a commercial, 592-gene DNA-based panel was performed of next generation sequencing data from 94 adrenocortical cancer tumors profiled for clinical care. We compared our data to the adrenocortical cancer database of The Cancer Genome Atlas containing survival data. We evaluated mutations, indels, amplifications, tumor mutation burden, microsatellite instability, and programmed death-ligand 1 protein expression.

RESULTS

Our cohort included 54 primary neoplasms and 40 metastatic lesions. The most frequently mutated genes were TP53 (36%) and CTNNB1 (19%). Low prevalence mutations were noted in 37 genes including DNA damage repair genes in 15 samples. High tumor mutation burden was seen in 3 patients, and programmed death-ligand 1 was positive in 12. Potential targets to Food and Drug Administration-approved drugs were seen in 16% of cases.

CONCLUSION

DNA sequencing panel tests may identify therapeutic options for some patients with adrenocortical cancer. TP53 and mutations were associated with an adverse outcome. An expanded repertoire of drugs and, perhaps, more expansive multi-omic sequencing are needed to advance the treatment of adrenocortical cancer.

Development of an Adrenocortical Cancer Humanized Mouse Model to Characterize Anti-PD1 Effects on Tumor Microenvironment

CONTEXT

Although the development of immune checkpoint inhibitors has transformed treatment strategies of several human malignancies, research models to study immunotherapy in adrenocortical carcinoma (ACC) are lacking.

OBJECTIVE

To explore the effect of anti-PD1 immunotherapy on the alteration of the immune milieu in ACC in a newly generated preclinical model and correlate with the response of the matched patient.

DESIGN, SETTING, AND INTERVENTION

To characterize the CU-ACC2-M2B patient-derived xenograft in a humanized mouse model, evaluate the effect of a PD-1 inhibitor therapy, and compare it with the CU-ACC2 patient with metastatic disease.

RESULTS

Characterization of the CU-ACC2-humanized cord blood-BALB/c-Rag2nullIl2rγnullSirpaNOD model confirmed ACC origin and match with the original human tumor. Treatment of the mice with pembrolizumab demonstrated significant tumor growth inhibition (60%) compared with controls, which correlated with increased tumor infiltrating lymphocyte activity, with an increase of human CD8+ T cells (P < 0.05), HLA-DR+ T cells (P < 0.05) as well as Granzyme B+ CD8+ T cells (<0.001). In parallel, treatment of the CU-ACC2 patient, who had progressive disease, demonstrated a partial response with 79% to 100% reduction in the size of target lesions, and no new sites of metastasis. Pretreatment analysis of the patient's metastatic liver lesion demonstrated abundant intratumoral CD8+ T cells by immunohistochemistry.

CONCLUSIONS

Our study reports the first humanized ACC patient-derived xenograft mouse model, which may be useful to define mechanisms and biomarkers of response and resistance to immune-based therapies, to ultimately provide more personalized care for patients with ACC.

Response to Immunotherapy in Combination With Mitotane in Patients With Metastatic Adrenocortical Cancer

Adrenocortical carcinoma (ACC) is a rare orphan disease with a dismal prognosis. Surgery remains the first-line treatment, but most patients eventually develop metastatic disease. Mitotane is often used with chemotherapy with modest success. Little information is available concerning the efficacy of immunotherapy in combination with mitotane. We conducted a retrospective review of our initial six patients with metastatic ACC, for whom mitotane alone or with chemotherapy failed, and who were subsequently treated with a combination of pembrolizumab and mitotane, between July 2016 and March 2019. Imaging was analyzed per Response Evaluation Criteria in Solid Tumours 1.1 criteria. Two patients had a partial response and four patients had stable disease (8 to 19 months). One patient had grade 3 hepatitis and pembrolizumab was discontinued after 8 months. She died with disease progression 16 months after initiating pembrolizumab. One patient developed brain metastasis after 19 months of treatment and was transitioned to hospice. One patient had focal pneumonitis after 18 months of treatment, and pembrolizumab was discontinued. Three remaining patients continue pembrolizumab plus mitotane at the time of this writing. The current standard of care for ACC is a combination of etoposide, doxorubicin, cisplatin, and mitotane with an overall survival of 14.8 months. All six patients lived for at least 16 months after starting pembrolizumab added to mitotane therapy. The therapy appeared to be effective in both microsatellite instability-high and microsatellite stable tumors, suggesting some synergistic effect with mitotane. Combined immunotherapy and mitotane should be considered in future clinical trials in patients with ACC.

Phase II clinical trial of pembrolizumab efficacy and safety in advanced adrenocortical carcinoma

Background

Adrenocortical carcinoma (ACC) is a rare malignancy without good treatment options. There are limited data about the use of immunotherapy in ACC. We investigated the efficacy and safety of pembrolizumab in patients with metastatic ACC.

Methods

This is a pre-specified cohort of a single-center, investigator-initiated, phase II clinical trial using pembrolizumab monotherapy in patients with rare malignancies. Patients must have had prior treatment fail in the past 6 months before study enrollment. Patients were enrolled from August 2016 to October 2018. Follow-up data were updated as of March 26, 2019.

Patients received 200 mg pembrolizumab intravenously every 3 weeks without concomitant oncologic therapy. The primary endpoint was non-progression rate (NPR) at 27 weeks. Other endpoints included adverse events, tumor responses measured independently by objective radiologic criteria, and select immunological markers.

Results

Sixteen patients with ACC (including eight women [50%]) were included in this cohort. Ten patients (63%) had evidence of hormonal overproduction (seven had cortisol-producing ACC). Non-progression rate at 27 weeks was evaluable in 14 patients, one patient was lost to follow-up, and one patient left the study because of an adverse event. Five of 14 patients were alive and progression-free at 27 weeks (non-progression rate at 27 weeks was 36, 95% confidence interval 13–65%). Of the 14 patients evaluable for imaging response by immune-related Response Evaluation Criteria in Solid Tumors, two had a partial response (including one with cortisol-producing ACC), seven had stable disease (including three with cortisol-producing ACC), and five had progressive disease, representing an objective response rate of 14% (95% confidence interval 2–43%). Of those who had stable disease, six had disease stabilization that lasted ≥4 months. Severe treatment-related adverse events (≥grade 3) were seen in 2 of 16 patients (13%) and resulted in one patient discontinuing study participation. All studied tumor specimens (14/14) were negative for programmed cell death ligand-1 expression. Thirteen of 14 tumor specimens (93%) were microsatellite-stable. Eight of 14 patients (57%) had a high tumor-infiltrating lymphocyte score on immunohistochemistry staining.

Conclusions

Single-agent pembrolizumab has modest efficacy as a salvage therapy in ACC regardless of the tumor’s hormonal function, microsatellite instability status, or programmed cell death ligand-1 status. Treatment was well tolerated in most study participants, with a low rate of severe adverse events.

Trial registration

ClinicalTrials.gov identifier: NCT02721732, Registered March 29, 2016.

A novel heterozygous large deletion of MSH6 gene in a Chinese family with Lynch syndrome

Lynch syndrome (LS) is a common cancer syndrome that is inherited in an autosomal dominant manner. Its pathogenesis is thought to be closely related to germline mutations of mismatch repair (MMR) genes such as the MLH1, MSH2, PMS2 and MSH6 genes. This study identifies a Chinese family with LS clinically diagnosed according to the Amsterdam II criteria. In these patients, immuno-histochemical staining showed negative MSH6 expressions but positive MLH1, MSH2, and PMS2 expressions. In order to further explore the molecular biology of this LS family, we used targeted next-generation sequencing (NGS) and Multiplex ligation dependent probe amplification (MLPA) to identify the mutation and verify the authenticity of the mutation in 15 family members. For NGS, two panels have been used, one is of MLH1, MSH2, PMS2 and MSH6 genes, the other one is of 139 cancer genetic susceptibility genes. And for the large deletions/duplications can also be identified by NGS panel, an adjusted data analysis strategy of NGS has been used. As a result, we identified a novel heterozygous large deletion in MSH6 gene that was found to be co-segregated among affected family members. This deletion results in the loss of a 3246 bp-sized fragment in MSH6 gene exons 5-9 which represents the coding regions of the MSH6 ATPase domain. This novel mutation has yet to be documented in the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) database. This mutation resulted in MSH6 protein losing gene mismatch repair function, and further caused the microsatellite instable. We speculate that this mutation may significantly impact MMR function through impaired ATP domain function. Theoretically, this proband would likely benefit from PD-1 immune check-point blockade therapy, but conversely, we observed that tumors appeared to rapidly progress after 4 sessions of anti-PD-1 treatment. Further studies to validate the effectiveness of anti-PD-1 treatments in carriers of this mutation are necessary.