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Purpose: Checkpoint-inhibitors have limited efficacy for children with unselected solid and brain tumors. We report the first prospective pediatric trial (NCT02992964) using nivolumab exclusively for refractory non-hematological cancers harboring tumor mutation burden (TMB) ≥5 mutations/megabase (mut/Mb) and/or mismatch-repair deficiency (MMRD). Patients and methods: Twenty patients were screened, and ten ultimately included in the response cohort of whom nine had TMB >10mut/Mb (three initially eligible based on MMRD) and one patient had TMB between 5-10 mut/Mb. Results: Delayed immune responses contributed to best overall response of 50%, improving on initial objective responses (20%) and leading to 2-year overall survival (OS) of 50% (95% CI; 27, 93). Four children, including three with refractory malignant gliomas are in complete remission at a median follow-up of 37-months (range: 32.4-60), culminating in 2-year OS of 43% (95% CI; 18.2, 100). Biomarker analyses confirmed benefit in children with germline MMRD, microsatellite instability, higher activated and lower regulatory circulating T-cells. Stochastic mutation accumulation driven by underlying germline MMRD impacted the tumor microenvironment, contributing to delayed responses. No benefit was observed in the single patient with a MMR-proficient tumour and TMB 7.4 mut/Mb. Conclusions: Nivolumab resulted in durable responses and prolonged survival for the first time in a pediatric trial of refractory hypermutated cancers including malignant gliomas. Novel biomarkers identified here need to be translated rapidly to clinical care to identify children who can benefit from checkpoint-inhibitors, including for upfront management of their cancers.

POLE germline mutations from the IRRDC and literature

Supplementary Figure S1 (related to Figure 1): PoleP286R mouse model design, validation, and tumor findings. Supplementary Figure S2 (related to Figure 1): PoleS459F mouse model design, validation, and tumor findings. Supplementary Figure S3 (related to Figure 2): WES analysis reveals a stochastic accumulation of mutations in Pole mutant tumors. Supplementary Figure S4 (related to Figure 2): Tumors from Pole mutant mice exhibit mutational signatures found in POLE driven human cancers. Supplementary Figure S5 (related to Figure 2): Exome data from tumor fractions from a single mouse were compared for 3 additional mice. Supplementary Figure S6. Determination of cell of origin for PoleS459F/S459F and PoleS459F/+ mice lymphomas (Related to Figure 3). Supplementary Figure S7. Characterization of T cell malignancies in PoleS459F/S459F and PoleS459F/+ mice (Related to Figure 3). Supplemental Figure S8. Extrinsic effect of 'Group B' malignant T cells on B cell population; (Related to Figure 3).

POLE mutations are a major cause of hypermutant cancers, yet questions remain regarding mechanisms of tumorigenesis, genotype–phenotype correlation, and therapeutic considerations. In this study, we establish mouse models harboring cancer-associated POLE mutations P286R and S459F, which cause rapid albeit distinct time to cancer initiation in vivo, independent of their exonuclease activity. Mouse and human correlates enabled novel stratification of POLE mutations into three groups based on clinical phenotype and mutagenicity. Cancers driven by these mutations displayed striking resemblance to the human ultrahypermutation and specific signatures. Furthermore, Pole-driven cancers exhibited a continuous and stochastic mutagenesis mechanism, resulting in intertumoral and intratumoral heterogeneity. Checkpoint blockade did not prevent Pole lymphomas, but rather likely promoted lymphomagenesis as observed in humans. These observations provide insights into the carcinogenesis of POLE-driven tumors and valuable information for genetic counseling, surveillance, and immunotherapy for patients.Significance:Two mouse models of polymerase exonuclease deficiency shed light on mechanisms of mutation accumulation and considerations for immunotherapy.See related commentary by Wisdom and Kirsch p. 5459

CyTOF panel antibodies

Tumor incidence of Pole mutant mice

Supplemental Titles and Figure Legends

PURPOSE Diagnosis of Mismatch Repair Deficiency (MMRD) is crucial for tumor management and early detection in patients with the cancer predisposition syndrome constitutional mismatch repair deficiency (CMMRD). Current diagnostic tools are cumbersome and inconsistent both in childhood cancers and in determining germline MMRD. PATIENTS AND METHODS We developed and analyzed a functional Low-pass Genomic Instability Characterization (LOGIC) assay to detect MMRD. The diagnostic performance of LOGIC was compared with that of current established assays including tumor mutational burden, immunohistochemistry, and the microsatellite instability panel. LOGIC was then applied to various normal tissues of patients with CMMRD with comprehensive clinical data including age of cancer presentation. RESULTS Overall, LOGIC was 100% sensitive and specific in detecting MMRD in childhood cancers (N = 376). It was more sensitive than the microsatellite instability panel (14%, P = 4.3 × 10−12), immunohistochemistry (86%, P = 4.6 × 10−3), or tumor mutational burden (80%, P = 9.1 × 10−4). LOGIC was able to distinguish CMMRD from other cancer predisposition syndromes using blood and saliva DNA ( P < .0001, n = 277). In normal cells, MMRDness scores differed between tissues (GI > blood > brain), increased over time in the same individual, and revealed genotype-phenotype associations within the mismatch repair genes. Importantly, increased MMRDness score was associated with younger age of first cancer presentation in individuals with CMMRD ( P = 2.2 × 10−5). CONCLUSION LOGIC was a robust tool for the diagnosis of MMRD in multiple cancer types and in normal tissues. LOGIC may inform therapeutic cancer decisions, provide rapid diagnosis of germline MMRD, and support tailored surveillance for individuals with CMMRD.

Although replication repair deficiency, either by mismatch repair deficiency (MMRD) and/or loss of DNA polymerase proofreading, can cause hypermutation in cancer, microsatellite instability (MSI) is considered a hallmark of MMRD alone. By genome-wide analysis of tumors with germline and somatic deficiencies in replication repair, we reveal a novel association between loss of polymerase proofreading and MSI, especially when both components are lost. Analysis of indels in microsatellites (MS-indels) identified five distinct signatures (MS-sigs). MMRD MS-sigs are dominated by multibase losses, whereas mutant-polymerase MS-sigs contain primarily single-base gains. MS deletions in MMRD tumors depend on the original size of the MS and converge to a preferred length, providing mechanistic insight. Finally, we demonstrate that MS-sigs can be a powerful clinical tool for managing individuals with germline MMRD and replication repair–deficient cancers, as they can detect the replication repair deficiency in normal cells and predict their response to immunotherapy. Significance: Exome- and genome-wide MSI analysis reveals novel signatures that are uniquely attributed to mismatch repair and DNA polymerase. This provides new mechanistic insight into MS maintenance and can be applied clinically for diagnosis of replication repair deficiency and immunotherapy response prediction. This article is highlighted in the In This Issue feature, p. 995

POLE mutations are a major cause of hypermutant cancers, yet questions remain regarding mechanisms of tumorigenesis, genotype–phenotype correlation, and therapeutic considerations. In this study, we establish mouse models harboring cancer-associated POLE mutations P286R and S459F, which cause rapid albeit distinct time to cancer initiation in vivo, independent of their exonuclease activity. Mouse and human correlates enabled novel stratification of POLE mutations into three groups based on clinical phenotype and mutagenicity. Cancers driven by these mutations displayed striking resemblance to the human ultrahypermutation and specific signatures. Furthermore, Pole-driven cancers exhibited a continuous and stochastic mutagenesis mechanism, resulting in intertumoral and intratumoral heterogeneity. Checkpoint blockade did not prevent Pole lymphomas, but rather likely promoted lymphomagenesis as observed in humans. These observations provide insights into the carcinogenesis of POLE-driven tumors and valuable information for genetic counseling, surveillance, and immunotherapy for patients. Significance: Two mouse models of polymerase exonuclease deficiency shed light on mechanisms of mutation accumulation and considerations for immunotherapy. See related commentary by Wisdom and Kirsch p. 5459

OBJECTIVE Gliomas in adolescents and young adults (AYA) are commonly treated with a standard chemo-radiation approach. Molecular alterations have not been comprehensively described to date. METHODS We compiled a multi-institutional cohort of patients diagnosed with glioma between 15-39.9 years over 20 years. Molecular analysis, therapeutic data and outcome was collected. For specific alterations, analysis included patients aged 0-39.9 years. RESULTS A total of 1900 patients with 876 AYA gliomas were included. Ongoing analysis reveals genetic alterations in 95% of available tumours. IDH p.R132H was found in 49% of tumours, while non-canonical IDH mutations were found in 7%. Paediatric-type mutations were found in 33% of AYA tumours with IDH-WT GBM accounting for the remaining 11%. The most common paediatric alterations in AYAs included BRAF p.V600E (11%) and FGFR alterations (7%) while BRAF fusions, H3 p.K27M and H3.3 p.G34R were rarely observed (4%, 4% and 1% respectively). BRAF fused tumours with non-canonical binding partners were enriched in AYAs. Analysis of BRAF-V600E gliomas between ages 0-40 revealed increased tendency for malignant tumours in patients > 20 years suggesting malignant transformation possibly due to higher rate of secondary hits. This resulted in worse overall-survival for AYA patients with BRAF-V600E glioma when compared to children under 20 years (p=0.0032). Ten-year OS of 100%, 90% and 95% was seen for BRAF fused, BRAF-V600E and FGFR-altered AYA low grade glioma respectively, compared to 14% and 25% for BRAF-V600E and FGFR-altered high grade glioma. In contrast, continuous decline was observed in the IDH-mutant gliomas with 10-year OS of 50% which declined to 29% at 15 years. CONCLUSIONS Gliomas in AYA often have non-canonical alterations that may evade standard molecular analysis. They are enriched for paediatric-type alterations with distinct molecularly-based outcomes. These tumours may respond to targeted inhibitors and would benefit from comprehensive diagnostic and therapeutic approaches.

Mismatch repair deficiency (MMRD) is a pan-cancer mechanism resulting in universal hypermutation and aggressive cancers that are resistant to chemoradiation yet sensitive to immunotherapy. MMRD mutations can occur somatically or be inherited as a part of Lynch Syndrome or Constitutional Mismatch Repair Deficiency (CMMRD). Although MMRD affects children, adolescents and young adults (CAYA, ages 0-40) with gliomas, its prevalence and impact of germline inheritance is unknown. Given that high microsatellite instability (MSI) is a key characteristic of MMRD, we previously developed a robust low-coverage whole genome-based tool to quantify MSI, which allows for accurate MMRD detection. We are therefore performing a large-scale MMRD screen of CAYA high grade gliomas (HGGs) and utilizing data from the International Replication Repair Deficiency Consortium (IRRDC) to determine the impact of germline mutations in MMRD gliomas. Ongoing data on 346 HGGs from CAYA patients reveals that MMRD is identified in 6% of HGGs and is not present in tumors with pediatric type alterations. Moreover, of MMRD tumors with IDH1 mutations, none harbor 1p/19q co-deletions. Of patients with available information, all are diagnosed with Lynch Syndrome (69%) or CMMRD (31%), with all Lynch Syndrome diagnoses occurring in patients above 18 years of age. Complementary data from the IRRDC on 113 MMRD patients with gliomas reveal that the median age of glioma is 9.7 and 17.5 years in CMMRD and Lynch Syndrome, respectively (p < 0.001). Strikingly, CMMRD gliomas are enriched for secondary polymerase mutations (60%, p < 0.001) and exhibit ultra-hypermutation, while MMRD gliomas with Lynch Syndrome are enriched for IDH1 mutations (32%, p < 0.025) and harbor a lower mutational burden. Our data reveal a high prevalence of MMRD in CAYA HGGs with alarming impact of germline predisposition. These data can support universal screening for MMRD in high grade glioma diagnostics and identify patients for precision therapeutics.

OBJECTIVE: Gliomas in adolescents and young adults (AYA) are commonly treated with a standard chemo-radiation approach based on data from adults. The clinical impact of paediatric-type alterations in these tumours is unknown. METHODS: We compiled a multi-institutional cohort of patients diagnosed with glioma between 15-39.9 years over 20 years. Complete molecular analysis, therapeutic data and outcome was collected. For specific alterations, analysis included patients aged 0-39.9 years. RESULTS: A total of 1900 patients with 876 AYA gliomas were included. Ongoing analysis reveals genetic alterations in 95% of available tumours. IDH-mutant tumours account for only 53%, while paediatric-type mutations were found in 35% of AYA tumours with IDH-WT GBM accounting for the remaining 12%. The most common paediatric alterations in AYAs included BRAF p.V600E (11%) and FGFR alterations (6%) while BRAF fusions, H3 p.K27M and H3.3 p.G34R were rarely observed (4%, 4% and 1% respectively). BRAF fused tumours with non-canonical binding partners were enriched in AYAs. Analysis of BRAF-V600E gliomas between ages 0-40 revealed increased tendency for malignant tumours in patients >20 years suggesting malignant transformation possibly due to higher rate of secondary hits including TP53, CDKN2A and ATRX mutations. This resulted in worse overall-survival for AYA patients with BRAF-V600E glioma when compared to children under 20 years (p=0.0032). Ten-year OS of 100%, 90% and 95% was seen for BRAF fused, BRAF-V600E and FGFR-altered AYA low grade glioma respectively, compared to 14% and 25% for BRAF-V600E and FGFR-altered high grade glioma. In contrast, continuous decline was observed in the IDH-mutant gliomas with 10-year OS of 50% which declined to 29% at 15 years. CONCLUSIONS: Gliomas in AYA are enriched for paediatric-type alterations with distinct molecularly-based outcomes. As these tumours carry different outcomes than childhood glioma and may respond to targeted inhibitors, AYA gliomas would benefit from comprehensive diagnostic and therapeutic approaches.

Cancers arising from germline DNA mismatch-repair or polymerase-proofreading deficiencies (MMRD and PPD) in children harbour the highest mutational and microsatellite insertion/deletion (MS-indel) burden in humans and are lethal due to inherent resistance to chemo-irradiation. Although immune checkpoint inhibitors (ICI) have failed to benefit children in previous studies, we hypothesized that hypermutation caused by MMRD and PPD will improve outcomes following ICI in these patients. ICI treatment of 45 progressive/recurrent tumours from 38 patients revealed durable objective responses in the majority, culminating in 3-year survival of 41.4%. High mutation burden predicted response for ultra-hypermutant cancers (>100 mutations/Mb) enriched for combined MMRD+PPD, while MS-indels predicted response in MMRD tumours with lower mutation burden (10-100 mutations/Mb). Further, both mechanisms were associated with increased immune infiltration even in “immunologically-cold” tumours such as gliomas, contributing to the favorable response. Pseudo-progression (flare) was common and associated with immune activation in both the tumour microenvironment and systemically. Further, patients with flare continuing ICI treatment achieved durable responses. Our study demonstrates improved survival for patients with tumours not previously known to respond to ICI, including CNS and synchronous cancers, and identifies the dual roles of mutation burden and MS-indels in predicting sustained responses to immunotherapy.

Cancers arising from germline DNA mismatch repair deficiency or polymerase proofreading deficiency (MMRD and PPD) in children harbour the highest mutational and microsatellite insertion–deletion (MS-indel) burden in humans. MMRD and PPD cancers are commonly lethal due to the inherent resistance to chemo-irradiation. Although immune checkpoint inhibitors (ICIs) have failed to benefit children in previous studies, we hypothesized that hypermutation caused by MMRD and PPD will improve outcomes following ICI treatment in these patients. Using an international consortium registry study, we report on the ICI treatment of 45 progressive or recurrent tumors from 38 patients. Durable objective responses were observed in most patients, culminating in a 3 year survival of 41.4%. High mutation burden predicted response for ultra-hypermutant cancers (>100 mutations per Mb) enriched for combined MMRD + PPD, while MS-indels predicted response in MMRD tumors with lower mutation burden (10–100 mutations per Mb). Furthermore, both mechanisms were associated with increased immune infiltration even in ‘immunologically cold’ tumors such as gliomas, contributing to the favorable response. Pseudo-progression (flare) was common and was associated with immune activation in the tumor microenvironment and systemically. Furthermore, patients with flare who continued ICI treatment achieved durable responses. This study demonstrates improved survival for patients with tumors not previously known to respond to ICI treatment, including central nervous system and synchronous cancers, and identifies the dual roles of mutation burden and MS-indels in predicting sustained response to immunotherapy., Hypermutation and microsatellite burden determine responses and long-term survival following PD-1 blockade in children and young adults with refractory cancers resulting from germline DNA replication repair deficiency.

Background To date, little research has examined the quality of life and cancer-associated needs of bladder cancer patients. The objective of the current study was to assess the quality of life (QoL), informational needs, and supportive care needs (SCN) in a large sample of muscle invasive (MIBC) and non-muscle invasive (NMIBC) bladder cancer survivors across the treatment trajectory (newly diagnosed and undergoing treatment, post-treatment follow-up, and treatment for advanced/recurrent disease). Methods Questionnaires were distributed to a convenience sample of patients registered with Bladder Cancer Canada, the Princess Margaret Cancer Centre, or The Ottawa Hospital. Eligibility criteria included being > 18 years of age, English-speaking, and diagnosed with bladder cancer. The questionnaire included an adapted tool to measure informational needs, and validated measures for QoL (Bladder Utility Symptom Scale, BUSS) and SCN (Cancer Survivors’ Unmet Needs Measure, CaSUN). QoL scores and unmet needs were calculated and compared between disease groups and cancer trajectory groups. Results and limitations Of the 1126 surveys distributed, 586 were completed (response = 52%). Mean age was 67.3 ± 10.2 years, and 401 participants (68.7%) were male. The mean QoL score (BUSS) for the sample was 78.1 ± 17.9 (median 81.7). Respondents with MIBC had significantly lower QoL scores compared to NMIBC. Further, scores differed across the cancer phase groups with the follow-up surveillance group having significantly higher QoL scores compared to the newly diagnosed and advance/recurrent disease groups. The ten most highly ranked informational needs were from the medical, physical, and practical domains. Eighty-eight percent (95% CI 85–91%) of respondents reported at least one SCN, with a median of 12. Over half of the participants (54%, 95% CI 49–59%) had at least one unmet need and 15% had ≥ 10 unmet needs. Newly diagnosed participants had the highest number of unmet needs. Conclusion We found that the number of unmet supportive care needs and quality of life differed across cancer trajectory and disease groups. Future efforts should focus on the development and evaluation of tailored resources and programs to address the needs of people diagnosed and treated for BC. Electronic supplementary material The online version of this article (10.1007/s00520-019-4649-z) contains supplementary material, which is available to authorized users.

Objective To examine health behaviours in bladder cancer survivors including physical activity (PA), body mass index, diet quality, smoking and alcohol consumption, and to explore their relationship with health‐related quality of life (HRQoL). Subjects/Patients and Methods Cross‐sectional questionnaire packages were distributed to bladder cancer survivors (muscle‐invasive bladder cancer [MIBC] and non‐muscle‐invasive bladder cancer [NMIBC]) aged >18 years, and proficient in English. Lifestyle behaviours were measured using established measures/questions, and reported using descriptive statistics. HRQoL was assessed using the validated Bladder Utility Symptom Scale, and its association with lifestyle behaviours was evaluated using analysis of covariance (ancova) and multivariate regression analyses. Results A total of 586 participants completed the questionnaire (52% response rate). The mean (SD) age was 67.3 (10.2) years, and 68% were male. PA guidelines were met by 20% (n = 117) and 22.7% (n = 133) met dietary guidelines. In all, 60.9% (n = 357) were overweight/obese, and the vast majority met alcohol recommendations (n = 521, 92.5%) and were current non‐smokers (n = 535, 91.0%). Health behaviours did not differ between MIBC and NMIBC, and cancer treatment stages. Sufficient PA, healthy diet, and non‐smoking were significantly associated with HRQoL, and the number of health behaviours participants engaged in was positively associated with HRQoL (P

Pediatric brain tumors with replication repair deficiency (RRD) are hypermutant and may respond favorably to immune checkpoint inhibition (ICI). We are collecting ongoing clinical and molecular data from patients with RRD hypermutant cancers treated with ICI as a part of our consortium registry study. Companion biomarkers include tumor mutational burden (TMB), neoantigens and genetic signatures obtained from whole genome and exome sequencing. Immune inference is obtained from RNAseq. Additionally, T-cell receptor rearrangement data are collected from the tumor and blood throughout treatment. From 2015–2018, 53 patients were treated with ICI and combination therapies. Of these 39 had brain tumors, with 93% having high grade gliomas. Two-year overall survival for the entire cohort is 47+/-8%, which compares favorably with historical controls. Tumor location had major impact on outcome. Non-CNS solid tumor patients have 2-year OS of 78+/-11%, all failures occurring within the first 2 months, and sustained responses are observed for 3 years. In contrast, OS for brain tumors is 39+/-10% with late recurrences observed even after 2 years of therapy (p=0.02). Large tumor size and total tumor burden are associated with higher rates of “flare” and poor outcome throughout all cancers. While all tumors are hypermutant, TMB and predicted neoantigens do not correlate with response. However, specific signatures extracted from SNVs and indels are significantly associated with response to ICI and favorable outcome (p=0.005). Notably, RRD IDH1 mutant glioblastomas have particularly poor response to ICI. Interestingly, glioblastomas (n=8) which failed single agent ICI had favorable responses to combination immunotherapies with prolonged survival of 65%+/-8% one year after failure vs 0 for untreated patients (p=0.01). The favorable outcome and responses to ICI are encouraging. Since brain tumors respond less favorably to ICI than other solid tumors, combination therapies based on tumor and immune signatures of these cancers may be beneficial.

Pediatric brain tumors with replication repair deficiency (RRD) are hypermutant and may respond to immune checkpoint inhibition (ICI). We performed a consortium registry study of ICI in recurrent RRD cancers. Clinical and companion biomarkers were collected longitudinally on all patients. Biomarkers included tumor mutational burden (TMB), neoantigens and genetic signatures obtained from whole genome and exome sequencing. Immune inference was obtained by RNAseq and T cell rearrangement was collected in the tumor and in blood throughout treatment. Of the 46 tumors on the study, 32 were brain tumors with glioblastoma in 96%. Rapid, objective responses (>50%) were observed in 50% of glioblastomas. Three year overall survival for the whole cohort was 48+/-8% which compares favorably with historical controls. Brain tumors fared worse with OS of 39+/-10% and late recurrences observed even after 2 years of therapy (p=0.02). Tumor size and acute “flare” constitute poor outcome throughout all cancers. While all tumors are hypermutant, TMB and predicted neoantigens correlated with response to ICI (p=0.02). Specific signatures extracted from SNVs and total mutations predicted response to ICI and favorable outcome (p=0.005). RNA inference and TCR reveal that the FLARE phenotype is mostly acute nonspecific immune response and not true progression. Finally, glioblastomas (n=8) which failed single agent ICI had favorable responses to combinational immunotherapies with prolonged survival of 65%+/-8% at one year after failure vs 0 for other patients (p=0.01). RRD glioblastomas exhibit favorable outcome and responses to ICI. Combinational therapies based on tumor and immune signatures of these cancers are necessary.

We present an extensive assessment of mutation burden through sequencing analysis of >81,000 tumors from pediatric and adult patients, including tumors with hypermutation caused by chemotherapy, carcinogens, or germline alterations. Hypermutation was detected in tumor types not previously associated with high mutation burden. Replication repair deficiency was a major contributing factor. We uncovered new driver mutations in the replication-repair-associated DNA polymerases and a distinct impact of microsatellite instability and replication repair deficiency on the scale of mutation load. Unbiased clustering, based on mutational context, revealed clinically relevant subgroups regardless of the tumors' tissue of origin, highlighting similarities in evolutionary dynamics leading to hypermutation. Mutagens, such as UV light, were implicated in unexpected cancers, including sarcomas and lung tumors. The order of mutational signatures identified previous treatment and germline replication repair deficiency, which improved management ofpatients and families. These data will inform tumor classification, genetic testing, and clinical trial design.