Genetic Predisposition to Sarcoma: What Should Clinicians Know?

OPINION STATEMENT: Pathogenic germline variants in the setting of several associated cancer predisposition syndromes (CPS) may lead to the development of sarcoma. We would consider testing for a CPS in patients with a strong family history of cancer, multiple primary malignancies, and/or pediatric/adolescent/young adult patients diagnosed with other malignancies strongly associated with CPS. When a CPS is diagnosed in a patient with sarcoma, additional treatment considerations and imaging options for those patients are required. This applies particularly to the use of radiation therapy, ionizing radiation with diagnostic imaging, and the use of alkylating chemotherapy. As data and guidelines are currently lacking for many of these scenarios, we have adopted a shared decision-making process with patients and their families. If the best chance for cure in a patient with CPS requires utilization of radiation therapy or alkylating chemotherapy, we discuss the risks with the patient but do not omit these modalities. However, if there are treatment options that yield equivalent survival rates, yet avoid these modalities, we elect for those options. Considering staging imaging and post-therapy evaluation for sarcoma recurrence, we avoid surveillance techniques that utilize ionizing radiation when possible but do not completely omit them when their use is indicated.

A Real-World Comparison of Regorafenib and Trifluridine/Tipiracil in Refractory Metastatic Colorectal Cancer in the United States.

BACKGROUND: Trifluridine/Tipiracil (TAS-102) and regorafenib are FDA-approved in the United States for treatment of refractory metastatic colorectal cancer (mCRC). FDA approvals of these agents were based on modest improvements in overall survival (OS) compared with best supportive care + placebo in the RECOURSE and CORRECT trials, respectively. This study compared real-world clinical outcomes with the use of these agents. METHODS: A nationwide deidentified electronic health record-derived database was reviewed for patients diagnosed with mCRC between 2015 and 2020. Patients who received at least 2 lines of standard systemic therapy followed by treatment with either TAS-102 or regorafenib were included for analysis. Kaplan-Meier and propensity score-weighted proportional hazards models were used to compare survival outcomes between groups. RESULTS: The records of 22,078 patients with mCRC were reviewed. Of these, 1,937 patients received at least 2 lines of standard therapy followed by regorafenib and/or TAS-102. Median OS for the TAS-102 alone or prior regorafenib group (n=1,016) was 6.66 months (95% CI, 6.16-7.18 months) compared with 6.30 months (95% CI, 5.80-6.79 months) for regorafenib alone or prior to TAS-102 (n=921; P=.36). A propensity score-weighted analysis controlling for potential confounders did not demonstrate a significant difference in survival between groups (hazard ratio, 0.99; 95% CI, 0.90-1.09; P=.82). A subgroup analysis did not identify any significant differences in outcomes regarding age, performance status, tumor sidedness, microsatellite instability status, or RAS/RAF status. CONCLUSIONS: This analysis of real-world data found that OS was similar for patients with mCRC who were treated with TAS-102 compared with regorafenib. Median OS with both agents in a real-world setting was similar to that shown in the clinical trials that led to their approvals. A prospective trial comparing TAS-102 and regorafenib would unlikely change current management of patients with refractory mCRC.

Treatment outcomes in recurrent versus de novo metastatic pancreatic adenocarcinoma: a real world study.

BACKGROUND: A majority of patients undergoing curative intent surgery for pancreatic ductal adenocarcinoma (PDAC) will unfortunately develop recurrent disease. Treatment outcomes for patients with metastatic disease remain suboptimal. In this study, we evaluated clinical outcomes of patients with recurrent PDAC who received systemic therapy and compared outcomes to patients with de novo metastatic PDAC undergoing systemic therapy. METHODS: Patients diagnosed with metastatic PDAC between 2014 and 2019 were included using a real-world database. Patients were characterized as either de novo or recurrent based on the date of metastatic diagnosis and history of surgical resection. Overall survival (OS) was summarized within groups via Kaplan-Meier survival estimates and compared using Cox proportional hazards models. RESULTS: We included 5170 patients with metastatic PDAC, of which 1101 (21.3%) were classified as having recurrent disease. Median OS for the recurrent group was significantly greater at 10.8 m (95% CI 9.9-11.7) than in the de novo group at 7.3 m (95% CI 7.0-7.7, p < 0.001). We did not observe a significant difference in OS based on when patients recurred after surgery: 10.0 m (95% CI 8.7-11) within six months of surgery versus 11.6 m (95% CI 10-12, p = 0.256) greater than six months from surgery. CONCLUSIONS: These data support the inclusion of patients with recurrent PDAC in clinical trials for advanced disease, including those who develop recurrent disease within six months of surgery. Due to observed differences in survival, randomization should be stratified by disease presentation (recurrent vs de novo).

Clinical Development of Anti-TIGIT Antibodies for Immunotherapy of Cancer.

PURPOSE OF REVIEW: T-cell immunoglobulin and ITIM domain (TIGIT) is a next-generation inhibitory receptor with multiple antibodies under exploration in cancer therapy. Here, we review the available data from the early trials and overview upcoming clinical trials on anti-TIGIT antibodies. RECENT FINDINGS: There is a promising activity of anti-TIGIT, particularly in combination with anti-PD-1/PD-L1 in non-small cell lung cancer (NSCLC) with already phase 3 trials currently ongoing to confirm these early findings. Numerous anti-TIGIT antibodies are in clinical trials currently, and others are in preclinical development. Therefore, more data are expected in the next few years regarding the efficacy of this new checkpoint inhibitor in multiple solid and hematologic malignancies. However, preliminary data are promising, and anti-TIGIT treatment seems to confer more favorable responses when combined with anti-PD-1/anti-PD-L1 compared to either agent alone.

Clinical Activity of Selitrectinib in a Patient With Mammary Analogue Secretory Carcinoma of the Parotid Gland With Secondary Resistance to Entrectinib.

NTRK gene fusions are found in <1% of all cancers but are uniformly present in mammary analog secretory carcinomas (MASC) of the salivary glands. Two selective histology-agnostic tropomyosin receptor kinase (TRK) inhibitors are currently approved for malignancies with these oncogenic fusions. Resistance to TRK inhibition has been recognized, and the mediating mechanisms are presently being studied. This report describes a patient diagnosed with an MASC of the parotid gland who after undergoing multiple lines of treatment was found to have an ETV6-NTRK3 fusion and initiated TRK-targeted therapy using entrectinib. Upon disease progression, we performed tumor genetic sequencing that showed a secondary resistance mutation. The patient subsequently responded to selitrectinib, a next-generation TRK inhibitor.

Current Management of Angiosarcoma: Recent Advances and Lessons From the Past.

OPINION STATEMENT: Despite their rarity, angiosarcomas are one of the most aggressive soft tissue sarcomas. Management can often be challenging due to their location and infiltrative nature. A multidisciplinary treatment approach is always warranted, but the recurrence remains high even for localized tumors despite multimodality treatment. In the metastatic setting, cytotoxic chemotherapies, targeted therapies, and, more recently, immunotherapy are used. The sequence of systemic therapies remains currently a topic of active investigation. Over the last couple of years, there have been significant advances in understanding angiosarcoma biology, most notably via patient-driven initiatives like the Angiosarcoma Project. The knowledge derived from such translational work has led to identifying potential biomarkers of response to treatments and exploring new therapeutic avenues. More clinical trials are underway to expand treatment options and improve patient outcomes.

Outcomes associated with immune-related adverse events in metastatic non-small cell lung cancer treated with nivolumab: a pooled exploratory analysis from a global cohort.

BACKGROUND: Immune-related adverse events (irAEs) comprise a distinct spectrum of auto-inflammatory manifestations triggered due to immune checkpoint inhibitors (ICI). Current data on the association of irAEs with outcomes in NSCLC treated with nivolumab are limited. METHODS AND OBJECTIVES: We pooled data from 531 metastatic NSCLC patients from five centers treated with nivolumab after failing platinum-based chemotherapy. The primary objective was to investigate the relationship between irAEs with clinical benefit to nivolumab as well as to elucidate patterns of irAE-related ICI discontinuations and their impact on survival. RESULTS: 33.0% (173/531) of patients treated with nivolumab were noted to have an irAE. Patients with irAEs had a significantly longer median PFS [6.1 vs. 3.1 months, HR 0.68 95% CI (0.55-0.85); p = 0.001] and OS [14.9 vs. 7.4 months, HR 0.66 95% CI (0.52-0.82); p < 0.001)] compared to those without irAEs. In multivariate analysis, the presence of irAEs showed a significantly better PFS [HR 0.69, 95% CI (0.55-0.87); p = 0.002] and a trend for better OS [HR 0.62, 95% CI (0.55-1.03); p = 0.057]. Patients with permanent ICI discontinuation secondary to index irAE had a significantly shorter median PFS [2.3 vs. 6.6 months, HR 1.74 95% CI (1.06-2.80); p = 0.02] and median OS [3.6 vs. 17.6 months; HR 2.61 95% CI (1.61-4.21); p < 0.001] compared to those that did not have permanent ICI discontinuation. CONCLUSIONS: Our pooled exploratory analysis demonstrates improved clinical benefit to nivolumab in NSCLC patients experiencing irAEs. We also observed negative impact of irAE-related treatment discontinuation on survival in this group of patients.

Correction to: Outcomes associated with immune-related adverse events in metastatic non-small cell lung cancer treated with nivolumab: a pooled exploratory analysis from a global cohort.

The original version of this article unfortunately contained a mistake. The second sentence of the section "irAEs and ICI efficacy" should read as.

Axitinib plus pembrolizumab in patients with advanced sarcomas including alveolar soft-part sarcoma: a single-centre, single-arm, phase 2 trial.

BACKGROUND: VEGF promotes an immunosuppressive microenvironment and contributes to immune checkpoint inhibitor resistance in cancer. We aimed to assess the activity of the VEGF receptor tyrosine-kinase inhibitor axitinib plus the anti-PD-1 immune checkpoint inhibitor pembrolizumab in patients with sarcoma. METHODS: This single-centre, single-arm, phase 2 trial was undertaken at a tertiary care academic medical centre in Miami, FL, USA, and participants were recruited from all over the USA and internationally. Patients were eligible if they were aged 16 years or older, and had histologically confirmed advanced or metastatic sarcomas, including alveolar soft-part sarcoma (ASPS); measurable disease with one site amenable to repeated biopsies; an ECOG performance status of 0-1; and progressive disease after previous treatment with at least one line of systemic therapy (unless no standard treatment existed or the patient declined therapy). The first five patients were enrolled in a lead-in cohort and were given axitinib 5 mg orally twice daily and pembrolizumab 200 mg intravenously for 30 min on day 8 and every 3 weeks for cycles of 6 weeks for up to 2 years. Thereafter, patients received escalating doses of axitinib (2-10 mg) plus flat dose pembrolizumab according to the schedule above. The primary endpoint was 3-month progression-free survival. All patients were evaluable for survival and safety analyses. This study is registered with ClinicalTrials.gov, number NCT02636725, and is closed to accrual. FINDINGS: Between April 19, 2016, and Feb 7, 2018, of 36 patients assessed for eligibility, 33 (92%) were enrolled and given study treatment (intention-to-treat population and safety population), 12 (36%) of whom had ASPS. With a median follow-up of 14·7 months (IQR 10·1-19·1), 3-month progression-free survival for all evaluable patients was 65·6% (95% CI 46·6-79·3). For patients with ASPS, 3-month progression-free survival was 72·7% (95% CI 37·1-90·3). The most common grade 3 or 4 treatment-related adverse events included hypertension (five [15%] of 33 patients), autoimmune toxicities (five [15%]), nausea or vomiting (two [6%]), and seizures (two [6%]). Serious treatment-related adverse events occurred in seven (21%) patients, including autoimmune colitis, transaminitis, pneumothorax, haemoptysis, seizures, and hypertriglyceridemia. There were no treatment-related deaths. INTERPRETATION: Axitinib plus pembrolizumab has manageable toxicity and preliminary activity in patients with advanced sarcomas, particularly patients with ASPS, warranting further investigation in randomised controlled trials. FUNDING: Merck, Pfizer, American Cancer Society, and Sylvester Comprehensive Cancer Center.

Current and Future Directions for Angiosarcoma Therapy.

OPINION STATEMENT: Angiosarcomas are rare vascular neoplasms that are among the most aggressive subtypes of soft tissue sarcomas. Surgical resection is often challenging even in localized disease, as the infiltrative nature of these cancers leads to frequent local and metastatic recurrences. Cytotoxic chemotherapy, including anthracycline-based regimens and taxanes can produce significant responses in a subset of patients but durability is limited with most patients ultimately succumbing to metastatic disease. Targeted therapy with tyrosine kinase inhibitors is usually well-tolerated but prone to development of resistance. Few head-to-head trials have addressed the optimal sequence of therapies, or demonstrated conclusive benefits of one therapy over another based on clinical and etiologic factors. Novel therapies in clinical trials, including antibodies to endoglin and checkpoint inhibitors have demonstrated exciting early activity in patients with angiosarcoma. Improved understanding of the genetic heterogeneity within various angiosarcoma subtypes may identify predictive biomarkers to match patients to effective existing and future therapies. Overall, angiosarcoma patients with optimal performance status are best served in clinical trials that incorporate novel combinations of cytotoxic chemotherapy, targeted therapies, and immunotherapies.

Latest advances in adult gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are the most common GI tract mesenchymal tumors. GIST patients are optimally managed by a precision medicine approach. Herein, we discuss the latest advances in precision medicine and ongoing clinical trials relevant to GIST. Circulating tumor DNA for detection of mutational changes could replace tissue biopsies and radiographic imaging once validated. Most GISTs are KIT/PDGFRα mutated, and despite the good clinical response to imatinib, treatment is generally not curative, more often due to secondary mutations. New mechanisms to bypass this resistance by inhibiting KIT downstream pathways and by targeting multiple KIT or PDGFRα mutations are being investigated. Immunotherapy for GIST patients is in its infancy. These approaches may lead to more effective, less toxic therapies.

Genomic Profiling of Rare Undifferentiated Sarcomatoid Subtypes of Pancreatic Carcinomas: In Search of Therapeutic Targets.

PURPOSE: The highly aggressive undifferentiated sarcomatoid carcinoma (USC) subtype of pancreatic ductal adenocarcinoma (PDAC) remains poorly characterized because of its rarity. Previous case reports suggest that immune checkpoint inhibitors could be a promising treatment strategy, but the prevalence of established predictive biomarkers of response is largely unknown. The objective of this study was to leverage comprehensive genomic profiling of USC PDAC tumors to determine the prevalence of biomarkers associated with potential response to targeted therapies. METHODS: USC tumors (n = 20) underwent central pathology review by a board-certified gastrointestinal pathologist to confirm the diagnosis. These samples were compared with non-USC PDAC tumors (N = 5,562). Retrospective analysis of DNA and RNA next-generation sequencing data was performed. RESULTS: USC PDACs were more frequently PD-L1+ by immunohistochemistry than non-USC PDAC (63% v 16%, respectively, P < .001). Furthermore, USC PDAC had an increase in neutrophils (8.99% v 5.55%, P = .005) and dendritic cells (1.08% v 0.00%, q = 0.022) and an increased expression of PDCD1LG2 (4.6% v 1.3%, q = 0.001), PDCD1 (2.0% v 0.8%, q = 0.060), and HAVCR2 (45.9% v 21.7%, q = 0.107) than non-USC PDAC. Similar to non-USC PDAC, KRAS was the most commonly mutated gene (86% v 90%, respectively, P = 1). CONCLUSION: To our knowledge, this work represents the largest molecular analysis of USC tumors to date and showed an increased expression of immune checkpoint genes in USC tumors. These findings provide evidence for further investigation into immune checkpoint inhibitors in USC tumors.

Cutaneous Side Effects of Modern Targeted Therapy and Immunotherapy in Patients with Dermatological Malignancies.

The advent of immunotherapy and targeted therapies in treating dermatological malignancies has dramatically changed the landscape of dermato-oncology in recent years. Their superior efficacy compared to previous therapeutic options, such as chemotherapy, has resulted in their use in treating devastating malignancies, such as melanoma or unresectable/metastatic basal cell and squamous cell carcinoma. Skin toxicity is a critical safety consideration, among other adverse reactions, that can occur under treatment with these agents. This article aims to summarize the cutaneous side effects of immune checkpoint inhibitors and targeted dermato-oncological therapies. Although the skin side effects of these agents are primarily mild, they can occasionally affect the decision for treatment continuation and the quality of life of the affected patients. Therefore, physicians must be acquainted with the specific cutaneous toxicity profile of such treatments to mitigate their impact on the patients and optimize the overall outcome of dermato-oncological therapy.

Durable response to first-line PARP inhibition in BRCA-mutated metastatic cholangiocarcinoma: case report.

Background: Cholangiocarcinoma (CCA) is an increasingly prevalent malignancy worldwide, with poor outcomes even when diagnosed at an early stage. While recent trials have shown benefit from the addition of immunotherapy to standard-of-care chemotherapy, the improvement in overall survival is modest. Multiple novel therapies for advanced CCA targeting actionable genetic alterations have been approved in recent years; BRCA1/2 mutations are identified in up to 5% of CCA patients and may be an additional target for novel treatment approaches. While BRCA mutations have been shown in clinical trials to predict response to poly(ADP-ribose) polymerase (PARP) inhibitors in several solid tumors including breast, ovarian, prostate, and pancreas, no similar large-scale trials have been published in CCA to date. We report here a durable response to PARP inhibitor monotherapy in BRCA-mutated extrahepatic CCA; to our knowledge, this is the second report of first-line PARP inhibitor monotherapy and the first reported use of the second-generation PARP inhibitor talazoparib in this setting. Case Description: We report the case of a 79-year-old man with metastatic extrahepatic CCA harboring a somatic BRCA1 mutation who declined chemotherapy and was instead treated in the first-line metastatic setting with the PARP inhibitor talazoparib; he experienced a complete radiographic response six months into treatment and has remained on talazoparib for over three years without evidence of disease recurrence. Conclusions: This case adds to a growing list of retrospective studies supporting the clinical activity of PARP inhibitors in BRCA-mutated extrahepatic CCA. However, prospective data are clearly needed prior to adoption of this strategy in clinical practice. Fortunately, multiple trials investigating novel combination therapies utilizing PARP inhibitors in CCA are underway.

Comparative Genomic Analysis of Pancreatic Acinar Cell Carcinoma (PACC) and Pancreatic Ductal Adenocarcinoma (PDAC) Unveils New Actionable Genomic Aberrations in PACC.

PURPOSE: Pure pancreatic acinar cell carcinomas (PACC) are rare malignancies with no established treatment. PACC demonstrates significant genetic intertumoral heterogeneity with multiple pathways involved, suggesting using targeted cancer therapeutics to treat this disease. We aggregated one of the largest datasets of pure PACC to examine the genomic variability and explore patient-specific therapeutic targets. EXPERIMENTAL DESIGN: PACC specimens (n = 51) underwent next-generation sequencing of DNA (n = 29) or whole exome (n = 22) and RNA (whole transcriptome, n = 29) at a commercial laboratory. We performed comparative analyses of a genomic cohort of pancreatic ductal adenocarcinomas (PDAC; n = 4,205). In parallel, we conducted a retrospective review of patients with PACC treated at Huntsman Cancer Institute (HCI). RESULTS: The real-world dataset included samples from 51 patients with PACC. We found key molecular differences between pure PACC and PDAC, highlighting the unique characteristics of pure PACC. Major differences in PACC include lower MAPK signaling and less stromal cell abundance compared with PDAC. Pure PACC showed genomic loss-of-heterozygosity to largely coincide with mutations in BRCA1, BRCA2, and PALB2. Of the 7 patients treated at HCI, one had a tumor that harbored a BRAF-V600E mutation. Leveraging precision oncology, this patient is being treated with encorafenib plus binimetinib, achieving an exceptionally durable and ongoing complete response of more than 3 years. CONCLUSIONS: There are major differences between PACC and PDAC, including downregulation of the MAPK signaling pathway, and less stromal cell abundance. In addition, genomic characterization of pure PACC revealed frequent targetable alterations, which can guide patient treatment.

Real-world pan-cancer landscape of frameshift mutations and their role in predicting responses to immune checkpoint inhibitors in cancers with low tumor mutational burden.

BACKGROUND: Pembrolizumab is FDA approved for tumors with tumor mutational burden (TMB) of ≥10 mutations/megabase (mut/Mb). However, the response to immune checkpoint inhibitors (ICI) varies significantly among cancer histologies. We describe the landscape of frameshift mutations (FSs) and evaluated their role as a predictive biomarker to ICI in a clinical cohort of patients. METHODS: Comprehensive genomic profiling was performed on a cohort of solid tumor samples examining at least 324 genes. The clinical cohort included patients with metastatic solid malignancies who received ICI monotherapy and had tumor sequencing. Progression-free survival (PFS), overall survival, and objective response rates (ORR) were compared between the groups. RESULTS: We analyzed 246,252 microsatellite stable (MSS) and 4561 samples with microsatellite instability across solid tumors. Histologies were divided into groups according to TMB and FS. MSS distribution: TMB-L (<10 mut/Mb)/FS-A (absent FS) (N=111,065, 45%), TMB-H (≥10 mut/Mb)/FS-A (N=15,313, 6%), TMB-L/FS-P (present ≥1 FS) (N=98,389, 40%) and TMB-H/FS-P (N=21,485, 9%). FSs were predominantly identified in the p53 pathway. In the clinical cohort, 212 patients were included. Groups: TMB-L/FS-A (N=80, 38%), TMB-H/FS-A (N=36, 17%), TMB-L/FS-P (N=57, 27%), TMB-H/FS-P (N=39, 18%). FSs were associated with a higher ORR to ICI, 23.8% vs 12.8% (p=0.02). TMB-L/FS-P had superior median PFS (5.1 months) vs TMB-L/FS-A (3.6 months, p<0.01). The 12-month PFS probability was 34% for TMB-L/FS-P vs 17.1% for TMB-L/FS-A. CONCLUSIONS: FSs are found in 47% of patients with MSS/TMB-L solid tumors in a pan-cancer cohort. FS may complement TMB in predicting immunotherapy responses, particularly for tumors with low TMB.

Emerging mechanisms of immunotherapy resistance in sarcomas.

Sarcomas are a heterogeneous group of over 150 mesenchymal neoplasms of bone and soft tissue. Clinical prognosis remains poor in the metastatic and refractory setting, despite treatment with traditional chemotherapies. A subset of sarcoma patients can exhibit remarkable responses to novel immune therapies; however, most patients will not respond. Emerging data from genetic and transcriptomic datasets suggests that patients who are resistant to checkpoint inhibitor monotherapy may have low expression of immune-related genes, suggesting that the sarcoma was not sufficiently immunogenic to trigger or maintain an immune response to generate tumor-specific immune effector cells. In this review, we discuss the emerging data surrounding potential mechanisms of resistance, including various biomarkers explored in clinical trials of immune therapy for sarcomas. We also review future directions in clinical trials that are focused on boosting tumor immunogenicity to improve the activity of checkpoint inhibitors, as well as adoptive cellular therapy approaches to bypass deficiencies in neoantigens or antigen presentation.

Considerations for immunotherapy in patients with cancer and comorbid immune dysfunction.

Immune checkpoint inhibitors have been widely incorporated for cancer treatment in a variety of solid and hematologic malignancies. Multiple clinical trials have demonstrated the efficacy of PD-1/PD-L1 and CTLA-4 axis inhibition in the metastatic and adjuvant settings. Due to the risks of autoimmune toxicity with these agents, stringent inclusion/exclusion criteria were employed in those initial clinical trials. These criteria led to exclusion or underrepresentation of a variety of patient populations with underlying immune dysfunction. These populations included patients with preexisting autoimmune diseases, solid organ or bone marrow transplant recipients, patients with HIV or viral hepatitis infections, patients receiving concurrent chronic steroid therapy, as well as patients who were elderly, pregnant, or had poor performance status. Thus, established guidelines on the use of immune checkpoint inhibitors in these patients are lacking, and evidence to support efficacy or toxicity are overall limited to retrospective studies and case series. Fortunately, ongoing clinical trials are now including these patients and are shedding light on whether these underrepresented populations can also safely benefit from immune checkpoint inhibitor therapies. In this review, we summarize the most clinically relevant available data on the use of checkpoint inhibitors in immunocompromised patient groups with a primary focus on safety.

The emerging landscape of immune checkpoint inhibitor based clinical trials in adults with advanced rare tumors.

"Rare cancers" are a diverse collection of cancers that collectively account for approximately 20% of all adult cancers in the United States. Their rarity has caused an underrepresentation of these cancers in preclinical research and clinical trials, leading to fewer (and often no) treatment options for patients backed by robust clinical evidence. The recent advent of immune checkpoint inhibitors (ICIs) into the oncologist's armamentarium, while revolutionizing the treatment of many common cancers, has also started to make gradual inroads into the treatment of certain rare cancers. One reason is that the efficacy of ICIs depends more on factors intrinsic to the tumor cells and the tumor microenvironment and less on tumor histology. Recent years have seen ICI approvals in many rare cancers, and many trials are being designed using ICIs as single agents or in combination. In this commentary, we present an overview of the emerging role of ICIs in some rare cancers.

Biomarkers of therapeutic response with immune checkpoint inhibitors.

Immune checkpoint inhibitors (ICPIs) have revolutionized the treatment paradigm of a wide range of malignancies with durable responses seen in even advanced, refractory cancers. Unfortunately, only a small proportion of patients with cancer derive meaningful benefit to ICPI therapy, and its use is also limited by significant immune and financial toxicities. Thus, there is a critical need for the development of biomarkers to reliably predict response to ICPI therapy. Only a few biomarkers are validated and approved for use with currently Food and Drug administration (FDA)-approved ICPIs. The development and broad application of biomarkers is limited by the lack of complete understanding of the complex interactions of tumor-host environment, the effect of immunotherapies on these already complex interactions, a lack of standardization and interpretation of biomarker assays across tumor types. Despite these challenges, the field of identifying predictive biomarkers is evolving at an unprecedented pace leaving the clinician responsible for identifying the patients that may derive optimal benefit from ICPIs. In this review, we provide clinicians with a current and practical update on the key, clinically relevant biomarkers of response to ICPIs. We categorize the current and emerging biomarkers of response to ICPIs in four major categories that govern anticancer response-the inflamed tumor, tumor antigens, immune suppression, and overall host environment.