Evidence Items (EIDs) form the fundamental unit of the CIViC knowledgebase. EIDs derive structured clinical statements from peer reviewed, PubMed-indexed publications and American Society of Clinical Oncology (ASCO) abstracts, which act as Sources for Evidence Items. EIDs link back to their sources. EIDs are hand-curated units of knowledge, and one evidence source may supply enough data to create multiple EIDs. EIDs are displayed throughout the CIViC application, for example as a summary (Figure 1) and as a data table row (Figure 3).
CIViC Evidence is added and curated via a moderation process that includes submitting, evaluating, accepting (or rejecting), and suggesting changes (Figure 2). CIViC Curators may add or suggest revisions to curated content at each step. Adding content involves submitting new Evidence Items or Assertions that subsequently undergo revision and Editor review. Revision of content involves adding or revising the clinical summary and/or its associated features. Once changes are made within the CIViC database, the additions/revisions become visible directly or on a separate revision page depending on the type of submission. Curation is listed as a “Submitted” (i.e., pending) until it is accepted by an Editor, who are given power to accept or reject Curator submissions. Curators may reject (but not accept) their own submissions/revisions.
It is important to note that once evidence is submitted into CIViC as a new Evidence Item, then the EID is visible to the community in the unmoderated/non-reviewed state, and these EIDs are labeled in orange (Figure 3). This enables the public to comment or create moderations on the submitted evidence. It is also important to note that orange Evidence Items may be incomplete, not accurately fit into the CIViC data model, or contain problems which the moderation process is designed to capture and fix. Once a CIViC EID has been reviewed by editors, and all revisions reviewed and accepted, then the EID is accepted by an editor, and its label changes to green.
When an Evidence Item has a pending revision, it is labeled with a blue exclamation mark icon (Figure 3). Note that revisions can be made to EIDs in both the Submitted/Unreviewed Status (orange) and the Accepted Status (green).
General Evidence Item Curation Practices¶
Evidence Items should generally be prepared from primary literature rather than from review articles. It is recommended that curators use reviews to identify potential primary literature referenced in the review and to curate individual Evidence Items based on these cited articles. Review articles can also be used to develop Gene and Variant summaries.
When curating new evidence, the curator should review the existing evidence already curated into CIViC for that Variant to look for the following issues:
For clinical trials and case reports (Levels A, B, and C), overlapping patient populations (i.e. the same patient treatment and outcome described in multiple reports) should be avoided, or carefully noted to alert users of this nuance and avoid conclusions that mistake these studies as independent. Note also that reports describing different phases of the same patient treatment (i.e. erlotinib and subsequently afatinib), or different clinically relevant conclusions (i.e. predictive evidence and simultaneous diagnostic evidence) are independent/non-overlapping entities.
For Predisposing EIDs, which generally describe germline variants, the same patient may appear in multiple studies. Curators should be careful to note these cases and review existing germline EIDs for the same variant in CIViC.
Disease stage, prior treatments, and other experimental details influencing evidence interpretation should be captured within the Evidence Statement to maximize user comprehension of the underlying study and the appropriate context in which it is relevant. Such details are critical parts of clinical guidelines and can impact which clinical guidelines should be used as well as drug sensitivities (see EID1008 and EID1009).
Six types of EID exist in CIViC (Figure 4), giving structured clinical annotation to a Variant. Three types of clinical statements, Predictive/Therapeutic, Prognostic, Diagnostic and Oncogenic Evidence Types are usually associated with somatic variants, while Predisposing evidence is generally linked to germline variation. Functional studies are often performed in vitro, so associated EIDs will have the Unknown field selected for Variant Origin.
Predictive/Therapeutic Evidence Items (EIDs) capture evidence supporting or refuting the role of a variant in conferring drug sensitivity, resistance or adverse response in the context of a specific disease.
Below is an example of an EID that illustrates the Predictive Evidence Type (Figure 5). This example describes the CLEOPATRA trial (NCT00567190), which evaluated 808 patients with HER2-positive metastatic breast cancer. These patients demonstrated significant sensitivity/response when treated with combination therapy of docetaxel, pertuzumab and trastuzumab.
Predictive Evidence Curation Practices¶
Predictive Evidence Items should include the Drug Name(s) and Drug Interaction Type (for multiple drugs).
The most current name of the Drug (excluding trade names) should be used in the Drug field to reduce duplication. The Evidence Statement should contain the drug name used in the study with the current name in brackets, when applicable.
Drug Interaction Types are required anytime more than one drug is mentioned for a given study. If multiple drug interaction types are at play (e.g., combinations and substitutes), considering separating these concepts into more than one Evidence Item.
If applicable, the Clinical Trial name should be included in the Evidence Statement. Any clinical trial IDs available in PubMed for the Source linked to this Evidence Item will be automatically imported and linked to this Evidence Item when the PubMed Source is imported into CIViC.
The duration of exposure to the drug and confounding interactions (e.g., wash-out periods, previous treatment, cancer stage) should be listed.
Assigning a Clinical Significance of Sensitivity/Response can depend on factors such as response rate, which will vary significantly with disease and treatment. In some cases a response rate of 15% may represent a significant improvement, and merit a valuation of Sensitivity/Response. A general guideline for CIViC curation is to follow the author’s published (and peer-reviewed) interpretations and conclusions of the results.
Extensive guidelines, use cases, and examples for curation of predictive evidence are given in Figure 14 and Table 1.
Below is an example of an EID that illustrates the Diagnostic Evidence Type. This example describes the World Health Organization guidelines for classifying chronic myelomonocytic leukemia (CMML). Specifically, if a patient has a PCM1-JAK2 fusion or a rearrangement involving PDGFRA, PDGFRB, or FGFR1, especially in the setting of eosinophilia, the patient does not have CMML.
Diagnostic Evidence Curation Practices¶
Diagnostic Evidence Items should only be used if the variant assists in labeling the patient with a specific disease or disease subtype and should not be used to denote that the particular variant is prevalent in a specific disease.
Generally, Diagnostic Evidence Items describe variants that can help accurately diagnose a cancer type or subtype with high sensitivity and specificity, for which diagnoses may otherwise be challenging.
Diagnostic Evidence Items are very closely tied to the terms of the Disease Ontology (DO) in CIViC. The Disease Ontology works to actively generate mappings to other highly used ontologies, but the terms in the DO are generally accepted diseases which are part of medical practice. Therefore, literature proposing a novel disease type - for instance studies suggesting a novel cancer subtype defined by the presence of a specific oncogenic variant - are not generally admitted as part of the CIViC data model. Alternatively, if a curator with expertise in the field feels that the novel subtype has met with a sufficient level of acceptance, they may submit this type of Evidence Item using a non-DO term, and suggest that DO admit this term into the ontology.
Literature describing diagnostic practice guidelines (such as those of the World Health Organization) may be used in curation and submitted as A-level Evidence Items.
Literature describing small numbers of observations in patient samples of a certain variant, where the authors state that the variant may have diagnostic value, may be admitted as lower star Case Study (C-level) data. Similar literature employing larger numbers could be labeled as Clinical (B-level).
Guidelines and use cases for curation of diagnostic evidence are given in Table 1.
Below is an example of an Evidence Item that describes a Prognostic Evidence Type. This example describes a 406-patient trial whereby observation of any somatic TP53 mutation in chronic lymphoblastic leukemia conferred poor prognosis relative to wildtype TP53.
Prognostic Evidence Curation Practices¶
Prognostic Evidence Items should include the measured outcome (e.g., overall survival, complete response, partial response), number of subjects and applicable statistics.
If described in the literature, a definition of the measured outcome should be given.
Prognostic evidence is characterized by either better outcomes for patient subpopulations with the given variant, which are not specific to any particular treatment context, or worse outcomes which are not indicative of variant resistance to a specific treatment. Instead, the change in outcome should be largely correlated to the presence of the variant.
In some cases, a variant subpopulation with worse outcome may benefit from subsequent therapy targeted to that variant (e.g., HER2 amplification in breast cancer).
Guidelines, use cases, and examples for curation of prognostic evidence are given in Figure 14 and Table 1.
Predisposing Evidence Items were first introduced in CIViC v1 to capture the role of a variant in increasing the likelihood of developing cancer. This is comparable to the concept of heritable genomic variants that increase risk for “cancer predisposition syndromes” or “cancer susceptibility”. In CIViC v2, Predisposing Evidence Items include both this historical clinical significance of “cancer predisposition variants”, as well as evidence items that decrease risk for cancer susceptibility by conferring a protective effect (“cancer protectiveness variants”). The structure of Predisposing Evidence Items (EIDs) mirrors the structure of other EID types in CIViC by having multiple clinical significance classifications under which evidence can be evaluated. (Figure 8). Thus, just as Prognostic EIDs capture better and worse outcomes, and Predictive EIDs include the ability to capture sensitivity and resistance, the Predisposing EID can capture detrimental pathogenic and also beneficial protective qualities. CIViC Predisposing Evidence Items which pertain to the Pathogenic axis in Figure 8 can be aggregated at the CIViC Assertion level for a formal pathogenicity evaluation utilizing ACMG/AMP Codes.
The Pathogenic axis for Predisposing EIDs (right side in Figure 8) documents evidence which describes either the presence or absence of a pathogenic property for a variant. It is important to realize that evidence supporting both a pathogenic or benign classification are captured using the Predisposition clinical significance, associated with the right (red) axis (labeled Pathogenic) by use of the CIViC Evidence Direction (Supports or Does not support) (Figure 9). To summarize, a CIViC Predisposing EID that Supports clinical significance of Predisposition suggests a potentially pathogenic variant. A Predisposing EID that Does Not Support clinical significance of Predisposition suggests a potentially benign variant. These EIDs do not make any final classification of pathogenicity and may or may not fully support any specific ACMG criteria but point in the direction of such classifications.
As mentioned above, the Predisposing Evidence Type may utilize ACMG/AMP Codes when applicable. If the curator wishes to capture evidence that indicates a variant may be benign or pathogenic, and this evidence meets one or more of the published criteria from ACMG/AMP guidelines (termed ACMG codes in CIViC), then the curator can indicate the ACMG codes that were met in the body of the EID. The general format for a predisposing EID of this type is a summary of the reported data relevant to the variant and disease of interest, followed by an enumeration of ACMG Code(s) derived from the reported information with a brief justification for the presence of each code.
Below is an example of an Evidence Item (EID5546) that describes a Predisposing Evidence Type (Figure 10) that Supports a clinical significance of Predisposition. This example describes a study where the VHL - R167Q (c.500G>A) Variant was described in a set of patients and evidence for the PP1 ACMG-AMP criteria was documented. Hemangioblastoma and pheochromocytoma were seen in patients and are reported as Associated Phenotypes, while the Disease is Von Hippel-Lindau Disease.
Predisposing Evidence Curation Practices¶
Typically, but not always, Predisposing Evidence Items are written for rare germline variants. In rare circumstances, the patient can have a predisposing variant that develops as a result of a somatic mutation or mosaicism during embryogenesis that is widespread, but not necessarily heritable. Common germline variants may also be associated with predisposition to cancer.
For evidence that indicates the presence or lack of a protective quality for a germline variant, this will be annotated with Supports Protectiveness or Does not support Protectiveness, respectively. Although not yet well-described in cancer predisposition, we anticipate examples will become available with time based on other complex diseases, such as the APOE2 allele which has evidence that it is protective against Alzheimer’s disease.
Evidence supporting variant pathogenicity will be captured by a curator by selecting Supports, and then Predisposition using the menus available on the Add Evidence form in CIViC. Importantly, evidence supporting a benign annotation will be captured during curation by choosing Does not support and then Predisposition in the menus available in the Add Evidence form.
For EIDs that utilize the Clinical Significance of Predisposition, ACMG evidence criteria (Richards et al 2015) (termed ACMG codes for short) are derived from the evidence presented in the specific Evidence Source and are listed at the end of the Evidence Statement with a brief justification for each code’s use. ACMG evidence codes that can not be directly derived from the Evidence Source (e.g., population databases for PM2) should be captured in the Variant Summary or at the level of the Assertion. The EID depicted here is part of Assertion number 4 (AID4), where the Evidence Items combine to create a pathogenic Assertion. Predisposing Evidence Items do not individually determine ACMG/AMP Pathogenicity, but simply show in which direction the evidence derived from the particular publication or abstract is “leaning”, e.g., if it is leaning towards a pathogenic or benign final classification.
Oncogenic Evidence Type¶
Oncogenic Evidence Items (EIDs) capture clinically relevant information associated with either a somatic variant’s protective qualities or, more commonly, its involvement in tumor pathogenesis as described by the Hallmarks of Cancer. An Evidence Statement for an Oncogenic EID includes a summary of the reported data relevant to the variant and disease of interest by describing assays performed and experimental results. The Evidence Summary for an Oncogenic EID may contain Oncogenicity Codes from the ClinGen/CGC/VICC Standards for the classification of oncogenicity of somatic variants in cancer.
In a system similar to the one described above for Predisposing Evidence Items, the Protective Clinical Significance is used to capture evidence associated with a somatic variant’s ability to reduce the development or harmful effects of a tumor. For example, the association of enhanced DNA-damage repair with significant TP53 copy number gains (PMID: 27642012).
The Oncogenic Clinical Significance is used to capture evidence supporting an oncogenic or benign final classification of a somatic variant at the Assertion level. In the case where evidence suggests a variant has oncogenic properties, a curator will select Supports, and then Oncogenicity using the menus available on the Add Evidence form in CIViC (Figure 11). Importantly, evidence supporting a benign annotation will be captured during curation by choosing Does not support and then Oncogenicity in the menus available in the Add Evidence form.
Below is an example of an Evidence Item with an Oncogenic Evidence Type (Figure 12). This EID describes a study wherein KRAS Q61H was transfected into cells resulting in multilayered growth indicative of a loss of contact inhibition. Oncogenicity code OS2 is noted in the Evidence Statement, since the EID describes a well established in vitro experiment (focus formation assay), which supports an oncogenic effect for this variant.
Oncogenic Evidence Curation Practices¶
The Oncogenic Evidence Type describes literature-derived evidence pertaining either to a somatic variant’s protective effects or its role in tumor formation, growth, survival or metastasis, as summarized by Hanahan and Weinberg in Hallmarks of Cancer. Disease type should be specified, as oncogenic effects may depend on cellular context. For cases where a disease type is difficult to ascertain, such as experiments in highly de-differentiated cell lines, the Disease Ontology term ‘Cancer’ can be used. The Evidence Statement should contain a summary of the experiments or findings suggesting a protective, oncogenic, or benign variant effect.
The Oncogenic Evidence Item may be associated with Oncogenicity Codes developed by the Knowledge Curation and Interpretation Standards (KCIS) working group of the GA4GH VICC in collaboration with ClinGen working groups. Oncogenicity codes assess oncogenicity of a given somatic variant in a mechanism similar to that used in the 2015 ACMG/AMP Guidelines for germline pathogenicity. Enumeration of Oncogenicity Codes derived from the literature along with a brief justification for the presence of each code can be included in the Evidence Statement.
Functional Evidence Type¶
The Functional Evidence Type describes data from in vivo or in vitro experiments that assess the impact of a variant at the protein level. Functional Evidence should be disease agnostic and if the Evidence being entered relies on disease or cell context, consider another Evidence Type. The variant origin for this Evidence Type is anticipated to primarily be N/A and entries should be classified under the Evidence Level of D - Preclinical. Variant impact on protein structure, folding, binding, activity, activation, phosphorylation, and downstream pathway signaling are all types of evidence that fall under the Functional Evidence Type.
Below is an example of a Evidence Item that describes a Functional Evidence Type (Figure 13). The authors performed an experiment to determine the impact of the variant on normal protein function related to cell cycle arrest. Expression of wildtype CDKN2A arrests the cell cycle in CDKN2A deficient cells, whereas expression of CDKN2A D108Y does not impact cell cycle progression in the CDKN2A deficient cells. These results indicate the innate ability of CDKN2A to arrest cell cycle progression has been lost as a result of the presence of the protein variant.
Functional Evidence Curation Practices¶
Functional Evidence Items describe how the variant alters (or does not alter) biological function from the reference state. The Evidence Statement should include details on the experimental conditions (e.g., specification of cell type and/or model system, expression vector, vector entry system, and selection method) and the results related to the potential impact on function (including statistics, if applicable).
Clinical Significance for Functional Evidence Types adhere to the following rules related to Muller’s Morphs:
Gain of Function
A variant whereby new/enhanced function is conferred on the gene product
Loss of Function
A variant whereby the gene product has diminished or abolished function
A variant whereby the function of the gene product is unchanged
A variant whereby the function of the gene product is a new function relative to the wildtype function
A variant whereby the function of a wildtype allele gene product is abrogated by the gene product of the allele with the variant
A variant that cannot be precisely defined by gain-of-function, loss-of-function, or unaltered function.
Functional Evidence Items may be used to support certain ACMG codes (e.g. PM1). In these cases, the ACMG code should be listed in the Evidence Statement along with a brief justification for its inclusion. Functional Evidence Items may appear as supporting evidence for Predisposing Assertions.
The table below (Table 1) gives an in depth set of cases for assigning the Clinical Significance to an Evidence Item (EID) where either the “Supports” or “Does Not Support” Evidence Direction is used in combination with a Predictive/Therapeutic, Diagnostic or Prognostic Clinical Significance annotation.
Note that “Reduced Sensitivity” Clinical Significance is used to compare the variant of interest to a known, sensitizing variant. It is not used to compare the efficacy of one drug for a variant against a different drug for the same variant. In the latter case, the curator may simply make a Predictive evidence item with independently evaluates the efficacy of the drug against the variant of interest.
The “Sensitivity/Response” annotation is used to assess sensitizing variants, which are usually in the form of a primary sensitizing somatic mutation (e.g SNV, amplification, deletion, etc).
The “Resistance” annotation is used in situations where the variant of interest has been observed to induce resistance in a context where, in the absence of the variant, the system being assayed would be deemed sensitive which induce resistance to treatment (e.g. T790M mutation in cis with a background variant of EGFR L858R). In cases where a variant fails to induce sensitivity, then that variant is best annotated with “Does not Support Sensitivity”.
Both Predictive and Prognostic evidence types may be obtained from the same data set in some cases. Figure 14, displayed below, gives hypothetical examples of predictive and prognostic structured annotation derived from patient data.
Curating Evidence from Clinical Trials¶
When curating evidence obtained from clinical trials performed with groups of patients, where data is pooled by mutation type (e.g. EGFR MUTATION), Level B clinical results may be obtained, which may report a statistically significant difference on a clinically relevant parameter such as partial response (PR) between wildtype vs. mutant patients. In addition, the publication may sometimes give outcomes on important individual patient parameters, such as variant, age, sex, best response, overall survival, etc. In these cases, this aggregate of data may be integrated into multiple Evidence Items in the following manner (The figure below is loosely based on a data set in CIViC obtained from PMID:21531810, which can be seen in CIViC on its Evidence Source page).
Statistical results may be obtained from the study to annotate a Categorical (sometimes colloquially called bucket-type) CIViC Variant, which pools together a category of sequence variants (for example EGFR MUTATION). Significantly longer progression free survival (PFS) may be observed in the mutant group (grouped under the Categorical CIViC Variant) vs. the wildtype group, when given a certain drug. In this case, this result may be reported in a CIViC Level B Evidence Item under the CIViC Categorical Variant EGFR MUTATION, with Evidence Direction and Clinical Significance “Suggests Sensitivity/Response” to the drug used.
When a sufficient level of individual patient detail is present, including the individual patient variants along with an important clinical parameter such as their best response, then this data set can be used to generate a set of CIViC Level C Evidence Items for the patients, each one associated with the respective CIViC Variant that was observed in the individual patient, along with the outcome. Note that even if the entire group showed statistically significant improvement with the Categorial Variant, this does not mean every patient did better, e.g. if a patient with variant X123Y had progressive disease as best response, then this would result in a Level C EID with Evidence Direction and Clinical Significane of “Does not support Sensitivity” for the CIViC Variant X123Y.