| Consensus, statements or clinical guidelines |
Consensus Study: An original study which seeks a consensus among experts using a formal methodology such as a Delphi study, an online or in person survey or voting process (consensus conference) and published as a position statement/recommendation. This is distinct from simple published surveys, letters to editors or opinion articles.
Clinical Practice Guidelines are defined as systematically developed statements or processes to assist clinician and patient decisions about appropriate health care for specific clinical circumstances. We will include if the abstract states ‘guideline or statement’ developed by a panel of experts or professional societies or official institutions or its abstract refers to the use of some systematic methods for the development of clinical practice guidelines or recommendations (i.e. GRADE, IOM Standards, G-I-N Standards or Guidelines 2.0).
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| Systematic Review |
A review of the scientific evidence which applies strategies that limit bias in the assembly, critical appraisal, and synthesis of all relevant studies on the specific topic. With meta-analysis: systematic review followed by a statistical analysis of results from separate studies, examining sources of differences in results among studies, and leading to a quantitative summary of the results if the results are judged sufficiently similar or consistent to support such synthesis.
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This code includes also: Umbrella Review. Umbrella Reviews or Overviews of Reviews are reviews of systematic reviews. Overviews are often broader in scope than any individual systematic review, meaning that they can examine a broad range of evidence.
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| Animal Study (mechanistic) |
A study that uses animals or animal samples (including cell lines) as research subject including xenograft models (models of cancer where the human tissue or cells are implanted into an animal). Studies carried out in the areas of basic research (mechanistic studies) and medicine referring to human oncology. Research concerning veterinary medicine purposes are to be excluded.
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| Other Mechanistic Basic Science Studies |
Studies without clinical data associated. In vitro/in silico studies that use human derived samples for fundamental/basic science/biological experimental work (such as living cells lines or tissues, molecules, or studies using organoids, three-dimensional miniature versions of organs or tissues generated from cells with stem potential). This does not include studies of clinical tests carried out in the lab on patient tissues taken for clinical purposes (these are considered in vivo clinical/epidemiological or diagnostic studies instead).
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Are included here:
- In silico studies: computer simulation or evaluations of synthetic data with known properties.
- Molecular database derived studies: Databases from cohort or case-control consortia are considered human data (i.e., Practical, TGCA). The rest of studies using data derived from online molecular, genetic, or another biological database repository are included here.
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| Ecological Study |
A study in which the units of analysis are populations or groups of people rather than individuals (aggregated data). Geographical comparisons with aggregated outcomes such as temporal trends including joinpoint analysis, time series, interrupted time series and correlations between aggregated variables.
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| Case Report |
Detailed description of observations at the individual level, documented from a single patient or clinical case. This code also includes small case series with less than five subjects (n<5).
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| Case Series/Longitudinal Case Series |
Case series: A collection of subjects (usually patients) with common characteristics used to describe some clinical, pathophysiological, or operational aspect of a disease, treatment, exposure, or diagnostic procedure. Without non-tumoral comparison group.
Longitudinal case series: A single-group research design in which measurements are made at several different times, thereby allowing trends to be detected.
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| Population-based Descriptive Study |
Population-based Descriptive Study: Studies carried out from Population-based Cancer Registries (or other population-based registries, i.e. official country mortality data) that seek to describe a population group, but without a comparison group (there may be comparisons based on sociodemographic variables such as sex, age, or ethnic groups). A hospital registry is not a population-based registry.
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| Diagnostic Test Agreement/Reproducibility Study |
A study where the repeatability (reproducibility) of a specific diagnostic test or procedure is evaluated by multiple observers (pathologists or others) or machines (image analysis, AI), or their combination. This may take the form of a test being repeated multiple times on the same cases at different time points or, more often, where different observers (e.g., a group of pathologists) evaluate and interpret/report the results of the test independently. The results of repeated testing are compared between the observers. Sometimes diagnostic agreement/reproducibility design may accompany diagnostic accuracy studies.
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| Laboratory Test Validation Study |
These studies validate the performance of a laboratory test or assay in a controlled laboratory environment (i.e., pathology laboratory), usually in cherry-picked cases/samples. The focus is primarily on the technical aspects of the laboratory method to ensure that it produces consistent and valid results when compared to the reference method. These studies are foundational for ensuring that a test is suitable for further clinical evaluation.
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| Diagnostic Test Accuracy Study |
These studies evaluate the effectiveness and reliability of diagnostic tests in the clinical settings and focus on their ability to accurately detect the presence or absence of a particular disease or condition. The focus here is on the clinical utility of the test, i.e., assessing how well it helps to make accurate diagnostic decisions for a specific clinical question/situation. Therefore, the identification of selected patients and controls is mandatory as well as a comprehensive statistical analysis.
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Key metrics used in these studies must include at least one of these options:
- The area under the curve (AUC) of the receiver operating characteristic (ROC) curve.
- Sensitivity, specificity, PPV, NPV: at least two of them and with 95% confidence interval (CI 95%).
- Sensitivity, specificity, PPV, NPV: all of them without CI 95%.
These studies are designed to quantify the performance of a test in a clinical setting and inform clinicians about the reliability of the test for making diagnostic decisions.
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| Randomized Controlled Trial |
A clinical-epidemiological experiment in which subjects are randomly allocated into groups, usually called intervention/test and control groups, to receive or not to receive a preventive or a therapeutic procedure or intervention.
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| Other Clinical Trial |
A clinical-epidemiological experiment in which subjects are not randomly allocated into groups, to receive or not to receive a preventive or a therapeutic procedure or intervention.
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Includes several types of study:
- Quasi-experimental: situation in which the investigator lacks full control over the allocation and/or timing of intervention but nonetheless conducts the study as if it were an experiment, allocating subjects to groups.
- Single-arm trials, with no control group.
- Historical control: The control group are subjects who were studied before the main group receive the intervention.
- Experimental before-after studies: An approach in which the outcome is measured before and after an intervention that has been delivered to all participants.
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| Observational Longitudinal Study RCT derived |
The information and/or samples collected in an RCT are used to test a different hypothesis (i.e. the prognostic value of a biomarker). Patients were not randomized according to the new objective, so it is an observational study taking advantage of the systematic collection of data and the quality control measures usually included in RCTs.
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| Cohort study |
Study design in which the investigator observes participants (free of the event that is going to be evaluated) who are exposed and unexposed and follows them up to see if they develop the disease or event of interest. In a cohort study, the investigator observes and does not assign the participants’ exposure status as in the experimental design. They could be prospective or retrospective (conducted by reconstructing data about participants at a time or times in the past).
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Includes Nested Case-Control and Case-Cohort studies |
| Other Longitudinal Studies |
Observational before-after Study: An approach in which the outcome is measured before and after an exposure has occurred to all participants. In contrast to the experimental ones, the exposure is not defined by the researcher.
Other follow up studies: other longitudinal studies that do not meet the stated criteria for cohorts, they may compute percentage of survival patients or other index typical of cohort studies, but without controlling losses of follow-up and/or using survival analytical methods.
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| Self-matched Case-Control Study |
In this design, each participant (case) serves as its own matched control. I.e., when the tumour tissue from a cancer case is compared with the corresponding “healthy” tissue from the same patient to assess the association between some characteristic/feature/exposure with the outcome (disease or cancer subtype).
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| Cross-Sectional Study |
Study in which the outcome and other variables are determined in each participant of the study at one particular time. It can refer to a period, however observed photographically (without evolution).
There is no formal selection of controls, this means that firstly the participants are recruited and only after that, they are classified depending on their diagnosis into the comparison groups (sometimes referred as cases and controls). Comparisons of histological, immunohistochemical, genetic, etc. profiles between groups of tumours are included here (exception: in this case it is considered cross-sectional even with a formal selection of controls).
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| Classic Case-Control Study |
Study design in which the investigator selects participants with the outcome (cancer type or subtype) (cases) and a comparison group without that particular outcome (controls) to study the association between previous exposures or previous characteristics with the outcome. Cases and controls are very often matched by age, sex, or other variables.
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