How to Read: Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries [Reading Guide]

This guide will help you efficiently read "Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries" using the three-pass approach.

First pass (5–10 min)

The goal of the first pass is to get a high-level overview of the paper's main contributions, the problem it addresses, and its overall scope.

• What to skim:

  • Title: Immediately tells you the subject (global cancer statistics), the source (GLOBOCAN 2018), and the scope (incidence and mortality for 36 cancers in 185 countries).
  • Abstract: Provides a concise summary of the key findings, including the estimated number of new cases and deaths, and the leading cancer types globally and by sex. It also highlights geographic variability and data quality issues.
  • Introduction (first and last paragraphs): The opening paragraph will set the context for the global cancer burden, while the concluding paragraph of the introduction will state the paper's objectives and the importance of the GLOBOCAN 2018 estimates.
  • Conclusion: Read the final section to quickly grasp the main takeaways and the implications of the findings.

• What to notice:

  • Contributions: The paper provides the most up-to-date (as of 2018) comprehensive global estimates of cancer incidence and mortality. It offers a detailed breakdown by 36 cancer types, sex, and 185 countries, emphasizing geographic and economic disparities.
  • Problem: There is a continuous need for reliable, standardized, and current global cancer statistics to inform evidence-based cancer control policies and resource allocation, especially given the varying quality of cancer registry data worldwide.
  • Setting: This is a global epidemiological study, leveraging the GLOBOCAN database, which synthesizes data from various sources to produce estimates for countries with varying levels of data availability.

Second pass (up to 1 hour)

Using SpatialRead in the Second Pass

• Use the Screenshot tool to capture figures, tables, diagrams, and formulae from the PDF and use AI for simple explanations.
• Ask: "Explain Figure X at a high level", "Compare Table 2 vs 3", or "What does the y-axis represent here?"
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In the second pass, delve deeper into the paper to understand its core arguments, methods, and key results without getting bogged down in every detail.

• What sections/figures to focus on:

  • Introduction: Read this section fully to understand the background, the rationale behind GLOBOCAN, and the specific aims of the 2018 estimates.
  • Methods: Skim this section to understand the general approach. Pay attention to the data sources (e.g., cancer registries, vital statistics), the estimation methods used (especially for countries with limited data), and the definition of age-standardized rates (ASR). Note how the 20 world regions and Human Development Index (HDI) categories are used for analysis.
  • Results: This is the core of the paper. Focus on the main findings presented in the text and, crucially, the figures and tables.
    • Table 1: This table is central, providing global cancer incidence and mortality estimates by cancer type and sex. It's a quick reference for the overall burden.
    • Figure 1: Examine the world maps illustrating age-standardized incidence and mortality rates. These visually highlight global patterns and disparities.
    • Figure 2: Review the pie charts showing the proportion of global cancer cases and deaths by leading cancer types. This offers a quick visual summary of the most impactful cancers.
    • Figures 3 & 4: These figures are critical for understanding geographic and economic disparities, presenting age-standardized incidence and mortality rates by world region and Human Development Index (HDI) categories, respectively.
    • Tables presenting regional breakdowns: Look for tables (e.g., Table 2 or 3, depending on the paper's exact numbering) that provide more detailed breakdowns of incidence and mortality by specific regions or countries if you have a particular geographic interest.
  • Discussion: Read the initial paragraphs to grasp the authors' interpretation of the main findings and the concluding paragraphs to understand the limitations of the data and the implications for future cancer control.

• Key terms/questions to note:

  • What are age-standardized rates (ASR) and why are they used?
  • How does the GLOBOCAN methodology account for varying data quality across countries?
  • What are the leading cancer types globally for incidence and mortality, and how do these differ by sex?
  • How do cancer patterns (incidence and mortality) vary across different world regions and Human Development Index (HDI) categories?
  • What are the major limitations acknowledged by the authors regarding the data and estimates?

Third pass (1–5 hours)

Using SpatialRead in the Third Pass

• Highlight complex keywords, dense paragraphs, equations, or proofs and ask for a plain-English explanation that preserves notation.
• Use AI to explain the concepts in a way that is easy to understand.
• Ask for alternative phrasings or analogies to confirm understanding without changing technical meaning.
• Connect concepts with each other using AI to build a comprehensive understanding of the paper.
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The third pass involves a deep, critical reading of the entire paper, scrutinizing the methodology, evaluating the results, and understanding the implications.

• Deep reading guidance:

  • Methods: Read this section thoroughly. Understand the specific statistical models and assumptions used to generate estimates, especially for countries with incomplete or absent cancer registry data. Critically assess the validity of these methods and how they might influence the accuracy of the results. Pay attention to how population data and specific cancer definitions are handled.
  • Results: Go through every table and figure in detail. Analyze the specific numbers, trends, and comparisons presented. For instance, compare incidence and mortality rates for specific cancers to understand their lethality. Cross-reference findings across different tables and figures (e.g., how do the leading cancers globally in Figure 2 align with regional patterns in Figure 3?). Consider potential reasons for observed disparities (e.g., lifestyle, screening, access to treatment).
  • Discussion: Engage critically with the authors' interpretation. Do their conclusions logically follow from the results? Are the limitations adequately addressed? Think about the broader implications of these statistics for public health policy, research priorities, and resource allocation, particularly in low- and middle-income countries where data quality is a significant challenge.
  • Supplementary Material: If available, review any supplementary tables or appendices, as they often contain detailed country-specific data or additional methodological explanations that can deepen your understanding.

• Replication pointers:

  • This paper presents statistical estimates rather than an experimental study. Therefore, "replication" focuses on verifying the methodology and data interpretation.
  • To verify the estimates, you would need to:
    • Scrutinize Data Sources: Examine the references for the primary data sources (e.g., specific cancer registries, national vital statistics, UN population data) to understand their quality and coverage.
    • Understand Estimation Models: Deeply analyze the statistical models and algorithms described in the Methods section that are used to impute or estimate data where direct registry information is unavailable. While you cannot "re-run" GLOBOCAN without access to their proprietary systems and raw data, understanding the models allows you to assess their robustness.
    • Compare with Other Sources: Compare the GLOBOCAN 2018 estimates with previous GLOBOCAN reports (e.g., 2012) or other global cancer burden studies (e.g., from the Global Burden of Disease project) to identify consistencies, discrepancies, and the reasons for any changes over time.