JCO Formatting Requirements: Complete Author Guide

JCO requires a structured abstract for all Original Articles and Review Articles. The structure follows a clinical research format that's specific to JCO.

Structured abstract headings (Original Articles):

• Purpose
• Methods (or Patients and Methods for clinical studies)
• Results
• Conclusion

Abstract specifications:

• Word limit: 250 words for Original Articles and Reviews; 150 words for Rapid Communications
• Structure: Mandatory subheadings as listed above
• Citations: Not allowed
• Trial registration: The abstract must include the ClinicalTrials.gov identifier for clinical trials

Critical detail: JCO uses "Purpose" not "Objective," "Background," or "Introduction." Using the wrong heading triggers a formatting return. Similarly, "Conclusion" is singular, not "Conclusions."

The abstract for a clinical trial paper should follow a specific formula: Purpose states the hypothesis and primary endpoint. Patients and Methods describes the design, population, intervention, and statistical approach. Results presents the primary endpoint result with confidence intervals. Conclusion states the clinical implication.

Include specific numbers in the abstract. "Overall survival was significantly improved" isn't acceptable at JCO. "Median overall survival was 18.2 months vs 14.1 months (HR, 0.73; 95% CI, 0.60 to 0.89; P = .002)" is what's expected.

JCO allows up to 5 display items (figures and tables combined) in the main manuscript. Additional items go in the Data Supplement.

Figure specifications:

Table requirements:

• Tables must be created in Word, not as images
• Every column must have a header
• Horizontal rules at top, bottom, and below headers only
• No vertical rules
• Abbreviations defined in footnotes
• P values reported to 2-3 decimal places
• Hazard ratios and odds ratios include 95% confidence intervals

Survival curves: Kaplan-Meier curves are the most common figure type at JCO. The journal expects:

• Number at risk displayed below the x-axis at regular intervals
• Median survival values annotated or in the legend
• Hazard ratios with 95% CIs reported
• P values from log-rank test (or Cox model if adjusted)

Waterfall plots and swimmer plots: Increasingly common at JCO for response data. Ensure bars are clearly labeled and that response criteria (RECIST, etc.) are defined in the legend.

JCO follows the AMA Manual of Style, 11th edition, for references. This is identical to JAMA's reference format.

In-text citations: Superscript numbers after punctuation (e.g., "as previously reported.^1,2"). Numbers assigned in order of first appearance.

Reference list format:

1. Smith AB, Jones CD, Williams EF. Title of article in sentence case. J Clin Oncol. 2025;43(12):1234-1242. doi:10.1200/JCO.2025.12.3456

Key formatting details:

• Author names: Last name, initials without periods (e.g., "Smith AB")
• List all authors for 6 or fewer. For 7+, list the first 3 followed by "et al"
• Journal names abbreviated per NLM standards
• Volume, issue number in parentheses, and page range
• DOIs encouraged but not strictly required
• No "Retrieved from" language for online sources

JCO self-citation: Use "J Clin Oncol" as the abbreviated journal name.

There's a soft cap of approximately 40 references for Original Articles. Editors won't reject a paper at 45 references, but if you're at 60, you'll be asked to trim. Reviews can have up to 100 references.

Common AMA style errors at JCO:

• Including issue numbers for journals with continuous pagination (remove them)
• Using "et al" after the wrong number of authors (3 for 7+, not 6 for 7+)
• Placing citation numbers before punctuation instead of after

JCO uses the term "Data Supplement" for supplementary material. It's published online and is peer-reviewed.

Data Supplement contents:

• Extended methods and statistical details
• Appendix figures (labeled Appendix Fig A1, Fig A2, etc.)
• Appendix tables (labeled Appendix Table A1, etc.)
• Trial protocols or Protocol Summaries
• CONSORT flow diagrams (if not in the main manuscript)
• Patient-level data (when appropriate)

Protocol Summary requirement: This is a JCO-specific requirement for clinical trial papers. The Data Supplement must include a Protocol Summary that describes:

• Study design and objectives
• Eligibility criteria
• Treatment interventions
• Primary and secondary endpoints
• Sample size calculation
• Statistical analysis plan
• Protocol amendments and their rationale

The Protocol Summary isn't a full trial protocol. It's a structured summary of the key protocol elements. JCO introduced this requirement to improve transparency in clinical trial reporting. Most authors learn about it only after submission, causing delays.

CONSORT compliance: All randomized controlled trial papers must include a CONSORT flow diagram and adhere to CONSORT reporting guidelines. The CONSORT checklist should be submitted alongside the manuscript. This is strictly enforced.

Title page (first page of manuscript):

• Full title (no abbreviations)
• Running title (50 characters max)
• All author names with degrees and institutional affiliations
• Corresponding author name, address, phone, fax, and email
• Manuscript word count (body text only)
• Number of figures, tables, and references
• Sources of support (funding)
• ClinicalTrials.gov identifier (if applicable)
• ORCID iD of corresponding author

Cover letter requirements:

• Confirm the manuscript is original and not under consideration elsewhere
• List any related manuscripts by the same authors
• Describe the clinical significance of the work
• State whether the work was previously presented at a meeting (and which one)
• Suggest 3-5 qualified reviewers and list any excluded reviewers

JCO's cover letter is particularly important for clinical trial papers. The editor needs to assess whether the trial is large enough, well-designed enough, and clinically relevant enough for JCO's audience. Include the sample size, primary endpoint, and a brief statement of the main finding.

Clinical trial registration is mandatory. All clinical trials must be registered in ClinicalTrials.gov, ISRCTN, EU Clinical Trials Register, or an equivalent registry before the first patient is enrolled. The registration number must appear on the title page and in the abstract. Unregistered trials will be rejected outright.

Protocol Summary in Data Supplement. Described above but worth repeating: this is mandatory for clinical trial papers and is the single most commonly missed JCO requirement.

ASCO conflict of interest form. JCO uses its own COI disclosure form, separate from ICMJE. All authors must complete it through the submission system. This includes disclosure of any relationships with pharmaceutical or biomedical companies within the past 2 years.

Prior presentation disclosure. If any of the data was presented at a conference (ASCO Annual Meeting, ESMO, ASH, etc.), you must disclose this on the title page and in a footnote. JCO considers previously presented abstracts as prior publication in a limited sense.

Author contributions statement. Required. Must specify each author's role. CRediT taxonomy or free text.

IRB/ethics approval. Mandatory for all studies involving human subjects. Must include the IRB name, approval number, and confirmation of informed consent.

Statistical methods. JCO expects detailed statistical reporting. All analyses must specify: the statistical test used, whether tests were one-sided or two-sided, the significance level, the software used, and whether analyses were pre-specified or exploratory.

Genomic data. Manuscripts reporting genomic data must include data deposition in GEO, TCGA, or equivalent repositories. The accession number must be in the manuscript.

Abbreviations. JCO maintains a specific list of accepted abbreviations. Standard oncology abbreviations (OS, PFS, ORR, CR, PR, HR, CI) don't need definition. Other abbreviations must be defined at first use.

1. Protocol Summary is mandatory for clinical trials. This is the number one thing authors miss. Don't submit a trial paper without it.

1. CONSORT checklist and flow diagram. Both are required for RCTs. The checklist must be submitted as a separate file.

1. ClinicalTrials.gov number in the abstract. Not just on the title page. The registration ID must appear in the abstract itself.

1. 3,000-word limit is strict. JCO will return manuscripts that exceed this before review. Count carefully.

1. ASCO COI form is different from ICMJE. JCO uses its own conflict of interest disclosure system. All authors must complete it.

1. Prior presentation disclosure. If you presented at ASCO or any other meeting, disclose it. Failure to do so is considered an ethical issue.

1. Number at risk in Kaplan-Meier curves. JCO expects this. Survival curves without number-at-risk tables beneath them will be sent back.

1. 5 display items maximum. Figures plus tables. Plan your visual strategy to fit within this tight limit.

1. Line numbers and double spacing. Required throughout the manuscript.

1. Corresponding author ORCID. Required at submission.

In our pre-submission review work with manuscripts targeting Journal of Clinical Oncology, four patterns generate the most consistent desk-rejection outcomes.

Biostatistical review not documented for trial manuscripts. JCO author guidelines require that clinical trial manuscripts include a statement confirming that a qualified biostatistician reviewed the statistical methods. Submissions where this statement is absent, or where the statistical methods section lacks detail on primary endpoint analysis, power calculation, and handling of missing data, are flagged for correction before peer review begins. Reviewers specifically check whether the stated primary endpoint matches the registered protocol.

Non-compliant CONSORT reporting for randomized controlled trials. JCO mandates a completed CONSORT checklist and CONSORT flow diagram for all randomized trial reports. The guidelines explicitly state that both must be submitted as supplementary materials. Manuscripts that describe a randomized design in the methods but arrive without the checklist are returned for correction. The flow diagram must account for all participants through each stage from enrollment to analysis.

Protocol not attached for registered trials. For prospective clinical trials, JCO requires submission of the registered study protocol. Manuscripts reporting trial results that reference a ClinicalTrials.gov or other registry identifier without attaching the protocol document are routinely returned. This applies to both primary and secondary endpoint analyses.

Structured abstract not following JCO format for Original Reports. JCO Original Reports require a structured abstract with the following headings: Purpose, Patients and Methods, Results, and Conclusion. Manuscripts submitted with unstructured abstracts or with non-standard heading labels (Background, Methods, Discussion) are corrected before peer review. The Conclusion statement must reflect the primary endpoint finding, not a general synthesis.

A Journal of Clinical Oncology formatting and readiness check evaluates manuscript structure, statistical documentation, and trial reporting compliance against these desk-rejection patterns before you submit.