Sex Differences in Gastrointestinal Cancer Surgery

DATA SOURCE

As database the German diagnosis-related group statistic (DRG statistic) will be queried. The dataset is provided by the German Federal Statistical Office. It includes standardized demographic information (age, sex), diagnostic codes (ICD-10-GM), procedural codes (OPS), and outcomes (mortality, length of stay, complications). Patients will be included if they underwent resection for one of the five specified cancers; exclusions applied for age <18 years, missing sex/age data, or non-matching diagnosis-procedure pairs.

OUTCOMES

Primary Endpoints:

Mortality: Death during the hospital stay. Failure-to-Rescue (FTR): Death among patients who developed postoperative complications (defined via appropriate ICD-10-GM/OPS codes)

Secondary Endpoints: 30-day mortality, complication rates, intensive care unit (ICU) admission, reoperation, and prolonged hospitalization (>75th percentile for procedure-specific stay). Failure to rescue rates of patients with extended medical treatment (eg. after reoperation, ICU admission, possibly in combination with a complication).

Adjustment Variables: Age, Elixhauser comorbidities (categorized using Quan's algorithm), admission type (elective/emergent), annual hospital procedure volume (to account for surgical expertise and routine), and year of surgery (to account for temporal trends).

Descriptive Analysis:

Data Validation: Checks will be performed to identify implausible values (e.g., age >120 years) or inconsistencies (e.g., mortality coded without complication for FTR analysis). Comorbidity Coding: Elixhauser comorbidities will be determined. Hospital Volume Metrics: Annual procedure volumes will be calculated to control for institutional expertise.

Statistical Analysis Plan As primary analysis, multivariable logistic regression models will be calculated that assessed sex differences in mortality/FTR, adjusting for covariates (age, individual Elixhauser comorbidities, hospital volume, and admission type, year of surgery). Adjusted odds ratios (aORs) and adjusted risk differences (aRD) with 95% confidence intervals (CIs) will be reported.

Subgroup / Sensitivity Analyses:

To ensure robustness of results multiple sensitivity analyses will be performed. These include subgroup analysis where tha analysis will be perfomed by startified groups:

• by admission type (elective vs. emergent),
• by comorbidity burden (≤3 vs. >4 Elixhauser conditions), and
• by hospital volume (above/below median).

REPORTING

Descriptive/Univariable analysis:

This study will report descriptively baseline patient characteristics and compare the charachteristics between male and female patients. Tests will be selected according to variable type (categorical vs. continuous) and type of distribution (normal vs non-normal distributed).

Observed outcome rates will be reported and compared between male and female patients. Observed risk differences and risk ratios will be calculated.

Multivariable analysis:

Results of the multivariable logistic regressions will be reported as adjusted risk differences and/or adjusted risk ratios. Appropriate figures will be produced to communicate the results. Sensitivity analyses stratified by admission type, comorbidity burden, and hospital volume will reinforce the robustness of these results.

Inclusion criteria

• at least 18 years old at the time of the operation
• Rectum resection for carcinoma (ICD-10: C19, C20, C218, D01.1, D01.2) and appropriate resection procedure (5-484, 5-485)
• Colon resection for carcinoma (ICD-10: C18, D01.0) and appropriate resection procedure (5-455, 5-456, 5-458)
• Complex esophageal surgery for carcinoma (ICD-10: C15, C16.0) and appropriate resection procedure (5-423, 5-424, 5-425, 5-426, 5-427.0, 5-427.1, 5-438.0, 5-438.1, 5-438.x)
• Pancreatic resection for carcinoma (ICD-10: C25, C24.1) and appropriate resection procedure (5-524, 5-525.0, 5-525.1, 5-525.2, 5-525.x, 5-525.y, 5-528)
• Gastric resection for carcinoma (ICD-10: C16) and appropriate resection procedure (5-436, 5-437, 5-438)

Exclusion criteria

• missing data for age and/or sex
• implausible combination of diagnosis and resection procedure (eg. a patient with a gastrectomy but without appropriate ICD-10 diagnosis)