RECIST 1.1 Response Calculator
Use this tool to evaluate tumor response based on RECIST 1.1 criteria by comparing baseline and current tumor measurements.
Enter the sum of the longest diameters of all target lesions at baseline.
Enter the sum of the longest diameters of all target lesions at the current assessment.
Check this box if any new lesions have appeared since baseline.
Check this box if there is unequivocal progression of non-target lesions.
RECIST 1.1 Response:
' + response + '' + explanation + "; // Add details for PR/PD/SD if applicable and baselineSLD is not 0 if (response === 'Partial Response (PR)' || response === 'Progressive Disease (PD)' || response === 'Stable Disease (SD)') { resultDiv.innerHTML += 'Baseline SLD: ' + baselineSLD.toFixed(1) + ' mm'; resultDiv.innerHTML += 'Current SLD: ' + currentSLD.toFixed(1) + ' mm'; if (baselineSLD !== 0) { // Avoid showing percentage/absolute change if baseline was 0, as it's not directly applicable resultDiv.innerHTML += 'Percentage Change: ' + percentageChange.toFixed(2) + '%'; resultDiv.innerHTML += 'Absolute Change: ' + absoluteChange.toFixed(1) + ' mm'; } } }Understanding RECIST 1.1: Response Evaluation Criteria in Solid Tumors
The Response Evaluation Criteria in Solid Tumors (RECIST) is a set of published rules used by medical professionals to assess how well a cancer patient responds to treatment. Specifically, RECIST 1.1 is the most widely adopted version, providing a standardized framework for evaluating changes in tumor size in clinical trials and routine oncology practice.
Why is RECIST 1.1 Important?
- Standardization: It provides a consistent method for evaluating treatment efficacy across different studies and institutions.
- Clinical Decision Making: Helps oncologists decide whether a treatment is working, needs adjustment, or should be discontinued.
- Drug Development: Essential for clinical trials to determine the effectiveness of new cancer therapies.
Key Concepts in RECIST 1.1
To use the RECIST criteria, tumors are categorized into two main types:
- Target Lesions: These are measurable lesions selected at baseline to track changes in tumor size. Up to 5 target lesions can be selected, with a maximum of 2 per organ. They must have a longest diameter of at least 10 mm (or 15 mm for lymph nodes). The sum of the longest diameters (SLD) of these target lesions is the primary metric for response assessment.
- Non-Target Lesions: These are other identifiable lesions that are either too small to be target lesions or are not easily measurable (e.g., bone lesions, ascites, pleural effusions). Their presence or absence is noted, but they are not measured.
- Baseline: The initial assessment of tumor burden before treatment begins. This serves as the reference point for all subsequent evaluations.
- Nadir: The smallest sum of longest diameters (SLD) recorded since baseline. This is particularly important for determining progressive disease.
RECIST 1.1 Response Categories
Based on changes in target lesions, non-target lesions, and the appearance of new lesions, a patient's response to treatment is classified into one of four categories:
1. Complete Response (CR)
- Target Lesions: Disappearance of all target lesions.
- Non-Target Lesions: All non-target lesions must be considered non-existent. Any pathological lymph nodes must be reduced to <10 mm in short axis.
- New Lesions: No new lesions.
2. Partial Response (PR)
- Target Lesions: At least a 30% decrease in the sum of the longest diameters (SLD) of target lesions, taking as reference the baseline SLD.
- Non-Target Lesions: No progression of non-target lesions.
- New Lesions: No new lesions.
3. Progressive Disease (PD)
- Target Lesions: At least a 20% increase in the SLD of target lesions, taking as reference the smallest SLD recorded since baseline (nadir). AND an absolute increase of at least 5 mm.
- Non-Target Lesions: Unequivocal progression of non-target lesions.
- New Lesions: Appearance of one or more new lesions.
- Note: Any of these conditions alone is sufficient for PD.
4. Stable Disease (SD)
- Neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD.
- Non-Target Lesions: No progression of non-target lesions.
- New Lesions: No new lesions.
How to Use the RECIST 1.1 Calculator
Our calculator simplifies the RECIST 1.1 assessment for a single comparison between baseline and a current assessment. Follow these steps:
- Baseline Sum of Longest Diameters (SLD): Enter the total sum of the longest diameters of all target lesions measured at the start of treatment.
- Current Sum of Longest Diameters (SLD): Enter the total sum of the longest diameters of the same target lesions at the current assessment.
- New Lesions Detected?: Check this box if any new lesions have been identified since the baseline scan.
- Non-Target Lesion Progression?: Check this box if there is clear evidence of growth or worsening of non-target lesions.
- Click "Calculate RECIST Response": The calculator will then display the determined response category (CR, PR, SD, or PD) along with an explanation.
Examples:
- Example 1: Partial Response (PR)
- Baseline SLD: 100 mm
- Current SLD: 65 mm
- New Lesions: No, Non-Target Progression: No
- Calculation: (65 – 100) / 100 = -0.35 = -35%. Since -35% is ≤ -30%, the result is Partial Response (PR).
- Example 2: Progressive Disease (PD) – Target Lesions
- Baseline SLD: 100 mm
- Current SLD: 125 mm
- New Lesions: No, Non-Target Progression: No
- Calculation: (125 – 100) / 100 = 0.25 = 25%. Absolute change = 25 mm. Since 25% is ≥ 20% AND 25 mm is ≥ 5 mm, the result is Progressive Disease (PD).
- Example 3: Stable Disease (SD)
- Baseline SLD: 100 mm
- Current SLD: 95 mm
- New Lesions: No, Non-Target Progression: No
- Calculation: (95 – 100) / 100 = -0.05 = -5%. This is not ≤ -30% (for PR) and not ≥ 20% (for PD). The result is Stable Disease (SD).
- Example 4: Complete Response (CR)
- Baseline SLD: 80 mm
- Current SLD: 0 mm
- New Lesions: No, Non-Target Progression: No
- Calculation: Current SLD is 0 mm. The result is Complete Response (CR).
- Example 5: Progressive Disease (PD) – New Lesions
- Baseline SLD: 70 mm
- Current SLD: 50 mm
- New Lesions: Yes, Non-Target Progression: No
- Calculation: Despite a decrease in target lesion size, the presence of new lesions automatically classifies the response as Progressive Disease (PD).
- Example 6: Progressive Disease (PD) – Baseline 0, Current > 0
- Baseline SLD: 0 mm
- Current SLD: 15 mm
- New Lesions: No, Non-Target Progression: No
- Calculation: If baseline SLD was 0 and current SLD is > 0, it indicates growth or appearance of target lesions, resulting in Progressive Disease (PD).
Important Considerations
This calculator provides a simplified assessment based on the core RECIST 1.1 criteria for a single comparison. In clinical practice, a comprehensive RECIST evaluation involves:
- Careful selection and consistent measurement of target lesions by trained radiologists.
- Tracking the nadir (smallest SLD) for accurate PD assessment over multiple time points.
- Clinical judgment and correlation with other clinical data (e.g., patient symptoms, lab markers).
Always consult with a qualified medical professional for accurate diagnosis and treatment decisions. This tool is for informational and educational purposes only.