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Calcimator

Tumor Doubling Time Calculator

Calculate tumor volume doubling time, specific growth rate, and projected size from serial imaging measurements. Includes RECIST-like diameter change assessment.

Inputs

Results

Volume doubling time (days)

54.3

Specific growth rate (%/day)

1.28

Volume at scan 1 (mm³)1,767.1
Volume at scan 2 (mm³)5,575.3
Projected diameter (mm)47.3
Days to target diameter73
Diameter change (%)46.7
How to Use This Calculator
  1. Enter tumor doubling time inputs: initial and follow-up tumor size measurements and time interval.
  2. Read estimated tumor doubling time (days or weeks).
  3. Review tumor volume doubling time to assess growth kinetics and aggressiveness.
  4. Use doubling time to estimate time to clinically significant progression.
  5. Note: growth rates vary widely — use results for relative comparison, not absolute prognosis.

How the result changes with Second measurement diameter (mm)

Second measurement diameter (mm)Volume doubling time (days)Specific growth rate (%/day)
3128.62.42
10610.66.52
1958.18.55
2707.29.64

What each input means

First measurement diameter (mm)
Longest diameter of the tumor on the first scan.
Second measurement diameter (mm)
Longest diameter of the tumor on the follow-up scan.
Days between scans
Calendar days between the two imaging studies.
Project forward (days)
Number of days to project tumor growth forward from the second scan.
Target diameter (mm)
Calculate time to reach this diameter (e.g., surgical threshold).

What each result means

Volume at scan 1 (mm³)
Estimated tumor volume assuming spherical geometry.
Volume at scan 2 (mm³)
Estimated tumor volume at follow-up.
Volume doubling time (days)
Time for tumor volume to double. Negative = tumor is shrinking (halving time).
Specific growth rate (%/day)
Exponential growth rate. Negative indicates tumor regression.
Projected diameter (mm)
Estimated tumor diameter at the projection time point.
Days to target diameter
Estimated time to reach the specified target diameter.
Diameter change (%)
RECIST-like percent change in longest diameter between scans.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    First measurement diameter (mm) = 15, Second measurement diameter (mm) = 22, Days between scans = 90, Project forward (days) = 180 = 5 input(s) provided
  2. Calculate Volume doubling time
    Volume doubling time
    54.3 = 54.3
  3. Calculate Specific growth rate
    Specific growth rate = (lnRatio / daysBetween) * 100
    1.277 = 1.277
  4. Calculate Volume at scan 1
    Volume at scan 1 = (4 / 3) * π * r1 * r1 * r1
    1767.1 = 1767.1
  5. Calculate Volume at scan 2
    Volume at scan 2 = (4 / 3) * π * r2 * r2 * r2
    5575.3 = 5575.3

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