psa_doubling_time: PSA Doubling Time (PSADT) Calculator

In cliot: Clinical Indices and Outcomes Tools

PSA Doubling Time (PSADT) Calculator

Description

Calculates the PSA Doubling Time, a kinetic measure of prostate cancer growth, using linear regression of the natural logarithm of PSA over time. This metric is commonly used to assess prognosis and guide treatment in patients with biochemical recurrence after definitive therapy.

Usage

psa_doubling_time(psa_date1, psa_value1, psa_date2, psa_value2,
                  psa_date3 = NULL, psa_value3 = NULL)

Arguments

psa_date1	Date string (YYYY-MM-DD). Date of the first PSA measurement.
psa_value1	Numeric. First PSA value in ng/mL.
psa_date2	Date string (YYYY-MM-DD). Date of the second PSA measurement.
psa_value2	Numeric. Second PSA value in ng/mL.
psa_date3	Date string (YYYY-MM-DD) (Optional). Date of the third PSA measurement.
psa_value3	Numeric (Optional). Third PSA value in ng/mL.

Details

The calculation performs a linear regression of \ln(PSA) versus time (in months). The doubling time is calculated as \frac{\ln(2)}{slope}. At least two data points are required, but three provide a more robust estimate.

Value

A list containing:

PSA_Doubling_Time_Months

The estimated time in months for the PSA level to double.

References

Pound CR, Partin AW, Eisenberger MA, Chan DW, Pearson JD, Walsh PC. Natural history of progression after PSA elevation following radical prostatectomy. JAMA. 1999;281(17):1591-1597. doi:10.1001/jama.281.17.1591

Examples

# Example 1: Two points
# Jan 1: PSA 4.0, July 1: PSA 8.0 (6 months later)
# Should double in approx 6 months
psa_doubling_time("2023-01-01", 4.0, "2023-07-01", 8.0)

# Example 2: Three points
# Jan: 2.0, Apr: 3.0, Jul: 4.5
psa_doubling_time("2023-01-01", 2.0, "2023-04-01", 3.0, "2023-07-01", 4.5)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.