What is the utility of this Prostate Volume and PSA density Calculator?
You can calculate the volume of the prostate gland using this calculator using values acquired on MRI or Ultrasound. This will give an estimate of the size of the prostate gland. The normal prostate gland is approximately 25-30cc in volume.
Prostate-specific antigen (PSA) is a tumor marker for prostate cancer. PSA density can be used to prognosticate prostate malignancies. Patients with low PSA density can undergo active surveillance while those with higher values may need intervention. As stated by PSA-density might inform biopsy decisions, and spare some men from the morbidity associated with a prostate biopsy and diagnosis of low-grade prostate cancer.
What formulas are used for calculating prostate volume, and what are the cut-off values?
Prostate Volume = (Anteroposterior (AP) length x Transverse (TR) length x Craniocaudal Length )*0.523
Note that the PIRADS 2.1 ACR white paper recommends that the AP and TR length should be measured on the sagittal plane as shown in the image above.
A prostate gland volume of more than 30cc is considered prostatomegaly.
A rough grading system for prostatomegaly is :
30-50cc: Mild Prostatomegaly
50-80cc : Moderate Prostatomegaly
>80cc: Marked Prostatomegaly.
What formulas are used for calculating PSA density, and what are the cut-off values?
PSA density = PSA value/Prostate Volume
Although the cut-off values vary, most papers suggest a cut-off value of 0.15-0.20 above which there is a high chance of the patient having clinically significant prostate cancer.
A recent study states the following optimal cut-off values of PSA density to diagnose clinically significant prostate cancer :
- 0.10 ng/ml2 in biopsy naïve patients i.e. patients who have not had a prostate biopsy
- 0.15 ng/ml2 in patients with a previous negative biopsy.
Sasaki et. al suggested in their study: “To avoid unnecessary biopsies, the PSA density cutoff value of 0.18 would be recommendable for determining a prostate biopsy for Japanese males with a serum total PSA level of 4.1-10.0 ng/ml.”
What are the common causes of prostatomegaly (prostate gland enlargement)?
- Benign prostatic hyperplasia (BPH) – Most common cause of prostatomegaly in elderly men. This causes urinary symptoms due to indentation on the posterior bladder wall.
- Prostate cancer
- Prostatitis
- Prostatic abscess
Should we use PSA or PSA density to prognosticate prostate cancers?
PSA density is preferred over PSA alone as the latter can be elevated in inflammation and in a larger prostate gland.
As per a study by Bruno et. al: “At multivariable analysis adjusting for age, biopsy history, DRE and prostate volume, PSA density emerged as a strong predictor of clinically significant prostate cancer (csPCA) but was not associated with prostatic inflammation. The optimal cutoffs of PSA density to diagnose csPCa and rule out the presence of prostatic inflammation in patients with an elevated PSA (>4 ng/ml) were 0.10 ng/ml2 in biopsy naïve patients and 0.15 ng/ml2 in patients with a previous negative biopsy. PSA density rather than PSA should be used to evaluate patients at risk of prostate cancer who may need additional testing or prostate biopsy. This readily available parameter can potentially identify men who do not have PCa but have an elevated PSA secondary to benign conditions.”
In another study, Sasaki et.al conclude: “PSA density was significantly more accurate than other variables in predicting PCa. To avoid unnecessary biopsies, the PSA density cutoff value of 0.18 would be recommendable for determining a prostate biopsy for Japanese males with a serum total PSA level of 4.1-10.0 ng/ml.”
What is clinically significant prostate cancer (csPCA)?
Clinically significant cancer is usually defined as a Gleason Score of more than or equal to 7 on biopsy.
Check out other radiology useful calculators:
Disclaimer: The author makes no claims of the accuracy of the information contained herein; this information is for educational purposes only and is not a substitute for clinical judgment.
References:
- Bruno, Salvatore, et al. “PSA Density Help to Identify Patients With Elevated PSA Due to Prostate Cancer Rather Than Intraprostatic Inflammation: A Prospective Single Center Study.” Frontiers in Oncology, vol. 11, 2021, https://doi.org/10.3389/fonc.2021.693684. Accessed 17 Dec. 2022.
- Sasaki R, Habuchi T, Sato K, et al. The clinical utility of measuring total PSA, PSA density, gamma-seminoprotein and gamma-seminoprotein/total PSA in prostate cancer prediction. Jpn J Clin Oncol. 2000;30(8):337-342. doi:10.1093/jjco/hyd089.
- Nordström T, Akre O, Aly M, Grönberg H, Eklund M. Prostate-specific antigen (PSA) density in the diagnostic algorithm of prostate cancer. Prostate Cancer Prostatic Dis. 2018;21(1):57-63. doi:10.1038/s41391-017-0024-7