6. What is age-related PSA?
The term age-related PSA refers to the different ranges of normal PSA values established for different age groups to improve the sensitivity of PSA in detecting the prostate in various age groups and to improve its specificity for application in the elderly population.
The PSA level in the prostate gland increased by 1.0 cm3 with age, and the PSA level increased by about 32% for every 1.0 cm3 increase in the prostate gland; 92% of healthy men aged 50 years had PSA less than 40 ng/ml, 79% of those aged 60-69 years, and 60% of those aged 70 years or older. ~Oesterling et al. concluded that the reference range of PSA for each age group after a survey of PSA levels in 2119 healthy men aged ~49 years: 40-49 years, 0-2.5ng/ml; 50-59 years, 0-3.5ng/ml; 60-69 years, 0-4.5ng/ml; 70-79 years, 0-6.5ng/ml.
Age-related PSA has some predictive value for prostate cancer screening in the population, but the value of clinical application for individuals needs to be further elucidated.
7.What is prostate-specific antigen density (PSAD)?
Prostate specific antigen density (PSAD) is the ratio of serum PSA to the entire prostate volume. The formula for calculating prostate volume is: (anterior-posterior diameter x left-right diameter x upper-lower diameter) x Л ÷ 6. All three prostate diameters can be measured by transrectal prostate ultrasound.
The PSAD was proposed based on the theory that serum PSA is dependent on the number of prostate cells, i.e., correlated with prostate volume. The average PSA level of benign cells is more stable than that of cancer cells, whereas the elevated PSA value per unit volume of cancer tissue is 10 times higher than that of benign tissue. Therefore, the presence of prostate cancer can be suspected when serum PSA levels exceed the upper limit of PSA that should be present in that volume of the prostate.
Benson reported a mean PSAD of 0.58 in a group of patients with prostate cancer and 0.04 in patients with prostate enlargement. PSA at the upper limit of normal or mildly elevated (4.0 to 10.0 ng/ml) If PSAD is elevated (>0.15), the risk of prostate cancer will increase and is likely to conceal a malignant lesion. For those with persistently elevated PSA concentration and no cancer detected on prostate biopsy, such as those with PSAD >0.15, the likelihood of finding prostate cancer on subsequent biopsy is 82%, and close follow-up and timely biopsy are needed for these patients.
Most scholars now believe that when PSA concentration is mildly elevated or normal (e.g. 4.0~10.0ng/ml), it can identify prostate cancer and non-prostate cancer disease caused by elevated PSA disease, which can guide physicians to decide whether to perform biopsy or follow up.
8.What is PSA velocity (PSAV)?
PSA velocity refers to the rate of change in serum PSA, expressed in ng/(ml?yr), which is the value of change in serum PSA per year. As prostate epithelial cells proliferate and become malignant, serum PSA levels gradually increase, while prostate cancer tissue multiplies much more rapidly than prostate hyperplasia. Therefore, dynamic observation of PSA values can differentiate between prostate cancer and prostate hyperplasia.
Brawer suggested that rectal examination, transrectal prostate ultrasound and biopsy should be performed for early detection of prostate cancer if the serum PSA value increases by 20% or more each year. In addition, it was found that 87.5% of the detected prostate cancer specimens were staged pathologically and the tumor was confined to the prostate envelope, and no penetration of the prostate envelope, lymph nodes or other distant metastases were found, which shows that determination of PSA velocity can be an effective indicator for early diagnosis of prostate cancer and early detection of its recurrence. Another group performed PSA and PSA velocity measurements after prostate cancer surgery, and the results showed that PSA velocity can be used to monitor the recurrence of prostate cancer after surgery, and the greater the PSA velocity value, the greater the probability of prostate.
It is proposed that PSA velocity values of size or equal to ng/(ml?yr) with an elevation rate greater than or equal to 20% should be immediately followed by prostate biopsy.
9. What is prostate-specific antigen migration density (PSAT)?
The PSAT is the ratio of the serum PSA value to the volume of the prostate migratory zone. The prostate is divided into peripheral, central and migratory zones, and prostatic hyperplasia mainly occurs in the central and migratory zones, while hyperplasia caused by the peripheral zone of the prostate is rare.Lloyd et al. concluded that the main area affecting the serum PSA value is the migratory zone, and the best method to measure the volume of the migratory zone of the prostate is transrectal ultrasound, which shows a relatively hypoechoic zone that is the migratory zone of the prostate.Kalish et al. The PSA, PSAD and PSAT were measured in 59 patients with PSA values between 4.0 and 10.0 ng/ml and the results showed that PSA was 6.55 ng/ml, PSAD was 0.26 and PSAT was 1.39 in the prostate cancer group; PSA was 6.55 ng/ml, PSAD was 0.26 and PSAT was 0.60 in the non-prostate cancer group, which showed that PSAT was elevated. Therefore, it is believed that PSAT is more accurate and reliable than PSA and PSAD in identifying PSA elevation caused by cancer and non-cancerous diseases.
10.What is the clinical significance of measuring the free PSA ratio?
PSA in serum mainly exists in free and complex forms, accounting for 15% and 85% of the total PSA level, respectively. Complex PSA is a complex formed by the binding of PSA and a1 chymotrypsin cool (cPSA). PSA is generally determined clinically by monoclonal enzyme immunoassay as the sum of free PSA (fPSA) and (cPSA) of total PSA (tPSA). The free PSA ratio is fPSA/ tPSA x 100%.
Stensan first demonstrated that fPSA serum concentrations were lower in patients with prostate cancer than in patients with prostate hyperplasia, and that measuring fPSA improved the specificity of PSA in the diagnosis of prostate cancer. thtel, after measuring fPSA in 1,081 patients with prostate disease, concluded that the possibility of prostate cancer should be highly guarded for fPSA ratios <7%, while fPSA ratios >25% can be largely excluded. Reissigl et al. found that the fPSA ratio in patients with prostate cancer was significantly lower than that in patients with prostatic hyperplasia, and that if the fPSA ratio <22% was used as a biopsy index, its sensitivity was as high as 98% and 30% of negative biopsies could be avoided. fPSA is thought to greatly improve the PSA diagnosis not only when the PSA is in the critical range of 2.5~10.0ng/ml prostate, but also increases the specificity of the diagnosis.
Screening for prostate cancer using the fPSA ratio is also related to prostate volume. When the prostate volume is <40 cubic centimeters, a critical value of fPSA ratio <13.7% can be determined in 90% of prostate cancer patients, excluding 76% of negative biopsies. For larger glands, a threshold value of <20.5% is appropriate and will detect at least 90% of prostate cancer patients and exclude 38% of unnecessary biopsies.
Many studies have shown that PSA values in the range of 2.5 to 10.0 ng/ml should be determined as a percentage of fPSA, which can greatly improve the sensitivity and specificity of the diagnosis and avoid unnecessary repeat biopsies. Because of the influence of many factors such as PSA level, prostate volume, age, race, reagents, and biopsy history, it is not possible to determine a range of fPSA ratios that can be used for clinical application.
11.What is prostate-specific membrane antigen (PSM)?
Prostate specific membrane antigen (PSM) is a tissue-specific antigen of the prostate gland located within the cell membranes, and its high expression in prostate cancer, especially in hormone-refractory prostate cancer and metastases, makes it clinically important. It has the potential to provide a new diagnostic tool for prostate cancer (especially hormone-refractory prostate cancer).
PSM is difficult to be detected in serum, and a more sensitive method is to measure PSM mRNA in peripheral blood of patients. Therefore, examination of PSMmRN expression in peripheral blood can help to detect clinically unknown early prostate cancer hematogenous metastases, and also help to determine tumor recurrence and progression.
In conclusion, PSM is a clinically important membrane protein, and the study of it is still in its initial stage and there are many questions to be solved.