The controversy over the analytical assessment of vitamin D and PSA in prostate cancer screening: Contribution from the clinical laboratory
27/11/2024
From the XXI Conference of the Scientific Committee of the Spanish Society of Laboratory Medicine, which was held on February 29 and March 1
• There is no consensus in the scientific community when it comes to defining the state of vitamin D deficiency, which generates social alarm and leads to an increase in requests for this vitamin without a justified cause.
• The use of PSA in prostate cancer screening allows early detection of the disease, but also has drawbacks such as overdiagnosis or overtreatment.
An analytical parameter is any measurable magnitude in a specific specimen (blood, urine, feces, or biological fluid...) that is used for the diagnosis, monitoring, prevention, and treatment of a pathology. However, there are some magnitudes that generate controversy in their interpretation or assessment for various reasons, either because in some cases there is no pattern that allows for standardization of the different methods or because the normal values of the population are not clear, among other factors.
The Spanish Society of Laboratory Medicine (SEQCML), within the framework of the XXI Scientific Committee Conference, which was held on February 29 and March 1 in Seville, presented the current evidence on the use of some of these conflicting parameters, such as vitamin D and PSA in prostate cancer screening.
Vitamin D is one of the most controversial elements, as there is no consensus among the scientific community for defining the standard of vitamin D deficiency. This was stated by Dr. María Monsalud Arrebola, member of the SEQCML Evidence-Based Laboratory Medicine Commission, who addressed the main guidelines available for understanding the bases of the discrepancies related to this parameter in her presentation, “Vitamin D: a very controversial parameter”. According to the specialist, this controversy “is creating social alarm and an increase in scientific literature without sufficient scientific evidence, which results in a greater number of requests for vitamin D in the population without justified cause, and an increase in the use of oral supplements.”
Dr. María Monsalud Arrébola also presented the main results obtained on methodology in an international external quality control program. Finally, as she explained, “we will analyze which clinical situations require a vitamin D determination, according to the evidence.”
The risk of overdiagnosing prostate cancer
Vitamin D is not the only conflictive parameter in the field of Laboratory Medicine. Prostate-specific antigen or PSA is the tumor marker of choice in the management of patients with prostate cancer, with utility in both the prognosis and monitoring of the disease. However, as noted by Dr. Xavier Filella, also a member of the SEQCML Evidence-Based Laboratory Medicine Commission, its use in prostate cancer screening has been the subject of a long and heated debate.
In the words of Dr. Filella, one of the main drawbacks of its use is the overdiagnosis and overtreatment of the disease. "That is, the detection of tumors with a low probability of progression, which will not cause symptoms throughout the patient's life and whose treatment may result in harm to the patient." On the other hand, elevation of this antigen above the reference range does not always mean the presence of prostate cancer. Even so, as Dr. Filella highlighted, ruling out PSA screening “can mean a delay in the diagnosis of prostate cancer and, ultimately, the detection of tumors at a more advanced stage when, in many cases, curative treatment may no longer be possible."
Currently, most clinical guidelines indicate that the patient should be informed of the possible benefits and harm derived from the practice of prostate cancer screening with PSA in order to be able to make, together with his doctor, the best possible decision. On this matter, as Dr. Filella commented, “the European Commission recommends that Member States implement organized programs for prostate cancer screening for men up to 70 years of age on the basis of PSA measurements, in combination with magnetic resonance".
Active vigilance, key in screening
Dr. Filella used his presentation, “Prostate cancer screening with PSA: analysis of a disputed controversy”, to address those data on which this debate has been based and analyze the validity of the results obtained to date, while “at the same time highlighting the pros and cons of the practice of prostate cancer screening with PSA." In turn, he focused on new developments that would allow the inconveniences of screening to be overcome. From active surveillance aimed at correcting problems derived from overtreatment to the implementation of new tumor markers, “whose objective would be to detect only those tumors that are clinically significant and require treatment.”
Finally, during the XXI Conference of the Scientific Committee, the option of a new approach to screening was presented, which consists of screening only those patients with a high risk of developing a clinically significant carcinoma. In this way, as Dr. Filella highlighted, “the stratification of patients using a PSA measurement may represent an improvement in the management of prostate cancer.”
The work of the Laboratory Medicine specialist is essential in the interpretation and assessment of any type of analytical parameter. As Dr. María Monsalud Arrebola noted, Clinical Laboratories must put themselves in the best position to inform and educate, since they are the ones that best know the factors they measure. “In this way, they have a direct responsibility with the clinician, imparting knowledge, and also an indirect one with the patients, through the information provided to the clinician with the laboratory results and their interpretation, “she concluded.