Multiparametric magnetic resonance imaging: a method preventing unnecessary biopsies in prostate cancer

Findings on a digital rectal examination and/or suspicious increases in blood PSA levels suggest prostate cancer and are sufficient for a prostate biopsy decision. Prostate cancer Many diagnosis, treatment and follow-up guidelines consider a serum total PSA level above 3.0 ng/ml elevated and recommend a biopsy at PSA levels above this value. The biopsy needed for diagnosis carries risks such as bleeding, pain and infection, and also has some margin of error. There is also a risk of performing an unnecessary intervention on people without cancer. For these reasons, researchers have sought a more reliable test with fewer risks.

Studies have focused on MP-MRI (multiparametric magnetic resonance imaging). Researchers have turned to this field because MP-MRI provides information not only about tissue anatomy but also about tissue characteristics, cell structure and vascularization.

Study

In January 2017, Lancetpublished a study in which researchers started from the hypothesis that MP-MRI could replace an initial biopsy in men with elevated serum PSA levels. The study included men who had never undergone a prostate biopsy, whose PSA levels had risen over 3 months to as high as 15 ng/mL, and whose prostate volume was below 100 ml: 576 men in total. As it samples the entire prostate and is known to have an accuracy of %95, the reference test selected was TPM biopsy (Transperineal template Prostate Mapping Biopsies), against which MP-MRI and TRUS biopsy were evaluated.

According to the study results

• TPM biopsy diagnosed cancer in 230 individuals and found 346 individuals to be healthy (the most accurate results).
• MP-MRI diagnosed cancer in 418 individuals and found 158 individuals to be healthy. Comparing its data with the reference test, TPM biopsy, its sensitivity (the ability to detect patients with disease) was calculated as %93. In other words, of 230 individuals with cancer, 213 (%93) were diagnosed correctly, while 17 had false-negative results (interpreted as healthy despite having the disease). Its specificity (accuracy rate) was calculated as %41. Of 346 healthy individuals, it gave a correct result for 141 (%41), while 205 had false-positive results (interpreted as diseased despite being healthy). Among the 418 individuals diagnosed with cancer by MP-MRI, its results were correct in %51; among the 158 it found healthy, the results were correct in %89.
• TRUS biopsy diagnosed cancer in 124 individuals and found 452 individuals healthy. Comparing its data with the reference test, sensitivity was calculated as %48 (111 individuals), and specificity as %96 (333). Among the 124 individuals diagnosed with cancer by TRUS biopsy, its results were correct in %90; among the 452 it found healthy, the results were correct in %74.

In summary, MP-MRI was found to be more successful than TRUS biopsy in making the correct diagnosis

It should also be noted that individuals diagnosed with cancer by MP-MRI have a high probability of a false-positive result.

However, despite false positives, it was highly successful in identifying healthy individuals . In conclusion, based on this study, using multiparametric prostate MRI before TRUS biopsy could substantially reduce unnecessary interventions in healthy individuals.

2. Study

In another MRI study, researchers examined images from three different centers involving 70 individuals and found differences in shape and density in the images of individuals with prostate cancer. They then created an atlas using 35 images of cancerous prostates and 35 images of healthy prostates. When images were obtained again from 5 different centers and examined, the differences between cancerous and healthy prostate images were found to be consistent. Following these developments, researchers are developing new algorithms to make a diagnosis from the shape of the prostate using imaging systems and, if cancer has been diagnosed, to determine its aggressiveness.