Prostate biopsy is performed to determine whether prostate cancer is present in men with a high PSA (Prostate Specific Antigen) test or a suspicious mass in the prostate by imaging methods.
In people with high PSA levels, the classical approach is to perform a manual rectal examination followed by a rectal prostate biopsy. A small portion of prostate cancers may be felt with hand examination and a biopsy can be performed if there is a suspicious finding. The classic prostate biopsy is performed by taking samples randomly (6-12) from various parts of the prostate, seeing the prostate with an ultrasound probe inserted through the rectum, but without seeing the tumor. These samples are then examined in pathology, and it is not only clarified whether there is cancer or not, but also the agresiveness of the tumor is evaluated by a grading called Gleason score. For this evaluation, the pathologist gives a score ranging from 1 to 5, depending on the extent to which the tumor is different from the normal tissue. Then, the most commonly seen two scores are taken into consideration. Therefore, Gleason score is given as binary values like 4 + 3, 3 + 5, 4 + 5 and the sum of these values in practice varies between 5-10. Gleason 5 is the slowest and Gleason 10 shows the fastest (aggressive) tumor type.
In prostate cancer, the Gleason score shows the grade of the tumor and gives an idea of the tumor's growth rate and the likelihood of metastasis. The extention of the tumor in the body is determined by the stage of the tumor and is demonstrated by imaging methods such as PET-CT, CT and MRI. As with many other cancers, prostate cancer is also divided into 4 phases; In stage 1 and 2 the tumor is limited to prostate, in stage 3 the tumor is spread out of the prostate or into regional lymph nodes. In stage 4, there are distant metastases (usually bones).
There are some problems in the classical diagnostic methods of prostate cancer:
1. In other organs, such as the liver and lung, a suspicious mass is first detected with imaging methods such as ultrasound, CT and MRI, and then a biopsy is performed under imaging, by seeing the tumor. However, in the prostate, the tumor is usually not seen on imaging, at least on ultrasound, so patients with a high suspicion of cancer (high PSA) are tried to be diagnosed by random biopsies taken from the prostate. The prostate is the only organ that has been diagnosed by "blind" biopsy in our body.
2. In classical prostate biopsies, approximately 1/3 of prostate cancers can be omitted. Furthermore, in about 1/4 of the cases, the Gleason score is lower than it actually is, which means it may appear to be less aggressive than it really is, which may result in delayed or unsuccessful treatment.
3. In most patients, the PSA is high but the biopsy may be normal. In this case, the biopsy is repeated taking even more samples but again in a blind manner. However, recurrent biopsies can cause problems such as bleeding and infection, and the second biopsy may not detect cancer in many cases. In some patients, the biopsy can be done from the region called perineum between the anus and the penis, and not through the rectum. In this method, called saturation biopsy, multiple needle biopsies are performed from equally spaced holes using a mold placed on the perineum. This method is superior to the classical random biopsy in detecting cancer, but requires needle biopsy from more holes.
Modern biopsy methods in prostate cancer
While prostate cancer can not normally be seen by radiological imaging methods, it has been possible for the first time to detect it at an early stage with the recent developments in MR imaging. Especially in new MR devices, approximately 80% of prostate cancers can now be detected early with a technique called "multiparametric imaging". It is also thought that cancers that MRI cannot show are more slowly progressing and thus, have less clinical importance. The tumors, which are detected by MRI, can then be subjected to "imaging-guided" biopsy rather than "blind", and the patient can be diagnosed more accurately by less needle trauma. Imaging-guided prostate biopsy can be performed directly on the MRI device, as well as on ultrasound devices using fusion imaging which combines MRI and ultrasound images.
MRI 's ability to show prostate cancer at an early stage dramatically changed both the diagnosis and treatment methods of prostate cancer. Today, classical approaches are still applied in many centers around the world. However, in many well-developed centers, rectal biopsy performed in prostate cancer was abandoned. In these centers, a multiparametric MRI is made in patients with high PSA levels and if a suspicious mass is detected image-guided biopsy is performed. If the MRI is normal, the patient is just followed up periodically.
Interventional oncology in cancer management
Prof Saim Yilmaz, MD