Rationale for MRI and Genetic Analysis Prior to Brachytherapy

MRI and genetic analysis tests are utilized in some but not all patients. These tests are sometime used to determine if more aggressive therapy should be added to the course of treatment in order to improve the rate of cure.

MRI

Preoperative triple phasic or multiparametric MRI is occasionally ordered to evaluate the tumor burden in the prostate. Not all patients require this analysis however. The three phases of this sophisticated MRI are

  1. Phase 1 is typical MRI assessment of the prostate including tumor invasion through the capsule, seminal vesicle involvement, large areas of abnormal MRI signal indicating large tumors.
  2. Phase 2 is evaluation of the speed that the contrast washes in and washes out of the prostate. Cancer has more blood vessels than normal tissue and therefore the contrast washes in and out of cancer tissue faster than in normal tissue. The MRI software can detect these differences in rate of wash in and wash out at multiple points in the prostate. The software creates a map that the radiologist interprets as to where the cancer is in the prostate.
  3. Phase 3 is evaluation of how much water exists between the cells. The less water between cells means more cancer since there is less space between adjoining cancer cells compared to the space between normal prostate cells.

The radiologist interprets all three phases together to give an accurate estimation of how much cancer exists in the prostate as well as how aggressive it is. An estimation of the Gleason score based on the MRI findings is commonly made but must be corroborated with the biopsy findings.

Normal MRI showing anatomy

Figure 1.
Normal MRI showing anatomy.

Abnormal MRI, arrow points to cancer extending to capsule of prostate

Figure 2.
Abnormal MRI Arrow points to cancer extending to capsule of prostate.

Arrow points to extension of the cancer (orange) out of the capsule

Figure 3. Abnormal MRI.
Arrow points to extension of the cancer (orange) out of the capsule.

Genetic Analysis of the Biopsy Specimen

Several genetic analysis tests now exist for prostate cancer. They are performed on the existing specimen so another biopsy is not needed. The DNA from the cancer cells is extracted, sequenced and analyzed. The sequence is compared to the sequences of a library of thousands of patients who underwent sequencing and analysis over ten years ago at various academic institutions. These patients have been closely followed as part of scientific studies and the outcomes of their cancers are known and studied.

The DNA of a current patient is compared and matched with the DNA of the patients who have been followed for many years. A prediction of the behavior of the current patients DNA can then be made based on the behavior of the DNA of the patients that match it. A prediction of the aggressiveness of the current patient’s cancer and the chance of metastasis can be made.

The MRI and genetic analysis tests are utilized in some but not all patients. These tests are sometime used to determine if more aggressive therapy should be added to the course of treatment in order to improve the rate of cure.