Clinical aspects of prostate cancer in patients with germinal and somatic mutations in DNA homologous recombination repair genes

Background. In clinical practice, there is a need to predict clinical behavior of prostate cancer with germinal and somatic mutations in DNA homologous recombination repair (HRR) genes due to an atypical response to standard treatment methods. Also, the expediency of testing the mutational status of HRR genes is dictated by the possibility of using the PARP-inhibition strategy in metastatic castration-resistant prostate cancer (mCRPC). In addition to expanding the possibilities for targeted therapy the necessity to inform the relatives of mutation carriers is underestimated. It is also important to realize the fact of accumulation of somatic changes both in the primary tumor and in the metastatic lesion during tumor evolution and under treatment, which dictates the possibility of repeated biopsy with exhausted therapy possibilities.
Aim. Evaluation of prostate cancer clinical behavior features and response to drug therapy depending on the identified mutations in the HRR genes.
Materials and methods. The study was performed at the Clinical Oncological Dispensary No. 1 (Krasnodar). Clinical and morphological data of 27 patients with prostate cancer and identified germinal and somatic mutations in HRR genes (BRCA1, BRCA2, ATM, BARD, BRIP1, CDK12, CHEK1, CHEK2, PALB2, RAD51B, RAD51C, RAD54L, FANCL) were retrospectively analyzed. Statistical analysis was performed using the IBM SPSS Statistics v.22 statistical package.
Results and conclusion. The median age of patients was 61 years. The most frequent were mutations in the BRCA2 (37 %), CHEK2 (18.5 %), ATM (14.8 %) genes. More than half of the patients (69 %) had primary metastatic disease. The differentiation grade of G2 and G3 according to the classification of the International Society of Urological Pathologists (ISUP) with Gleason score of 7 (3 + 4) and 7 (4 + 3) were both detected in 27 % of cases. The type of mutation did not affect the time of castration resistance development (p = 0.216). The time to castration resistance increased close to statistical significance in the case of primary stage of T3–4N0M0 compared to other stages (log-rank p = 0.092). Progression-free survival (PFS) with docetaxel monochemotherapy was significantly longer when prescribed for metastatic hormone-sensitive prostate cancer with mutations in HRR genes compared to mCRPC (p = 0.061) and to primary metastatic disease (p = 0.04). At the same time, the risk of progression during therapy was higher for presence of regional lymph node metastases with primary advancement (p = 0.005; hazard ratio 1.167; 95 % confidence interval 2.765–267). There was also an advantage in PFS when prescribing docetaxel for BRCA1/2 and ATM mutations in comparison with other mutations (p = 0.038). When prescribing therapy with 2nd generation antiandrogens or abiraterone, progression-free survival is higher in the group of patients with prostate cancer with Gleason score of 7 (4 + 3) compared to cohort with other morphological types, and this difference is almost statistically significant (log-rank p = 0.091, Breslow p = 0.076, Taron-Ware p = 0.074). Targeted therapy with the PARP inhibitor Olaparib in the performed trial was received by 10 patients with HRR mutations. At the same time, according to the data of the PROfound trial, the advantage of Olaparib in radiological PFS was shown in germinal and somatic mutations in group A (BRCA1, BRCA2, ATM) and in the general group (A and B – other HRR mutations).

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