Contribution of immunohistochemical and molecular markers in predicting prognosis in prostate cancer

Prostate cancer is the second most common malignancy in men worldwide, following lung cancer. According to the American Joint Committee on Cancer (AJCC), the 5-year survival rate for individuals with metastatic prostate cancer is 31%. The primary cause of death related to prostate cancer is its resistance to current treatment regimens and the emergence of metastatic disease. Transmembrane protease serine 2 (TMPRSS2) is a member of the transmembrane serine protease family. The ETS-related gene (ERG) is an oncogene that plays a significant role in tumor pathogenesis. Increased abnormal expression of ERG as a result of TMPRSS2-ERG fusion is effective in prostatic epithelial differentiation, invasion, and metastasis. Inhibition of ERG expression is a potential target in prostate cancer treatment because it halts cell growth. Protein tyrosine phosphatase and tensin homolog (PTEN) is a tumor suppressor gene. The activation of the mammalian target of rapamycin (mTOR) pathway due to loss of PTEN expression has gained importance in terms of targeted therapies against mTOR. Marker of Proliferation Kiel-67 (Ki-67) proliferation index is not routinely used in the assessment of prostate cancer but is one of the determinants of aggressiveness and prognosis in many cancers. The Apparent Diffusion Coefficient (ADC) tumor value is known to be associated with the aggressiveness of tumors in many different cancer types. The correlation between ADC tumor value, ADC ratio, and the aggressiveness of prostate cancer has been analyzed in numerous studies in the literature. Our study aims to contribute to the selection of patients for active surveillance and the planning of treatment by evaluating immunohistochemical (IHC) and molecular parameters that may predict the Gleason score (GS), aggressiveness, and prognosis using transrectal needle biopsy (TRNB) material and subsequent radical prostatectomy (RP) material. The study included a total of 150 patients diagnosed with prostate adenocarcinoma between 2011 and 2022 in the Department of Pathology at Pamukkale University, Faculty of Medicine. Two samples were obtained from transrectal needle biopsy (TRNB) and radical prostatectomy (RP) materials for each patient. Clinical data and laboratory findings were obtained from the hospital information management system. TMPRSS2-ERG fusion was evaluated by fluorescent in situ hybridization (FISH) examination. For the IHC analysis, antibodies against PTEN (Clone D4.3), ERG (Clone EPR3864), and Ki-67 (Clone 30-9) were used. In our study, which involved 150 patients, some of the samples experienced tissue loss after technical procedures. In the RP samples, ERG fusion was detected in 61 out of 105 patients (58.1%), and in the TRNB samples, ERG fusion was observed in 18 out of 49 patients (36.7%). Fusion through deletion was observed in only two patients, while in all other patients, fusion occurred through the break-apart. In RP samples, among prostate cancers with positive TMPRSS2-ERG gene fusion, 9.5% are GS 6, and 48.6% are GS 7. A statistically significant relationship has been observed between the presence of fusion and the primary and secondary patterns of patients with GS 7 (p<0.04 and p<0.01, respectively). For RP materials, there is a statistically significant increase in ERG fusion rate in the patient group with a higher GS (p=0.026). There was no statistically significant relationship between fusion status and distant metastasis, positivity of the surgical margin, perineural invasion (PNI), and biochemical recurrence (p> 0.05). When the threshold value while evaluating ERG is accepted as 150, expression was detected in 19.5% of TRNB samples and 10.6% of RP samples. When assessed as the presence or absence of nuclear expression, ERG expression was detected in 42.2% of TRNB samples and 40.4% of RP samples. In RP samples, a statistically significant correlation was found between the presence of ERG expression detected by both algorithms and the presence of fusion detected by the FISH method (p=0.00 and p=0.023, respectively). In RP samples, a statistically significant increase in the rate of perineural invasion (PNI) and a decrease in the rate of high-grade prostatic intraepithelial neoplasia (HGPIN) was found in non-expressing patients in both algorithms of ERG evaluation (p=0.014 and p=0.032, respectively). In the absence of ERG expression in TRNB materials, a statistically significant difference was found in the increase of PTEN expression loss in the TRNB material of the same patients (p=0.013). In patients with the absence of ERG expression in the TRNB material, there was a statistically significant difference in the increase of PTEN expression loss in both the TRNB and the RP materials (p=0.042). When grouping by GS and GG in TRNB and RP samples, there was no statistically significant relationship between PTEN expression loss between these groups (p>0.05). When the Ki-67 proliferation index threshold value was taken as 1%, a statistically significant difference was detected in TRNB samples with GG 2 and GG 3 (p = 0.01). A positive correlation was detected between the Ki-67 proliferation index, PSA density, and tumor size (p=0.001). When threshold values were taken as ≤1 and ≥3 in TRNB and RP samples, no statistically significant relationship was detected between the Ki-67 proliferation index and other clinicopathological parameters (p>0.05). In RP samples, no statistically significant relationship was detected between the Ki-67 proliferation index and GG with both evaluation algorithms (p>0.05). In MRI, the ADC value of the tumor is used as a marker in the diagnosis and evaluation of the aggressiveness of the tumor in many different types of cancers. In our study, the ADC tumor value was found to be statistically significantly lower in the GG 2 and GG 3 (GS7) groups compared to the GG 1 (GS 6) group (p = 0.01). There was no statistically significant difference between the ADC ratio value, GS, and GG (p>0.05). In TRIB and RP samples, ADC tumor values were observed to be lower in those with PTEN loss compared to those with PTEN preserved. However, this difference was not found to be statistically significant (p>0.05). By FISH examination, ADC values were found to be relatively lower in patients with ERG fusion in RP materials compared to patients without fusion. However, this difference was also not statistically significant (p>0.05). Our study will be the first study in the literature comparing ERG and ADC values evaluated using the FISH and IHC methods combined. Further studies are needed on larger patient series to obtain data that will contribute to the routine on this subject.