Descriptive analysis of patients

The clinical characteristics of all patients are shown in Table 1.

Table 1 Characteristics of the study cohortPatients with TZ lesions demonstrate a higher incidence of upgrading from grade 1 to higher and 2, 3 to 4, 5 compared to PZ lesions

Among the enrolled patients, 84 cases (38.7%) experienced an upgrading in the ISUP grade upon RP pathology, while 19 cases (8.8%) showed a downgrading, and 114 cases (52.5%) had consistent grading. The rate of upgrading was significantly higher than that of downgrading (38.7% vs. 8.8%, p < 0.001). Furthermore, patients with ISUP grades 1 experienced a higher rate of upgradation compared to those with grades 2, 3 and 4 (70.0% vs. 47.5% vs. 30.0% vs. 24.1%, respectively, p < 0.05). Similarly, ISUP grade 2 patients showed a higher upgradation rate than those with grades 3 and 4 (47.5% vs. 30.0% vs. 24.1%, respectively, p < 0.05). (Fig. 1, details in Online Resource 1)

Fig. 1

The ISUP grade upgradation of enrolled cases. (a) An overview of the upgrading, downgrading, and consistent grading of enrolled cases. (b) The upgrading among the PZ, TZ, and PZ + TZ subgroups. Patients with TZ lesions experienced a higher rate of upgrading from 1 to higher and 2, 3 to 4, 5 compared to PZ lesions (Details in Online Resource 2). (*: p < 0.05, **: p < 0.01)

Subgroup analysis of patients with lesions located in the TZ, PZ, and TZ + PZ revealed that patients with TZ lesions experienced a higher rate of upgrading from 1 to higher and 2, 3 to 4, 5 (28.9% vs. 15.7%, p = 0.021) and a higher rate of upgrading from 1 to higher (16.9% vs. 5.0%, p = 0.005) compared to PZ lesions (Fig. 1, details in Online Resource 2).

Univariate logistic regression analysis identified TZ lesions as a risk factor for upgrading from 1 to higher and from 2, 3 to 4, 5 in enrolled patients (OR: 2.698, 97.5% CI: 1.394–5.315, p = 0.004). In multivariate analysis, TZ lesions were also an independent risk factor (OR: 2.406, 97.5% CI: 1.182–4.980, p = 0.016). Additionally, univariate analysis identified TZ lesions as a risk factor for upgrading from 1 to higher (OR: 4.601, 97.5% CI: 1.783–13.398, p = 0.003), and multivariate analysis confirmed them as an independent risk factor (OR: 4.594, 97.5% CI: 1.569–15.238, p = 0.008). (Online Resource 3–4).

Upgrading rates of TZ tumors vary by biopsy methods and TZ subregion

In a detailed analysis of patients with TZ lesions, combined systematic and targeted biopsies tend to have lower rates of upgrading compared to systematic biopsies alone and targeted biopsies alone (Combined biopsies vs. Systematic biopsies and Targeted biopsies: [Upgrading] 38.6% vs. 51.8% and 49.4%, p = 0.08, p = 0.15; [Upgrading from 1 to higher and 2, 3 to 4, 5] 28.9% vs. 44.6% and 39.8%, p = 0.03, p = 0.14; [Upgrading from 1 to higher] 16.9% vs. 33.7% and 28.9%, p = 0.01, p = 0.06) (Fig. 2, details in Online Resource 5).

Comparing the upgrading rates across different zones of the TZ, no significant difference was observed in the upgrading rates between the TZ anterior (TZa) and TZ posterior (TZp) (31.7% vs. 28.0%, p = 0.410). However, there was a trend towards higher rates of upgrading from 1 to higher and 2, 3 to 4, 5 in the TZa compared to the TZp (Upgrading from 1 to higher and 2, 3 to 4, 5: 30.0% vs. 12.5%, p = 0.109; Upgrading from 1 to higher: 18.6% vs. 4.0%, p = 0.104) (Fig. 2, details in Online Resource 6).

Fig. 2

The upgrading rates of different biopsy techniques and various sub-regions in the TZ tumor. (a) Combined biopsies tend to have lower rates of upgrading compared to systematic biopsies alone and targeted biopsies alone (details in Online Resource 5). (b) There was a trend towards higher rates of upgrading from 1 to higher and 2, 3 to 4, 5 in the TZa compared to the TZp (details in Online Resource 6)

Factors associated with upgrading in TZ tumors

A comparative analysis of clinical profiles was conducted among patients with TZ tumors to identify factors associated with ISUP grade upgrading. In patients with upgrading from 1 to higher and 2, 3 to 4, 5, there were fewer positive cores compared to those without important upgrading (2 vs. 3, p = 0.037). However, there were no statistically significant differences in terms of PSA levels, PSA density, largest lesion diameter, lesion volume, lesion volume ratio, prostate volume, TZ volume, TZ volume ratio, age, and the free-to-total PSA ratio (f/t PSA) (p > 0.05) between patients with and without upgrading from 1 to higher and 2, 3 to 4, 5 (Fig. 3 and Online Resource 7).

Patients with upgrading from 1 to higher had lower PSA (11.91 vs. 17.79 ng/ml, p = 0.036), PSA density (0.23 vs. 0.43 ng/ml^2, p = 0.027), largest lesion diameter (11 vs. 16 mm, p = 0.040), lesion volume (0.37 vs. 1.02 ml, p = 0.040), lesion volume ratio (1.26% vs. 3.36%, p = 0.027), and fewer positive biopsy cores (1 vs. 3, p = 0.001) compared to those without significant upgrading. However, no statistically significant differences were found in prostate volume, TZ volume, TZ volume ratio, age, and f/t PSA (p > 0.05) between patients with and without upgrading from 1 to higher (Fig. 3and Online Resource 7).

Multivariate logistic regression analysis of these indicators revealed that the number of positive biopsy cores (OR: 0.586, 97.5% CI: 0.336–0.891, P = 0.029) and lesion location in the TZa (OR: 10.797, 97.5% CI: 1.503-248.727, p = 0.048) were independent factors for upgrading from 1 to higher in TZ patients (Online Resource 8).

Fig. 3

Factors associated with important and significant upgrading in TZ tumors. (a) Lower PSA levels were associated with upgrading from 1 to higher. (b) Lower PSA density was linked to upgrading from 1 to higher. (c) A smaller largest lesion diameter was related to upgrading from 1 to higher. (d) Lower lesion volume was associated with upgrading from 1 to higher. (e) A smaller lesion volume ratio indicated a likelihood of upgrading from 1 to higher. (f) Fewer positive biopsy cores were associated with upgrading from 1 to higher and 2, 3 to 4, 5. (*: p < 0.05, ***: p < 0.001)