Analysis of the local control in lymph-node staged localized prostate cancer treated by external beam radiotherapy, assessed by digital rectal examination, serum prostate-specific antigen and biopsy

Objective To describe local disease control after radical external beam radiotherapy of prostatic carcinoma, as judged by digital rectal examination (DRE), transrectal ultrasonography (TRUS)-guided biopsies and estimates of serum prostate-specific antigen (PSA). Patients and methods The study comprised 175 patients (mean age 67.5 years, range 49-82; >30% aged greater than or equal to 60 years) with localized prostatic carcinoma (T1-T3C, NO, MO) who underwent external beam radiation therapy (70 Gy), and were then regularly followed with a DRE, measurements of serum PSA and TRUS-guided biopsies to determine the outcome. Results The DRE revealed four patients with evidence of residual cancer in the prostate and biopsies showed no evidence of residual cancer in 131 (75%) of the patients. There was no correlation of residual cancer with tumour stage or grade but tumour size, as estimated by TRUS, correlated with the results of the biopsy, The nadir serum PSA level was less than or equal to 1.0 ng/mL in 116 (66%) of the patients, of whom 76 (43%) had a nadir serum PSA level of 60.5 ng/mL, The median time to the nadir level was 11 months, Serum PSA progression (>4.0 ng/mL) at the latest PSA measurement after reaching the nadir occurred in 13% of the patients with a nadir PSA of 60.5 ng/mL and in 25 of the 29 (86%) patients with a nadir serum PSA >2.0 ng/mL, Cox regression analysis showed that tumour size and rectal irradiation dose were the most important factors for local control, Conclusions Radiotherapy is effective in achieving local control in small prostate cancer tumours but less effective in large tumours. Tumour size and dorsal extension of the irradiated target, the rectal dose, were the two important factors for local control. A serum PSA level of less than or equal to 1.0 ng/mL was associated with a higher chance of prolonged disease control.