The role of postimplant dosimetry in predicting permanent brachytherapy effectiveness in patients with low and intermediate risk prostate cancer

Apolihin O.I., Sivkov A.V., Oschepkov V.N., Roschin D.A., Koryakin A.V.

Materials and Methods. The analysis included 117 patients who meet the following criteria: disease stage T1-T2c, low or intermediate risk of disease (criteria D`Amico), follow-up period of 5 years or more, and performed PDA, which was carried out based on the day 30 CT data. According to the results of PDA patients were divided into 2 groups: group I figure D90 was ≥140 Gray, group II < 140 Gray. Biochemical failure was defined by ASTRO. PSA blood test was carried out on 3, 6, 12, 18 and 24 months after brachytherapy and further on every year of life.

Results. Overall 5-year biochemical desease- free survival (bDFS) for both groups was 83.8%. 5-year bDFS in the first group for stage T1 was 96.4%, for stage T2 – 82.9 % (p < 0.01). Group 2 bDFS for stage T1 was 85.2 %, stage T2 – at 71.9 %. When analyzing the influence of histopathology, we obtained the following values of 5-year bBRV : low-grade adenocarci- noma – 96.2%, with moderately differentiated prostate cancer ( Gleason < 7) – 90.9 %, which has no significant difference (p> 0 , 05). On average, 90% of the prostate volume (D90) received a dose of 167.4 Gy in the first group and 134.4 Gy in the second. 5-year bBRV was significantly higher in the group D90≥140 Gy, compared to patients with a dose of < 140 Gy : 90.2% and 77.6 %, respectively ( p < 0.05) . Evaluation of complications of radiation therapy showed that the most significant symptom was dysuria, observed in 25 (42.4%) patients in group 1 and – 34 (58.6% ) in group 2.

Summary. The study showed an unambiguous relationship between the D90 and the prognosis of the disease for all patients who receive more or less than 140 Gy in a statistically balanced groups of patients with localized prostate cancer. In fact, the dose received is a significant predictor of treatment outcome. Performing PDA allows not only to predict cancer outcomes, but is an important tool for quality control and skills improvement.

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