Percentage Of Prostate Volume Research Articles

Control charts for evaluation of quality of low-dose-rate brachytherapy for prostate cancer.

PurposeVariations in dosimetric outcomes among patients treated with low-dose-rate brachytherapy for prostate cancer exist, even when implants are within dose constraints. Here, we used control charts to investigate reasons for intra-patient dosimetric variability.Material and methodsUnivariate and multivariate control charts for prostate V100 (percentage of prostate volume that received 100% of prescribed radiation dose), D90 (radiation dose to 90% of prostate volume), and RV100 (rectal wall volume that received 100% of prescribed radiation dose) were generated for 212 consecutive prostate cancer patients implanted with iodine-125 (125I) radioactive seeds at the Princess Margaret Cancer Centre. Control limits were calculated based on the first fifty implants. Data points that were out of control were identified, and their pre-treatment and post-treatment dosimetric and clinical parameters were compared to data points that were in-control, using Student’s t-test.ResultsAll implants were clinically acceptable. Twelve data points exceeded multivariate control limits. Ten of those points fell below the lower control limit of V100 control chart. Average prostate edema in the 10 out-of-control patients on both multivariate and V100 charts was 8.3%, as compared to 0.4% for in-control patients (p < 0.04). Two patients were observed to be out-of-control on multivariate control chart, but not on V100 control chart, and were found to have a reduction in prostate volume of 19.1% and 20.1% at one month after seed implant, compared to prostate volumes of pre-implantation evaluations.ConclusionsControl charts helped in identifying cases with out-of-control variability in post-plan prostate dosimetry. Post-treatment prostatic edema and contraction are important factors predicting variability in patients treated with 125I permanent seed brachytherapy.

Sector analysis of dosimetry of prostate cancer patients treated with low-dose-rate brachytherapy

Brachytherapy is an effective single treatment modality for low- and intermediate-risk prostate cancer. Here, we compare the radiation doses in different prostate sectors between the preimplant planning images and the postimplant dosimetry. Two hundred fifteen consecutive patients treated for prostate cancer by (125)I seed brachytherapy were assessed. Pretreatment plans using transrectal ultrasound images of the prostate were compared with the dose calculated on posttreatment MRI and CT scans obtained 1month after seed implantation. Twelve sectors were generated by dividing the prostate base, midgland, and apex into four quadrants each. Pretreatment and posttreatment dosimetry were compared between the 12 different sectors of the prostate. Average V100 (percentage of prostate volume that receives 100% of the prescribed dose) in the preimplant planning images of the prostate was 99.9±0.25% compared with postimplant V100 of 94.8±3.77% (p < 0.0001). Prostate V100 in the postimplant dosimetry was >91% in all sectors, except the anterior base sector, in which it was 64.87±20.96%. Average 1-month D90 (the dose to 90% of the prostate volume) was 114.5±10.55%. D90 at 1month compared with preimplant planning was lower in the prostate base and higher in the prostate apex (p < 0.001). Our results show that in (125)I seed brachytherapy, prostate base receives a lower dose and apex receives a higher dose compared with preimplant planned dose coverage.

Serum Total Testosterone Is a Significant Preoperative Variable Independently Contributing to Separating the Prostate Cancer Population into Prostatectomy Gleason Score Groups

Aim: To investigate the potential of preoperative serum total testosterone (TT) in contributing to the definition of separate prostatectomy Gleason score (pGS) groups of the prostate cancer (PCa) population. Materials and Methods: The data of 220 patients operated on for PCa were retrospectively reviewed. No patient had previously received 5α-reductase inhibitor, luteinizing hormone-releasing analogs or testosterone replacement treatment. The patient population was grouped according to the pGS as 6 = 3+3, 7 = 3+4, 7 = 4+3 and 8-10. Eight variables were simultaneously investigated in each group: prostate-specific antigen (PSA), TT, free testosterone, age, percentage of positive prostate biopsy cores (P+), biopsy Gleason score (bGS), overall cancer volume estimated as percentage of prostate volume (V+) and prostate weight (Wi). Univariate analysis of variance (ANOVA), multivariate analysis of variance (MANOVA) and multivariate discriminant analysis (MDA) were the statistical methods used for evaluating the data. Results: There were 89 patients in pGS 6 = 3+3, 84 in pGS 7 = 3+4, 24 in pGS 7 = 4+3 and 23 in pGS 8-10. ANOVA showed that bGS (p < 0.0001), P+ (p < 0.0001), V+ (p < 0.0001), PSA (p = 0.0001), Wi (p = 0.0002) and TT (p = 0.01) were significantly different in the four pGS groups. MANOVA tests showed that only bGS (p < 0.0001), V+ (p = 0.0003), TT (p = 0.001) and, to a lesser extent, PSA (p = 0.06) were the significant variables that individually and independently contributed a significant amount to separation of the four pGS groups of the PCa population. MDA showed that the independent variables ranked as bGS (p < 0.0001), TT (p = 0.001), V+ (p = 0.001) and PSA (p = 0.06). Conclusions: Serum TT is a significant preoperative variable that independently contributes to separating the PCa population into pGS score groups. Pretreatment baseline serum TT levels should be measured and their inclusion in neural networks predicting PCa natural history be considered in the patient population diagnosed with PCa.

Upgrading of Gleason score and prostate volume: a clinicopathological analysis

Objective To more clearly elucidate the association between prostate volume and Gleason score (GS) upgrading. Patient and Methods We reviewed 451 patients with prostate cancer with a GS of 6 on biopsy, who underwent radical prostatectomy without neoadjuvant treatment. As a preoperative variable, we assessed the independent effect of prostate volume on GS upgrading. To evaluate the association between prostate volume and GS upgrading, we developed multivariate models with volumetric pathological variables, including postoperative tumour volume and percent tumour volume (tumour volume as a percentage of prostate volume). Results GS upgrading was observed in 194 patients (43.0%). As a preoperative variable, smaller prostate volume was an independent predictor of GS upgrading. In regression analysis, prostate volume and postoperative tumour volume were inversely correlated. On multivariate analysis including volumetric pathological variables, tumour volume was a strong independent factor influencing GS upgrading, and prostate volume lost statistical significance after adjusting for tumour volume. Percent tumour volume was inversely correlated with GS upgrading after adjusting for tumour volume. Conclusions Smaller prostate volume was an independent predictor of GS upgrading as a preoperative variable. The inverse relationship between prostate volume and GS upgrading seems to be attributable to cancer biology, which was represented by tumour volume in our study. Percent tumour volume was also inversely associated with GS upgrading. These results suggest that biological factors and sampling error both play important roles in GS upgrading.

SU-FF-J-92: A Dosimetric Study of the Potential for Margin Reduction in Prostate IMRT Using Image-Guided Target Localization

Purpose: To evaluate the potential for planning target volume margin reduction using image‐guided target localization for patients receiving IMRT for prostate cancer using on‐line CBCTimaging.Method and Materials: Eight patients being treated with IMRT were included in the study. Planning was performed with a conventional planning CT using an 8 mm planning margin everywhere except 6 mm posteriorly. Patient setup was performed by first aligning to skin markers and subsequently shifting to the actual treatment position determined using kV imaging of implanted fiducial markers in the prostate. Both setup positions were recorded for each fraction. CBCTimages were obtained weekly of the patients in the treatment position at the time of treatment. The prostate and organs‐at‐risk (OARs) were contoured on each image by a physician and retrospective dose calculations were performed on each CTimage by applying the original treatment plan to the image using the isocenters obtained via skin marker and image‐guided localization. To study the effects of margin reduction, IMRTtreatment fields were replanned for each patient with two reduced margins and applied to the CBCTimages for dose calculation using both the skin marker and image‐guided isocenters. Results: The endpoint of the study was V98, the percentage of prostate volume that received 98% of the prescribed dose. This was calculated for each CBCTimage of each patient. With image‐guided localization V98 exceeded 98% for all treatments based on the actual treatment plan, 97% for plans based on a 6 mm margin (4 mm posteriorly), and 95% for plans based on 4 mm margin (3 mm posteriorly). Conclusion:Image‐guided localization may facilitate margin reduction without significant loss of dose coverage to the prostate. Conflict of interest: This research is partially supported by a Varian research grant.

A Comparison of the Incidence and Location of Positive Surgical Margins in Robotic Assisted Laparoscopic Radical Prostatectomy and Open Retropubic Radical Prostatectomy

Surgical technique, patient characteristics and method of pathological review may influence surgical margin status. We evaluated the incidence and location of positive surgical margins in 200 sequential robotic assisted laparoscopic radical prostatectomy and 200 sequential open radical retropubic prostatectomy cases. From July 2002 until December 2006 a total of 1,747 patients underwent radical prostatectomy at our institution (robotic assisted laparoscopic radical prostatectomy in 1,238, radical retropubic prostatectomy in 509). From these we selected the last 200 consecutive radical retropubic prostatectomies and 200 robotic assisted laparoscopic radical prostatectomies performed before August 2006. Preoperative clinical characteristics including age, clinical stage, prostate specific antigen and Gleason score were evaluated. Postoperatively pathological specimens were assessed for specimen weight, Gleason score, tumor volume, pathological stage and margin status. The incidence and location of positive surgical margins were compared between robotic assisted laparoscopic radical prostatectomy and radical retropubic prostatectomy. Patients undergoing robotic assisted laparoscopic radical prostatectomy compared to radical retropubic prostatectomy had more favorable tumor characteristics including lower prostate specific antigen, clinical stage and Gleason score. No statistically significant differences were found between groups for prostate volume or tumor volume. However, tumor volume as a percentage of prostate volume was higher among radical retropubic prostatectomy compared to robotic assisted laparoscopic radical prostatectomy cases (17.7% vs 13%, p = 0.001). The overall incidence of positive surgical margins was significantly lower among the robotic assisted laparoscopic radical prostatectomy compared to radical retropubic prostatectomy cases (15% vs 35%, p <0.001). The incidence of positive surgical margins according to pathological stage for robotic assisted laparoscopic radical prostatectomy vs radical retropubic prostatectomy cases was 16 of 171 (9.4%) vs 33 of 137 (24.1%) for pT2 (p <0.001) and 14 of 28 (50%) vs 36 of 60 (60%) for pT3. In both groups the apex was the most common site of positive surgical margins with 52% in the robotic assisted laparoscopic radical prostatectomy group vs 37% in the radical retropubic prostatectomy group (p >0.05). In the hands of surgeons experienced in robotic assisted laparoscopic radical prostatectomy and radical retropubic prostatectomy, there was a statistically significant lower positive margin rate for patients undergoing robotic assisted laparoscopic radical prostatectomy. The most common location of a positive surgical margin in robotic assisted laparoscopic radical prostatectomy and radical retropubic prostatectomy cases was at the apex. Patients treated with radical retropubic prostatectomy had higher risk features which may have independently influenced these results. The method of pathological specimen analysis and reporting may account for the higher positive margin rates in both groups compared to some reports.

Impact of postimplant edema on V 100 and D 90 in prostate brachytherapy: can implant quality be predicted on day 0?

Purpose : To determine the effect of edema on the dosimetric parameters V 100 (percentage of prostate volume that received a dose equal to or greater than the prescribed dose) and D 90 (minimal dose delivered to 90% of prostate volume) in 125I prostate brachytherapy and to determine whether the edema can be used to predict implant quality on the day of the implant (Day 0). Methods and Materials : Fifty consecutive patients treated with 125I implants who had two postimplant CT scans were selected for this study. The mean interval between the studies was 46 ± 23 days. The implants were preplanned to deliver 150 Gy to the prostate plus a 3–5-mm symmetric dose margin using peripherally loaded 0.4–0.6-mCi (NIST-99) 125I seeds. A dose-volume histogram was compiled for each postimplant CT scan. The V 100 and D 90 from the first and second CT scans were compared to determine the effect of edema on these parameters. A multivariate regression analysis was performed to define the linear relationships for predicting the V 100 or D 90 at 30–60 days after implant from the magnitude of the edema and the values of V 100 and D 90 on Day 0. Results : V 100 and D 90 increased by 5% ± 6% and 15% ± 17%, respectively, during the interval between the first and second postimplant CT scans. The mean edema was 1.53 ± 0.20. The increases in V 100 and D 90 were found to be proportional to the edema and the values of V 100 and D 90 on Day 0. The increase in V 100 was also found to depend on the width of the preplan dose margin. Linear relationships were derived that predict the V 100 and D 90 at 30–60 days after implant with a standard error of ±4% and ±24 Gy, respectively. Conclusion : V 100 and D 90 increased by 5% ± 6% and 15% ± 17%, respectively, during the first 30–60 days after implant. The results of a multivariate linear regression analysis showed that the increases in V 100 and D 90 were proportional to both the magnitude of the edema and the values of these parameters on Day 0. The relationships derived by linear regression analysis predict V 100 and D 90 at 30–60 days after implant to within ±4% and ±24 Gy, respectively. However, predicting the 30–60-day V 100 and D 90 on Day 0 is a poor substitute for obtaining a 30–60-day CT scan, because the uncertainty in the predicted values is greater by a factor of ≥2. Nevertheless, on average, the predicted values should provide a more reliable estimate of the actual V 100 and D 90 than the Day 0 values that ignore the effect of edema altogether. The increase in V 100 was also found to depend on the width of the preplan dose margin; therefore, our results for V 100 are only valid for implants planned with a 3–5-mm margin.