Preimplant factors affecting postimplant CT-determined prostate volume and the CT/TRUS volume ratio after transperineal interstitial prostate brachytherapy with 125I free seeds

Impact of neoadjuvant androgen deprivation therapy on postimplant prostate D90 and prostate volume after low-dose-rate brachytherapy for localized prostate cancer

OBJECTIVE

Higher quality of postimplant dosimetric evaluation is associated with higher biochemical recurrence-free survival rates after low-dose-rate brachytherapy for localized prostate cancer. Postimplant prostate D90 is a key dosimetric parameter showing the quality of low-dose-rate brachytherapy. In this study, to improve the quality of low-dose-rate brachytherapy for localized prostate cancer, we investigated pre-implant factors affecting the reduction of postimplant prostate D90.

METHODS

A total of 441 patients underwent low-dose-rate brachytherapy monotherapy and 474 patients underwent low-dose-rate brachytherapy with external beam radiation therapy. Logistic regression analysis was carried out to identify predictive factors for postimplant D90 decline. The cut-off value of the D90 decline was set at 170 Gy and 130 Gy in the low-dose-rate brachytherapy monotherapy group and low-dose-rate brachytherapy with external beam radiation therapy group, respectively.

RESULTS

On multivariate analysis, neoadjuvant androgen deprivation therapy was identified as an independent predictive factor for the decline of postimplant D90 in both the low-dose-rate brachytherapy monotherapy group (P < 0.001) and low-dose-rate brachytherapy with external beam radiation therapy group (P = 0.003). Prostate volume changes and computed tomography/transrectal ultrasound prostate volume ratio were significantly and negatively correlated with the postimplant D90. The prostate volume changes and computed tomography/transrectal ultrasound prostate volume ratio were significantly higher in patients with neoadjuvant androgen deprivation therapy than those without neoadjuvant androgen deprivation therapy (P < 0.001).

CONCLUSIONS

Neoadjuvant androgen deprivation therapy decreased postimplant D90 with substantial prostate gland swelling after low-dose-rate brachytherapy. When neoadjuvant androgen deprivation therapy is required to reduce prostate volume for patients with large prostate glands and offer adequate local control for patients with high-risk prostate cancer before low-dose-rate brachytherapy, intraoperative D90 adjustment might be necessary.

Prostate-specific antigen percentage: An early predictive tool after iodine-125 interstitial brachytherapy for prostate cancer

BACKGROUND

After interstitial prostate iodine-125 brachytherapy (BT), prostate-specific antigen (PSA) evolution in time could predict overall biochemical relapse, but, considering the single patient, it is influenced by the presentation PSA amount and by the prostatic volume. It is also challenging to differentiate a PSA bounce from a biochemical relapse.

PURPOSE

To determine the usefulness of PSA percentage (PP) defined as the rate between PSA presented by a patient at time "t" and the PSA that the same patient had presented at the time of diagnosis (t0) assumed as 100% in predicting biochemical relapse and in differentiating them from PSA Bounces.

METHODS AND MATERIALS

We included 721 patients from Milan S. Raffaele Turro (399) and Lucca Campo di Marte (then S. Luca) Hospital (322). The mean age of patients was 66.5 years (range, 50-79). Mean followup was 150 months (range, 24-180). For each patient, PSA was recorded before and after iodine-125 BT, and PPs were calculated. Cox regression model, relative operating characteristic curves, and Kaplan-Meier regression model were elaborated, and a cutoff of 20% was defined.

RESULTS

We observed that PP >20% is an independent variable highly associated with relapse risk (p < 0.0001) with a sensitivity of 79.7%, a specificity of 82%, and an hazard ratio of 12.1, since the 6 months of followup. A PSA increase above the nadir should be because of bounce (sensitivity and specificity of 81.4%, p < 0.0001) if patient had experienced at 6 months a PP <20%.

CONCLUSIONS

PP might represent an early and useful tool, predictive of clinical outcome in patients after BT for prostate cancer.

Dosimetric quality and evolution of edema after low-dose-rate brachytherapy for small prostates: implications for the use of newer isotopes

PURPOSE

To characterize prostate swelling and dosimetry in patients with small prostate volumes (PVs) undergoing brachytherapy.

METHODS AND MATERIALS

We studied 25 patients with PV <25 cc (range, 15.1-24.8) and 65 patients with PV ≥25 cc (range, 25.0-66.2) based on three-dimensional ultrasound contours who underwent brachytherapy monotherapy with intraoperative planning. Postoperative Days 1 and 30 dosimetry was done by CT-MRI fusion.

RESULTS

Small PVs had greater Day 1 swelling than large PVs (32.5% increase in volume vs. 23.7%, p = 0.04), but by Day 30, swelling was minimal and not significantly different (p = 0.44). Small PVs had greater seed and needle densities at implant (p < 0.001). Rectal and urethral doses were nearly identical by Day 30 (small PV rectum receiving 100% of the prescription dose [145 Gy] [V100] = 0.32 cc; large PV rectum V100 = 0.33 cc, p = 0.99; small PV urethra receiving 150% of the prescription dose [145 Gy] [V150] = 0.20, large PV urethra V150 = 0.20, p = 0.91). Swelling at Day 1 created some cool implants (rate dose that covers 90% of the prostate volume [D90 <140 Gy = 12.0% and 9.4% for the small and large PV groups, respectively, p = 0.71), but Day 30 planning target volume coverage was excellent (rate D90 <140 Gy = 0% for both groups).

CONCLUSIONS

Although smaller prostates have greater Day 1 swelling, good Day 30 dosimetry can be achieved, making them excellent candidates for (125)I seeds (half-life [t½] = 60 days). Smaller prostates may be suboptimal for shorter t½ sources such as (131)Cs (t½ = 9.7 days), in which the majority of the dose may be delivered to an edematous gland, unless the planning is adjusted to anticipate the edema.

Is prostate-specific antigen percentage decrease predictive of clinical outcome after permanent iodine-125 interstitial brachytherapy for prostate cancer?

OBJECTIVE

To determine the usefulness of prostate-specific antigen (PSA) percentage (vs. pretreatment value assumed as 100%) in prediction of biochemical relapse, after iodine-125 ((125)I) permanent brachytherapy for prostate cancer, to employ a parameter independent by the initial PSA amount and by the individual prostatic volume.

METHODS AND MATERIALS

Our study included 133 patients, 102 still disease free (Group A) and 31 who experienced proven biochemical recurrence (Group B). PSA levels before and after (125)I brachytherapy were recorded, and PSA percentage vs. pretreatment values were calculated. Cox regression model, receiver operating characteristic curves, and Kaplan-Meier regression model with log-rank test were calculated.

RESULTS

We observed that, in patients submitted to brachytherapy for prostate cancer, a PSA percentage >20% of pretreatment value is highly associated with relapse risk (p<0.0001) and that this association is strongly present since t=6 months of followup (p<0.0001), with a hazard ratio near to five times (4.965), a sensitivity of 72.4%, and specificity of 79.8% related to the chosen cutoff.

DISCUSSION

Despite the amount of PSA is the only parameter that the clinicians can deploy to monitor patient's followup after permanent interstitial brachytherapy for prostate cancer, its evolution in time seems unable to predict early biochemical relapse as it is influenced by prostatic volume and initial PSA amount.

CONCLUSIONS

Our data suggest that a PSA percentage >20% of pretreatment value at 6 months might represent an early, inexpensive, and useful predictive tool of bad outcome in patients after permanent brachytherapy.