Kent Wallner .IJROBP 2003:57:1297

Of a planned total of 600 patients with 1997 American Joint Committee on Cancer clinical Stage T1c–T2a prostate carcinoma (Gleason score 5–6, prostate-specific antigen [PSA] 4–10 ng/mL), 126 were randomized to implantation with ¹²⁵I (144 Gy) vs. ¹⁰³Pd (125 Gy). The prostate biopsies were reviewed for Gleason score by one of us (L.T.). A single manufacturer of ¹²⁵I sources (Model 6711, Amersham, Chicago, IL) and ¹⁰³Pd sources (Theraseed, Theragenics, Buford, Georgia) was used. Isotope implantation was performed with standard techniques, using a modified peripheral loading pattern. Of a total of 126 patients randomized, 11 were excluded, leaving 115 randomized patients for this analysis. Twenty patients received a short course of preimplant hormonal therapy, none of whom continued hormonal therapy after their implant procedure. Postimplant CT was obtained 2–4 hours after implantation. The dosimetric parameters analyzed included the percentage of the postimplant prostate or rectal volume covered by the prescription dose (V₁₀₀) and the dose that covered 90% of the postimplant prostate volume (D₉₀). Freedom from biochemical failure was defined as a serum PSA level =0.5 ng/mL at last follow-up. Patients were censored at last follow-up if their serum PSA level was still decreasing. Patients whose serum PSA had reached a nadir at a value >0.5 ng/mL were scored as having failure at the time at which their PSA had reached a nadir. The follow-up period for patients without failure ranged from 2.0 to 4.9 years (median 2.9). Freedom-from-failure curves were calculated by the Kaplan-Meier method. Differences between groups were determined by the log–rank method.

Results: The actuarial biochemical freedom-from-failure rate at 3 years was 89% for ¹²⁵I patients vs. 91% for ¹⁰³Pd patients (p = 0.76). The 3-year biochemical freedom-from-failure rate for patients with a D₉₀ <100% of the prescription dose was 82% vs. 97% for patients with a D₉₀ =100% of the prescription dose (p = 0.01). Similarly, the 3-year biochemical freedom-from-failure rate for patients with a V₁₀₀ <90% of the prescription dose was 87% vs. 97% for patients with a V₁₀₀ =90% of the prescription dose (p = 0.01). The effect of the dosimetric parameters on biochemical control was most pronounced for ¹²⁵I, but also apparent for ¹⁰³Pd.

Conclusion : The 3-year actuarial biochemical control rates for low early-stage prostate cancer are similar after ¹²⁵I and ¹⁰³Pd.

Int J Radiat Oncol Biol Phys 2000 Jan 1;46(1):221-30

The American Brachytherapy Society recommendations for permanent prostate brachytherapy postimplant dosimetric analysis.

Nag S, The ABS recommends that postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy for optimal patient care. At present, computed tomography (CT)-based dosimetry is recommended, based on availability cost and the ability to image the prostate as well as the seeds. Additional plane radiographs should be obtained to verify the seed count. Until the ideal postoperative interval for CT scanning has been determined, each center should perform dosimetric evaluation of prostate implants at a consistent postoperative interval. This interval should be reported. Isodose displays should be obtained at 50%, 80%, 90%, 100%, 150%, and 200% of the prescription dose and displayed on multiple cross-sectional images of the prostate. A dose-volume histogram (DVH) of the prostate should be performed and the D90 (dose to 90% of the prostate gland) reported by all centers. Additionally, the D80, D100, the fractional V80, V90, V100, V150 and V200 (i.e., the percentage of prostate volume receiving 80%, 90%, 100%, 150%, and 200% of the prescribed dose, respectively), the rectal, and urethral doses should be reported and ultimately correlated with clinical outcome in the research environment.

Int J Radiat Oncol Biol Phys 1999 Jul 1;44(4):789-99

American Brachytherapy Society (ABS) recommendations for transperineal permanent brachytherapy of prostate cancer.

Nag The recommended prescription doses for monotherapy are 145 Gy for 125I and 115-120 Gy for 103Pd. The corresponding boost doses (after 40-50 Gy EBRT) are 100-110 Gy and 80-90 Gy, respectively. Post implant dosimetry and evaluation must be performed on all patients. It is suggested that the dose that covers 90% (D90) and 100% (D100) of the prostate volume and the percentage of the prostate volume receiving the prescribed dose (V100) be obtained from a dose-volume histogram (DVH) and reported.

Int J Radiat Oncol Biol Phys 1997 Sep 1;39(2):347-53

CT-based dosimetry for transperineal I-125 prostate brachytherapy.

Willins J, Wallner. The prescribed minimum peripheral prostate dose was 140 Gy, based on a preimplant CT scan of the prostate. Target volumes were determined based on planar reconstruction of the prostate. RESULTS: An average of 84% of the target (range: 76-92%) was covered by the 140 Gy isodose line. An average of 90% of the target (range: 81-96%) was covered by the 120 Gy isodose line. The average minimum target dose was 57 Gy (range: 40-70 Gy). There was a loose correlation between the minimum dose and the degree of target coverage (r = 0.33). CONCLUSIONS: Based on CT scanning on the day of the implant, coverage of 80% or more of the target volume by the prescription dose is probably adequate.

Int J Radiat Oncol Biol Phys 1998 Apr 1;41(1):101-8

A dose-response study for I-125 prostate implants.

Stock Using TG43 guidelines, dose-volume histograms were calculated. The dose delivered to the gland was defined as the D90 (dose delivered to 90% of prostate tissue as defined by CT). The D90s ranged from 26.8 to 256.3 Gy (median: 140.8 Gy). Improvements in freedom from biochemical failure (FFBF) rates were seen with increasing D90 levels. The 4-year FFBF rates for patients with D90 values < 100 Gy, 100-119.9 Gy, 120-13.9 Gy, 140-159.9 Gy, and > or =160 Gy were 53, 82, 80, 95, and 89%, respectively (p = 0.02). Patients receiving a D90 < 140 Gy (65 patients) were similar with respect to presenting disease prognostic factors to those receiving a D90 > or =140 Gy (69 patients). Patients receiving a D90 < 140 Gy had a 4-year FFBF rate of 68% compared to a rate of 92% for those receiving a D90 > or =140 Gy (p = 0.02). Two-year posttreatment biopsies were negative in 70% (33 of 47) of patients with a D90 < 140 Gy compared to a rate of 83% (24 of 29) in patients with a D90 > or =140 Gy (p = 0.2). A multivariate analysis using dose, PSA, score, and stage revealed that dose was the most significant predictor of biochemical failure (p = 0.001). This dose response was more pronounced in patients presenting with PSA levels > 10 ng/ml. In these patients, the 4-year FFBF rates were 51 and 100% for the low and high dose groups, respectively (p = 0.009) and the negative biopsy rates were 64% (14 of 22) and 100% (8 of 8), respectively (p = 0.05). In patients with presenting PSA <10 ng/ml, the 4-year FFBF rates were 82 and 88% for the low and high dose groups, respectively (p = 0.29). CONCLUSION: A dose response was observed at a level of 140 Gy. Adequate I-125 implants should deliver a dose of 140-160 Gy using TG43 guidelines.

Int J Radiat Oncol Biol Phys 1999 Jun 1;44(3):483-91

A comprehensive review of prostate cancer brachytherapy: defining an optimal technique.

Vicini To evaluate implant quality, 28% of studies calculated some type of dose-volume histogram, 21% calculated the matched peripheral dose, 19% the minimum peripheral dose, 14% used some type of CT-based qualitative review and, in 18% of studies, no implant quality evaluation was mentioned. Six studies correlated outcome with implant dose. One study showed an association of implant dose with the achievement of a PSA nadir < or = 0.5. Two studies showed an improvement in biochemical control with a D90 (dose to 90% of the prostate volume) of 120 to 140 Gy or higher, and 2 additional studies found an association of clinical outcome with implant dose.  Our comprehensive review of prostate cancer brachytherapy literature failed to identify an optimal treatment approach when studies were analyzed for treatment outcome based upon pretreatment PSA and biochemical control. Although several well-designed studies showed an improvement in outcome with total dose or implant quality, the numerous techniques for implantation and the varied and inconsistent methods to specify dose or evaluate implant quality suggest that standardized protocols should be developed to objectively evaluate this treatment approach.

Int J Radiat Oncol Biol Phys 1999 Jun 1;44(3):717-24

Potential role of various dosimetric quality indicators in prostate brachytherapy.

Merrick The American Brachytherapy Society has recently proposed that prostate brachytherapy quality be measured in terms of the following parameters: D90, V100, and V150 where D90 is defined as the minimal dose covering 90% of the prostate volume and V100 and V150 are defined as the percent volume of the prostate receiving at least 100% or 150% of the prescribed minimal peripheral dose (mPD), respectively. We report detailed day 0 dosimetric evaluation for 60 consecutive prostate brachytherapy patients implanted via a standard transperineal ultrasound guided approach in terms of D90, D100, V90, V100, and V150 and also the maximal and average rectal and urethral dose. RESULTS: Dosimetric evaluation resulted in a V100 greater than 80% of the prostate volume and a D90 greater than 90% of the mPD in the entire patient population. There was a statistically significant difference between the quality scores of 125I implants and 103Pd implants with the 125I mean V100 and D90 at 95.3% volume and 109.9% mPD, respectively, vs. 103Pd at 91.8% volume and 103.7% mPD. Likewise, the rectal and urethral doses as a fraction of mPD were significantly lower in 103Pd than in 125I implants. This occurred despite the fact that palladium implants were typically preplanned with significantly better coverage and hotter V150 than iodine implants. We consider V150 to be an important parameter for determining dose homogeneity although the clinical utility of dose homogeneity remains unknown. The mean V150 was 45.6 +/- 9.6% volume. There was no additional dosimetric utility from a determination of V90 while D100 was found to be overly sensitive to steep dose gradients at the periphery of the prostate. CONCLUSIONS: This report represents the first detailed postimplant day 0 dosimetric evaluation comparing ABS recommended quality parameters used to evaluate prostate brachytherapy. At the present time, no long-term clinical outcomes are available because of short follow-up. As PSA based follow-up data becomes available, however, this report may help define what represents an adequate implant.