Postimplant dosimetry for (125)I prostate implants: definitions and factors affecting outcome

Analysis of outcomes after non-contour-based dose painting of dominant intra-epithelial lesion in intra-operative low-dose rate brachytherapy

Purpose

To compare the outcomes of patients with intermediate risk prostate cancer (IR-PCa) treated with low-dose rate I-125 seed brachytherapy (LDR-BT) and targeted dose painting of a histologic dominant intra-epithelial lesion (DIL) to those without a DIL.

Methods

455 patients with IR-PCa were treated at a single center with intra-operatively planned LDR-BT, each following the same in-house dose constraints. Patients with a DIL on pathology had hot spots localized to that region but no specific contouring during the procedure.

Results

396 (87%) patients had a DIL. Baseline tumor characteristics and overall prostate dosimetry were similar between patients with and without DIL except the median number of biopsy cores taken: 10 (10–12) vs 12 (10–12) (p = 0.002).

19 (5%) and 18 (5%) of patients with and 1 (2%) and 0 (0%) of those without DIL experienced CTCAE grade 2 and 3 toxicity respectively. Overall, toxicity grade did not significantly correlate with presence of DIL (p = 0.10).

Estimated 7-year freedom from biochemical failure (FFBF) was 84% (95% confidence interval: 79–89) and 70% (54–89) in patients with and without a DIL (log-rank p = 0.315). In DIL patients, cox regression revealed location of DIL (“Base” vs “Apex” HR: 1.03; 1.00–1.06; p = 0.03) and older age (70 vs 60 HR: 1.62; 1.06–2.49; p = 0.03) was associated with poor FFBF.

Conclusions

Targeting DIL through dose painting during intraoperatively planned LDR-BT provided no statistically significant change in FFBF. Patients with DILs in the prostate base had slightly lower FFBF despite DIL boost.

Dosimetric and radiobiological investigation of permanent implant prostate brachytherapy based on Monte Carlo calculations

PURPOSE

Permanent implant prostate brachytherapy plays an important role in prostate cancer treatment, but dose evaluations typically follow the water-based TG-43 formalism, ignoring patient anatomy and interseed attenuation. The purpose of this study is to investigate advanced TG-186 model-based dose calculations via retrospective dosimetric and radiobiological analysis for a new patient cohort.

METHODS AND MATERIALS

A cohort of 155 patients treated with permanent implant prostate brachytherapy from The Ottawa Hospital Cancer Centre is considered. Monte Carlo (MC) dose calculations are performed using tissue-based virtual patient models. Dose-volume histogram (DVH) metrics (target, organs at risk) are extracted from 3D dose distributions and compared with those from calculations under TG-43 assumptions (TG43). Equivalent uniform biologically effective dose and tumor control probability are calculated.

RESULTS

For the target, D₉₀ (V₁₀₀) is 136.7 ± 20.6 Gy (85.8% ± 7.8%) for TG43 and 132.8 ± 20.1 Gy (84.1% ± 8.2%) for MC; D₉₀ is 3.0% ± 1.1% lower for MC than TG43. For organs at risk, MC D_1cc = 104.4 ± 27.4 Gy (TG43: 106.3 ± 28.3 Gy) for rectum and 80.8 ± 29.7 Gy (TG43: 78.4 ± 28.4 Gy) for bladder; D_1cc = 185.9 ± 30.2 Gy (TG43: 191.1 ± 32.0 Gy) for urethra. Equivalent uniform biologically effective dose and tumor control probability are generally lower when evaluated using MC doses. The largest dosimetric and radiobiological discrepancies between TG43 and MC are for patients with intraprostatic calcifications, for whom there are low doses (cold spots) in the vicinity of calcifications within the target, identified with MC but not TG43.

CONCLUSIONS

DVH metrics and radiobiological indices evaluated with TG43 are systematically inaccurate by upward of several percent compared with MC patient-specific models. Mean cohort DVH metrics and their MC:TG43 variances are sensitive to patient cohort and clinical practice, underlining the importance of further retrospective MC studies toward widespread clinical adoption of advanced model-based dose calculations.

Comparison of multiparametric MRI-based and transrectal ultrasound-based preplans with intraoperative ultrasound-based planning for low dose rate interstitial prostate seed implantation

PURPOSE

Transrectal ultrasound images are routinely acquired for low dose rate (LDR) prostate brachytherapy dosimetric preplanning (pTRUS), although diagnostic multiparametric magnetic resonance imaging (mpMRI) may serve this purpose as well. We compared the predictive abilities of TRUS vs MRI relative to intraoperative TRUS (iTRUS) to assess the role of mpMRI in brachytherapy preplanning.

MATERIALS AND METHODS

Retrospective analysis was performed on 32 patients who underwent iTRUS-guided prostate LDR brachytherapy as either mono- or combination therapy. 56.3% had pTRUS-only volume studies and 43.7% had both 3T-mpMRI and pTRUS preplanning. MRI was used for preplanning and its image fusion with iTRUS was also used for intraoperative guidance of seed placement. Differences in gland volume, seed number, and activity and procedure time were examined, as well as the identification of lesions suspicious for tumor foci. Pearson correlation coefficient and Fisher's Z test were used to estimate associations between continuous measures.

RESULTS

There was good correlation of planning volumes between iTRUS and either pTRUS or MRI (r = 0.89, r = 0.77), not impacted by the addition of hormonal therapy (P = 0.65, P = 0.33). Both consistently predicted intraoperative seed number (r = 0.87, r = 0.86). MRI/TRUS fusion did not significantly increase surgical or anesthesia time (P = 0.10, P = 0.46). mpMRI revealed suspicious focal lesions in 11 of 14 cases not visible on pTRUS, that when correlated with histopathology, were incorporated into the plan.

CONCLUSIONS

Relative to pTRUS, MRI yielded reliable preplanning measures, supporting the role of MRI-only LDR treatment planning. mpMRI carries numerous diagnostic, staging and preplanning advantages that facilitate better patient selection and delivery of novel dose escalation and targeted therapy, with no additional surgical or anesthesia time. Prospective studies assessing its impact on treatment planning and delivery can serve to establish mpMRI as the standard of care in LDR prostate brachytherapy planning.

Sliding mode control of a shape memory alloy actuated active flexible needle

In medical interventional procedures such as brachytherapy, biopsy and radio-frequency ablation, precise tracking through the preplanned desired trajectory is very essential. This important requirement is critical due to two major reasons: anatomical obstacle avoidance and accurate targeting for avoiding undesired radioactive dose exposure or damage to neighboring tissue and critical organs. Therefore, a precise control of the needling device in the unstructured environment in the presence of external disturbance is required to achieve accurate target reaching in clinical applications. In this paper, a shape memory alloy actuated active flexible needle controlled by an adaptive sliding mode controller is presented. The trajectory tracking performance of the needle is tested while having its actual movement in an artificial tissue phantom by giving various input reference trajectories such as multi-step and sinusoidal. Performance of the adaptive sliding mode controller is compared with that of the proportional, integral and derivative controller and is proved to be the effective method in the presence of the external disturbances.

A retrospective analysis after low-dose-rate prostate brachytherapy with permanent 125I seed implant: clinical and dosimetric results in 70 patients

Aims and background

To evaluate the biochemical disease-free survival (bDFS) rate after 125I permanent-implant prostate brachytherapy.

Methods

Patients with a diagnosis of prostate adenocarcinoma and adequate PSA follow-up were selected for this retrospective study. Brachytherapy with permanent 125I seeds was performed as monotherapy, with a prescribed dose of 145 Gy to the prostate. Patients were stratified into recurrence risk groups according to the National Comprehensive Cancer Network (NCCN) guidelines. Biochemical failure was defined using the American Society of Therapeutic Radiology and Oncology (ASTRO) guidelines. The post-implant D90 (defined as the minimum dose covering 90% of the prostate) was obtained for each patient. Two cutoff points were used to test the correlation between D90 and bDFS results: 130 Gy and 140 Gy. bDFS was calculated from the implant date to the date of biochemical recurrence. Univariate and multivariate analysis were performed using the SPSS software and included clinical stage, pretreatment PSA, Gleason score (GS), androgen deprivation therapy, D90, and risk groups. In the univariate analysis we used a cutoff point of 5.89 ng/mL for PSA and 5 for GS.

Results

From June 2003 to April 2007, 70 patients were analyzed. The patients' distribution into recurrence risk groups was as follows: 39 patients (56%) in the low-risk group, 23 patients (33%) in the intermediate-risk group, and 8 patients (11%) in the high-risk group. At a median follow-up of 47 months (range, 19–70 months) bDFS was 88.4%, with a global actuarial 5-year bDFS of 86%. Disease-related factors including initial PSA level, GS and risk group were significant predictors of biochemical failure (P = 0.01, P = 0.01, P = 0.006, respectively). In multivariate analysis, risk group (P = 0.005) and GS (P = 0.03) were statistically significant.

Conclusion

Our data are in agreement with those in the literature and, despite the short follow-up, confirm the advantage of brachytherapy for patients at low and intermediate risk of recurrence.

The impact of body mass index on dosimetric quality in low-dose-rate prostate brachytherapy

Purpose

Low-dose-rate (LDR) brachytherapy has been established as an effective and safe treatment option for men with low and intermediate risk prostate cancer. In this retrospective analysis, we sought to study the effect of body mass index (BMI) on post-implant dosimetric quality.

Material and methods

After institutional approval, records of patients with non-metastatic prostate cancer treated in Puerto Rico with LDR brachytherapy during 2008-2013 were reviewed. All patients were implanted with ¹²⁵I seeds to a prescription dose of 145 Gy. Computed tomography (CT) based dosimetry was performed 1 month after implant. Patients with at least 1 year of prostate-specific antigen (PSA) follow-up were included. Factors predictive of adequate D₉₀ coverage (≥ 140 Gy) were compared via the Pearson χ² or Wilcoxon rank-sum test as appropriate.

Results

One-hundred and four patients were included in this study, with 53 (51%) patients having a D₉₀ ≥ 140 Gy. The only factor associated with a dosimetric coverage detriment (D₉₀ < 140 Gy) was BMI ≥ 25 kg/m² (p = 0.03). Prostate volume (p = 0.26), initial PSA (p = 0.236), age (p = 0.49), hormone use (p = 0.93), percent of cores positive (p = 0.95), risk group (p = 0.24), tumor stage (p = 0.66), and Gleason score (p = 0.61) did not predict D₉₀.

Conclusions

In this study we show that BMI is a significant pre-implant predictor of D₉₀ (< 140 Gy vs. ≥ 140 Gy). Although other studies have reported that prostate volume also affects D₉₀, our study did not find this correlation to be statistically significant, likely because all of our patients had a prostate volume < 50 cc. Our study suggests that in patients with higher BMI values, more rigorous peri-implant dosimetric parameters may need to be applied in order to achieve a target D₉₀ > 140 Gy.

Feasibility of Shape Memory Alloy Wire Actuation for an Active Steerable Cannula

Needle insertion is used in many diagnostic and therapeutic percutaneous medical procedures such as brachytherapy, thermal ablations, and breast biopsy. Insufficient accuracy using conventional surgical cannulas motivated researchers to provide actuation forces to the cannula's body for compensating the possible errors of surgeons/physicians. In this study, we present the feasibility of using shape memory alloy (SMA) wires as actuators for an active steerable surgical cannula. A three-dimensional (3D) finite element (FE) model of the active steerable cannula was developed to demonstrate the feasibility of using SMA wires as actuators to bend the surgical cannula. The material characteristics of SMAs were simulated by defining multilinear elastic isothermal stress–strain curves that were generated through a matlab code based on the Brinson model. Rigorous experiments with SMA wires were done to determine the material properties as well as to show the capability of the code to predict a stabilized SMA transformation behavior with sufficient accuracy. In the FE simulation, birth and death method was used to achieve the prestrain condition on SMA wire prior to actuation. This numerical simulation was validated with cannula deflection experiments with developed prototypes of the active cannula. Several design parameters affecting the cannula's deflection such as the cannula's Young's modulus, the SMA's prestrain, and its offset from the neutral axis of the cannula were studied using the FE model. Real-time experiments with different prototypes showed that the quickest response and the maximum deflection were achieved by the cannula with two sections of actuation compared to a single section of actuation. The numerical and experimental studies showed that a highly maneuverable active cannulas can be achieved using the actuation of multiple SMA wires in series.

Dosimetric differences between intraoperative and postoperative plans using Cs-131 in transrectal ultrasound-guided brachytherapy for prostatic carcinoma

The aim of the study was to investigate the differences between intraoperative and postoperative dosimetry for transrectal ultrasound-guided transperineal prostate implants using cesium-131 ((131)Cs). Between 2006 and 2010, 166 patients implanted with (131)Cs had both intraoperative and postoperative dosimetry studies. All cases were monotherapy and doses of 115 were prescribed to the prostate. The dosimetric properties (D90, V150, and V100 for the prostate) of the studies were compared. Two conformity indices were also calculated and compared. Finally, the prostate was automatically sectioned into 6 sectors (anterior and posterior sectors at the base, midgland, and apex) and the intraoperative and postoperative dosimetry was compared in each individual sector. Postoperative dosimetry showed statistically significant changes (p < 0.01) in every dosimetric value except V150. In each significant case, the postoperative plans showed lower dose coverage. The conformity indexes also showed a bimodal frequency distribution with the index indicating poorer dose conformity in the postoperative plans. Sector analysis revealed less dose coverage postoperatively in the base and apex sectors with an increase in dose to the posterior midgland sector. Postoperative dosimetry overall and in specific sectors of the prostate differs significantly from intraoperative planning. Care must be taken during the intraoperative planning stage to ensure complete dose coverage of the prostate with the understanding that the final postoperative dosimetry will show less dose coverage.

On the sensitivity of α/β prediction to dose calculation methodology in prostate brachytherapy

PURPOSE

To study the relationship between the accuracy of the dose calculation in brachytherapy and the estimations of the radiosensitivity parameter, α/β, for prostate cancer.

METHODS AND MATERIALS

In this study, Monte Carlo methods and more specifically the code ALGEBRA was used to produce accurate dose calculations in the case of prostate brachytherapy. Equivalent uniform biologically effective dose was calculated for these dose distributions and was used in an iso-effectiveness relationship with external beam radiation therapy.

RESULTS

By considering different levels of detail in the calculations, the estimation for the α/β parameter varied from 1.9 to 6.3 Gy, compared with a value of 3.0 Gy suggested by the American Association of Physicists in Medicine Task Group 137.

CONCLUSIONS

Large variations of the α/β show the sensitivity of this parameter to dose calculation modality. The use of accurate dose calculation engines is critical for better evaluating the biological outcomes of treatments.

Impact of experience and technical changes on acute urinary and rectal morbidity in low-dose prostate brachytherapy using loose seeds real-time implantation

PURPOSE

To assess the impact of experience and technical changes on morbidity during the first year after permanent prostate brachytherapy.

METHODS AND MATERIALS

From July 2003 to May 2010, 150 patients with prostate cancer underwent low-dose iodine-125 prostate brachytherapy as a monotherapy by the same medical team (one urologist and one radiation oncologist). Patients were divided into three periods: P1 (n = 64), P2 (n = 45), and P3 (n = 41) according to technical changes: use of an automatic stepper from P2, use of a high-frequency ultrasound probe in P3. Urinary toxicity was analyzed according to the incidence of acute urinary retention (AUR), Delta International Prostate Symptom Score (Δ IPSS) defined as IPPS maximal - IPSS at baseline, and proportion of patients with Δ IPSS ≥5 and IPSS total >15. The Radiation Therapy Oncology Group classification was used to evaluate the rectal morbidity.

RESULTS

The incidence of AUR (6% overall) decreased significantly with time: 12.5% (8/64) during P1, 2.2% (1/45) in P2, and 0% in P3 (p = 0.014). Mean Δ IPSS (11.6) remained stable during the three periods. Patients with Δ IPSS ≥5 and IPSS total >15 were 58.7%, 58.1%, and 56.1% for P1, P2, and P3 (p = 0.96), respectively. Grade 1 and 2 proctitis were observed in 15.3% and 9.3% of the patients without any significant difference between the three periods.

CONCLUSION

The incidence of AUR decreased significantly with time. This was probably because of the experience of the practitioner and the use of an automatic stepper that allowed reducing prostatic traumatism. Experience and technical changes did not seem to affect rectal morbidity.

Long-term results of a phase II trial of ultrasound-guided radioactive implantation of the prostate for definitive management of localized adenocarcinoma of the prostate (RTOG 98-05)

PURPOSE

To evaluate the long-term effectiveness of transrectal ultrasound-guided permanent radioactive I125 implantation of the prostate for organ confined adenocarcinoma of the prostate compared with historical data of prostatectomy and external beam radiotherapy within a cooperative group setting.

METHODS AND MATERIALS

Patients accrued to this study had histologically confirmed, locally confined adenocarcinoma of the prostate clinical stage T1b, T1c, or T2a; no nodal or metastatic disease; prostate-specific antigen level of ≤10 ng/ml; and a Gleason score of ≤6. All patients underwent transrectal ultrasound-guided radioactive I125 seed implantation into the prostate. The prescribed dose was 145 Gy to the prostate planning target volume.

RESULTS

A total of 101 patients from 27 institutions were accrued to this protocol; by design, no single institution accrued more than 8 patients. There were 94 eligible patients. The median follow up was 8.1 years (range, 0.1-9.2 years). After 8 years, 8 patients had protocol-defined biochemical (prostate-specific antigen) failure (cumulative incidence, 8.0%); 5 patients had local failure (cumulative incidence, 5.5%); and 1 patient had distant failure (cumulative incidence, 1.1%; this patient also had biochemical failure and died of causes not related to prostate cancer). The 8-year overall survival rate was 88%. At last follow-up, no patient had died of prostate cancer or related toxicities. Three patients had maximum late toxicities of Grade 3, all of which were genitourinary. No Grade 4 or 5 toxicities were observed.

CONCLUSIONS

The long-term results of this clinical trial have demonstrated that this kind of trial can be successfully completed through the RTOG and that results in terms of biochemical failure and toxicity compare very favorably with other brachytherapy published series as well as surgical and external beam radiotherapy series. In addition, the prospective, multicenter design highlights the probable generalizability of the outcomes.

Displacement of periurethral stranded seeds and its dosimetric consequences in prostate brachytherapy

PURPOSE

The use of stranded seeds for prostate brachytherapy has raised concern that displacement of strands, particularly in the periurethral region, may result in inadequate coverage of the prostate. We sought here to evaluate the displacement of periurethral stranded seeds after a prostate brachytherapy implant (Day 0) and its dosimetric consequences 1 month later (Day 30).

METHODS AND MATERIALS

Subjects were 10 consecutive patients who underwent implantation with (125)I stranded seeds via a peripheral-loading technique. Computed tomography scanning was done on Days 0 and 30. Seeds were located and dose distributions calculated with a Variseed 7.2 treatment planning system (Varian Medical Systems). Images were registered by two methods, one using the penile bulb as reference and the other using the pubic bones for verification. Only seeds within the periurethral strands were analyzed.

RESULTS

The mean displacement of periurethral stranded seeds relative to the prostate did not exceed 1mm in any direction. Calculated displacements were not affected by the registration method used. The mean dose covering 90% of the prostate volume (D(90)) and prostate volume receiving 100% of the prescribed dose (V(100)) were 169Gy and 97% on Day 0 and 186.5Gy and 98.7% on Day 30 (p<0.001 for D(90)).

CONCLUSIONS

Displacement of periurethral stranded seeds 30 days after implantation was minimal and did not compromise dosimetric coverage of the prostate.

Brachytherapy for prostate cancer: a systematic review

Low-dose rate brachytherapy has become a mainstream treatment option for men diagnosed with prostate cancer because of excellent long-term treatment outcomes in low-, intermediate-, and high-risk patients. To a great extend due to patient lead advocacy for minimally invasive treatment options, high-quality prostate implants have become widely available in the US, Europe, and Japan. High-dose-rate (HDR) afterloading brachytherapy in the management of localised prostate cancer has practical, physical, and biological advantages over low-dose-rate seed brachytherapy. There are no free live sources used, no risk of source loss, and since the implant is a temporary procedure following discharge no issues with regard to radioprotection use of existing facilities exist. Patients with localized prostate cancer may benefit from high-dose-rate brachytherapy, which may be used alone in certain circumstances or in combination with external-beam radiotherapy in other settings. The purpose of this paper is to present the essentials of brachytherapies techniques along with the most important studies that support their effectiveness in the treatment of prostate cancer.

Critical discussion of different dose-volume parameters for rectum and urethra in prostate brachytherapy

PURPOSE

To compare different dose-volume histogram (DVH) parameter concepts used for rectum and urethra.

METHODS AND MATERIALS

Thirty-eight postplan CT scans were used to contour the rectum with only one outer contour and as a wall structure. DVH analysis included dose to absolute and relative volumes of both contour types, from RD(0.1cc) to RD(10cc) and from RDmax to RD30, respectively. Volume parameters are reported (RV50-RV300) in cubic centimeters and percentages. The analysis of urethral dose parameters was based on 55 CTs with a urethral catheter. Relative (UD100 to UDmax) and absolute volume parameters (UD(0.5cc) to UD(0.1cc), UV100, UV150) were evaluated, and also correlated to prostate parameters. The analysis was repeated for 10 MRI-based interstitial high-dose rate cases.

RESULTS

The correlation between organ and wall results was high for RD1, RD(2cc), and RD(0.1cc), with differences of <5%. DVH parameters reporting dose to a relative volume (e.g., RD10) or a relative volume related to a certain dose (e.g., RV100 [%]) are sensitive to the number of contoured slices. Dmax has a high uncertainty due to the sampling algorithm. RV100 (145Gy) of 1.5cc is similar to an RD(2cc) of 130Gy. The urethral UD10 and UD(0.1cc) correlate with a mean difference of 1%. The ratios of UD5/UD30, UD10/UD30, and UD5/UD10 were 1.12, 1.09, and 1.03, respectively. The correlation between D90 and D10 for prostate to urethra UD10 was poor.

CONCLUSIONS

Only absolute volume parameters are stable in relation to different contouring concepts. When delineating the outer rectum contour, only RD(2cc) and RD(0.1cc) can be used. RV(100) in cc correlates to RD(2cc). Reporting UD5, UD10, and UD30 together is redundant. Additional information is given when reporting UV100 or UV150.

Secondary effects and biochemical control in patients with early prostate cancer treated with (125)-I seeds

OBJECTIVE

To retrospectively evaluate the toxicity of low-dose-rate brachytherapy and to relate it to the dose-volume to organs at risk.

MATERIAL AND METHODS

We study 160 patients with early prostate cancer, treated with (125)-I implants. Most of them were T1c (63.1%), T2a (35.6%) and Gleason < or =6 (96.2%). Median PSA was 7.2 ng/ml (2.3-13.5); 85.6% were lowrisk cases and 14.4% high-risk cases. Mean follow-up was 24 months (7-48).

RESULTS

Acute urinary toxicity related to urological quality of life (UQL=CVU) was tolerable in 75% and unsatisfactory in 25%. Urinary retention was present in 6.9%. IPSS, V100 and D90 were related to the urinary toxicity grade. Rectal toxicity (RTOG) G2 was 0.6%. Sexual potency showed no changes with regard to the basal in 69%. Actuarial biochemical control was 89.8% at four years.

CONCLUSIONS

Brachytherapy with (125)-I seeds yields acceptable toxicity and excellent biochemical control.

[Brachytherapy of the prostate cancer]

Prostate cancer (PCA) is the most frequent onlocological disease in men. Every year there are ca. 202.000 new cases of prostate cancer in Europe. Curative treatment of this carcinoma via brachytherapy is becoming increasingly significant (20-30% of all curative approaches). Initial staging and thus allocation to risk groups prior to the commencement of therapy is esspecially important for successful brachytherapy treatment.Low-dose-rate (LDR) brachytherapy (i.e. SEED implantation) distinguishes itself both with respect to the procedure as well as the indication from high-dose-rate brachytherapy (afterloading procedure). Both treatment procedures are employed as monotherapy as well as in combination with external radiation.LDR monotherapy is reported to achieve biochemically relapse-free outcome of up to 90% in low-risk tumours during 10-year follow-up periods. Combined HDR tele- and brachytherapy is reported to achieve a biochemically relapse-free outcome of 80-90% with intermediate- and high-risk tumours in long-term follow-up.While randomized studies are as yet missing, it is still possible to derive the following application algorithms from monitoring studies and cohort studies: application of LDR monobrachytherapy must be restricted to low-risk tumorus. Combined HDR tele- and brachytherapy can be sucessfully applied in cases of intermediate- and high-risk tumours. The outcome depends significantly on the initial, pre-therapy PSA value and Gleason score. Posttherapeutically, the nadir value is crucial with respect to predicting the biochemically relapse-free outcome.

Permanent prostate seed brachytherapy: a current perspective on the evolution of the technique and its application

This Review highlights current areas of controversy and development in the field of transperineal permanent prostate seed implantation brachytherapy (PPI), in particular the technological evolution of PPI treatment planning that has led to intra-operative treatment planning and execution, the use of MRI spectroscopy and ultrasonography to target intraprostatic tumor foci, and the introduction of (131)Cs as a new PPI isotope. Here we present a comprehensive review of mature data for PPI monotherapy and PPI combined with supplemental external beam radiation therapy, and a critical discussion of issues pertinent to supplemental EBRT. We also present our current policies in the treatment of prostate cancer at the University of California, San Francisco.

Comparison of intraoperative ultrasound with postimplant computed tomography--dosimetric values at Day 1 and Day 30 after prostate brachytherapy

PURPOSE

To compare the results of intraoperative dosimetry with those of postimplant computed tomography (CT)-based dosimetry after (125)I prostate brachytherapy.

METHODS AND MATERIALS

We treated 412 prostate cancer patients with (125)I prostate brachytherapy, with or without external beam radiotherapy at our institution. Neoadjuvant hormone therapy was administered to 331 patients (80.3%). Implantation was performed using an intraoperative interactive technique. Postimplant dosimetry was performed on Day 1 and Day 30 using CT imaging. The dosimetric results for the prostate, urethra, and rectum were compared among intraoperative ultrasound, and CT scans of Day 1 and Day 30.

RESULTS

The mean intraoperative minimal dose received by 90% of the prostate volume (D(90)) was 118.8% of the prescribed dose vs. 106.4% for Day 1 (p < 0.01) and 119.2% for Day 30 (p = 0.25). There were no significant correlations between the intraoperative D(90) and the postimplant D(90) values (intraclass correlation coefficients=0.42 and 0.33 for Day 1 and Day 30, respectively). Prostatic edema at Day 1 had the largest effect on the Day 1 D(90) (p < 0.01). The factor significantly affecting the Day 30 D(90) was neoadjuvant hormone therapy (p < 0.01). The mean Day 30 D(90) for the hormone-treated patients was 117.9%, compared with 124.6% for those who remained hormone naïve. The intraoperative and postimplant dosimetric values differed significantly for the urethra and rectum.

CONCLUSIONS

Our results demonstrate that there are no significant differences between the D(90) assessments obtained intraoperatively and at Day 30 postoperatively. Furthermore, there are no definite correlations between intra- and postimplantation dosimetric values. Other D(90) values differed significantly between the intraoperative and postimplant dosimetry. This study suggests that dosimetry has negligible clinical utility for informing patients, at discharge, of whether or not their implants are adequate.

Modern brachytherapy for treatment of prostate cancer

BACKGROUND

Prostate cancer is the most common cancer diagnosed in men. An increasing number of these patients are seeking minimally invasive procedures such as transperineal interstitial permanent radioactive seed prostate brachytherapy.

METHODS

This paper reviews the historical perspective and the current advances in transperineal interstitial permanent radioactive seed prostate brachytherapy. The 10- to 15-year results data now published for brachytherapy alone or in combination with external-beam irradiation are also reviewed.

RESULTS

Modern brachytherapy using transperineal interstitial permanent radioactive seed prostate brachytherapy offers patients an excellent quality of life with convenient outpatient treatment with long-term (10- to 15-year) biochemical relapse-free survival rates ranging from 67% to 87%, depending on risk stratification.

CONCLUSIONS

Modern-day brachytherapy utilizing either radioactive iodine-125 or palladium-103 alone or in combination with supplemental external-beam treatment offers patients a successful treatment outcome with acceptable toxicity.

Effect of Edema on Postimplant Dosimetry in Prostate Brachytherapy Using CT/MRI Fusion

PURPOSE

To investigate the time course of prostatic edema and the effect on the dose-volume histograms of the prostate for patients treated with brachytherapy.

METHODS AND MATERIALS

A total of 74 patients with prostate cancer were enrolled in this prospective study. A transrectal ultrasound-based preplan was performed 4 weeks before implantation and computed tomography/magnetic resonance imaging fusion-based postimplant dosimetry was performed on the day after implantation (Day 1) and 30 days after implantation (Day 30). The prostate volume, prostate volume covered by 100% of the prescription dose (V100), and dose covering 90% of the prostate (D90) were evaluated with prostatic edema over time.

RESULTS

Prostatic edema was greatest on Day 1, with the mean prostate volume 36% greater than the preplan transrectal ultrasound-based volume; it thereafter decreased over time. It was 9% greater than preplan volume on Day 30. The V(100) increased 5.7% from Day 1 to Day 30, and the D90 increased 13.1% from Day 1 to Day 30. The edema ratio (postplan/preplan) on Day 1 of low-quality implants with a V(100) of <80% was significantly greater than that of intermediate- to high-quality implants (>80% V100; p = 0.0272). The lower V100 on Day 1 showed a greater increase from Day 1 to Day 30. A V100 on Day 1 of >92% is unlikely to increase >0% during the interval studied.

CONCLUSION

Low-quality implants on Day 1 were highly associated with edema; however, such a low-quality implant on Day 1, with significant edema, tended to improve by Day 30. If a high-quality implant (V100 >92%) can be obtained on Day 1, a re-examination is no longer necessary.

Intraoperative real-time planned conformal prostate brachytherapy: Post-implantation dosimetric outcome and clinical implications

PURPOSE

To report the dosimetric outcome of patients with clinically localized prostate cancer treated with I-125 permanent implantation using an intraoperative real-time conformal planning technique.

METHODS AND MATERIALS

Five hundred and sixty-two patients with prostate cancer were treated with I-125 permanent interstitial implantation using a transrectal ultrasound-guided approach. Real-time intraoperative treatment planning software that incorporates inverse planning optimization was used. Dose-volume constraints for this inverse-planning system included: prostate V100 >or=95%, maximal urethral dose <or=120%, and average rectal dose <80% of the prescription dose. Day zero computed tomography scans were acquired for post-implantation dosimetric evaluation.

RESULTS

The median V100 and D90 to the prostate target were 96% and 166 Gy, respectively. In 91% of cases a D90 of >or=140 Gy was achieved. In these patients, the V100 and D90 values did not have a significant influence on PSA relapse-free survival outcomes. The median maximum rectal dose and urethral doses were 104 Gy (72% of the prescription dose) and 187 Gy (130% of the prescription dose). The average and maximum rectal doses exceeding 100% of the prescription dose were less than 1% and 10% of patients, respectively. Average and maximum urethral doses exceeding 150% of the prescription dose were noted in 3% and 24% of patients, respectively. Average and maximum urethral doses exceeded 120% of the prescription dose in 21% and 58% of patients, respectively. Among patients where >or=2.5 cm(3) of the rectum was exposed to the prescription dose, the incidence of late grade 2 toxicity rectal toxicity was 9% compared to 4% for smaller volumes of the rectum exposed to similar doses (p=0.003). No dosimetric parameter in these patients with tight dose confines for the urethra influenced acute or late urinary toxicity.

CONCLUSION

Real-time intraoperative planning was associated with a 90% consistency of achieving the planned intraoperative dose constraints for target coverage and maintaining planned urethral and rectal constraints in a high percentage of implants. Rectal volumes of >or=2.5 cm(3) exposed to the prescription doses were associated with an increased incidence of grade 2 rectal bleeding. Further enhancements in imaging guidance for optimal seed deposition are needed to guarantee optimal dose distribution for all patients. Whether such improvements lead to further reduction in acute and late morbidities associated with therapy requires further study.

Dosimetry of an Extracapsular Anulus Following Permanent Prostate Brachytherapy

PURPOSE

Recent studies have suggested that extracapsular brachytherapy treatment margins correlate with biochemical control. It is likely that volumetric geographic dosimetric parameters will be more robust than selected radial measurements. Accordingly, we evaluated extracapsular volumetric dosimetric parameters in low-risk patients.

MATERIALS AND METHODS

A total of 263 low-risk prostate cancer patients randomized to Pd-103 versus I-125 were implanted with a brachytherapy target volume consisting of the prostate with a 5-mm periprostatic margin. The median follow-up was 4.2 years. All patients were implanted at least 3 years prior to analysis. Within 2 hours of implantation, an axial CT was obtained for postimplant dosimetry. A 5-mm three-dimensional periprostatic anulus was constructed around the prostate and evaluated in its entirety and in 90 degrees segments. Prostate and anular dosimetric parameters consisted of V100/V150/V200 and D90. Biochemical progression-free survival (bPFS) was defined as a PSA < or =0.50 ng/mL after nadir.

RESULTS

The Pd-103 and I-125 arms were well-matched in terms of clinical, biochemical, and pathologic presentation. Six-year bPFS was 96.8% versus 99.2% for I-125 versus Pd-103 (P = 0.149). The most recent median posttreatment PSA was <0.04 ng/mL for both isotopes. No significant differences in postoperative anular doses were discerned between bPFS and failed patients.

CONCLUSIONS

A postimplant 5-mm, three-dimensional periprostatic anulus provides substantial information regarding dosimetric coverage. However, with a median follow-up of 4.2 years, such volumetric and geographic parameters have not proven useful in predicting biochemical outcome in low-risk patients.

Tumour and target volumes in permanent prostate brachytherapy: A supplement to the ESTRO/EAU/EORTC recommendations on prostate brachytherapy

The aim of this paper is to supplement the GEC/ESTRO/EAU recommendations for permanent seed implantations in prostate cancer to develop consistency in target and volume definition for permanent seed prostate brachytherapy. Recommendations on target and organ at risk (OAR) definitions and dosimetry parameters to be reported on post implant planning are given.

The Effect of Brachytherapy, External Beam Irradiation and Hormonal Therapy on Prostate Volume

PURPOSE

We describe the effects of prostate brachytherapy with or without hormonal therapy, or external beam irradiation on gland volume.

MATERIALS AND METHODS

A total of 600 men with localized prostate cancer underwent 125I (357), 103Pd (118) or partial 103Pd combined with external beam irradiation (125) brachytherapy. Of the 600 men 299 (49.8%) received 3 to 9 months of hormonal therapy, which was initiated 3 months before implantation. Hormonal therapy consisted of luteinizing hormone-releasing hormone agonist plus antiandrogen in 251, luteinizing hormone-releasing hormone agonist in 41 and flutamide plus finasteride in 7. Prostate volume measurements were made before the initiation of hormonal therapy, at implantation and yearly. Median followup was 5.2 years. Associations were tested by chi-square analysis. Means were compared by 1-way ANOVA and the Student t test.

RESULTS

Median initial prostate volume was 38.5 cc (range 9.2 to 151.5). Pre-implantation hormonal therapy resulted in a median prostate volume decrease of 33.1%. The mean reduction for luteinizing hormone-releasing hormone agonist was 27.6%, for luteinizing hormone-releasing hormone agonist plus antiandrogen it was 32.8% and for flutamide plus finasteride it was 10.8% (p=0.003). Prostate volume decreased 36.6% by year 1, 42.4% by year 4, 45.6% by year 6 and 51.2% by year 8 (p<0.0001). There was no difference in prostate volume reduction at year 1 between men receiving hormonal therapy vs implantation alone. Patients treated with 103Pd had a greater prostate volume reduction at 1 year than those who received 125I (p=0.004). Conversely patients treated with hormonal therapy and 125I had a smaller prostate volume reduction than those implanted with 125I alone (p=0.023). After year 1 there were no longer differences between any groups.

CONCLUSIONS

Luteinizing hormone-releasing hormone agonist plus antiandrogen is more successful for reducing prostate volume before prostate brachytherapy than luteinizing hormone-releasing hormone agonist or flutamide plus finasteride. Hormonal therapy offered no advantage over implantation alone for post-implantation prostate volume reduction. 103Pd appears to reduce prostate volume more rapidly than 125I but this advantage is lost by year 2. No rebound in prostate volume was noted at longer followup.

Long-Term Urinary, Sexual, and Rectal Morbidity in Patients Treated with Iodine-125 Prostate Brachytherapy Followed Up for a Minimum of 5 Years

OBJECTIVES

To define the long-term morbidity in patients with prostate cancer who underwent iodine-125 brachytherapy.

METHODS

A total of 325 men with localized prostate cancer treated with iodine-125 brachytherapy had a median follow-up of 7 years (range 5 to 15). The American Urological Association symptom score, erectile function status, rectal bleeding incidence, and presence of urinary incontinence were collected prospectively before implantation and every 6 months thereafter. Comparisons were made between the pretreatment and treatment-related factors and their associations with quality-of-life changes. Associations were tested using the Student t, chi-square, and Wilcoxon signed rank tests.

RESULTS

The median prostate volume and maximal dose to 90% of the prostate was 36.6 cm3 and 167 Gy, respectively. Of the 325 men, 15.7% experienced prostate-specific antigen failure and 4% started androgen deprivation therapy. The mean total symptom and bother scores increased from baseline (P <0.001) to 6 months after implantation, steadily decreased, and were unchanged at the last follow-up visit (P = 0.6). There were no significant associations among patient age, race, hormonal therapy use, prostate size, radiation dose, and urinary morbidity. Incontinence occurred in 4 (1.2%) of the 325 patients at the last follow-up visit and was associated with transurethral resection of the prostate (odds ratio 8.8, 95% confidence interval 1.3 to 62, P = 0.008). Before implantation, 77.2% were able to have an erection adequate for intercourse and 50.6% were able to at the last follow-up visit. A significant correlation was found between potency preservation and age (P <0.001). Rectal bleeding occurred in 78 men (24%) 1 to 3 years after implantation. Nine patients (2.8%) complained of minor bleeding beyond 5 years, which was associated with greater radiation doses (P = 0.023).

CONCLUSIONS

The preservation of urinary, sexual, and rectal quality of life is excellent at long follow-up for patients implanted with iodine-125.

Magnetic resonance imaging compatible robotic system for fully automated brachytherapy seed placement

OBJECTIVES

To introduce the development of the first magnetic resonance imaging (MRI)-compatible robotic system capable of automated brachytherapy seed placement.

METHODS

An MRI-compatible robotic system was conceptualized and manufactured. The entire robot was built of nonmagnetic and dielectric materials. The key technology of the system is a unique pneumatic motor that was specifically developed for this application. Various preclinical experiments were performed to test the robot for precision and imager compatibility.

RESULTS

The robot was fully operational within all closed-bore MRI scanners. Compatibility tests in scanners of up to 7 Tesla field intensity showed no interference of the robot with the imager. Precision tests in tissue mockups yielded a mean seed placement error of 0.72 +/- 0.36 mm.

CONCLUSIONS

The robotic system is fully MRI compatible. The new technology allows for automated and highly accurate operation within MRI scanners and does not deteriorate the MRI quality. We believe that this robot may become a useful instrument for image-guided prostate interventions.

Five-year outcome of intraoperative conformal permanent I-125 interstitial implantation for patients with clinically localized prostate cancer

PURPOSE

To report the 5-year tumor control and toxicity outcomes for patients with localized prostate treated with I-125 permanent implantation using an intraoperative real-time conformal planning technique.

METHODS AND MATERIALS

Between January 1998 and June 2002, 367 patients with prostate cancer were treated with I-125 permanent interstitial implantation using a transrectal ultrasound-guided approach. Real-time intraoperative treatment planning which incorporated inverse planning optimization was used. The median follow-up time was 63 months.

RESULTS

The median V100 and D90 were 96% and 173 Gy, respectively. In 96% of cases a D90 of >140 Gy was achieved. The median urethral and rectal doses were 100% and 33% of the prescription doses, respectively. The 5-year PSA relapse-free survival outcomes for favorable and intermediate risk patients according to the ASTRO definition were 96% and 89%, respectively. In these patients no dosimetric parameter was identified which influenced the biochemical outcome. Of 38% who developed acute Grade 2 urinary symptoms, 63% had resolution of their symptoms within a median time of 6 months. The incidence of late rectal and urinary Grade 3 or higher toxicities were 1% and 4%, respectively. Seven percent (n = 27) developed late rectal bleeding (Grade 2) and 19% experienced late Grade 2 urinary symptoms.

CONCLUSION

Real-time intraoperative planning consistently achieved optimal coverage of the prostate with the prescription dose with concomitant low doses delivered to the urethra and rectum. Biochemical control outcomes were excellent at 5 years and late toxicity was unusual. These data demonstrate that real-time planning methods can consistently and reliably deliver the intended dose distribution to achieve an optimal therapeutic ratio between the target and normal tissue structures.

Results of a phase II trial of transrectal ultrasound-guided permanent radioactive implantation of the prostate for definitive management of localized adenocarcinoma of the prostate (Radiation Therapy Oncology Group 98-05)

PURPOSE

To evaluate the effectiveness of transrectal ultrasound-guided permanent radioactive (125)I implantation of the prostate for organ-confined adenocarcinoma of the prostate compared with historical data of prostatectomy and external beam radiotherapy within a cooperative group setting.

METHODS AND MATERIALS

Patients accrued to this study had histologically confirmed, locally confined, adenocarcinoma of the prostate with clinical Stage T1b, T1c, or T2a, no nodal or metastatic disease, prostate-specific antigen level of < or =10 ng/mL, and Gleason score of < or =6. All patients underwent transrectal ultrasound-guided radioactive (125)I permanent seed implantation into the prostate. The prescribed dose was 145 Gy to the prostate planning target volume.

RESULTS

A total of 27 institutions accrued a total of 101 patients to this protocol, with no institution accruing >8 patients. Six patients were ineligible, leaving 95 properly entered as eligible in the study. The median follow-up was 5.3 years (range, 0.4-6.5 years). At 5 years, 5 patients had local failure, 1 had evidence of distant failure, and 6 (6%) had biochemical failure. The overall survival rate at 5 years was 96.7%. At last follow-up, no patient had died of prostate cancer or related toxicities. Eight patients had a maximal acute toxicity level of 3, and no patient had Grade 4 or 5 acute toxicity. During follow-up, 2 patients had maximal Grade 3 toxicity, both related to bladder issues, and no patient experienced Grade 4 or 5 toxicity.

CONCLUSION

The results of this clinical protocol (a multi-institutional trial of brachytherapy for localized adenocarcinoma of the prostate) have demonstrated that this type of trial can be successfully completed through the Radiation Therapy Oncology Group. Biochemical disease-free survival was comparable with other brachytherapy published series and with the results after surgery and external beam radiotherapy.

Urinary symptom flare after brachytherapy for prostate cancer is associated with erectile dysfunction and more urinary symptoms before implantation

OBJECTIVE

To examine the relationship of 'symptom flare' with sexual function and lower urinary tract symptoms (LUTS) before brachytherapy, as we noted that after brachytherapy for prostate cancer, some patients had recurrent LUTS after an asymptomatic period; this secondary exacerbation of symptoms ('symptom flare') occurred at approximately 2 years after implantation and was transient in most patients.

PATIENTS AND METHODS

In all, 854 patients with organ-confined prostate carcinoma had transrectal ultrasonography-guided transperineal 125I interstitial brachytherapy of the prostate gland between June 1991 and September 2002, and were considered candidates for this study. Detailed information on urinary function was self-administered and prospectively collected before treatment and at intervals using the International Prostate Symptom Score (IPSS). Sexual function was evaluated with the Sexual Health Inventory for Men (SHIM), a five-question, self-administered diagnostic test that can help to indicate the presence or absence of erectile dysfunction (ED). We used previously established criteria to estimate the risk of prostate-specific antigen (PSA) failure by dividing the men into three risk groups, i.e. low-risk, with a PSA level of < or = 10 ng/mL, stage < or = T2a, Gleason < or = 6; medium-risk, with a PSA level of < or = 15 ng/mL, Gleason 7 or stage T2b; and high-risk, with a PSA level of > 15 ng/mL, stage > T2b, or Gleason > or = 8.

RESULTS

There was a significant association of flare with ED; men with flare reported significantly more ED than men without (P = 0.020). Men with high-risk disease reported more ED because they received more intensive treatment (hormones and increased radiation dose) than men with medium- or low-risk disease. To correct for this confounding factor, multivariate linear regression was used; the regression was significant overall (P < 0.001), and the effects of risk group (P < 0.001) and flare (P < 0.026) on SHIM score were significant and independent of each other. Flare was also significantly associated with a higher pre-implant IPSS; the probability of flare was 62% for a pre-implant IPSS of zero, to 94% for an IPSS of 30.

CONCLUSIONS

Radiation reaction and radiation sensitivity contribute to ED and greater LUTS in men who have had brachytherapy for prostate cancer. This contribution is evident, e.g. in men with ataxia-telangiectasia (ATM) gene mutations. Sequence variants in the ATM gene, particularly those that encode for an amino-acid substitution, are associated with adverse radiotherapy responses among patients treated with 125I prostate brachytherapy. Our finding of the association of urinary symptom flare with ED suggests it would be worthwhile to determine whether sildenafil is as effective in men with flare, and if not, whether higher sildenafil doses would be of value. Alternatively, alpha1-selective adrenoceptor-blocking agents, e.g. terazosin, combined with sildenafil, might be of benefit. Also, patients with a high IPSS before brachytherapy can be warned that they have a greater risk of flare and ED.