Comparison between two iodine-125 brachytherapy implant techniques: pre-planning and intra-operative by various dosimetry quality indicators

Acute and late side-effects after low dose-rate brachytherapy for prostate cancer; incidence, management and technical considerations

PURPOSE

To review common reported side effects and complications after primary LDR-BT (monotherapy) and discuss some of the technical aspects that could impact the treatment outcomes.

METHODS AND MATERIALS

A literature search was undertaken using medical subject headings (MeSH) complemented by the authors' personal and institutional expertise.

RESULTS

The reported incidence of acute and late grade 2 or above urinary, bowel and sexual side effects is very variable across the literature. The learning curve and the implant quality have a clear impact on the toxicity outcomes. Being aware of some of the technical challenges encountered during the procedure and ways to mitigate them could decrease the incidence of side effects. Careful planning of seed placement and seed deposition allow sparing of the organs at risk and a lower incidence of urinary and gastro-intestinal toxicity.

CONCLUSIONS

Low dose-rate brachytherapy remains a standard monotherapy treatment in the setting of favorable-risk prostate cancer. High disease control and low long-term toxicities are achievable in expert hands with a good technique.

Comparison of three different techniques of low-dose-rate seed implantation for prostate cancer

Purpose

Three different techniques of low-dose-rate seed implantation for prostate cancer have been used since its use started in our hospital. The purpose of this study was to compare the results of the three different techniques.

Material and methods

The data of 305 prostate cancer patients who underwent low-dose-rate seed implantation were retrospectively analyzed. Pre-plan technique (n = 27), intraoperative pre-plan technique (n = 86), and interactive plan technique (n = 192) were tried in chronological order. The prescribed dose was set at 145 Gy.

Results

Median follow-up was 66 months (range: 12-94 months). The 5-year biochemical control rate was 95.5% (pre-plan group: 100%, intraoperative pre-plan group: 90.7%, interactive plan group: 97.0%; p = 0.08). Dosimetric parameters were generally increased from the pre-plan group to the interactive group. The differences in some dosimetric parameters between the planning phase and the CT analysis were significantly reduced with the interactive plan compared to the other techniques. The interactive plan showed a significant reduction of the seed migration rate compared to the two other groups. Acute genitourinary toxicity, acute gastrointestinal toxicity, frequency, and urinary retention increased gradually from the pre-plan period to the interactive plan period.

Conclusions

There was no significant difference in biochemical control among the three groups. Dose-volume parameters were increased from the pre-plan technique to the interactive plan technique. However, this may not necessarily be due to technical improvements, since dose escalation was started during the same period. Lower seed migration rates and the smaller differences between the planning phase and CT analysis with the interactive plan technique suggest the superiority of this technique to the two other techniques.

Comparison between preoperative and real-time intraoperative planning ¹²⁵I permanent prostate brachytherapy: long-term clinical biochemical outcome

Background

The purpose of the study is to evaluate the long-term clinical outcome through biochemical no evidence of disease (bNED) rates among men with low to intermediate risk prostate cancer treated with two different brachytherapy implant techniques: preoperative planning (PP) and real-time planning (IoP).

Methods

From June 1998 to July 2011, 1176 men with median age of 67 years and median follow-up of 47 months underwent transperineal ultrasound-guided prostate ¹²⁵I-brachytherapy using either PP (132) or IoP (1044) for clinical T1c-T2b prostate adenocarcinoma Gleason <8 and prostate-specific antigen (PSA) <20 ng/ml. Men with Gleason 7 received combination of brachytherapy, external beam radiation and 6-month androgen deprivation therapy (ADT). Biological effective dose (BED) was calculated using computerized tomography (CT)-based dosimetry 1-month postimplant. Failure was determined according to the Phoenix definition.

Results

The 5- and 7-year actuarial bNED rate was 95% and 90% respectively. The 7-year actuarial bNED was 67% for the PP group and 95% for the IoP group (P < 0.001). Multivariate Cox regression analyses identified implant technique or BED, ADT and PSA as independent prognostic factors for biochemical failure.

Conclusions

Following our previous published results addressing the limited and disappointing outcomes of PP method when compared to IoP based on CT dosimetry and PSA kinetics, we now confirm the long-term clinical, bNED rates clear cut superiority of IoP implant methodology.

Re-implantation of suboptimal prostate seed implantation: technique with intraoperative treatment planning

Purpose

Post-implant dosimetry following prostate seed implantation (PSI) occasionally reveals suboptimal dosimetric coverage of the gland. Published reports of re-implantation techniques have focused on earlier-generation techniques, including preplanned approaches and stranded seeds. The purpose of this case report is to describe a customizable approach to perform corrective re-implantation using loose seeds and intraoperative planning technique.

Material and methods

This case report describes a 63-year-old male with favorable risk prostate adenocarcinoma receiving PSI. Thirty day post-implant dosimetric evaluation revealed suboptimal coverage of the base of the gland. Using guidance from post-implant CT-images and real-time planning, the patient received a corrective re-implantation with intraoperative planning.

Results

Post-implant dosimetry after re-implantation procedure with intraoperative planning yielded improved target volume coverage that achieved standard dosimetric criteria.

Conclusions

Re-implantation as a salvage treatment technique after sub-optimal PSI is a valid treatment option performed with intraoperative real-time planning.

Progressive transition from pre-planned to intraoperative optimizing seed implant: post implementation analysis

Purpose

To perform a dosimetric comparison between a pre-planned technique and a pre-plan based intraoperative technique in prostate cancer patients treated with I-125 permanent seed implantation.

Material and methods

Thirty patients were treated with I-125 permanent seed implantation using TRUS guidance. The first 15 of these patients (Arm A) were treated with a pre-planned technique using ultrasound images acquired prior to seed implantation. To evaluate the reproducibility of the prostate volume, ultrasound images were also acquired during the procedure in the operating room (OR). A surface registration was applied to determine the 6D offset between different image sets in arm A. The remaining 15 patients (Arm B) were planned by putting the pre-plan on the intraoperative ultrasound image and then re-optimizing the seed locations with minimal changes to the pre-plan needle locations. Post implant dosimetric analyses included comparisons of V₁₀₀(prostate), D₉₀(prostate) and V₁₀₀(rectum).

Results

In Arm A, the 6D offsets between the two image sets were θ_x=−1.4±4.3; θ_y=−1.7±2.6; θ_z=−0.5±2.6; X=0.5±1.8 mm; Y=−1.3±−3.5 mm; Z=−1.6±2.2 mm. These differences alone degraded V₁₀₀ by 6.4% and D₉₀ by 9.3% in the pre-plan, respectively. Comparing Arm A with Arm B, the pre-plan based intraoperative optimization of seed locations used in the plans for patients in Arm B improved the V₁₀₀ and D₉₀ in their post-implant studies by 4.0% and 5.7%, respectively. This was achieved without significantly increasing the rectal dose (V₁₀₀(rectum)).

Conclusions

We have progressively moved prostate seed implantation from a pre-planned technique to a pre-plan based intraoperative technique. In addition to reserving the advantage of cost-effective seed ordering and efficient OR implantation, our intraoperative technique demonstrates increased accuracy and precision compared to the pre-planned technique.

Comparison of preplanning and intraoperative planning for I-125 prostate brachytherapy

OBJECTIVE

To compare two widely used permanent prostate brachytherapy techniques, preplanning and intraoperative planning, based on postimplant dosimetry, toxicity and biochemical outcomes.

METHODS

Between 2003 and 2006, 665 men with localized prostate cancer were treated with permanent interstitial implantation. The first 227 consecutive men were treated with the preplanning technique, followed by 438 men treated with the intraoperative technique. Late toxicity was scored by the Common Terminology Criteria for Adverse Events v.4.0. Biochemical failure was defined as a prostate-specific antigen increase of more than 2 ng/ml above the nadir value excluding a benign bounce. Univariate and multivariate analyses were performed to identify the variables associated with biochemical failure-free survival.

RESULTS

Postimplant target coverage was similar in the two groups, with a small difference in risk organ doses. Mean V100 was 96.3 vs. 96.7% (P = 0.205), D90 was 119.6 vs. 119.4% (P = 0.884), urethral D10 was 157.5 vs. 146.1% (P = 0.010), rectal V100 was 0.57 vs. 0.43 cc (P = 0.002) in the preplanning and intraoperative planning groups, respectively. Acute and late Grade 3 genitourinary and gastrointestinal toxicities were <1% for both methods. The 5-year biochemical failure-free survival rate was 95.4% for the preplanning and 94.0% for the intraoperative planning group (P = 0.776). Multivariate analysis revealed Gleason score, biopsy positive rate and V100 to be predictors of biochemical failure-free survival, while the planning technique was not significant.

CONCLUSION

This large-scale analysis of high-quality implants revealed similar postimplant dosimetry, toxicity profiles and biochemical failure-free survival for the preplanning and intraoperative planning methods.

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.

Long-term experience with 181 patients who received transperineal I-125 implants for prostate cancer: Efficacy and urinary toxicity

Background: In low-risk prostate cancer, the target volume for radiotherapy is the prostate gland only and prostate brachytherapy with an I-125 implant provides the most conformal radiotherapy.

Methods: Patients underwent a pre-implant prostate volume study from which a treatment plan was developed 2 weeks prior to implant. A dosimetric study was performed 1 month following the implant. The prescription dose was 145 Gy with the 95% isodose line covering the entire target volume. The maximal dose to the urethra was less than 210 Gy. Follow-up included serum PSA and IPSS evaluation every 3 months during the first year and then every 6 months beginning in the second year.

Results: During December 2000–March 2009, 181 patients with early prostate cancer underwent I-125 implant. The median post-implant PSA value of the entire cohort was 0.7 ng/ml. No patient developed clinical failure. In the follow-up, nine patients had biochemical failure according to the RTOG-ASTRO Phoenix definition (Nadir + 2.0 ng/ml). Of these, one patient refused hormonal therapy desiring to preserve sexual potency, and eight patients received hormonal therapy with a decreased serum PSA to 0.0 ng/ml. The treatment side effects were primarily urinary disturbances.

Conclusion: An I-125 implant is an effective and well-tolerated treatment and should be recommended for patients with low-risk prostate cancer.

An intraoperative real-time sleeved seed technique for permanent prostate brachytherapy

PURPOSE

To describe a novel technique that integrates customized sleeved seed production to reduce seed migration using preloaded needles with real-time intraoperative dosimetric planning for patients treated with iodine-125 (I-125) permanent prostate seed implants.

METHODS AND MATERIALS

Customized seed-spacer sequences were calculated for patients in real time based on an intraoperative transrectal ultrasound-guided volume study. Using a Fox Chase Cancer Center modified Best Iodine-125 seed loader (Best Medical, Springfield, VA), the seeds and spacers were inserted into a hollow suture material (sleeve) and then loaded into the implant needles. Needles were placed sequentially under transrectal ultrasound guidance with sagittal plane visualization of the dropped sleeved seeds.

RESULTS

This technique was successfully implemented allowing intraoperative planning to be combined with real-time sleeved seed production.

CONCLUSIONS

The use of sleeves for seeds combined with real-time intraoperative planning allowed for the intraoperative customization of implants with the practical advantages of linked seeds.

Detection of prostate specific transcripts in the peripheral blood during brachytherapy predicts postoperative PSA kinetics

BACKGROUND

We evaluated whether detection of prostate-specific antigen (PSA) and human kallikrein 2 (hK2) transcripts in the peripheral blood during brachytherapy could predict biochemical outcome.

METHODS

Eighty-one patients who underwent (125)Iodine-based brachytherapy for localized prostate cancer (Gleason score <8, PSA <20 ng/ml, stage <T3), participated in the study. Brachytherapy was given to 35 patients as monotherapy, to 36 in combination with androgen deprivation therapy (ADT), and to 10 in combination with external beam radiation and ADT. Blood samples from 80 patients were available for analysis. Nested RT-PCR means was used to detect mRNA expression of PSA and hK2 in the peripheral blood. Their expression was analyzed before, during and 1 month after brachytherapy. Patients' biochemical outcome (blood PSA levels) during 3 years of follow-up was correlated with the PCR results.

RESULTS

The incidence of PSA and hK2 mRNA expression in the peripheral blood was significantly higher during than before or after the procedure. Patients with concurrent positive PSA and hK2 PCR results during brachytherapy had higher postoperative blood PSA values and a slower decline rate of PSA compared with patients with negative PSA and hK2 PCR results. No correlations were found between pre- and postbrachytherapy PCR results and biochemical outcome. ADT was the only significant factor that affected PSA and hK2 mRNA expression during brachytherapy.

CONCLUSIONS

Our short-term results suggest that detection of PSA and hK2 transcripts in the peripheral blood of prostate cancer patients during brachytherapy could serve as a predictor of biochemical outcome.

Preimplant Predictive Factors of Urinary Retention After Iodine 125 Prostate Brachytherapy

OBJECTIVES

To assess the rate and predictive factors of urinary retention after iodine 125 brachytherapy for localized prostate cancer.

METHODS

Between 1998 and 2006, 655 patients with localized prostate cancer (T1-2, Gleason score 7 or less) were treated with brachytherapy at our institution. 42% received neoadjuvant hormonotherapy for prostate downsizing or when brachytherapy was combined with external beam radiation (10%). They underwent real-time interactive implantation (79%) or a preplanned technique (21%). Clinical, treatment-related and dosimetric factors were evaluated for catheterization requirement because of urinary retention. All patients received alpha1-blockers before and throughout at least 30 days posttreatment.

RESULTS

Twenty-one (3.2%) patients required catheterization because of urinary retention. Median time to retention onset was 1 day postimplantation. Univariate and multivariate analyses demonstrated that preimplant ultrasound (US)-based prostate volume and preimplant international prostate symptom scores (IPSS) were significant independent predictive factors for urinary retention (odds ratio [OR] = 6.8 and 3.1, 95% CI = 2.3-11.4 and 0.2-5.9, P = 0.02 and P = 0.03, respectively). Eight catheterized patients were successfully relieved from their catheter by nonsurgical means and 13 underwent minimal (channeling) transurethral resection of the prostate (TUR-P) not earlier than 6 months postimplant. Mean volume of resected prostate tissue was 9.9 mL (range 4.5-15). The perioperative and postoperative courses were uneventful. There was no TUR-P-related incontinence.

CONCLUSIONS

Catheterization for acute urinary retention after brachytherapy is an uncommon event. Our data suggest that preimplant US-based prostate volume and IPSS are the strongest predictors for catheterization. Catheterized patients who are refractory to medical therapy can safely undergo a minimal TUR-P.

Techniques, indications et résultats de la curiethérapie interstitielle par implants permanents dans le cancer localisé de la prostate

Permanent seed brachytherapy as a monotherapy is an appropriate treatment in patients with low risk localized prostate cancer such as intraprostatic cancer, T1-2 stage, PSA less than 10 ng/mL, low tumour volume, well differentiated cancer (Gleason score less than 7), gland size less than 50 mL, no micturition symptoms that could decompensate after implantation. A brachytherapy program needs a specialized multidisciplinary team with the collaboration of urologists, radiotherapists (authorized person to manipulate radioactive elements), and physicists. The 10-year oncologic and morbidity results have been published in the literature and are comparable to those of other standard treatments of localized prostate cancer such as radical prostatectomy and external beam radiation therapy.

Clinical-oriented collaboration over the Web during interventional radiology procedures

Multidisciplinary collaboration is a key requirement in several contemporary interventional radiology procedures (IRPs). We proposed a hybrid system (NetAngio) to enable "on the fly" heterogeneous collaboration to support IRP providing intraoperating essential services, and investigate its feasibility and effectiveness in a referral medical center. We have developed a Web-based, cost-effective structure, able to support real-time mentoring, image manipulation, and education services beyond the boundaries of the single institution and potentially allow sub specialists to participate in opinion and decision making in more complex cases. Supported services based on a Motion Joint Photographic Experts Group (MJPEG) coder/decoder (CODEC) can be easily accessible by authorized collaborators, within a user-friendly interface by using a typical Web-browser. Ten interventional radiologists, two vascular surgeons and two medical physicists participated in 33 "fully collaborative" cases during a 13-month period from January 2004 to February 2005. In addition, fifteen 90-minute open seminars and finally, 75 expert's module activations, and 255 learner's module activations were performed during the evaluation period. Collaborative procedures are able to enhance outcomes performance especially in more complex cases where the simultaneous presence of a remote expert interventionist and a medical physicist or a surgeon is required. Further research is needed to promote integration of additional data sources and services.

Dosimetric comparison of interactive planned and dynamic dose calculated prostate seed brachytherapy

PURPOSE

To compare the dosimetrical results of an interactive planning procedure and a procedure based on dynamic dose calculation for permanent prostate brachytherapy.

MATERIALS AND METHODS

Between 6/2000 and 11/2005, 510 patients underwent (125)I implants for T1-T2 prostate cancer. Before 4/2003, 187 patients were treated using an interactive technique that included needle updating. After that period, 323 patients were treated with a more refined dynamic technique that included constant updating of the deposited seed position. The comparison is based on postimplant dose - volume parameters such as the V(100) and d(90) for the target, V(100)(r) for the rectum and d(10)(u) for the urethra. Furthermore, the target volume ratios (TVR identical with V(100)(body)/V(100)), and the homogeneity indices (HI identical with [V(100)-V(150)]/V(100)) were calculated as additional quality parameters.

RESULTS

The dose outside the target volume was significantly reduced, the V(100)(r) decreased from 1.4 cm(3) for the interactive technique to 0.6 cm(3) for the dynamic technique. Similarly the mean TVR reduced from 1.66 to 1.44. In addition, the mean V(100) increased from 92% for the interactive procedure to 95% for the dynamic procedure. More importantly, the percentage of patients with a V(100) < 80% reduced from 5% to 1%. A slight decline was observed with regard to the d(10)(u) (136% vs. 140%) and the HI (0.58 vs. 0.51).

CONCLUSION

The dynamic implant procedure resulted in improved implants. Almost ideal dose coverage was achieved, while minimizing the dose outside the prostate.

Combination therapy-permanent interstitial brachytherapy and external beam radiotherapy for patients with localized prostate cancer

BACKGROUND

Combination of permanent interstitial brachytherapy based on radioactive iodine with external beam radiotherapy is an alternative to other treatment modalities, such as radical prostatectomy or external beam radiotherapy alone in patients with intermediate-risk localized prostate cancer. In this article we report our experience with this combination modality.

METHODS

Among patients who were treated in our institute with brachytherapy, there were 64 patients who received combination therapy for the above indication. Combination therapy enables administration of 110 Gy as brachytherapy and thereafter 45 Gy as external beam radiation. All patients received adjuvant androgen deprivation therapy for 6 months. The prospective follow-up was done with the aid of validated evaluation instruments (questionnaires).

RESULTS

Combination therapy was administered without additional urinary (IPSS-based) or sexual (IIEF-based) side effects above those with brachytherapy alone. No severe perianal and lower intestinal tract side effects were observed. Short-to-moderate-term results based on serum PSA levels are encouraging, and are not inferior to what is accepted by the literature for other radical therapies.

CONCLUSION

Combination of permanent interstitial brachytherapy and external beam radiotherapy in the appropriate patients does not cause any additional morbidity, and its biochemical results justify its application. This modality should be offered as an accepted and good alternative to other radical treatment options, to men with prostate cancer with moderate risk factors.

Permanent prostate brachytherapy: a century of technical evolution

PURPOSE

To summarise the practical aspects of the development of techniques of interstitial permanent prostate brachytherapy (PPB) implantation. Prostate brachytherapy dates back to Pasteau's publication in 1913 describing the insertion of a radium capsule into the prostatic urethra to treat carcinoma of the prostate. Various implantation methods were employed but with unsatisfactory results until the development of the transrectal ultrasound in the 1980s. The subsequent two-stage Seattle technique allowed for a planned homogenous distribution of radioactive sources throughout the gland resulting in biochemical control comparable to surgical and external beam radiotherapy series. With the advent of advanced computer software and improved imaging, the technique has developed accordingly to a single stage procedure with on-table dosimetric assessment. The principles of targeting dose to the prostate while avoiding surrounding organs at risk remain as relevant today as nearly a century ago. There is an array of techniques to consider for the novice PPB provider. Whether the evolution of PPB techniques will translate into improved biochemical control is yet to be seen.

Permanent prostate brachytherapy: Dosimetric results and analysis of a learning curve with a dynamic dose-feedback technique

PURPOSE

A permanent prostate brachytherapy (PPB) program utilizing intraoperative inverse-planned dynamic dose-feedback was initiated without prior firsthand experience of alternative techniques. The purpose of this study is to assess the dosimetric learning curve associated with this approach.

METHODS AND MATERIALS

A total of 77 patients underwent PPB implants as monotherapy for localized prostate cancer to a prescription dose of 145 Gy with loose 125I seeds between December 2003 and June 2004. Intraoperative and postoperative dosimetric values, total implanted radioactivity, and operating room (OR) times were compared by sequential case number for all cases.

RESULTS

The median intraoperative dosimetric values were: D90 (the minimum dose to 90% of the prostate) = 170 Gy (range, 135-203 Gy), V100 (the volume of the prostate that receives 100% of the prescription dose) = 96% (range, 86-100), V150 = 66% (range, 34-86). Median postoperative dosimetric values were as follows: D90 = 168 Gy (range, 132-197 Gy), V100 = 95% (range, 86-99), V150 = 74% (range, 51-84). Median implanted activity was 0.79 mCi per cubic centimeter of prostate (range, 0.541-1.13). There was no significant correlation by case number on any postoperative dosimetric parameter studied. Door-to-door OR time was reduced from median 138 to 97.5 min per case at the end of the series with a correlation coefficient of -0.76 for the initial 28 cases.

CONCLUSION

Satisfactory dosimetric parameters can be achieved from the outset without a learning curve effect in an appropriately trained environment. The learning curve for dynamic dose-feedback PPB in a clinic naïve to other techniques is apparent in terms of OR time.

Radiation exposure after permanent prostate brachytherapy

BACKGROUND AND PURPOSE

Limited information is available on the true radiation exposure and associated risks for the relatives of the patients submitted to prostate brachytherapy with permanent implant of radioactive sources and for any other people coming into contact with them. In order to provide appropriate information, we analyzed the radiation exposure data from 216 prostate cancer patients who underwent (125)I or (103)Pd implants at the European Institute of Oncology of Milan, Italy.

PATIENTS AND METHODS

Between October 1999 and October 2004, 216 patients with low risk prostate carcinoma were treated with (125)I (200 patients) or (103)Pd (16 patients) permanent seed implantation. One day after the procedure, radiation exposure measurements around the patients were performed using an ionization chamber survey meter (Victoreen RPO-50) calibrated in dose rate at an accredited calibration center (calibration Centre SIT 104).

RESULTS

The mean dose rate at the posterior skin surface (gluteal region) following (125)I implants was 41.3 microSv/h (range: 6.2-99.4 microSv/h) and following (103)Pd implants was 18.9 microSv/h (range 5.0-37.3 microSv/h). The dose rate at 50 cm from the skin decreased to the mean value of 6.4 microSv/h for the (125)I implants and to the mean value of 1.7 microSv/h for the (103)Pd implants. Total times required to reach the annual dose limit (1 mSv/year) recommended for the general population by the European Directive 96/29/Euratom and by the Italian law (Decreto Legislativo 241/2000) at a distance of 50 cm from the posterior skin surface of the implanted patient would be 7.7 and 21.6 days for (125)I and for (103)Pd. Good correlation between the measured dose rates and both the total implanted activity and the distance between the most posteriorly implanted seed and the skin surface of the patients was found.

CONCLUSIONS

Our data show that the dose rates at 50 cm away from the prostate brachytherapy patients are very low and that the doses possibly absorbed by the relatives and other members of the general population coming into contact with the treated patients are well below the dose limit set by the European Directive and by the Italian regulation. However, in order to meet the recommendation of the ALARA principle (As Low As Reasonably/Readily Achievable), some advice to the patients should be given, such as to maintain a minimum distance from the patient of 1m, at least for a period equal to one half life of used radionuclide (60 days for (125)I and 15 days for (103)Pd).

Effect of random seed placement error in permanent transperineal prostate seed implant

BACKGROUND AND PURPOSE

Random seed placement error may adversely effect dose distribution in transperineal prostate seed implants. In this study, we investigated the extent to which individual seed activity influences dose-distribution degradation due to random seed placement error.

PATIENTS AND METHODS

Separate initial treatment plans were prepared for three prostate sizes, 27.3, 43.2 and 48.9 cc, using 0.35, 0.55 and 0.75 mCi iodine-125 seeds. All stated activities are understood to be apparent activities. The combinations produced a total of nine treatment plans. Each initial treatment plan was subjected to 1000 stochastic three-dimensional Gaussian perturbations of seed location, with a standard deviation of 4mm for a total of 9000 treatment plans. The resulting plans were evaluated for target coverage and urethra involvement.

RESULTS

Satisfactory initial treatment plans were prepared for all prostate sizes and seed activities. All 9000 perturbed treatment plans showed acceptable target coverage under the D90/90 criterion. Some of the perturbed plans for the 27.3 and 43.2 cc prostates with 0.55 and 0.75 mCi seeds failed the V100/90 criterion. Some of the randomly perturbed seed distributions showed significantly increased doses to the urethra relative to the unperturbed treatment plan. This effect was more pronounced with greater seed activity.

CONCLUSIONS

There may be a higher probability of unfavorable target coverage due to random seed placement error when performing transperineal iodine-125 prostate seed implants using seeds with activity greater than 0.35 mCi. There may also be a higher probability of unfavorable urethra involvement when using higher activity seeds.

Difference in rectal dosimetry between pre-plan and post-implant analysis in transperineal interstitial brachytherapy for prostate cancer

BACKGROUND AND PURPOSE

To investigate differences in rectal dosimetry between pre-plan ultrasonography (US) and post-implant computed tomography (CT).

PATIENTS AND METHODS

Subjects comprised 49 patients who underwent prostate brachytherapy using (125)I seed implants. Prescribed dose was 145Gy to the periphery of the prostate. Differences in rectal dosimetry between pre-plan US and post-implant CT analysis were evaluated. In addition, patients were divided into two groups according to timing of pre-planning (pre-plan group, n=28; intraoperative pre-plan group, n=21), and differences in rectal dosimetry between groups were assessed.

RESULTS

The average of volume differences between pre-plan and post-implant analysis (pre-plan minus post-implant analysis) for all patients were follows: -0.08 cm(3) in V60 (volume of rectal wall receiving 60% of prescribed dose); -0.05 cm(3) in V70; -0.16 cm(3) in V80; -0.38 cm(3) in V90; -0.40 cm(3) in V100; -0.32 cm(3) in V110; -0.22 cm(3) in V120; -0.15 cm(3) in V130; -0.10 cm(3) in V140; -0.07 cm(3) in V150; and -0.05 cm(3) in V160. Apparent differences between pre-plan US and post-implant CT in rectal dosimetry were small. However, considering the steep curve of the relationship between tolerable volume and dose, a large actual difference should be assumed. No advantage was identified for the intraoperative pre-plan group. Safe volume to avoid proctitis tended to be smaller on ultrasonography than on CT at 1 month.

CONCLUSIONS

The present work shows that direct comparison of CT analysis and pre-plan US is unfavorable due to large differences in these modalities and overestimation of tolerable volume. However, by comprehending the degree of difference, comparison of data from CT analysis with a US pre-plan may be feasible and useful for providing feedback between these modalities.

Sexual function after permanent 125I-brachytherapy for prostate cancer

We prospectively assessed patients' erectile function (EF) using the International Index of Erectile Function (IIEF) and a global assessment questionnaire (GAQ) following permanent 125I-brachytherapy for localized prostate cancer. Of 378 treated patients, 220 had a minimal 2-y follow-up and 131/220 were sexually active prior to brachytherapy, with an EF domain score of > or = 11 (study group). Patients were allowed sildenafil at any time of the study. The patients' mean EF score, without excluding patients who used sildenafil, dropped within 3 months after brachytherapy, recovered at the end of the first year and remained unchanged for at least up to 2 y after treatment regardless of the addition of neoadjuvant hormone therapy to 125I-brachytherapy. Analysis of the GAQ revealed that 80% of the patients were satisfied with their sexual function up to 3 y after treatment. Any detrimental effect of permanent brachytherapy with or without the addition of hormone therapy on EF is reversible, and recovery is expected at 1 y after treatment in most patients.

Three-dimensional conformal brachytherapy for prostate cancer

Because innovations in radiation treatment planning have dramatically improved the precision of external beam radiotherapy for prostate cancer with the advent of conformal three-dimensional conformal therapy and intensity modulated radiotherapy, similar developments are emerging for prostate brachytherapy. Computer software programs are facilitating the ability to rapidly create conformal treatment plans in the operating room, taking into account the three-dimensional reconstruction of the prostate target and adhering to dose-volume constraints of the normal tissues including the urethra and rectum. Although excellent dose distributions can be achieved with pre-planning techniques, intraoperative planning takes into account the intraoperative geometry of the prostate and the surrounding normal tissues and can consistently produce seed implants with reduced urethral and rectal doses while delivering the intended prescription dose to the target volume. Current developments are pursuing methods to dynamically modify the treatment plan as the implant procedure is ongoing based on the coordinates of the deposited seeds. Such approaches will minimize the possibility of tumor underdosage and further enhance the conformality of prostate brachytherapy.