3D conformal HDR brachytherapy and external beam irradiation combined with temporary androgen deprivation in the treatment of localized prostate cancer

High-dose-rate brachytherapy for prostate cancer: Rationale, current applications, and clinical outcome

Background

High‐dose‐rate brachytherapy (HDR BRT) has been enjoying rapid acceptance as a treatment modality offered to selected prostate cancer patients devoid of risk group, employed either in monotherapy setting or combined with external beam radiation therapy (EBRT) and is currently one of the most active clinical research areas.

Recent findings

This review encompasses all the current evidence to support the use of HDR BRT in various clinical scenario and shines light to the HDR BRT rationale, as an ultimately conformal dose delivery method enabling safe dose escalation to the prostate.

Conclusion

Valid long‐term data, both in regard to the oncologic outcomes and toxicity profile, support the current clinical indication spectrum of HDR BRT. At the same time, this serves as solid, rigid ground for emerging therapeutic applications, allowing the technique to remain in the spotlight alongside stereotactic radiosurgery.

Long-Term Outcomes of Three-Dimensional High-Dose-Rate Brachytherapy for Locally Recurrent Early T-Stage Nasopharyngeal Carcinoma

Background: Brachytherapy (BT) is one of the techniques available for retreatment of patients with locally recurrent nasopharyng eal carcinoma (rNPC). In this study, we evaluated the treatment outcome and late toxicities of three-dimensional high-dose-rate brachytherapy (3D-HDR-BT) for patients with locally rNPC. Materials and Methods: This is a retrospective study involving 36 patients with histologically confirmed rNPC from 2004 to 2011. Of the 36 patients, 17 underwent combined-modality treatment (CMT) consisting of external beam radiotherapy (EBRT) followed by 3D-HDR-BT, while the other 19 underwent 3D-HDR-BT alone. The median dose of EBRT for the CMT group was 60 (range, 50-66) Gy, with an additional median dose of BT of 16 (range, 9-20) Gy. The median dose for the 3D-HDR-BT group was 32 (range, 20-36) Gy. The measured treatment outcomes were the 5- and 10-year locoregional recurrence-free survival (LRFS), disease-free survival (DFS), overall survival (OS), and late toxicities. Results: The median age at recurrence was 44.5 years. The median follow-up period was 70 (range, 6-142) months. The 5-year LRFS, DFS, and OS for the entire patient group were 75.4, 55.6, and 74.3%, respectively, while the 10-year LRFS, DFS, and OS for the entire patient group were 75.4, 44.2, and 53.7%, respectively. The 10-year LRFS in the CMT group was higher than that in the 3D-HDR-BT-alone group (93.8 vs. 58.8%, HR: 7.595, 95%CI: 1.233-61.826, p = 0.025). No grade 4 late radiotherapy-induced toxicities were observed. Conclusions: 3D-HDR-BT achieves favorable clinical outcomes with mild late toxicity in patients with locally rNPC.

The evolution of brachytherapy for prostate cancer

Brachytherapy (BT), using low-dose-rate (LDR) permanent seed implantation or high-dose-rate (HDR) temporary source implantation, is an acceptable treatment option for select patients with prostate cancer of any risk group. The benefits of HDR-BT over LDR-BT include the ability to use the same source for other cancers, lower operator dependence, and - typically - fewer acute irritative symptoms. By contrast, the benefits of LDR-BT include more favourable scheduling logistics, lower initial capital equipment costs, no need for a shielded room, completion in a single implant, and more robust data from clinical trials. Prospective reports comparing HDR-BT and LDR-BT to each other or to other treatment options (such as external beam radiotherapy (EBRT) or surgery) suggest similar outcomes. The 5-year freedom from biochemical failure rates for patients with low-risk, intermediate-risk, and high-risk disease are >85%, 69-97%, and 63-80%, respectively. Brachytherapy with EBRT (versus brachytherapy alone) is an appropriate approach in select patients with intermediate-risk and high-risk disease. The 10-year rates of overall survival, distant metastasis, and cancer-specific mortality are >85%, <10%, and <5%, respectively. Grade 3-4 toxicities associated with HDR-BT and LDR-BT are rare, at <4% in most series, and quality of life is improved in patients who receive brachytherapy compared with those who undergo surgery.

Brachytherapy boost for prostate cancer: Trends in care and survival outcomes

PURPOSE

Androgen suppression combined with elective nodal and dose-escalated radiation therapy recently demonstrated an improved biochemical failure-free survival in men who received external beam radiation therapy (EBRT) plus a brachytherapy boost (BB) compared with dose-escalated external beam radiotherapy (DE-EBRT). We sought to analyze the factors predictive for use of EBRT + BB as compared with DE-EBRT and report resulting survival outcomes on a national level using a hospital-based registry.

METHODS AND MATERIALS

We identified 113,719 men from the National Cancer Database from 2004 to 2013 with intermediate- or high-risk prostate cancer who were treated with EBRT + BB or DE-EBRT. We performed univariate and multivariate analyses of all available factors potentially predictive of receipt of treatment selection. Survival was evaluated in a multivariable model with propensity adjustment.

RESULTS

For intermediate-risk patients, utilization of BB decreased from 33.1% (n = 1742) in 2004 to 12.5% (n = 766) in 2013 and for high-risk patients, utilization dropped from 27.6% (n = 879) to 10.8% (n = 479). Numerous factors predictive for use of BB were identified. Cox proportional hazards analysis was performed-adjusting for age, Charlson-Deyo comorbidity score, T stage, prostate-specific antigen, Gleason score, and sociodemographic factors-and demonstrated BB use was associated with a hazard ratio of 0.71 (95% confidence interval, 0.67-0.75; p < 0.0005) and 0.73 (95% confidence interval, 0.68-0.78; p < 0.0005) for intermediate- and high-risk patients, respectively.

CONCLUSIONS

There has been a concerning decline in the utilization of BB for intermediate- and high-risk prostate cancer patients despite an association with improved on overall survival. Numerous factors predictive for use of BB have been identified.

Surgical management of complex rectourethral fistulas in irradiated and nonirradiated patients

BACKGROUND

Rectourethral fistulas are an uncommon, yet devastating occurrence after treatment for prostate cancer or trauma, and their surgical management has historically been nonstandardized. Anecdotally, irradiated rectourethral fistulas portend a worse prognosis.

OBJECTIVE

To review outcomes after surgical treatment of rectourethral fistulas in radiated and nonirradiated patients to construct a logical surgical algorithm.

DESIGN AND SETTING

A retrospective review was undertaken of all patients presenting to Duke University with the diagnosis of rectourethral fistula from 1996 to 2012.

PATIENTS

Thirty-seven patients presented with and were treated for rectourethral fistulas: 21 received radiation, and a rectourethral fistula from trauma or iatrogenic injury developed in 16.

MAIN OUTCOME MEASURES

The groups were compared regarding their functional outcomes, including healing, time to healing, continence, and recurrence.

RESULTS

There were no significant differences in patient characteristics between groups. Patients who had irradiated rectourethral fistulas had a significantly higher rate of passage of urine through the rectum and wound infections, a higher rate of crystalloid infusion and blood transfusion requirements, and a longer time to ostomy reversal than nonirradiated patients. Patients who had irradiated rectourethral fistulas underwent more complex operative repairs, including gracilis interposition flaps (38%) and pelvic exenterations (19%), whereas nonirradiated patients most commonly underwent a York-Mason repair (50%). There were no statistically significant differences in rectourethral fistula healing or in postoperative and functional outcomes. Only 55% of irradiated patients had their ostomy reversed versus 91% in the nonirradiated group.

LIMITATIONS

This study was limited by the small sample size and the retrospective nature of the review.

CONCLUSIONS

Repair of rectourethral fistulas caused by radiation has a significantly higher wound infection rate and median time to healing, and lower overall stomal reversal rate than nonradiation-induced rectourethral fistulas. Patients who had irradiated rectourethral fistulas required significantly more complex operations, likely contributing to the higher morbidity, mortality, and lower fistula closure rate. We propose an algorithm for approaching rectourethral fistulas based on etiology.

3D-image-guided high-dose-rate intracavitary brachytherapy for salvage treatment of locally persistent nasopharyngeal carcinoma

Background

To evaluate the therapeutic benefit of 3D-image-guided high-dose-rate intracavitary brachytherapy (3D-image-guided HDR-BT) used as a salvage treatment of intensity modulated radiation therapy (IMRT) in patients with locally persistent nasopharyngeal carcinoma (NPC).

Methods

Thirty-two patients with locally persistent NPC after full dose of IMRT were evaluated retrospectively. 3D-image-guided HDR-BT treatment plan was performed on a 3D treatment planning system (PLATO BPS 14.2). The median dose of 16 Gy was delivered to the 100% isodose line of the Gross Tumor Volume.

Results

The whole procedure was well tolerated under local anesthesia. The actuarial 5-y local control rate for 3D-image-guided HDR-BT was 93.8%, patients with early-T stage at initial diagnosis had 100% local control rate. The 5-y actuarial progression-free survival and distant metastasis-free survival rate were 78.1%, 87.5%. One patient developed and died of lung metastases. The 5-y actuarial overall survival rate was 96.9%.

Conclusions

Our results showed that 3D-image-guided HDR-BT would provide excellent local control as a salvage therapeutic modality to IMRT for patients with locally persistent disease at initial diagnosis of early-T stage NPC.

Feasibility and radiation induced toxicity regarding the first application of transperineal implementation of biocompatible balloon for high dose radiotherapy in patients with prostate carcinoma

Objective

To evaluate the feasibility of the transperineal implementation of biocompatible balloon (Prospace) and the acute toxicity of high dose 3DCRT in patients with localized low risk prostate cancer.

Materials and methods

Between December 2011 and April 2012, fifteen patients were treated with external 3DCRT consisted of 76–78 Gy in 38–39 daily fractions (2.0 Gy/ fraction). Before 3DCRT, we placed the Prospace though the perineum by a minimally invasive procedure in the intermediate space between the rectum and the prostate. The primary study endpoint was the evaluation of acute toxicity according to the EORTC/RTOG radiation toxicity scale. Erectile function was evaluated with the IIEF-5 questionnaire. Rectosigmoidoscopy was performed at baseline, at the end of 3DCRT and 3 months thereafter in order to assess also the rectal toxicity according to Subjective-RectoSigmoid (S-RS) scale. The evaluation of pain related to Prospace implementation was done with the visual analogue score (VAS).

Results

The acute toxicities were as follows: grade I GI toxicity in two patients and for GU toxicity, three patients with grade I of nocturia, four patients with grade I of frequency, two patients with grade I and two patients with grade II of dysouria. The mean score of rectal toxicity according to S-RS score was 1.8(±0.6). The mean VAS score related to Prospace was 1.4(±0.5). Erectile function was unchanged. The Prospace device was found stable in sequential CTs during irradiation.

Conclusions

The implementation of PROSPACE was feasible, while the acute radiation toxicity was low and comparable with IMRT techniques.

Gold marker displacement due to needle insertion during HDR-brachytherapy for treatment of prostate cancer: a prospective cone beam computed tomography and kilovoltage on-board imaging (kV-OBI) study

PURPOSE

To evaluate gold marker displacement due to needle insertion during HDR-brachytherapy for therapy of prostate cancer.

PATIENTS AND METHODS

18 patients entered into this prospective evaluation. Three gold markers were implanted into the prostate during the first HDR-brachytherapy procedure after the irradiation was administered. Three days after marker implantation all patients had a CT-scan for planning purpose of the percutaneous irradiation. Marker localization was defined on the digitally-reconstructed-radiographs (DRR) for daily (VMAT technique) or weekly (IMRT) set-up error correction. Percutaneous therapy started one week after first HDR-brachytherapy. After the second HDR-brachytherapy, two weeks after first HDR-brachtherapy, a cone-beam CT-scan was done to evaluate marker displacement due to needle insertion. In case of marker displacement, the actual positions of the gold markers were adjusted on the DRR.

RESULTS

The value of the gold marker displacement due to the second HDR-brachytherapy was analyzed in all patients and for each gold marker by comparison of the marker positions in the prostate after soft tissue registration of the prostate of the CT-scans prior the first and second HDR-brachytherapy. The maximum deviation was 5 mm, 7 mm and 12 mm for the anterior-posterior, lateral and superior-inferior direction. At least one marker in each patient showed a significant displacement and therefore new marker positions were adjusted on the DRRs for the ongoing percutaneous therapy.

CONCLUSIONS

Needle insertion in the prostate due to HDR-brachytherapy can lead to gold marker displacements. Therefore, it is necessary to verify the actual position of markers after the second HDR-brachytherapy. In case of significant deviations, a new DRR with the adjusted marker positions should be generated for precise positioning during the ongoing percutaneous irradiation.

Evaluation of clinical benefits achievable by using different optimization algorithms during real-time prostate brachytherapy

BACKGROUND AND PURPOSE

High dose rate (HDR) brachytherapy is a clinically used procedure in prostate cancer treatment. The purpose of this study was to present the influence of using different optimization algorithms in 3D-CBRT planning on the treatment plan quality.

MATERIALS AND METHODS

Treatment plans were calculated for 15 patients--three plans for each patient using: geometrical optimization (GO), inverse optimization (IO) and blind inverse optimization (BIO). For each patient, PTV and OAR volumes, number of needles and geometry of the implant were set equal. Differences between dose distributions were tracked using: D90, V100, V200, Dmax (for prostate); D10, Dmax (for urethra); D10, V100, Dmax (for rectum).

RESULTS

The analysis of mean values of D90 and V100 in the prostate showed that inverse algorithms gave the best results (mean D90 was 12.1% for BIO and 9.3% for IO better than for GO, mean V100 was 8.2% for BIO and 6.3% for IO better than for GO). From a clinical point of view, GO diminished the doses in the PTV and urethra in all analyzed parameters. The lowest mean doses in the rectum were achieved for plans optimized with IO and BIO (mean D10: 61.2% for GO, 58.1% for IO, 58.0% for BIO; mean Dmax: 92.8% for GO, 85.1% for IO, 83.6% for BIO).

CONCLUSIONS

Application of the blind inverse optimization (BIO) algorithm led to clinically best dose parameters for PTV and the rectum. Use of geometrical optimization (GO) led to smaller doses in the urethra, which was however associated with a certain dose decrease also in PTV.

High-dose-rate brachytherapy boost to the dominant intra-prostatic tumor region: hemi-irradiation of prostate cancer

BACKGROUND

To assess the feasibility, toxicity, and outcome of prostate hemi-irradiation with a high-dose-rate brachytherapy (HDR-BT) boost for patients presumed to harbor dominant intra-prostatic tumors in a single lobe.

METHODS

After 3D conformal external radiotherapy (3DCRT) to 64-64.4 Gy, 77 patients with non-metastatic locally aggressive prostate cancer have been treated from 2000 to 2004, with HDR-BT using temporary open MRI-guided (192) Ir implants, to escalate the dose in the boost region. Twenty patients (26%) had one lobe involvement (i.e., one sided endorectal MRI, rectal examination, and biopsies) and were boosted to one side of the gland only. A dose of 12, 14, and 16 Gy in two fractions was delivered to 5, 6, and 9 patients, respectively.

RESULTS

After a median follow-up 69 months, no differences in late rectal toxicity were observed between the unilaterally and bilaterally irradiated cohorts. Although, grade 2 late urinary toxicity was worse in the hemi-irradiated group (P = 0.03), severe grade ≥3 late urinary toxicity at 5 years was not different: 10% versus 8.8% in the unilaterally and bilaterally irradiated cohorts, respectively. Grade 4 late urinary toxicity, however, was exclusively observed in patients boosted to both lobes (5/57, 8.8%). Five-year biochemical relapse-free survival was 79.7% versus 70.5% for the unilateral and bilateral boost groups, respectively (P = 0.99).

CONCLUSION

Prostate hemi-irradiation with a HDR-BT boost to the dominant tumor region may be considered when rectal examination, MRI, and biopsies suggest one lobe involvement. Nevertheless, strict dosimetric optimization is needed in order to further reduce the risk of late severe toxicity.

Moderate dose escalation with single-fraction high-dose-rate brachytherapy boost for clinically localized intermediate- and high-risk prostate cancer: 5-year outcome of the first 100 consecutively treated patients

PURPOSE

To analyze the clinical outcome and toxicity data of the first 100 consecutive patients treated with a single-fraction high-dose-rate brachytherapy (HDR-BT) and external beam radiotherapy (EBRT).

METHODS AND MATERIALS

Two-hundred eighty patients have been treated with HDR-BT boost for localized intermediate- to high-risk prostate cancer. Among these, the outcome and toxicity of the first 100 patients treated with a single HDR-BT fraction were assessed. A median dose of 60Gy EBRT was given to the prostate and vesicles. Interstitial HDR-BT of 10Gy was performed during the course of EBRT.

RESULTS

Median followup time was 61.5 months. The 5-year actuarial rates of overall survival, cause-specific survival, disease-free survival, and biochemical no evidence of disease (bNED) for the entire cohort were 93.3%, 99.0%, 89.3%, and 85.5%, respectively. The 7-year actuarial rate of bNED was 84.2% for the intermediate-risk group and 81.6% for the high-risk group (p=0.8464). The 7-year actuarial rates of bNED for Grade 1, 2, and 3 tumors were 97.5%, 80.0%, and 67.1%, respectively. The 5-year probability for developing late Grade 3 gastrointestinal and genitourinary (GU) toxicity was 2.1% and 14.4%, respectively. Grade 3 GU complications occurred significantly more frequently in patients with a history of preirradiation transurethral resection (29.1% vs. 8.8%; p=0.0047).

CONCLUSIONS

Five-year outcome after 60Gy EBRT plus a single fraction of 10Gy HDR-BT boost is encouraging. Preradiation transurethral resection significantly increases the risk of late severe GU complications.

Dose-fractionation sensitivity of prostate cancer deduced from radiotherapy outcomes of 5,969 patients in seven international institutional datasets: α/β = 1.4 (0.9-2.2) Gy

PURPOSE

There are reports of a high sensitivity of prostate cancer to radiotherapy dose fractionation, and this has prompted several trials of hypofractionation schedules. It remains unclear whether hypofractionation will provide a significant therapeutic benefit in the treatment of prostate cancer, and whether there are different fractionation sensitivities for different stages of disease. In order to address this, multiple primary datasets have been collected for analysis.

METHODS AND MATERIALS

Seven datasets were assembled from institutions worldwide. A total of 5969 patients were treated using external beams with or without androgen deprivation (AD). Standard fractionation (1.8-2.0 Gy per fraction) was used for 40% of the patients, and hypofractionation (2.5-6.7 Gy per fraction) for the remainder. The overall treatment time ranged from 1 to 8 weeks. Low-risk patients comprised 23% of the total, intermediate-risk 44%, and high-risk 33%. Direct analysis of the primary data for tumor control at 5 years was undertaken, using the Phoenix criterion of biochemical relapse-free survival, in order to calculate values in the linear-quadratic equation of k (natural log of the effective target cell number), α (dose-response slope using very low doses per fraction), and the ratio α/β that characterizes dose-fractionation sensitivity.

RESULTS

There was no significant difference between the α/β value for the three risk groups, and the value of α/β for the pooled data was 1.4 (95% CI = 0.9-2.2) Gy. Androgen deprivation improved the bNED outcome index by about 5% for all risk groups, but did not affect the α/β value.

CONCLUSIONS

The overall α/β value was consistently low, unaffected by AD deprivation, and lower than the appropriate values for late normal-tissue morbidity. Hence the fractionation sensitivity differential (tumor/normal tissue) favors the use of hypofractionated radiotherapy schedules for all risk groups, which is also very beneficial logistically in limited-resource settings.

A pilot study of intensity modulated radiation therapy with hypofractionated stereotactic body radiation therapy (SBRT) boost in the treatment of intermediate- to high-risk prostate cancer

Clinical data suggest that large radiation fractions are biologically superior to smaller fraction sizes in prostate cancer radiotherapy. The CyberKnife is an appealing delivery system for hypofractionated radiosurgery due to its ability to deliver highly conformal radiation and to track and adjust for prostate motion in real-time. We report our early experience using the CyberKnife to deliver a hypofractionated stereotactic body radiation therapy (SBRT) boost to patients with intermediate- to high-risk prostate cancer. Twenty-four patients were treated with hypofractionated SBRT and supplemental external radiation therapy plus or minus androgen deprivation therapy (ADT). Patients were treated with SBRT to a dose of 19.5 Gy in 3 fractions followed by intensity modulated radiation therapy (IMRT) to a dose of 50.4 Gy in 28 fractions. Quality of life data were collected with American Urological Association (AUA) symptom score and Expanded Prostate Cancer Index Composite (EPIC) questionnaires before and after treatment. PSA responses were monitored; acute urinary and rectal toxicities were assessed using Common Toxicity Criteria (CTC) v3. All 24 patients completed the planned treatment with an average follow-up of 9.3 months. For patients who did not receive ADT, the median pre-treatment PSA was 10.6 ng/ml and decreased in all patients to a median of 1.5 ng/ml by 6 months post-treatment. Acute effects associated with treatment included Grade 2 urinary and gastrointestinal toxicity but no patient experienced acute Grade 3 or greater toxicity. AUA and EPIC scores returned to baseline by six months post-treatment. Hypofractionated SBRT combined with IMRT offers radiobiological benefits of a large fraction boost for dose escalation and is a well tolerated treatment option for men with intermediate- to high-risk prostate cancer. Early results are encouraging with biochemical response and acceptable toxicity. These data provide a basis for the design of a phase II clinical trial.

3D-CT implanted interstitial brachytherapy for T2b nasopharyngeal carcinoma

Background

To compare the results of external beam radiotherapy in combination with 3D- computed tomography (CT)-implanted interstitial high dose rate brachytherapy (ERT/3D-HDR-BT) versus conventional external beam radiotherapy (ERT) for the treatment of stage T2b nasopharyngeal carcinoma (NPC).

Methods

Forty NPC patients diagnosed with stage T2b NPC were treated with ERT/3D-HDR-BT under local anesthesia. These patients received a mean dose of 60 Gy, followed by 12-20 Gy administered by 3D-HDR-BT. Another 101 patients diagnosed with non-metastatic T2b NPC received a mean dose of 68 Gy by ERT alone during the same period.

Results

Patients treated with ERT/3D-HDR-BT versus ERT alone exhibited an improvement in their 5-y local failure-free survival rate (97.5% vs. 80.2%, P = 0.012) and disease-free survival rate (92.5% vs. 73.3%, P = 0.014). Using multivariate analysis, administration of 3D-HDR-BT was found to be favorable for local control (P = 0.046) and was statistically significant for disease-free survival (P = 0.021). The incidence rate of acute and chronic complications between the two groups was also compared.

Conclusions

It is possible that the treatment modality enhances local control due to improved conformal dose distributions and the escalated radiation dose applied.

Clinical outcome in patients with prostate cancer treated with external beam radiotherapy and high dose-rate iridium 192 brachytherapy boost: a 6-year follow-up

To report the long-term results for treatment of localized carcinoma of the prostate using high dose rate (HDR) brachytherapy, conformal external beam radiotherapy (3D EBRT) and neo-adjuvant hormonal therapy (TAB). From 1998 through 1999, 154 patients with localized prostate cancer were entered in the trial. Biologically no evidence of disease (bNED) was defined at PSA levels < 2 microg/l. In order to compare the results of this treatment with other treatment modalities, the patient's pre-treatment data were used to calculate the estimated 5-year PSA relapse free survival using Kattan's nomograms for radical prostatectomy (RP) and 3D EBRT. After 6 years of follow-up, 129 patients remain alive. The actual 5-year relapse-free survival is 84%. None of the patients demonstrated clinical signs of local recurrence. The median PSA at follow-up among the relapse-free patients was 0.05 microg/l. Among the 80 patients who presented with clinical stage T3 tumours, 55 (68%) were relapse-free. The expected 5-year relapse-free survival using nomograms for RP and 3D EBRT was 54% and 70%, respectively. Late rectal toxicity RTOG grade 3 occurred in 1% of the patients. Late urinary tract toxicity RTOG grade 3 developed in 4% of the patients. Combined treatment, utilizing HDR, 3D EBRT and TAB, produces good clinical results. Rectal toxicity is acceptable. Urinary tract toxicity, most likely can be explained by the fact that during the first years of this treatment, no effort was made to localize the urethra, which was assumed to be in the middle of the prostate.

Miniature LiF: Mg, Cu, P TLDs to study the effect of applicator material in 192-Ir brachytherapy

Dose calculations in brachytherapy planning typically don't take into account inhomogeneities and the material of applicators. We evaluated the justification of the latter by investigating the dose delivered in 192-Ir interstitial implants employing plastic catheters and steel needles using miniature LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs) which fit in the applicators. Within the uncertainty of the measurement (+/- 5%) no difference could be found in the dose distribution from 192Ir in steel needles or plastic catheters. Computerized treatment planning (Philips/ADAC Pinnacle) was in good agreement with the measured data.

Challenge of dose escalation in locally advanced unfavourable prostate cancer using HDR brachytherapy

In men with locally advanced/high-risk prostate cancer, there is an ongoing challenge to achieve improved results. Dose escalation studies using three-dimensional conformal radiotherapy (3D-CRT) or intensity modulated radiation therapy (IMRT) have shown benefit particularly in the intermediate and poor risk groups of patients. Of concern, however, is the increase in documented rectal toxicity. High-dose rate brachytherapy (HDR-BT) as a boost in combination with external beam radiotherapy (EBRT) is an alternative strategy of dose escalation that can potentially achieve an even higher biological equivalent dose (BED) to the tumour. The results so far are very encouraging for men with poor prognosis disease. Moreover the technique is associated with very low rates of acute and late toxicity.

Favorable clinical outcomes of three-dimensional computer-optimized high-dose-rate prostate brachytherapy in the management of localized prostate cancer

PURPOSE

To report PSA relapse-free survival and toxicity outcomes of prostate cancer patients who have undergone three-dimensional computer-optimized high-dose-rate (HDR) brachytherapy with external beam radiotherapy as definitive treatment.

METHODS AND MATERIALS

One hundred five patients consecutively treated between 1998 and 2004 are reported. All patients were treated with HDR boost with lr 192 (5.5-7.0 Gy), based upon postimplant CT three-dimensional treatment planning using an in-house treatment plan optimization algorithm. Three-dimensional conformal external beam radiotherapy (45-50.4 Gy) was also administered 3 weeks after the HDR procedure. Toxicity was measured using National Cancer Institutes Common Toxicity Criteria and International Prostate Symptom Score indices.

RESULTS

With a median followup of 44 months (8-79 months), the 5-year PSA relapse-free survival outcomes for low, intermediate and high-risk patients were 100%, 98%, and 92%, respectively, Median urinary toxicity, and 93% of patients denied rectal problems at the time of last followup. Erectile dysfunction was noted in 47% patients at the time of last followup, but overall 80% were able to achieve vaginal penetration when those who responded to sildenafil were included.

CONCLUSION

Computer-optimized three-dimensional HDR prostate brachytherapy provides excellent disease control for even high risk localized prostate cancer. Significant toxicity has been minimal.

Management of radiotherapy induced rectourethral fistula

PURPOSE

An increasing number of men are being treated with BT or a combination of external beam radiation therapy and BT for localized prostate cancer. Although uncommon, the most severe complication following these procedures is RUF. We reviewed our recent experience with RUF following radiotherapy for prostate cancer to clarify treatment in these patients.

MATERIALS AND METHODS

We recently treated 22 men with RUF following primary radiotherapy for adenocarcinoma of the prostate in 21 and adjuvant external beam radiation therapy following radical prostatectomy in 1. Time from the last radiation treatment to fistula presentation was 6 months to 20 years.

RESULTS

Four patients underwent proctectomy with permanent fecal and urinary diversion. RUF repair in 5 patients was performed with preservation of fecal or urinary function. Six patients were candidates for reconstruction with preservation of urinary and rectal function, including 5 who underwent proctectomy, staged colo-anal pull-through and BMG repair of the urethral defect. The additional patient underwent primary closure of the rectum, BMG repair of the urethra and gracilis muscle interposition. Successful fistula closure was achieved in the 9 patients who underwent urethral reconstruction. All 8 candidates for rectal reconstruction showed radiological and clinical bowel integrity postoperatively with 2 awaiting final diverting stoma closure.

CONCLUSIONS

With the increasing use of prostate BT the number of patients with severe rectal injury will likely continue to increase. Radiotherapy induced RUF carries significant morbidity and most patients are treated initially with fecal and urinary diversion. In properly selected patients good outcomes can be expected following repair using BMG for the urethral defect along with colo-anal pull-through or primary rectal repair and gracilis muscle interposition.

Dose-volume impact in high-dose-rate Iridium-192 brachytherapy as a boost to external beam radiotherapy for localized prostate cancer- a phase II study

BACKGROUND AND PURPOSE

Evaluation of dose-volume-time-related factors in 64 patients treated with high-dose-rate brachytherapy (HDR-BT) as a boost to external beam radiotherapy (EBRT) for localized prostate cancer.

PATIENTS AND METHODS

Clinical parameters were correlated with morbidity scores of the EPIC (Expanded Prostate Cancer Index) questionnaire. Median time after radiotherapy (HDR-BT up to 18 Gy in two fractions and EBRT up to a median dose of 50.4 Gy) was 1.5 and 3 years (first and second questionnaire).

RESULTS

A significant impact of a urethra D1 exceeding 15 Gy in at least one HDR fraction concerning urinary morbidity and a rectum D1 exceeding 6 Gy to the rectal mucosa in the first and second HDR fraction concerning the rectal bleeding rate was found. A higher number of needles was associated with lower urinary and bowel scores after 1.5 years. A prostate length >4.8 cm and a longer duration of EBRT (independently of the dose) predisposed for lower urinary and bowel scores. In contrast to a urethra D1 > 15 Gy as an independent factor, a rectum D1 > 6 Gy per HDR fraction correlated with a higher number of needles and an increased prostate length.

CONCLUSIONS

To minimize morbidity in HDR-BT for prostate cancer, a maximum dose to the urethra of 15 Gy and a maximum dose to the rectal mucosa of 6 Gy is advisable. Treatment- and patient-related factors have a major impact on toxicity.

A dosimetric comparison of Yb169 versus Ir192 for HDR prostate brachytherapy

For the purpose of evaluating the use of 169Yb for prostate High Dose Rate brachytherapy (HDR), a hypothetical 169Yb source is assumed with the exact same design of the new microSelectron source replacing the 192Ir active core by pure 169Yb metal. Monte Carlo simulation is employed for the full dosimetric characterization of both sources and results are compared following the AAPM TG-43 dosimetric formalism. Monte Carlo calculated dosimetry results are incorporated in a commercially available treatment planning system (SWIFT), which features an inverse treatment planning option based on a multiobjective dose optimization engine. The quality of prostate HDR brachytherapy using the real 192Ir and hypothetical 169Yb source is compared in a comprehensive analysis of different prostate implants in terms of the multiobjective dose optimization solutions as well as treatment quality indices such as Dose Volume Histograms (DVH) and the Conformal Index (COIN). Given that scattering overcompensates for absorption in intermediate photon energies and distances in the range of interest to prostate HDR brachytherapy, 169Yb proves at least equivalent to 192Ir irrespective of prostate volume. This has to be evaluated in view of the shielding requirements for the 169Yb energies that are minimal relative to that for 192Ir.

Acute genitourinary toxicity after high-dose-rate (HDR) brachytherapy combined with hypofractionated external-beam radiation therapy for localized prostate cancer: Correlation between the urethral dose in HDR brachytherapy and the severity of acute genitourinary toxicity

PURPOSE

Several investigations have revealed that the alpha/beta ratio for prostate cancer is atypically low, and that hypofractionation or high-dose-rate (HDR) brachytherapy regimens using appropriate radiation doses may be expected to yield tumor control and late sequelae rates that are better or at least as favorable as those achieved with conventional radiation therapy. In this setting, we attempted treating localized prostate cancer patients with HDR brachytherapy combined with hypofractionated external beam radiation therapy (EBRT). The purpose of this study was to evaluate the feasibility of using this approach, with special emphasis on the relationship between the severity of acute genitourinary (GU) toxicity and the urethral dose calculated from the dose-volume histogram (DVH) of HDR brachytherapy.

METHODS AND MATERIALS

Between September 2000 and December 2003, 70 patients with localized prostate cancer were treated by iridium-192 HDR brachytherapy combined with hypofractionated EBRT at the Gunma University Hospital. Hypofractionated EBRT was administered in fraction doses of 3 Gy, three times per week; a total dose of 51 Gy was delivered to the prostate gland and the seminal vesicles using the four-field technique. No elective pelvic irradiation was performed. After the completion of EBRT, all the patients additionally received transrectal ultrasonography (TRUS)-guided HDR brachytherapy. The fraction size and the number of fractions in HDR brachytherapy were prospectively changed, whereas the total radiation dose for EBRT was fixed at 51 Gy. The fractionation in HDR brachytherapy was as follows: 5 Gy x 5, 7 Gy x 3, 9 Gy x 2, administered twice per day, although the biologic effective dose (BED) for HDR brachytherapy combined with EBRT, assuming that the alpha/beta ratio is 3, was almost equal to 138 in each fractionation group. The planning target volume was defined as the prostate gland with 5-mm margin all around, and the planning was conducted based on computed tomography images. The number of patients in each fractionation group was as follows: 13 in the 5-Gy group; 19 in the 7-Gy group, and 38 in the 9-Gy group. The tumor stage was T1 in 10 patients, T2 in 36 patients, and T3 in 24 patients. The Gleason score was 2-6 in 11 patients, 7 in 34 patients, and 8-10 in 25 patients. Androgen ablation was performed in all the patients. The median follow-up duration was 14 months (range 3-42 months). The toxicities were graded based on the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer toxicity criteria.

RESULTS

The main symptoms of acute GU toxicity were dysuria and increase in urinary frequency or nocturia. The grade distribution of acute GU toxicity in the patients was as follows: Grade 0-1, 39 patients (56%), and Grade 2-4, 31 patients (44%). One patient who developed acute urinary obstruction was classified as having Grade 4 toxicity. Comparison of the distribution of the grade of acute GU toxicity among the different fractionation groups revealed no statistically significant differences among the groups. The urethral dose in HDR brachytherapy was evaluated using the following DVH parameters: V30 (percentage of the urethral volume receiving 30% of the prescribed radiation dose), V80, V90, V100, V110, V120, V130, and V150. The V30-110 values in the patients with Grade 2-4 acute GU toxicity were significantly higher than those in patients with Grade 0-1 toxicity. On the other hand, there were no significant differences in the V120-150 values between patients with Grade 0-1 and Grade 2-4 toxicity. Regarding the influence of the number of needles implanted for the radiation therapy, patients with 11 needles or less showed a significantly higher incidence of Grade 2-4 acute GU toxicity compared with those with 12 needles or more (p < 0.05).

CONCLUSIONS

It was concluded that HDR brachytherapy combined with hypofractionated EBRT is feasible for localized prostate cancer when considered from the viewpoint of acute toxicity. Increase in the fraction dose or reduction in the number of fractions in HDR brachytherapy did not affect the severity of acute GU toxicity, and the volume of urethra receiving an equal or lower radiation dose than the prescribed dose was more closely associated with the grade severity of acute GU toxicity than that receiving a higher than the prescribed dose.

The emerging role of high-dose-rate brachytherapy for prostate cancer

By placing radioactive sources directly into the cancer, brachytherapy allows delivery of a highly conformal radiation dose to the prostate. Permanent seed brachytherapy is most commonly used for low-risk cancer, whereas high-dose-rate (HDR) brachytherapy is combined with external-beam radiotherapy to treat higher risk disease. The high rate of dose delivery and the large fraction size may be a radiobiological advantage for tumours with high sensitivity to radiation fraction size. The ability to optimise dose delivery allows for exquisite shaping of dose around the prostate and sparing of normal tissues. HDR brachytherapy is most commonly delivered in two or more fractions of 810 Gy combined with 40-50 Gy external beam. Published studies are almost entirely limited to single-institution case series. Most of the patients treated have relatively unfavourable localised disease, with a reported disease-free survival of 68-93%, and a local control rate of over 90%. Treatment is well tolerated, with urethral stricture the most common late effect (risk around 8%). Early results using HDR monotherapy in low-risk disease seem promising. Patients most likely to benefit from a combined HDR/external-beam approach have bulky local disease (stage T2b-T3) or intermediate to high-grade cancers. Prospective multicentre studies of HDR brachytherapy have begun in this patient group in Canada and the USA, which hopefully will allow future comparisons with high-dose conformal external-beam techniques.