High-dose-rate brachytherapy in the treatment of carcinoma of the prostate

High dose rate prostate brachytherapy: an overview of the rationale, experience and emerging applications in the treatment of prostate cancer

The technological advances in real-time ultrasound image guidance for high dose rate (HDR) prostate brachytherapy places this treatment modality at the forefront of innovation in radiotherapy. This review article will explore the rationale for HDR brachytherapy as a highly conformal method of dose delivery and safe dose escalation to the prostate, in addition to the particular radiobiological advantages it has over low dose rate and external beam radiotherapy. The encouraging outcome data and favourable toxicity profile will be discussed before looking at emerging applications for the future and how this procedure will feature alongside stereotactic radiosurgery.

De novo detrusor underactivity after laparoscopic radical prostatectomy

OBJECTIVE

The aim of this study was to investigate bladder function following laparoscopic radical prostatectomy, with a focus on de novo detrusor underactivity.

METHODS

Records on pre- and postoperative urodynamic studies were retrospectively investigated in 110 patients who underwent laparoscopic radical prostatectomy. Patients exhibiting de novo detrusor underactivity were selected on the basis of an overt strain voiding pattern during the postoperative pressure flow study with detrusor pressure at a maximum flow rate <10 cm H(2)O accompanied by an increase in abdominal pressure. In these patients, a follow-up urodynamic study was performed to assess subsequent long-term changes in the bladder function.

RESULTS

Of the 110 patients, 10 (9.1%) were observed to exhibit de novo detrusor underactivity during the postoperative urodynamic study. During the voiding phase of the pre- and postoperative pressure flow study in these 10 patients, the mean detrusor pressure at maximum flow rate showed a significant decrease postoperatively from 57.6 to 3.0 cm H(2)O (P < 0.001), although the mean abdominal pressure at maximum flow rate significantly increased from 23.1 to 102.5 cm H(2)O (P < 0.001). The follow-up urodynamic study performed on seven patients at 36 months following surgery revealed no significant change in each urodynamic parameter. De novo detrusor underactivity persisted even over the long term following surgery, and no improvement in bladder function was observed.

CONCLUSIONS

Detrusor contractility may be impaired during radical prostatectomy. Postoperative detrusor underactivity following radical prostatectomy seems to be an irreversible phenomenon persisting even over the long term.

Clinical results of iridium-192 high dose rate brachytherapy with external beam radiotherapy

OBJECTIVE

Here, we report the clinical results of iridium-192 high dose rate brachytherapy at Kanazawa University Hospital.

METHODS

The study population consisted of 166 patients diagnosed with T1c-T3bN0M0 prostate cancer treated with high dose rate brachytherapy and external beam radiotherapy and followed up for 6 months or longer. Treatment consisted of external beam radiotherapy to the prostate at 44 Gy/22 fractions and high dose rate brachytherapy at 18 Gy/3 fractions.

RESULTS

Median follow-up interval was 31.5 months (range 6.2-88.7). The overall 5-year biological recurrence-free survival rate was 93.0%. The 5-year biological recurrence-free survival rates for the patients in low-, intermediate- and high-risk groups according to the D'Amico risk classification criteria were 96.1%, 89.0% and 91.6%, respectively. When limited to the group that did not receive adjuvant hormonal therapy, the 5-year biological recurrence-free survival rates for the patients in low-, intermediate- and high-risk groups were 96.0%, 96.3% and 82.9%, respectively. Grade 3 or greater adverse effects were rare. Urethral stricture was observed in only 1.0% of the patients. Eighty percent of patients retained erectile function after high dose rate brachytherapy and reported satisfaction with sexual function.

CONCLUSIONS

High dose rate brachytherapy is considered a good form of treatment for localized prostate cancer, although longer follow-up is necessary.

Novel treatment methods for localized prostate cancer: hypofractionated robotic radiation therapy and adjuvant chemotherapy

The standard localized therapies for prostate cancer include external-beam radiation therapy, brachytherapy and radical prostatectomy. There are several novel approaches in development aimed at improving local disease control and survival, and reducing post-treatment complications. In low-to-intermediate-risk patients, new radiation approaches are being explored to include hypofractionated robotic radiation therapy. For high-risk patients, the focus is on multimodality approaches, especially the addition of chemotherapy. Recent developments in radiation therapy and adjuvant chemotherapy are the focus of this review.

Combined curative radiotherapy including HDR brachytherapy and androgen deprivation in localized prostate cancer: a prospective assessment of acute and late treatment toxicity

Self-reported symptoms including urinary, bowel and sexual side effects were investigated prospectively at multiple assessment points before and after combined radiotherapy of prostate cancer including HDR brachytherapy and neoadjuvant androgen deprivation therapy. Between April 2000 and June 2003, patients with predominantly advanced localized prostate tumours subjected to this treatment were asked before treatment and on follow-up visits to complete a questionnaire covering urinary, bowel and sexual problems. The mainly descriptive analyses included 525 patients, responding to at least one questionnaire before or during the period 2-34 months after radiotherapy. Adding androgen deprivation before radiotherapy significantly worsened sexual function. During radiotherapy, urinary, bowel and sexual problems increased and were reported at higher levels up to 34 months, although there seemed to be a general tendency to less pronounced irritative bowel and urinary tract symptoms over time. No side effects requiring surgery were reported. Classic late irradiation effects such as mucosal bleeding were demonstrated mainly during the second year after therapy, but appear less pronounced in comparison with dose escalated EBRT series. In conclusion, despite the high radiation dose given, the toxicity seemed comparable with that of other series but long term (5-10 years) symptom outcome has to be determined.

Vibro-acoustography imaging of permanent prostate brachytherapy seeds in an excised human prostate--preliminary results and technical feasibility

OBJECTIVE

The objective in this work is to investigate the feasibility of using a new imaging tool called vibro-acoustography (VA) as a means of permanent prostate brachytherapy (PPB) seed localization to facilitate post-implant dosimetry (PID).

METHODS AND MATERIALS

Twelve OncoSeed (standard) and eleven EchoSeed (echogenic) dummy seeds were implanted in a human cadaver prostate. Seventeen seeds remained after radical retropubic prostatectomy. VA imaging was conducted on the prostate that was cast in a gel phantom and placed in a tank of degassed water. 2-D magnitude and phase VA image slices were obtained at different depths within the prostate showing location and orientation of the seeds.

RESULTS

VA demonstrates that twelve of seventeen (71%) seeds implanted were visible in the VA image, and the remainder were obscured by intra-prostatic calcifications. Moreover, it is shown here that VA is capable of imaging and locating PPB seeds within the prostate independent of seed orientation, and the resulting images are speckle free.

CONCLUSION

The results presented in this research show that VA allows seed detection within a human prostate regardless of their orientation, as well as imaging intra-prostatic calcifications.

Prostate cryotherapy monitoring using vibroacoustography: preliminary results of an ex vivo study and technical feasibility

The objective of this research is to prospectively evaluate the feasibility of vibroacoustography (VA) imaging in monitoring prostate cryotherapy in an ex vivo model. Baseline scanning of an excised human prostate is accomplished by a VA system apparatus in a tank of degassed water. Alcohol and dry ice mixture are used to freeze two prostate tissue samples. The frozen prostates are subsequently placed within the water tank at 27 degrees C and rescanned. VA images were acquired at prescribed time intervals to characterize the acoustic properties of the partially frozen tissue. The frozen prostate tissue appears in the images as hypoemitting signal. Once the tissue thaws, previously frozen regions show coarser texture than prior to freezing. The margin of the frozen tissue is delineated with a well-defined rim. The thawed cryolesions show a different contrast compared with normal unfrozen prostate. In conclusion, this pilot study shows that VA produces clear images of a frozen prostate at different temperature stages. The frozen tissue appears as a uniform region with well-defined borders that are readily identified. These characteristic images should allow safer and more efficient application of prostatic cryosurgery. These results provide substantial motivation to further investigate VA as a potential modality to monitor prostate cryotherapy intraoperatively.

High-Dose-Rate Brachytherapy Plus External Beam Radiotherapy for T1 to T3 Prostate Cancer: An Experience in Taiwan

OBJECTIVES

To report outcomes for localized prostate cancer patients treated with the combination of high-dose-rate (HDR) brachytherapy and external beam radiotherapy (EBRT).

METHODS

Eighty-five Stage T1c to T3b prostate cancer patients treated with HDR brachytherapy plus EBRT were included. An HDR dose of 16.5 Gy in 3 fractions over 24 hours was given 2 weeks before EBRT. An EBRT dose of 50.4 Gy was administered to the prostate and seminal vesicles. Younger patients (aged less than 75 years) with greater than 15% risk of nodal metastasis received whole-pelvis RT (45 Gy in 25 fractions) as part of EBRT.

RESULTS

Fifty percent of patients belonged to the high-risk (T3a or Gleason score 8-10 or prostate-specific antigen greater than 20 ng/mL) or very-high-risk (T3b) groups. After a median follow-up of 49 months (range, 24 to 70 months), 4-year biochemical control survival (less than nadir + 2) was 86% (100%, 91%, and 81% for patients in the low, intermediate, and high-risk groups, respectively. Three of four T3b patients experienced early biochemical failure. Four patients (5%) had grade 3 implant-related urinary retention. Chronic gastrointestinal toxicities were limited, but four grade 3 chronic genitourinary toxicities (5%) were noted in relation to urethral stricture and severe hematuria. Whole-pelvis EBRT was a major contributing factor to acute but not to chronic gastrointestinal toxicities. Among 60 patients with pretreatment sexual potency, 17 (26%) retained capability after 4 years. Six patients (10%) lost potency merely as a result of salvage hormone therapy.

CONCLUSIONS

High-dose-rate brachytherapy plus EBRT can achieve satisfactory biochemical control with acceptable complications for T1c to T3a prostate cancer patients.

Feasibility of high-dose-rate brachytherapy salvage for local prostate cancer recurrence after radiotherapy: The University of California–San Francisco experience

PURPOSE

The aim of this study was to evaluate the feasibility and safety of salvage high-dose-rate (HDR) brachytherapy for locally recurrent prostate cancer after external beam radiotherapy (EBRT).

METHODS AND MATERIALS

We retrospectively analyzed 21 consecutively accrued patients undergoing salvage HDR brachytherapy for locally recurrent prostate cancer after EBRT between November 1998 and December 2005. After pathologic confirmation of locally recurrent disease, all patients were treated with 36 Gy in six fractions using two transrectal ultrasound-guided HDR prostate implants, separated by 1 week. Eleven patients received neoadjuvant hormonal therapy immediately presalvage, whereas none received adjuvant hormonal therapy postsalvage. Median follow-up time from recurrence was 18.7 months (range, 6-84 months). Determination of subsequent biochemical failure after brachytherapy was based on the definition by the American Society for Therapeutic Radiology and Oncology.

RESULTS

Based on the Common Terminology Criteria for Adverse Events (CTCAE version 3), 18 patients reported Grade 1 to 2 genitourinary symptoms by 3 months postsalvage. Three patients developed Grade 3 genitourinary toxicity. Maximum observed gastrointestinal toxicity was Grade 2; all cases spontaneously resolved. The 2-year Kaplan-Meier estimate of biochemical control after recurrence was 89%. Thirteen patients have achieved a PSA nadir < or =0.1 ng/ml, but at the time of writing this endpoint has not yet been reached for all patients. All patients are alive; however 2 have experienced biochemical failure, both with PSA nadirs > or =1, and have subsequently been found to have distant metastases.

CONCLUSIONS

Salvage HDR prostate brachytherapy appears to be feasible and effective.

High Dose Rate Brachytherapy as a Boost for the Treatment of Localized Prostate Cancer

PURPOSE

We report the outcome and toxicities of high dose rate brachytherapy as a boost for localized prostate cancer.

MATERIALS AND METHODS

Between 1996 and 2003, 309 patients with prostate carcinoma were treated with external beam radiation therapy and high dose rate brachytherapy. Furthermore, 36% of the patients received neoadjuvant/concurrent or adjuvant androgen deprivation therapy. Patients were stratified into 3 groups. Group 1 of 67 patients had Gleason score 6 or less, pretreatment prostate specific antigen 10 ng/ml or less and clinical stage T2a or less. Group 2 of 109 patients had Gleason score 7 or greater, pretreatment prostate specific antigen greater than 10 ng/ml and clinical stage T2b or greater. Group 3 of 133 patients had 2 or more of these higher risk factors.

RESULTS

At a median followup of 59 months the 5-year biochemical control rate, as defined by the American Society for Therapeutic Radiation and Oncology, was 86%, cause specific survival was 98% and overall survival was 91%. Biochemical control in stratified groups 1 to 3 was 98%, 90% and 78%, respectively. On univariate analysis risk group, pretreatment prostate specific antigen and Gleason score were significant predictors of biochemical control. However, on multivariate analysis only risk group and pretreatment prostate specific antigen were significant. Using the Common Toxicity Criteria scale there were 2 cases of grade 3 acute urinary toxicity. Regarding late side effects 4% of patients had grade 3 genitourinary toxicity and 1 had a grade 4 rectal complication.

CONCLUSIONS

External beam radiation therapy and high dose rate brachytherapy for prostate cancer resulted in excellent biochemical control, cause specific survival and overall survival with minimal severe acute or late complications.

Six year experience of external beam radiotherapy, brachytherapy boost with a 1Ci 192Ir source, and neoadjuvant hormonal manipulation for prostate cancer

PURPOSE

To present preliminary outcomes of pulsed dose rate brachytherapy (PDR-BT), external beam radiotherapy (EBRT), and hormonal manipulation, for prostate cancer.

PATIENTS AND METHODS

Between December 1999 and January 2005, 165 consecutive patients with Stage T1-T3, N0, M0 prostate cancer were treated. Hormones were used in every patient. Median follow-up was 36 months. Risk groups were low (either Stage < or =T2a, +/- Gleason score < or =6, +/- Prostate-Specific Antigen [PSA] level < or =10 ng/mL); intermediate (either Stage T2b,c, +/- Gleason score 7, +/- PSA 10-20 ng/mL); and high (either Stage T3, +/- Gleason score 8-10, +/- PSA >20 ng/mL).

RESULTS

At 3 years, Radiotherapy Oncology Group (RTOG) Grade 3 and 4 genito-urinary toxicity was 4% and 1.4%; RTOG Grade 3 and 4 gastro-intestinal toxicity was 2.6% and 0%, respectively. Erectile preservation was 61%. Overall survival was 93% (154 of 165) and cause-specific survival was 98% (162 of 165). At 3 years, disease free survival (DFS) was 93% (153 of 165). DFS for low-, intermediate-, and high-risk groups was 100%, 97%, and 81%, respectively (chi(2) (2) = 16.02, p = 0.0003). The nadir plus 2 ng/mL definition (chi(2) (2) = 14.49, p = 0.0007) best predicted clinical failure, having the lowest false-positive rate (3 of 165). The nadir plus 2 ng/mL PSA-progression-free survival (PSA-PFS) rate was 100%, 95%, and 87% for the low-, intermediate, and high-risk groups, respectively. Overall ASTRO PSA-PFS rate was 88%.

CONCLUSIONS

Pulsed dose rate brachytherapy plus EBRT is effective in treating localized prostate cancer, with acceptable toxicity. However, a median 5-year PSA-PFS follow-up is required before providing a solid recommendation. This preliminary information supports continued use.

Brachytherapy technology and physics practice since 1950: a half-century of progress

The 50-year tenure of Physics in Medicine and Biology has coincided with some of the most important developments in radiological science, including the introduction of artificial radioactivity, computers and 3D imaging into medicine. These events have profoundly influenced the development of brachytherapy. Although it is not the dominant radiotherapy modality, it continues to play an important role in cancer therapy, more than a century after its introduction. This paper reviews the impact of three broad categories of innovation introduced since 1950 from the North American perspective: the introduction of artificial radioactivity, computer- and image-based treatment planning, and basic single-source dosimetry.

Four year clinical statistics of iridium-192 high dose rate brachytherapy

BACKGROUND

We evaluated the efficacy and complications of high dose rate (HDR) brachytherapy using iridium-192 (192Ir) combined with external beam radiotherapy (EBRT) in patients with prostate cancer.

METHODS

Ninety-seven patients underwent 192Ir HDR brachytherapy combined with EBRT at our institution between February 1999 and December 2003. Of these, 84 patients were analysed in the present study. 192Ir was delivered three times over a period of 2 days, 6 Gy per time, for a total dose of 18 Gy. Interstitial application was followed by EBRT at a dose of 44 Gy. Progression was defined as three consecutive prostate-specific antigen (PSA) rises after a nadir according to the American Society for Therapeutic Radiology and Oncology criteria. The results were classified into those for all patients and for patients who did not undergo adjuvant hormone therapy.

RESULTS

The 4-year overall survival of all patients, the nonadjuvant hormone therapy group (NAHT) and the adjuvant hormone therapy group (AHT) was 87.2%, 100%, and 70.1%, respectively. The PSA progression-free survival rate of all patients, NAHT, and AHT was 82.6%, 92.0%, and 66.6%, respectively. Of all patients, the 4-year PSA progression-free survival rates of PSA<20 and PSA>or=20 groups were 100%, and 46.8%, respectively. According to the T stage classification, PSA progression-free survival rates of T1c, T2, T3, and T4 were 100%, 82.8%, 100%, and 12.1%, respectively. Prostate-specific antigen progression-free survival rates of groups with Gleason scores (GS)<7 and GS>or=7 were 92.8% and 60.1%, respectively. Of NAHT, PSA progression-free survival of PSA<20 was 100% vs 46.8% for PSA>or=20, that of T1c was 100% vs 75% for T2, and that of GS<7 was 100% vs 75% for GS>or=7. No significant intraoperative or postoperative complications requiring urgent treatment occurred except cerebellum infarction.

CONCLUSIONS

192Ir HDR brachytherapy combined with EBRT was as effective as radical prostatectomy and had few associated complications.

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.

Randomized Trial Comparing Iridium Implant Plus External-Beam Radiation Therapy With External-Beam Radiation Therapy Alone in Node-Negative Locally Advanced Cancer of the Prostate

Purpose

To determine if iridium implant (IM) and external-beam radiation therapy (EBRT) is better than standard EBRT in locally advanced prostate cancer.

Methods

Patients with T2 and T3 prostate cancer with no evidence of metastatic disease were randomly assigned to EBRT of 66 Gy in 33 fractions during 6.5 weeks or to IM of 35 Gy delivered to the prostate during 48 hours plus EBRT of 40 Gy in 20 fractions during 4 weeks. The primary outcome consisted of biochemical or clinical failure (BCF). BCF was defined by biochemical failure, clinical failure, or death as a result of prostate cancer. Secondary outcomes included 2-year postradiation biopsy positivity, toxicity, and survival.

Results

Between 1992 and 1997, 51 patients were randomly assigned to receive IM plus EBRT, and 53 patients were randomly assigned to receive EBRT alone. The median follow-up was 8.2 years. In the IM plus EBRT arm, 17 patients (29%) experienced BCF compared with 33 patients (61%) in the EBRT arm (hazard ratio, 0.42; P = .0024). Eighty-seven patients (84%) had a postradiation biopsy; 10 (24%) of 42 in the IM plus EBRT arm had biopsy positivity compared with 23 (51%) of 45 in the EBRT arm (odds ratio, 0.30; P = .015). Overall survival was 94% in the IM plus EBRT arm versus 92% in the EBRT arm.

Conclusion

The combination of IM plus EBRT was superior to EBRT alone for BCF and postradiation biopsy. This trial provides evidence that higher doses of radiation delivered in a shorter duration result in better local as well as biochemical control in locally advanced prostrate cancer.

Analysis of serial CT scans to assess template and catheter movement in prostate HDR brachytherapy

PURPOSE

As prostate high-dose-rate (HDR) brachytherapy becomes more prevalent, varying amounts of catheter displacement have been noted. To investigate the constancy of catheter position and its impact on dose distribution, we analyzed serial dosimetric CT scans.

METHODS AND MATERIALS

The data from 50 patients were analyzed. During initial CT treatment planning, transverse images of the implant volume were collected, and all structures were digitized into the Nucletron Brachytherapy Planning System. Digitally reconstructed radiographs were generated with rendering of the catheter tips, ischial tuberosity, and perineal template. The distance from each catheter tip to the template and to the ischial tuberosity was measured. The distance between the ischial tuberosity and the template was similarly measured. A second CT set was obtained at different intervals and compared with the first measurement to assess catheter and/or template movement. In 10 patients, the second CT set was obtained before the third fraction in both 2-mm and 5-mm slice sequences, and the latter was used to re-create the HDR plan.

RESULTS

Although no interfraction catheter movement relative to the template was found, the template-catheter unit moved in a caudal direction between HDR fractions. The amount of displacement was time dependent: 2 mm before the second fraction, 8 mm before the third, and 10 mm before the fourth. When comparing the first HDR treatment with the third, median decreases in the following dosimetric parameters were noted: dose to 90% of the prostate volume, 35% (r = 0-60); minimal dose to the base, 35% (r = 17-65); and maximal dose to 1 cm(3), 13% (r = 3-19%).

CONCLUSION

The interstitial catheters did not slip within the template and were not caudally displaced independently but rather in conjunction with the template. The displacement occurred in a time-dependent fashion, and, without redress, significant dosimetric changes are encountered by the third fraction.

Feasibility of amifostine administration in conjunction with high-dose rate brachytherapy

This ongoing study was initiated to determine the feasibility of administering amifostine (Ethyol, WR-2721; MedImmune, Inc, Gaithersburg, MD) with monomodal high-dose rate (mHDR) brachytherapy and to assess the tolerability and side effects of this combination. To date, 18 patients suitable for prostate implant brachytherapy (<or=T2aN0; prostate-specific antigen <or= 10 ng/mL; Gleason score <or= 6) have been treated with mHDR brachytherapy, receiving four 9-Gy fractions administered twice daily for 2 days. Amifostine (500 mg) is administered subcutaneously on the day before implant and 30 to 60 minutes before the first and third mHDR treatments. All 18 patients have received amifostine and brachytherapy as planned. Nausea was manageable with oral prochlorperazine in the pretreatment phase and our standard antiemesis protocol (intravenous promethazine, with granisetron if needed) during the implant; hypotension and asthenia were not problematic. During the 2-week post-treatment phase, grade 1 cystitis occurred in eight of 18 patients; grades 1 and 2 proctitis occurred in six of 18 and five of 18 patients, respectively. Six patients developed urinary obstruction symptoms. Preliminary results support the feasibility and tolerability of subcutaneous amifostine in conjunction with mHDR brachytherapy. Total accrual goal is 50 patients to assess long-term efficacy. Additional studies of HDR with amifostine are planned for patients with recurrent prostate and gynecologic cancer.

Understanding Stereotactic Radiosurgery for Intracranial Tumors, Seed Implants for Prostate Cancer, and Intravascular Brachytherapy for Cardiac Restenosis

Our 21st century has moved us into a world of technology never imagined. The aim of our article is to move oncology nurses beyond the realm of external beam radiation therapy. We chose to present 3 modalities of high precision that are infiltrating the everyday world of radiation therapy. Stereotactic radiosurgery for intracranial brain tumors and brachytherapy for prostate cancer require an expanded knowledge base for nursing to deliver excellent patient care. Cardiac patients receiving radiation seeds is new in the world of oncology nursing. These patients are unique but they are now a part of our world. Expanding our knowledge base to include a radiation procedure in cardiac care does bring us beyond the world of external beam radiation. Patients often seek information from nurses. Having an understanding of the basic principles and techniques will enable oncology nurses to educate patients. The purpose of this article is to explain the procedure of stereotactic radiosurgery, brachytherapy for prostate cancer, and intravascular brachytherapy for cardiac restenosis. Our discussion will include selection criteria, potential sides effects and risks, and nursing care.

High dose rate brachytherapy in the treatment of prostate cancer

The optimal treatment of patients with localized prostate cancer remains controversial. Significant clinical data are available, however, demonstrating that patients treated with radiation therapy (RT) have a significantly better outcome as the dose to the gland is increased. What remains debatable, however, is how to best deliver these higher doses of RT without significantly increasing normal tissue toxicities. Conformal high dose rate brachytherapy (C-HDR BT) represents an alternative means of precise dose delivery that offers similar tumoricidal effects as three-dimensional (3D) conformal external beam radiotherapy (EBRT) or permanent interstitial prostate seed implants with potential additional advantages. Since C-HDR BT consists of temporarily placing afterloading needles or catheters directly into the prostate gland under real-time ultrasound guidance, a steep dose gradient between the prostate and adjacent normal tissues can be generated that is minimally affected by organ motion and edema or treatment setup uncertainties. The ability to control the amount of time the single HDR radioactive source "dwells" at each position along the length of each brachytherapy catheter further enhances the conformity of the dose. In addition, recent radiobiological data on prostate cancer treatment suggest that C-HDR BT should produce tumor control and late normal tissue side effects that are at least as good as achieved with conventional fractionation, with the additional possibility that acute side effects might be reduced. Published data from several groups performing C-HDR BT as boosts in patients with locally advanced disease have supported these assumptions. Combined with the physical advantages discussed above, C-HDR BT should provide similar tumor control as 3D conformal EBRT with the added advantages of reduced treatment times, less acute toxicity, and no additional technological requirements to account and correct for treatment setup uncertainties and organ motion. Due to the success of C-HDR BT as boost treatment in locally advanced disease, this form of radiation treatment has recently been applied to low-risk prostate cancer patients as an alternative brachytherapy technique to permanent interstitial seed implantation. Advantages in this setting include an improved ability to define and deliver the prescribed dose, a significantly shortened treatment schedule compared to 3D conformal EBRT, and the fact that patients are not radioactive after implantation.

Analysis of interaction between number of implant catheters and dose-volume histograms in prostate high- dose-rate brachytherapy using a computer model

PURPOSE

In prostate high-dose-rate brachytherapy, to determine before implant, using the standard geometric optimization algorithm, whether there is an optimal number of catheters.

MATERIALS AND METHODS

Transrectal ultrasound images of the prostate from 24 patients were transferred into the brachytherapy planning system. Urethra and prostate contours were digitized onto each axial slice of a CT scan, as well as hypothetical locations of the catheters (2/3 of the catheters along the prostate contour, 1/3 around the urethra). Each prostate was implanted with 9, 12, 15, 18, and 21 catheters. Dosimetry was optimized using a geometric optimization algorithm; prescription isodose was chosen so that 95% of planning target volume was covered by the 100% isodose.

RESULTS

A significant increase in mean volume of prostate receiving 150% of the dose (V150) when the number of catheters decreased (p < 0.0001). The 9-catheter group significantly differed from each of the other groups; no difference was seen in V150 among the 21-, 18-, and 15-catheter groups. Parallel results were observed for urethra V150 and homogeneity index; there was no difference in conformity index by catheter group.

CONCLUSION

V150 increased when fewer catheters were used. There was no significant difference among the 21-, 18-, and 15-catheter groups: the geometric optimization routine probably compensated for the larger distance between dwell positions. Based on the technique described in our study, we conclude that 15 to 21 catheters seem to cover the prostate adequately without creating excess hot spots.

Treatment of localized prostate cancer using a combination of high dose rate Iridium-192 brachytherapy and external beam irradiation: initial Australian experience

Combination high dose rate brachytherapy (HDRB) and external beam radiation therapy is technically and clinically feasible as definitive treatment for localized prostate cancer. We report the first large Australian experience using this technique of radiation dose escalation in 82 patients with intermediate- and high-risk disease. With a median follow up of 3 years (156 weeks), complications were low and overall prostate-specific antigen progression-free survival was 91% using the American Society for Therapeutic Radiology and Oncology consensus definition. The delivery of hypofractionated radiation through the HDRB component shortens overall treatment time and is both biologically and logistically advantageous. As a radiation boost strategy, HDRB is easy to learn and could be introduced into most facilities with brachytherapy capability.