High-dose-rate brachytherapy for localized prostate adenocarcinoma post abdominoperineal resection of the rectum and pelvic irradiation: Technique and experience

PurposeTreatment options are limited for patients with localized prostate cancer and a prior history of abdominoperineal resection (APR) and pelvic irradiation. We have previously reported on the successful utility of high-dose-rate (HDR) brachytherapy salvage for prostate cancer failing definitive external beam radiation therapy (EBRT). In this report, we describe our technique and early experience with definitive HDR brachytherapy in patients post APR and pelvic EBRT.Patients and MethodsSix men with newly diagnosed localized prostate cancer had a prior history of APR and pelvic EBRT. Sixteen to 18 HDR catheters were placed transperineally under transperineal ultrasound–guidance. The critical first two catheters were placed freehand posterior to the inferior rami on both sides of the bulbar urethra under cystoscopic visualization. A template was used for subsequent catheter placement. Using CT-based planning, 5 men received 36 Gy in six fractions as monotherapy. One patient initially treated with EBRT to 30 Gy, received 24 Gy in four fractions.ResultsMedian age was 67.5 (56–74) years. At a median followup of 26 (14–60) months, all patients are alive and with no evidence of disease per the Phoenix definition of biochemical failure, with a median prostate-specific antigen nadir of 0.19 ng/mL. Three men have reported grade 2 late genitourinary toxicity. There has been no report of grade 3–5 toxicity.ConclusionTransperineal ultrasound–guided HDR brachytherapy using the above technique should be considered as definitive therapy for patients with localized prostate cancer and a prior history of APR and pelvic EBRT.     

Brachytherapy provides comparable outcomes and improved cost-effectiveness in the treatment of low/intermediate prostate cancer

PurposeTo evaluate the cost-effectiveness and outcomes of low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy compared with intensity-modulated radiation therapy (IMRT) in patients with low/intermediate risk of prostate cancer.Methods and MaterialsOne thousand three hundred twenty-eight patients with low or intermediate risk of prostate cancer were treated with LDR (n = 207), HDR with four fractions (n = 252), or IMRT (n = 869) between January 1992 and December 2008. LDR patients were treated with palladium seeds to a median dose of 120 Gy, whereas HDR patients were treated to a median dose 38.0 Gy (four fractions). IMRT patients received 42–44 fractions with a median dose of 75.6 Gy. Clinical outcomes were compared, including biochemical failure, cause-specific survival, and overall survival.ResultsOverall, no differences in 5-year biochemical control (BC) or cause-specific survival were noted among treatment modalities. The calculated reimbursement for LDR brachytherapy, HDR brachytherapy with four fractions, and IMRT was $9,938; $17,514; and $29,356, respectively. HDR and LDR brachytherapy were statistically less costly to Medicare and the institution than IMRT (p < 0.001), and LDR brachytherapy was less costly than HDR brachytherapy (p = 0.01 and p < 0.001). Incremental cost-effectiveness ratios for cost to Medicare for BC with IMRT were $4045 and $2754 per percent of BC for LDR and HDR brachytherapy, respectively. Incremental cost-effectiveness ratio using institutional cost comparing IMRT with LDR and HDR brachytherapy was $4962 and $4824 per 1% improvement in BC.ConclusionsIn this study of patients with low and intermediate risk of prostate cancer, comparable outcomes at 5 years were noted between modalities with increased costs associated with IMRT.     

Outcomes of salvage high dose-rate brachytherapy with or without pelvic external beam radiotherapy in patients with palpable local recurrence of prostate cancer after radical prostatectomy

PurposeThis study aims to evaluate the outcomes and toxicities in patients with palpable local recurrence of prostate cancer after radical prostatectomy (RP), who were treated with salvage high dose-rate brachytherapy (HDR-BT) with or without pelvic external beam radiotherapy (EBRT).MethodsThis retrospective review included patients with palpable local recurrence of prostate cancer after RP who underwent salvage HDR-BT at a single institution between 2002 and 2020. HDR-BT regimens included 950 cGy x 2 (N = 4) or 1500 cGy x 1 (N = 2) combined with EBRT; or monotherapy with 950 cGy x 4 (N = 1) or 800 cGy x 2 (N = 1). Toxicity was graded according to CTCAE Version 5.0.ResultsA total of 8 patients were included. Median follow-up was 49 months (range: 9–223 months). Median age at time of salvage brachytherapy was 68 years (range: 59–85 years). Seven out of 8 patients were alive at last follow-up. There have been no locoregional recurrences. Three patients developed distant metastatic disease. One patient developed acute grade 3 urinary obstruction requiring catheterization, which lasted for 1 day postbrachytherapy. One patient developed late grade 3 urinary incontinence 18 months after brachytherapy. There were no other grade 2+ toxicities.ConclusionsThis study demonstrates the safety and efficacy of salvage HDR-BT in the setting of palpable local recurrence of prostate cancer after RP, with durable locoregional control and acceptable rates of toxicity. HDR-BT should be further explored as an option for dose-escalated salvage radiotherapy after prior radical prostatectomy.     

Cost-effectiveness of prostate boost with high-dose-rate brachytherapy versus intensity-modulated radiation therapy in the treatment of intermediate-high risk prostate cancer

PurposeThe recently published ASCENDE-RT randomized clinical trial demonstrated improved biochemical control, albeit with increased toxicity, for a prostate boost with brachytherapy versus external beam radiation therapy alone in patients with intermediate-high risk prostate cancer. In this study, we investigated the cost-effectiveness of these two modalities in the treatment of intermediate-high risk prostate cancer.Methods and materialsA multistate Markov model was created to model a patient with intermediate-high risk prostate cancer. The two treatment options modeled were (1) 23 fractions of intensity-modulated radiation therapy (IMRT) and two fractions of high-dose-rate prostate brachytherapy (brachytherapy boost) and (2) 44 fractions of IMRT (IMRT alone). Each patient received 1 year of hormone therapy, per the ASCENDE-RT protocol. Model assumptions, including clinical outcomes, toxicity, and utilities were derived from the medical literature. Costs of radiation therapy were estimated using Medicare reimbursement data.ResultsThe estimated expected lifetime cost of brachytherapy boost was $68,696, compared to $114,944 for IMRT alone. Brachytherapy boost significantly lowered expected lifetime treatment costs because it decreased the incidence of metastatic castration-resistant prostate cancer, cutting the use of expensive targeted therapy for metastatic castration-resistant prostate cancer. Brachytherapy boost had an expected quality-adjusted life years of 10.8 years, compared to 9.3 years for IMRT alone. One-way sensitivity analyses of our results found brachytherapy boost to be cost-effective over a wide range of cost, utility, and cancer progression rate assumptions.ConclusionsIMRT with high-dose-rate brachytherapy boost is a cost-effective treatment for intermediate-high risk prostate cancer compared to IMRT alone.     

Permanent seed brachytherapy for locally recurrent prostate cancer after radical prostatectomy: A case report and review of the literature

PurposeTo describe the management of a patient with locally recurrent prostate cancer in the prostate bed, 10 years after a radical prostatectomy.Methods and MaterialsA 71-year-old man had a radical prostatectomy for a Gleason 7 clinical T2a carcinoma of the prostate in 2000. Final pathologic stage was pT3a pN0. Postoperatively his prostate-specific antigen was undetectable, but by 2008 it was 1.0 ng/mL and in 2011 it reached to 1.43 ng/mL. He was referred for consideration of salvage radiotherapy. Staging workup was negative but transrectal ultrasound revealed a 15 cc recurrence in the prostate bed. A combination of external beam radiation therapy (4600/23/4.5 weeks to the pelvis) and a brachytherapy boost (115 Gy) was selected for definitive management. Androgen ablation was not used.ResultsThe treatment was well tolerated. The brachytherapy boost was planned in a similar fashion to a de novo implant for an intact prostate. The postimplant dosimetry was evaluated using magnetic resonance imaging-computed tomography (MR–CT) fusion and appeared satisfactory. Acute toxicity was minimal. Six months after brachytherapy, the prostate-specific antigen had fallen from 1.43 to 0.05 ng/mL.ConclusionsDose escalation with combined external beam and brachytherapy may be feasible if recurrent disease can be visualized using transrectal ultrasound and encompassed in an implanted volume. Although longer followup and a larger series of patients are required to demonstrate safety and efficacy, consideration should be given this approach.     

Four-year outcomes of hypofractionated high-dose-rate prostate brachytherapy and external beam radiotherapy

PurposeHigh-dose-rate (HDR) brachytherapy boost in prostate cancer allows dose escalation and delivery of higher biologically effective dose (BED). We evaluated the outcomes of intensity-modulated radiation therapy (IMRT) and HDR boost in a community setting.Methods and MaterialsBetween July 2003 and April 2008, 148 patients with prostate cancer were treated at Cancer Center of Irvine using two transperineal implants performed 1 week apart (22 Gy delivered in four fractions divided between two insertions and delivered twice daily), followed by IMRT (50.4 Gy). Hormonal therapy was given for 1 year to all patients with Gleason score of 8 or higher.ResultsPatient characteristics are as follows: median age at treatment, 71 years; American Joint Committee on Cancer Group IIB, 53%; Gleason score of 7, 41%; and Gleason score of 8 or higher, 14%. Median followup was 49 months, and median prostate-specific antigen (PSA) nadir was 0.15 ng/mL. The 4-year actuarial biochemical disease-free survival (bDFS) was 96.8/81% by Phoenix/PSA lower than 0.5 ng/mL criteria. According to National Comprehensive Cancer Center Clinical Practice Guidelines–defined recurrence risk groups, 4-year bDFS for low risk was 100/92.9%, intermediate risk was 100/86.7%, and high risk was 94/75.4% by Phoenix/PSA lower than 0.5 ng/mL criteria. No statistically significant difference in bDFS was detected by either failure criteria based on risk group, lymph node risk, or initial PSA. Treatment was well tolerated. Subacute/late genitourinary and gastrointestinal toxicities were limited to 10% and 5%, respectively of all patients.ConclusionsProstate IMRT plus HDR brachytherapy boost was well tolerated with appropriate PSA response and bDFS at 4 years, demonstrated in a community setting. This treatment schema provides a high BED, comparable with hypofractionated prostate regimens previously reported in the literature. Higher BED delivery should be explored in further dose escalation studies.     

Combined modality treatment with high-dose-rate brachytherapy boost for locally advanced prostate cancer

PURPOSE: This is a retrospective review of our experience using high-dose-rate (HDR) brachytherapy boost for prostate cancer. METHODS AND MATERIALS: During the study period, we recommended external beam radiotherapy (45 Gy) and HDR boost (18 Gy in three fractions) combined with hormonal therapy (HT) for 2 months before and during radiotherapy to patients with at least one of the following risk features: pretreatment prostate-specific antigen>10, Gleason score (GS)>or=7, and clinical T3 disease. Additional HT for 2 years after radiotherapy was recommended for patients with GS>7. To patients whose risk of positive nodes exceeded 15%, we recommended whole pelvic radiotherapy. We administered HDR via single implant, and all fractions were given within 24h. RESULTS: This report is based on our initial 64 patients treated with HDR boost. The median follow-up was 50 months (range 25-68 months). The 4-year estimates of overall and disease-free survival were 98% and 92%, respectively. One patient experienced late grade 4 gastrointestinal toxicity. CONCLUSIONS: HDR brachytherapy is an effective means of delivering conformal prostate radiotherapy, and may be used with whole pelvic radiotherapy and HT.     

Use of a rectal spacer with low-dose-rate brachytherapy for treatment of prostate cancer in previously irradiated patients: Initial experience and short-term results

BackgroundSalvage brachytherapy in patients with prior pelvic radiation carries a risk of rectal injury. Herein, we report our initial experience using a hydrogel spacer between the prostate and the rectum during salvage brachytherapy.Methods and MaterialsA total of 11 patients with prostate cancer and prior radiotherapy (5 prostate brachytherapy, 2 prostate external beam radiation therapy [EBRT], and 4 rectal cancer EBRT) received ¹²⁵I brachytherapy after attempted placement of 10 cc of a diluted hydrogel spacer between the prostate and rectum.ResultsSpacing was achieved in 8 of the 11 (73%) patients but was not possible in 3 (1 prior brachytherapy and 2 prior EBRT) owing to fibrosis and adhesions. For the 8 patients in whom spacing was accomplished, the median space between the prostate and rectum was 10.9 mm (prior EBRT) vs. 7.7 mm (prior brachytherapy), p = 0.048. Median followup was 15.7 months. One patient developed a prostato-rectal fistula requiring a diverting colostomy. The 16-month estimate of late Grade 3 or 4 gastrointestinal or genitourinary toxicity was 26%. One patient developed lymph node–positive recurrence. The 16-month prostate-specific antigen failure-free survival rate was 89%. Compared with baseline, Expanded Prostate Cancer Index Composite for Clinical Practice urinary quality of life (QoL) was significantly worse at 3 and 6 months but not significantly worse by 1 year. There were no significant changes throughout the study period in bowel or sexual QoL.ConclusionHydrogel spacer placements may be feasible in most patients with prior pelvic radiation. Further followup is needed to determine whether spacer placement will produce long-term improvements in toxicity or QoL.     

Salvage brachytherapy for recurrent prostate cancer

PurposeTo evaluate the role of salvage prostate brachytherapy for locally recurrent prostate cancer after external beam radiation alone.Methods and MaterialsSixty-nine consecutive patients treated with salvage brachytherapy after a local failure were analyzed. All patients were found to have pathologic proven recurrent prostate cancer at least 2 years after initial therapy and no regional or distant disease on imaging studies. Pd-103 was used with a prescribed pD₉₀ of 100 Gy. In total, 89.9% of patients received androgen suppression (AS) as part of their salvage therapy. Patients whose prostate-specific antigen >5.0 ng/mL while on AS were considered to have castration resistant prostate cancer (CRPC). Patients on AS >6 months before salvage brachytherapy were considered to have delayed therapy. Patients retreated within 5 years after their initial treatment were considered to have early failures.ResultsTotal median followup after salvage therapy was 5.0 years (0.6–13.7). From the date of salvage, 5-year biochemical control for low-risk patients was 85.6%, intermediate-risk patients 74.8%, and high-risk patients 66%. Five-year biochemical control was 73.8% for non-CRPC and 22% for CRPC cases (<0.001). Including and excluding CRPC cases, early treatment after failure vs. delayed treatment was significantly better (p < 0.05). Chronic adverse events were seen in few patients, with genitourinary Grade 3 toxicity of 8.7% and no genitourinary Grade 4 or gastrointestinal Grade 3 or higher toxicities.ConclusionsA subset of failures after definitive radiation is local in nature, and excellent control is possible with salvage brachytherapy.     

Clinical outcomes of high-dose-rate brachytherapy and external beam radiotherapy in the management of clinically localized prostate cancer

PurposeTo report prostate-specific antigen (PSA) relapse-free survival and treatment-related toxicity outcomes after combining high-dose-rate (HDR) brachytherapy with external beam radiotherapy (EBRT) for patients with clinically localized prostate cancer.Methods and MaterialsBetween 1998 and 2009, 229 patients were treated with HDR brachytherapy followed 3 weeks later by supplemental EBRT. The HDR brachytherapy boost consisted of three fractions of ¹⁹²Ir (5.5–7.5 Gy per fraction), and EBRT consisted of intensity-modulated radiotherapy delivering an additional 45.0–50.4 Gy directed to the prostate gland and seminal vesicles. Median follow-up was 61 months.ResultsSeven-year PSA relapse-free survival for low-, intermediate-, and high-risk patients were 95%, 90%, and 57%, respectively (p < 0.001). Among high-risk patients treated with biological equivalent doses in excess of 190 Gy, 7-year PSA relapse-free survival was 81%. In multivariate analysis, Gleason scores of ≥8 predicted for increased risk of biochemical failure, whereas the use of short-term neoadjuvant androgen deprivation therapy did not influence tumor-control outcomes even among intermediate- or high-risk patients. Seven-year incidence of distant metastases for low-, intermediate-, and high-risk patients were 5%, 3%, and 17%, respectively. Seven-year incidence of late Grade 2 and 3 genitourinary toxicities were 22.1% and 4.9%, respectively and the 7-year incidence of Grade 2 and 3 gastrointestinal toxicities were 1% and 0.4%, respectively.ConclusionHDR prostate brachytherapy in conjunction with supplemental EBRT results in excellent biochemical relapse-free survival rates with a low incidence of severe late genitourinary or gastrointestinal toxicities. The use of short-term neoadjuvant androgen deprivation did not influence long-term biochemical tumor control in this cohort.     

High-dose-rate endorectal brachytherapy for locally advanced rectal cancer in previously irradiated patients

PurposePreoperative high-dose-rate (HDR) endorectal brachytherapy is well tolerated among patients with locally advanced rectal cancer. However, these studies excluded patients who previously received pelvic radiation therapy (RT). Because a favorable toxicity profile has been published for HDR endorectal brachytherapy, we evaluated this technique in patients who have previously received pelvic irradiation.Methods and MaterialsWe included patients who had received pelvic irradiation for a previous pelvic malignancy and later received preoperative HDR endorectal brachytherapy for rectal cancer. Brachytherapy was delivered to a total dose of 26 Gy in 4 consecutive daily 6.5 Gy fractions.ResultsWe evaluated 10 patients who previously received pelvic external beam radiation therapy (EBRT) alone (n=6), EBRT and brachytherapy (n=2), or brachytherapy alone (n=2). The median interval between the initial course of RT and endorectal brachytherapy was approximately 11 years (range, 1-19 years). Two patients experienced a complete pathologic response while 1 patient had a near complete pathologic response. No acute grade ≥3 toxicity was observed. No intraoperative or postoperative surgical complications were observed.ConclusionsPreoperative HDR endorectal brachytherapy is an alternative to EBRT for patients with locally advanced rectal cancer who have previously received pelvic RT.     

High-dose-rate surface brachytherapy to boost elongated,curvilinear incisional scars after extrapleural pneumonectomy for malignant pleural mesothelioma treated with adjuvant intensity-modulated radiation therapy

PurposeProviding adequate dosimetric coverage of elongated, curvilinear incisions during adjuvant intensity-modulated radiation therapy (IMRT) after extrapleural pneumonectomy (EPP) for malignant pleural mesothelioma (MPM) creates technical challenges. We explored high-dose-rate (HDR) surface brachytherapy to supplement dose to multiple curvilinear incisions. This modality circumvents the technical limitations of relying on multiple en face electron fields while minimizing dose to adjacent normal tissues.Methods and MaterialsA 59-year-old man presented with a left-sided, Stage III, T3N2M0, epithelioid MPM. After undergoing a left EPP, adjuvant IMRT was recommended to improve local control. An eight-field IMRT plan was designed to encompass the postoperative hemithorax. Incisional scars were lengthy and extended beyond the hemithoracic target volume. Both en face electron and surface HDR plans were prepared and evaluated based on dosimetric coverage of the incisional scars, dose to normal tissues, reliability of setup, and treatment delivery.ResultsHDR was preferred. The patient was planned and treated in the right lateral decubitus position. HDR source catheters were placed along the incisions atop 5-mm bolus. A composite plan including IMRT and brachytherapy dose contributions was produced. Boosts of incisional scars were performed in six fractions (three fractions per week) of 3 Gy prescribed to 12 mm from the catheter. HDR brachytherapy was well tolerated.ConclusionsSurface HDR brachytherapy is a viable option for supplemental dose to incisional scars at risk of local recurrence after EPP for MPM. Advantages over electron beam therapy include avoidance of field abutments and feathering, less tissue–bone interface dose uncertainty and reproducibility of treatment delivery.     

The equivalent dose contribution from high-dose-rate brachytherapy to positive pelvic lymph nodes in locally advanced cervical cancer

PurposeDefinitive radiation therapy for locally advanced cervical cancer involves external beam radiation therapy (EBRT) and high-dose-rate (HDR) brachytherapy. There remains controversy and practice pattern variation regarding the optimal radiation dose to metastatic pelvic lymph nodes (LNs). This study investigates the contribution of the pelvic LN dose from HDR brachytherapy.Methods and MaterialsFor 17 patients with 36 positive pelvic LNs, each LN was contoured on a computed tomography (CT) plan for EBRT and on brachytherapy planning CTs using positron emission tomographic images obtained before chemoradiation. The mean delivered dose from each plan was recorded, and an equivalent dose in 2-Gy fractions (EQD2) was calculated. A Student's t test was performed to determine if the mean delivered dose is significantly different from the mean prescribed dose and EQD2.ResultsThe average prescribed dose from the total EBRT was 54.09 Gy. The average prescribed HDR dose to International Commission on Radiation Units point A was 26.81 Gy. The average doses delivered to the involved LNs from EBRT and brachytherapy were 54.25 and 4.31 Gy, respectively, with the corresponding EQD2 of 53.45 and 4.00 Gy. There was no statistically significant difference (p < 0.05) between the mean delivered and the prescribed doses for EBRT and between the delivered dose and the EQD2 for EBRT and brachytherapy.ConclusionsOur study shows that the HDR contribution is 7% (4.00 Gy) of the total EQD2 (57.45 Gy). The HDR contribution should be accounted for when prescribing the EBRT boost dose to pelvic LNs for the optimal therapeutic dose.     

Phase I/II trial of single-fraction high-dose-rate brachytherapy-boosted hypofractionated intensity-modulated radiation therapy for localized adenocarcinoma of the prostate

PurposeA Phase I/II protocol was conducted to examine the toxicity and efficacy of the combination of intensity-modulated radiation therapy (IMRT) with a single-fraction high-dose-rate (HDR) brachytherapy implant.Methods and MaterialsFrom 2001 through 2006, 26 consecutive patients were treated on the trial. The primary objective was to demonstrate a high rate of completion without experiencing a treatment-limiting toxicity. Eligibility was limited to patients with T stage ≤2b, prostate-specific antigen (PSA) ≤20, and Gleason score ≤7. Treatment began with a single HDR fraction of 6 Gy to the entire prostate and 9 Gy to the peripheral zone, followed by IMRT optimized to deliver in 28 fractions with a normalized total dose of 70 Gy. Patients received 50.4 Gy to the pelvic lymph node. The prostate dose (IMRT and HDR) resulted in an average biologic equivalent dose >128 Gy (α/β = 3). Patients whose pretreatment PSA was ≥10 ng/mL, Gleason score 7, or stage ≥T2b received short-term androgen ablation.ResultsMedian followup was 53 months (9–68 months). There were no biochemical failures by either the American Society of Therapeutic Radiology and Oncology or the Phoenix definitions. The median nadir PSA was 0.32 ng/mL. All the 26 patients completed the treatment as prescribed. The rate of Grade 3 late genitourinary toxicity was 3.8% consisting of a urethral stricture. There was no other Grade 3 or 4 genitourinary or gastrointestinal toxicities.ConclusionsSingle-fraction HDR-boosted IMRT is a safe effective method of dose escalation for localized prostate cancer.     

Early outcomes of high-dose-rate brachytherapy combined with ultra-hypofractionated radiation in higher-risk prostate cancer

PURPOSEThis study evaluated outcomes associated with a high-dose-rate (HDR) brachytherapy boost combined with stereotactic body radiation therapy (SBRT) for patients with higher-risk localized prostate cancer.MATERIALS AND METHODSWe identified 101 patients with National Comprehensive Cancer Network high-risk, unfavorable intermediate-risk, or favorable intermediate-risk with probable extra-prostatic extension treated with HDR brachytherapy (15 Gy x 1 fraction) followed by SBRT (5 Gy x 5 daily fractions to the prostate and/or seminal vesicles and/or pelvic lymph nodes). Androgen deprivation therapy was used in 55.4% of all patients (90% of high-risk, 33% of intermediate-risk). Toxicities according to Common Terminology Criteria for Adverse Events (CTCAE) v4.0 and International Prostate Symptom Scores were prospectively documented at each followup visit. Biochemical relapse was defined as PSA nadir +2ng/mL.RESULTSThe median follow-up time after SBRT was 24.1 months. No grade ≥3 toxicities were observed. The incidence of acute and late grade 2 gastrointestinal toxicities was both 0.99%. Acute and late grade 2 genitourinary (GU) toxicities were observed in 5.9% and 9.9%, respectively. Median time to a grade 2 GU toxicity was 6 months with a 14% 2-year actuarial rate of grade 2 GU toxicity. Median International Prostate Symptom Scores at 24 months was not significantly different than baseline (6 vs. 5; p = 0.24). Inclusion of pelvic lymph nodes and absence of a rectal spacer were significantly associated with more frequent grade ≥1 GU toxicity, but not grade ≥2 GU or gastrointestinal toxicity. The 2-year biochemical relapse free survival was 97%.CONCLUSIONSHDR brachytherapy combined with SBRT was associated with a favorable early toxicity profile and encouraging cancer control outcomes.     

Interfractional fluctuation of rectal dose in high dose rate brachytherapy for prostate cancer

Purpose The aim of the study was to explore the cause of the difference in the maximal rectal dose between the first and second high dose rate (HDR) brachytherapy applications by comparing the thickness of the anterior rectal wall. Materials and methods The rectal dose and the thickness of the anterior rectal wall were analyzed in 26 patients with prostate cancer. After undergoing external beam radiation treatment with a total isocenter dose of 50 Gy, they were treated with HDR brachytherapy of 7.5 Gy/fraction, two fractions daily. The interval between the first HDR brachytherapy session and the second was 5 h. The rectal doses were directly surveyed during irradiation of the HDR brachytherapy. Thickening of the anterior rectal wall was measured at the same level by axial computed tomography scans obtained before the first and second HDR brachytherapy applications. Results The maximal surveyed rectal doses during the first and second HDR brachytherapy applications were 188 ± 51 cGy and 220 ± 35 cGy, respectively (P < 0.01). The fluctuation ratio exceeded 1 in each case. The thickness of the anterior rectal wall before the first and second HDR brachytherapy applications was 18.78 ± 4.34 mm and 14.95 ± 4.09 mm (P < 0.01), respectively. The fluctuation difference exceeded 0 in each case. Conclusion The different rectal dose is attributable to thinning of the anterior rectal wall. The total rectal dose is within the range of doses at risk of exerting a toxic effect on the rectum.     

Analysis of high–dose rate brachytherapy dose distribution resemblance in CyberKnife hypofractionated treatment plans of localized prostate cancer

The present study is to analyze the CyberKnife hypofractionated dose distribution of localized prostate cancer in terms of high–dose rate (HDR) brachytherapy equivalent doses to assess the degree of HDR brachytherapy resemblance of CyberKnife dose distribution. Thirteen randomly selected localized prostate cancer cases treated using CyberKnife with a dose regimen of 36.25 Gy in 5 fractions were considered. HDR equivalent doses were calculated for 30 Gy in 3 fractions of HDR brachytherapy regimen. The D_5% of the target in the CyberKnife hypofractionation was 41.57 ± 2.41 Gy. The corresponding HDR fractionation (3 fractions) equivalent dose was 32.81 ± 1.86 Gy. The mean HDR fractionation equivalent dose, D_98%, was 27.93 ± 0.84 Gy. The V_100% of the prostate target was 95.57% ± 3.47%. The V_100% of the bladder and the rectum were 717.16 and 79.6 mm³, respectively. Analysis of the HDR equivalent dose of CyberKnife dose distribution indicates a comparable resemblance to HDR dose distribution in the peripheral target doses (D_98% to D_80%) reported in the literature. However, there is a substantial difference observed in the core high-dose regions especially in D_10% and D_5%. The dose fall-off within the OAR is also superior in reported HDR dose distribution than the HDR equivalent doses of CyberKnife.