High-dose-rate brachytherapy and hypofractionated external beam radiotherapy combined with long-term hormonal therapy for high-risk and very high-risk prostate cancer: outcomes after 5-year follow-up

The purpose of this study was to report the outcomes of high-dose-rate (HDR) brachytherapy and hypofractionated external beam radiotherapy (EBRT) combined with long-term androgen deprivation therapy (ADT) for National Comprehensive Cancer Network (NCCN) criteria-defined high-risk (HR) and very high-risk (VHR) prostate cancer. Data from 178 HR (n = 96, 54%) and VHR (n = 82, 46%) prostate cancer patients who underwent ¹⁹²Ir-HDR brachytherapy and hypofractionated EBRT with long-term ADT between 2003 and 2008 were retrospectively analyzed. The mean dose to 90% of the planning target volume was 6.3 Gy/fraction of HDR brachytherapy. After five fractions of HDR treatment, EBRT with 10 fractions of 3 Gy was administered. All patients initially underwent ≥6 months of neoadjuvant ADT, and adjuvant ADT was continued for 36 months after EBRT. The median follow-up was 61 months (range, 25–94 months) from the start of radiotherapy. The 5-year biochemical non-evidence of disease, freedom from clinical failure and overall survival rates were 90.6% (HR, 97.8%; VHR, 81.9%), 95.2% (HR, 97.7%; VHR, 92.1%), and 96.9% (HR, 100%; VHR, 93.3%), respectively. The highest Radiation Therapy Oncology Group-defined late genitourinary toxicities were Grade 2 in 7.3% of patients and Grade 3 in 9.6%. The highest late gastrointestinal toxicities were Grade 2 in 2.8% of patients and Grade 3 in 0%. Although the 5-year outcome of this tri-modality approach seems favorable, further follow-up is necessary to validate clinical and survival advantages of this intensive approach compared with the standard EBRT approach.     

External beam boost irradiation for clinically positive pelvic nodes in patients with uterine cervical cancer

The purpose of this study was to retrospectively analyze the treatment results of boost external beam radiotherapy (EBRT) to clinically positive pelvic nodes in patients with uterine cervical cancer. The study population comprised 174 patients with FIGO stages 1B1–4A cervical cancer who were treated with definitive radiotherapy (RT) or concurrent chemoradiotherapy (CCRT) and high-dose-rate intracavitary brachytherapy (HDR-ICBT). Patients with positive para-aortic or common iliac nodes (≥10 mm in the shortest diameter, as evaluated by CT/MRI) were ineligible for the study. Fifty-seven patients (33%) had clinically positive pelvic nodes. The median maximum diameter of the nodes was 15 mm (range, 10–60 mm) and the median number of positive lymph nodes was two (range, one to four). Fifty-two of 57 patients (91%) with positive nodes were treated with boost EBRT (6–10 Gy in three to five fractions). The median prescribed dose of EBRT for nodes was 56 Gy. The median follow-up time for all patients was 66 months (range, 3–142 months). The 5-year overall survival rate, disease-free survival rate and pelvic control rate for patients with positive and negative nodes were 73% and 92% (P = 0.001), 58% and 84% (P < 0.001), and 83% and 92% (P = 0.082), respectively. Five of 57 node-positive patients (9%) developed pelvic node recurrences. All five patients with nodal failure had concomitant cervical failure and/or distant metastases. No significant difference was observed with respect to the incidence or severity of late complications by application of boost EBRT. The current retrospective study demonstrated that boost EBRT to positive pelvic nodes achieves favorable nodal control without increasing late complications.     

Definitive radiotherapy for primary vaginal cancer: correlation between treatment patterns and recurrence rate

The purpose of this study was to determine the outcomes and optimal practice patterns of definitive radiotherapy for primary vaginal cancer. Between 1993 and 2012, 49 patients were treated with definitive radiotherapy for primary vaginal cancer in three hospitals. Of these, 15 patients (31%) had clinically positive regional lymph node metastasis. A total of 34 patients (70%) received external beam radiotherapy with high-dose-rate brachytherapy (interstitial or intracavitary), and 8 (16%) (with small superficial Stage I tumors) were treated with local radiotherapy. The median follow-up was 33 months (range: 1–169 months). The 3-year overall survival (OS), disease-free survival (DFS), and loco-regional control (LRC) rates were 83%, 59% and 71%, respectively. In multivariate analysis, the histological type (P = 0.044) was significant risk factors for LRC. In Federation of Gynecology and Obstetrics (FIGO) Stage I cases, 3 of 8 patients (38%) who did not undergo prophylactic lymph node irradiation had lymph node recurrence, compared with 2 of 12 patients (17%) who underwent prophylactic pelvic irradiation. For Stage III–IV tumors, the local recurrence rate was 50% and the lymph node recurrence rate was 40%. Patients with FIGO Stage I/II or clinical Stage N1 had a higher recurrence rate with treatment using a single modality compared with the recurrence rate using combined modalities. In conclusion, our treatment outcomes for vaginal cancer were acceptable, but external beam radiotherapy with brachytherapy (interstitial or intracavitary) was needed regardless of FIGO stage. Improvement of treatment outcomes in cases of FIGO Stage III or IV remains a significant challenge.     

Dose reduction trial from 60 Gy in 10 fractions to 54 Gy in 9 fractions schedule in high-dose-rate interstitial brachytherapy for early oral tongue cancer

To compare the effects of 60 Gy/10 fractions (twice a day) with those of 54 Gy/9 fractions in high-dose-rate interstitial brachytherapy (HDR-ISBT) for early tongue cancer, we performed a matched-pair analysis of patients with early tongue cancer (T1-2N0M0), who were treated with 60 or 54 Gy of radiation between 1996 and 2004. Seventeen patients treated with 54 Gy and 34 matched-pair patients treated with 60 Gy were extracted and analyzed. Local recurrence occurred in two patients in the 54-Gy arm and five patients in the 60-Gy arm. The 2-year local control rates were 88% for both the 54-Gy arm and 60-Gy arm (not significant). The 2-year overall survival rates were 88% in the 60-Gy arm and 82% in the 54-Gy arm. Two-year actuarial complication-free rates were 91% in the 60-Gy arm and 83% in the 54-Gy arm (not significant), respectively. There was no significant association between the total dose and local control rate and late complications. The outcome of 54 Gy/ 9 fractions was similar to that of 60 Gy/ 10 fractions in patients with early tongue cancer.     

Three-dimensional image-based high-dose-rate interstitial brachytherapy for mobile tongue cancer

To investigate the influence of a 3D image-based treatment-planning method for high-dose-rate interstitial brachytherapy (HDR-ISBT) for mobile tongue cancer, we analyzed dose–volume histogram results for the clinical target volume (CTV) and the mandible. Between October 2010 and November 2011, one and four patients having T2 and T3 tumors, respectively, were treated with HDR-ISBT. Multiplane implantation using 9–15 treatment applicators was performed. Lugol''s iodine staining, metal markers, ultrasonography, and magnetic resonance imaging were used to identify the contours of the gross tumor volume (defined as the CTV). The results of the image-based treatment plan were compared with those of the conventional simulated plan on the basis of a reference point 5 mm from the applicator position. The mean D90(CTV) and V100(CTV) were 112% of the prescribed dose (PD) and 98.1%PD, respectively, for the image-based plan, and 113%PD and 97.2%PD, respectively, for the conventional plan. The median CTV_ref/V_ref was 0.23 for the image-based plan and 0.16 for the conventional plan (P = 0.01). The mean D_{0.1 cm³} (mandible), D_{1 cm³} (mandible), and D_{2 cm³} (mandible) were 80.1%PD, 62.5%PD, and 55.7%PD, respectively, for the image-based plan, and 109.1%PD (P = 0.02), 82.4%PD (P = 0.005), and 74%PD (P = 0.004), respectively, for the conventional plan). Image-based treatment planning may achieve high-conformity radiotherapy for the CTV and decrease irradiated doses to the mandible.     

Preliminary results of magnetic resonance imaging-aided high-dose-rate interstitial brachytherapy for recurrent uterine carcinoma after curative surgery

This report presents initial experience with imaging-aided high-dose-rate interstitial brachytherapy (HDR-ISBT) for post-operative recurrence of uterine carcinoma. Fourteen patients presenting with post-operative recurrence of uterine carcinoma (nine cervix and five corpus) between July 2005 and October 2008 were enrolled in this study (median follow-up: 37 months, range: 6-59 months). We implanted magnetic resonance imaging (MRI)-compatible plastic applicators using our own ambulatory technique. HDR-ISBT treatment consisted of twice-a-day irradiation of 6 Gy each with at least a six-hour interval to provide the total prescribed dose. Treatment was based on treatment planning-computed tomography with MRI as a reference. Seven patients were treated with a combination of ISBT (median 30 Gy/5 fractions; range: 27-33 Gy) and external beam radiation therapy (EBRT), and the other seven with brachytherapy only (median 54 Gy/9 fractions; range: 48-54 Gy), one of whom had previously received pelvic EBRT. The three-year estimates of local control and overall survival rates were 77.9% (95% confidence interval (CI): 55.8-100%) and 77.1% (95% CI: 54.2-100%), respectively. Two patients, who had received combined treatment with EBRT showed untoward reactions, including a grade 3 subileus and grade 2 constipation. Another patient, who had been treated with ISBT alone, developed grade 2 urinary constriction. Our imaging-aided HDR-ISBT for post-operative recurrence of uterine carcinoma was found to be practical with promising preliminary results.     

Long-term results of high-dose-rate brachytherapy and external-beam radiotherapy in the primary treatment of endometrial cancer

In this report we update our long-term follow-up results of the prospective study whose aim was to evaluate the efficacy of high-dose-rate (HDR) brachytherapy in combination with external-beam radiotherapy (EBRT) in the treatment of medically inoperable endometrial cancer. Between 1995 and 1998, 29 patients with stages I-III medically inoperable carcinoma of endometrium were treated with definitive irradiation. All patients underwent combined intracavitary HDR brachytherapy and EBRT. The EBRT dose was 50 Gy with midline shield from 16 Gy. The HDR brachytherapy dose was 50 Gy, delivered in 5 fractions in a weekly schedule. Overall survival (OS) at 5 and 10 years was 48.3% and 20.7%, respectively. Disease-specific survival (DSS) at 5 and 10 years was 73.5% and 67.9%, respectively. The 10-year DSS rate was 73.5% for all stages, 85.7% for Stage I disease, 71.4% for Stage II, and 16.7% for stage III disease. Late Grade 1-2 radiation complications were observed in 4 patients (13.8%). Our long-term follow-up confirms that HDR brachytherapy with EBRT appears to be an effective and safe treatment for stage I and II medically inoperable endometrial cancer.     

Dose–volume histogram parameters of high-dose-rate brachytherapy for Stage I–II cervical cancer (≤4cm) arising from a small-sized uterus treated with a point A dose-reduced plan

We investigated the rectal dose-sparing effect and tumor control of a point A dose-reduced plan in patients with Stage I–II cervical cancer (≤4 cm) arising from a small-sized uterus. Between October 2008 and August 2011, 19 patients with Stage I–II cervical cancer (≤4 cm) were treated with external beam radiotherapy (EBRT) for the pelvis and CT-guided brachytherapy. Seven patients were treated with brachytherapy with standard loading of source-dwell positions and a fraction dose of 6 Gy at point A (conventional brachy-plan). The other 12 patients with a small uterus close to the rectum or small intestine were treated with brachytherapy with a point A dose-reduction to match D2cc of the rectum and <6 Gy as the dose constraint (‘point A dose-reduced plan’) instead of the 6-Gy plan at point A (‘tentative 6-Gy plan’). The total doses from EBRT and brachytherapy were added up and normalized to a biological equivalent dose of 2 Gy per fraction (EQD2). The median doses to the high-risk clinical target volume (HR-CTV) D90 in the conventional brachy-plan, tentative 6-Gy plan and point A dose-reduced plan were 62 GyEQD2, 80 GyEQD2 and 64 GyEQD2, respectively. The median doses of rectal D2cc in the corresponding three plans were 42 GyEQD2, 62 GyEQD2 and 51 GyEQD2, respectively. With a median follow-up period of 35 months, three patients developed Grade-1 late rectal complications and no patients developed local recurrence. Our preliminary results suggested that CT-guided brachytherapy using an individualized point A dose-reduced plan might be useful for reducing late rectal complications while maintaining primary tumor control.     

Analysis of prognostic factors in localized high-risk prostate cancer patients treated with HDR brachytherapy,hypofractionated 3D-CRT and neoadjuvant/adjuvant androgen deprivation therapy (trimodality therapy)

Trimodality therapy consisting of high dose rate (HDR) brachytherapy combined with external beam radiation therapy (EBRT), neoadjuvant hormonal therapy (NHT) and adjuvant hormonal therapy (AHT) has been used to treat localized high-risk prostate cancer. In this study, an analysis of patients receiving the trimodality therapy was performed to identify prognostic factors of biochemical relapse-free survival (bRFS). Between May 2005 and November 2008, 123 high-risk prostate cancer patients (D''Amico classification) were treated with NHT prior to HDR brachytherapy combined with hypofractionated EBRT. Among these patients, 121 had completed AHT. The patients were assigned by time to be treated with a low-dose or high-dose arm of HDR brachytherapy with subsequent hypofractionated 3D conformal radiation therapy (3D-CRT). Multivariate analysis was used to determine prognostic factors for bRFS. With a median follow-up of 60 months, the 5-year bRFS for all patients was 84.3% (high-dose arm, 92.9%; low-dose arm, 72.4%, P = 0.047). bRFS in the pre-HDR PSA ≤ 0.1 ng/ml subgroup was significantly improved compared with that in the pre-HDR PSA > 0.1 ng/ml subgroup (88.3% vs 68.2%, P = 0.034). On multivariate analysis, dose of HDR (P = 0.045, HR = 0.25, 95% CI = 0.038–0.97) and pre-HDR PSA level (P = 0.02 HR = 3.2, 95% CI = 1.18–10.16) were significant prognostic factors predicting bRFS. In high-risk prostate cancer patients treated with the trimodality therapy, the dose of HDR and pre-HDR PSA were significant prognostic factors. The pre-HDR PSA ≤ 0.1 subgroup had significantly improved bRFS. Further studies are needed to confirm the relevance of pre-HDR PSA in trimodality therapy.     

Clinical results of external beam radiotherapy alone with a concomitant boost program or with conventional fractionation for cervical cancer patients who did not receive intracavitary brachytherapy

A combination of external beam radiotherapy (EBRT) and intracavitary brachytherapy (ICBT) is well established as the standard radical radiotherapy (RT) for cervical cancer. However, it is sometimes necessary to perform EBRT alone for patients where ICBT is not feasible. For these patients, we initiated EBRT alone with three-dimensional conformal radiotherapy (3DCRT). The purpose of this study is to evaluate the results of EBRT alone without ICBT for patients with cervical cancer. Sixteen patients were treated with EBRT alone between 2002 and 2009. There were three stage IIB, six stage IIIB and seven patients with stage IVA disease. A total of 10 patients were treated with a median dose of 66 Gy with a median overall treatment time (OTT) of 40 days delivered by a concomitant boost (CCB), and a median dose of 60 Gy with a median OTT of 47 days was administered for six patients by conventional fractionation (CF). The 3-year overall survival (OAS) and local control (LC) rates were 43.8% and 75.0%, respectively. The 3-year LC rate was 90.0% for the CCB group, 50.0% for the CF group (P = 0.0692); 100% for OTT ≤42 days, 42.9% for OTT ≥43 days (P = 0.0095). No severe acute and late adverse effects were encountered for any of the patients. These outcomes suggest that EBRT with a CCB program may be a promising radical treatment for cervical cancer that provides better LC with minimal complications, especially in cases where ICBT cannot be performed.     

Technical report: a high-dose-rate interstitial brachytherapy boost for residual sinonasal undifferentiated carcinoma

Sinonasal undifferentiated carcinoma (SNUC) is a highly aggressive and uncommon neoplasm that arises from the mucosa of the nasal cavity or paranasal sinuses. The multidisciplinary approach that includes surgery, radiation therapy (RT), and chemotherapy has been proven to improve survival rates. However, there is no established evidence for the efficacy of further (boost) irradiation following definitive RT in SNUC patients with residual primary tumor. We describe a successful case of a patient with SNUC who had an uncontrolled primary tumor following induction chemotherapy and radical concurrent chemoradiotherapy (CCRT) and underwent a high-dose-rate interstitial brachytherapy (HDR-ISBT) boost. A 75-year-old Japanese woman with unresectable locally advanced SNUC (LA-SNUC) received induction chemotherapy followed by radical CCRT. However, because the residual primary tumor was evident after planned external beam RT, she underwent an HDR-ISBT boost, and the tumor decreased significantly. A complete response (the Response Evaluation Criteria in Solid Tumors, ver. 1.1) was achieved 2 months after brachytherapy, and the patient has been disease-free for 2 years following treatment initiation. In conclusion, an HDR-ISBT boost can be a safe and effective treatment option in patients with residual and inoperable LA-SNUC in the maxillary sinus after initial RT.     

Estimation of the total rectal dose of radical external beam and intracavitary radiotherapy for uterine cervical cancer using the deformable image registration method

We adapted the deformable image registration (DIR) technique to accurately calculate the cumulative intracavitary brachytherapy (ICBT) and external beam radiotherapy (EBRT) rectal dose for treating uterine cervical cancer. A total of 14 patients with primary cervical cancer radically treated with ICRT and EBRT were analysed using the Velocity AI^TM software. Computed tomography (CT) images were registered, and EBRT and ICBT dose distributions were determined. Cumulative D_2cm³, D_1cm³ and D_0.1cm³ were calculated by simple addition of fractional values or by DIR. The accuracy of DIR was evaluated by means of a virtual phantom mimicking the rectum. The dice similarity coefficient (DSC) was calculated to evaluate rectal contour concordance between CT images before and after DIR. Virtual phantom analysis revealed that the average difference between the DIR-based phantom D_mean and the simple phantom D_mean was 1.9 ± 2.5 Gy (EQD₂), and the DIR method included an uncertainty of ∼8.0%. The mean DSC between reference CT and CT was significantly improved after DIR (EBRT: 0.43 vs 0.85, P < 0.005; ICBT: 0.60 vs 0.87, P < 0.005). The average simple rectal D_2cm³, D_1cm³ and D_0.1cm³ values were 77.6, 81.6 and 91.1 Gy (EQD₂), respectively; the DIR-based values were 76.2, 79.5 and 87.6 Gy, respectively. The simple addition values were overestimated, on average, by 3.1, 3.7 and 5.5 Gy, respectively, relative to the DIR-based values. In conclusion, the difference between the simple rectal dose–volume histogram (DVH) parameter addition and DIR-based cumulative rectal doses increased with decreasing DVH parameters.     

Permanent interstitial re-irradiation with Au-198 seeds in patients with post-radiation locally recurrent uterine carcinoma

This study sought to analyze the outcome of patients with post-treatment locally recurrent uterine carcinoma treated with Au-198 seed permanent interstitial re-irradiation (Au-198 IRI). A retrospective review of the data of 15 patients with post-treatment locally recurrent uterine carcinoma treated with Au-198 IRI between 1991 and 2009 was performed to evaluate the disease response, local control, overall survival and complication rates. All the patients had received definitive radiation therapy or surgery as the initial treatment. None were judged as being suitable candidates for surgical treatment, and were referred for Au-198 IRI. Au-198 IRI was performed for the vaginal wall in 8 patients, vaginal stump in 4 patients, vulva in 2 patients, and cervix in 1 patient. The median tumor volume was 1.3 cm³(range, 0.4–6.9), the median treated volume was 6.3 cm³(range, 1.8–11), and the median prescribed dose was 76 Gy (range, 68–90). At a median follow-up duration of 19 months (range, 4.3–146.9), 13 of 15 patients (87%) showed complete responses after Au-198 IRI, although 10 of these 13 patients (77%) developed repeat central recurrence again between 2.5 and 49.7 months after the Au-198 IRI (median, 12.5 months). The overall 2-year local control rate and 2-year overall survival rate in the 15 patients were 33% and 64%, respectively. Two (13%) of the 15 patients experienced late complications that were more severe than Grade III. As a result, Au-198 IRI is considered to be one of the salvage treatment modalities with tolerable complications for inoperable centrally recurrent uterine carcinoma.     

Analysis of late toxicity associated with external beam radiation therapy for prostate cancer with uniform setting of classical 4-field 70 Gy in 35 fractions: a survey study by the Osaka Urological Tumor Radiotherapy Study Group

We aimed to analyse late toxicity associated with external beam radiation therapy (EBRT) for prostate cancer using uniform dose-fractionation and beam arrangement, with the focus on the effect of 3D (CT) simulation and portal field size. We collected data concerning patients with localized prostate adenocarcinoma who had been treated with EBRT at five institutions in Osaka, Japan, between 1998 and 2006. All had been treated with 70 Gy in 35 fractions, using the classical 4-field technique with gantry angles of 0°, 90°, 180° and 270°. Late toxicity was evaluated strictly in terms of the Common Terminology Criteria for Adverse Events Version 4.0. In total, 362 patients were analysed, with a median follow-up of 4.5 years (range 1.0–11.6). The 5-year overall and cause-specific survival rates were 93% and 96%, respectively. The mean ± SD portal field size in the right–left, superior–inferior, and anterior–posterior directions was, respectively, 10.8 ± 1.1, 10.2 ± 1.0 and 8.8 ± 0.9 cm for 2D simulation, and 8.4 ± 1.2, 8.2 ± 1.0 and 7.7 ± 1.0 cm for 3D simulation (P < 0.001). No Grade 4 or 5 late toxicity was observed. The actuarial 5-year Grade 2–3 genitourinary and gastrointestinal (GI) late toxicity rates were 6% and 14%, respectively, while the corresponding late rectal bleeding rate was 23% for 2D simulation and 7% for 3D simulation (P < 0.001). With a uniform setting of classical 4-field 70 Gy/35 fractions, the use of CT simulation and the resultant reduction in portal field size were significantly associated with reduced late GI toxicity, especially with less rectal bleeding.     

Efficacy and safety of nedaplatin-based concurrent chemoradiotherapy for FIGO Stage IB2–IVA cervical cancer and its clinical prognostic factors

Cisplatin-based concurrent chemoradiotherapy (CCRT) is a standard treatment for cervical cancer, but nedaplatin-based CCRT is not routinely administered. We evaluated the efficacy and safety of nedaplatin-based CCRT (35 mg/m² weekly) and analyzed prognostic factors for survival among 52 patients with International Federation of Gynecology and Obstetrics (FIGO) Stage IB2–IVA cervical cancer treated from 1999 to 2009. Patients were treated with a combination of external beam radiotherapy of 40–56 Gy (in 20–28 fractions) and 13.6–28.8 Gy (in 2–4 fractions) of high-dose-rate (HDR) intracavitary brachytherapy or 18 Gy (in 3 fractions) of HDR interstitial brachytherapy. Overall survival (OS), progression-free survival (PFS), and local control (LC) were estimated using the Kaplan–Meier method. The Cox proportional hazard model was used for multivariate analysis. Acute and late toxicities were evaluated using the Common Terminology Criteria for Adverse Events version 4.0. The median follow-up period was 52 months. The median patient age was 63 years. The 5-year OS, PFS and LC rates were 78%, 57% and 73%, respectively. Multivariate analysis showed that histologic type, maximum tumor diameter, and pretreatment hemoglobin level were independent risk factors for PFS. Regarding adverse effects, 24 patients (46%) had acute Grade 3–4 leukopenia and 5 (10%) had late Grade 3 gastrointestinal toxicities. No patient experienced renal toxicity. Nedaplatin-based CCRT for FIGO Stage IB2–IVA cervical cancer was efficacious and safe, with no renal toxicity. Histologic type, maximum tumor diameter, and pretreatment hemoglobin level were statistically significant prognostic factors for PFS.     

外照射联合腔内后装治疗T1、T2期鼻咽癌的疗效观察

目的探讨鼻咽癌外照射后期联合高剂量率腔内后装治疗的效果及并发症.方法有计划地对首程T1、T2期鼻咽癌患者52例,分为单纯外照射组(26例)和外照射联合高剂率腔内后装推量组(综合放疗组26例),其中综合放疗组在鼻咽癌外照射至DT40Gy、50Gy、60Gy时行腔内后装治疗一次.结果综合放疗组与单纯放疗组的三年肿瘤局部控制率分别是100%与73.08%,两组有显著性差异(P＜0.01);3年生存率是92.31%和84.61%,无明显差异(P＜0.05).结论 T1、T2期鼻咽癌外照射后期联合高剂量率腔内后装治疗能提高肿瘤局部控制率,减少外照射的剂量及降低其并发症的产生.     

125Iodine monotherapy for Japanese men with low- and intermediate-risk prostate cancer: outcomes after 5 years of follow-up

Data from 305 Japanese men with low-risk (n = 175) or intermediate-risk (n = 130) prostate cancer who underwent ¹²⁵I monotherapy were retrospectively analyzed. Of the 305 patients, 93 received hormonal therapy for a median of 6 months (range, 1–33 months) before implantation. The prescribed dose to the prostate plus 3- to 5-mm margin was set at 145 Gy. The mean dose to 90% of the prostate volume at 1 month (D90) and the prostate volume receiving at least 100% dose at 1 month (V100) were 173.4 Gy and 95.8%, respectively. The median follow-up was 66 months (range, 12–94 months). The 5-year biochemical non-evidence of disease rate was 95.5% (low-risk, 94.2%; intermediate-risk, 97.3%). The 5-year freedom from clinical failure rate was 98.9% (low-risk, 98.9%; intermediate-risk, 99.2%).The initial prostate-specific antigen level was identified as a significant predictive factor for biochemical recurrence (P = 0.029). The late Grade 3 genitourinary toxicity rate was 2.0%. No patients displayed late gastrointestinal toxicity of Grade 3 or worse. Monotherapy with ¹²⁵I showed excellent outcomes with limited morbidity for Japanese men with low- and intermediate-risk prostate cancer after 5 years of follow-up.