Validation of the bladder neck as an important organ at risk in prostate seed brachytherapy based on D2cc: A single-institution, retrospective review

Purpose

International guidelines recommend urethral dose volume constraints to minimize the risk of urinary toxicity after prostate brachytherapy. An association between dose to the bladder neck (BN) and toxicity has previously been reported, and we sought to evaluate the impact of this organ at risk on urinary toxicity, based on intra-operative contouring.

Material and methods

Rates of acute and late urinary toxicity (AUT and LUT, respectively) were graded according to CTCAE version 5.0 for 209 consecutive patients who underwent low-dose-rate (LDR) brachytherapy monotherapy, with approximately equal numbers treated before and after we began routinely contouring the BN. AUT and LUT were compared in patients treated before and after we began contouring the OAR, and also for those treated after we began contouring who had a D2cc of greater than or less than 50% prescription dose.

Results

AUT and LUT fell after intra-operative BN contouring was instituted. Rates of grade ≥ 2 AUT fell from 15/101 (15%) to 9/104 (8.6%), p = 0.245. Grade ≥ 2 LUT decreased from 32/100 (32%) to 18/100 (18%), p = 0.034. Grade ≥ 2 AUT was observed in 4/63 (6.3%) and 5/34 (15%) of those with a BN D2cc >/≤ 50%, respectively, of prescription dose. Corresponding rates for LUT were 11/62 (18%) and 5/32 (16%).

Conclusions

There were lower urinary toxicity rates for patients treated after we commenced routine intra-operative contouring of the BN. No clear relationship was observed between dosimetry and toxicity in our population.

The potential of low-dose-rate brachytherapy with iodine-125 in the treatment of local recurrences of prostate cancer after primary high-dose-rate monotherapy

Purpose

The incidence of local prostate cancer recurrences after monotherapy with high-dose-rate brachytherapy (HDR-BT) is low. However, a cumulated number of local recurrences during follow-up is naturally observed in highly specialized oncological centers. This retrospective study aimed to present the treatment of local recurrences after HDR-BT with low-dose-rate brachytherapy (LDR-BT).

Material and methods

Nine patients with low- and intermediate-risk prostate cancer with a median age of 71 years (range, 59-82 years) were diagnosed with local recurrences after previous monotherapy HDR-BT, 3 × 10.5 Gy (from 2010 to 2013). Median time to biochemical recurrence was 59 months (range, 21-80 months). All patients received 145 Gy with salvage LDR-BT (iodine-125). Gastrointestinal and urological toxicities were evaluated based on patients' records following CTCAE v. 4.0 and IPSS scales.

Results

The median follow-up after salvage treatment was 30 months (range, 17-63 months). Local recurrences (LR) were detected in two cases, and the actuarial 2-year local control was 88%. Biochemical failure was observed in four cases. Distant metastases (DM) were observed in 2 patients. In one patient, both LR and DM were diagnosed simultaneously. Four patients had no relapse of the disease, and a 2-year disease-free survival (DSF) was 58.3%. Before salvage treatment, median IPSS scores were 6.5 points (range, 1-23 points). At the first follow-up visit, after one month, the mean IPSS score was 20 points, and at the last follow-up visit, it was 8 points (range, 1-26 points). One patient had urinary retention after treatment. There was no significant change in IPSS scores before and after the treatment (p = 0.68). Two patients had grade 1 toxicity in the gastrointestinal tract.

Conclusions

Salvage LDR-BT for patients with prostate cancer previously treated with HDR-BT monotherapy is characterized by acceptable toxicity, and may result in local disease control.

A precise and simple isodose-volume-based verification method for HDR and LDR brachytherapy plans

PURPOSE

The American Association of Physicists in Medicine (AAPM) code of practice for brachytherapy physics recommends performing an independent treatment time calculation. For this we implemented an easy to use isodose-based verification method for HDR (high-dose-rate) and LDR (low-dose-rate) brachytherapy plans.

MATERIAL AND METHODS

Dose-volume-based methods have been developed for Ir-192-based high-dose-rate (HDR) and I-125 prostate low-dose-rate (LDR) brachytherapy. They allow checking the integral dwell time or activity when the volume of a suitable isodose is known. The verification method was validated for 55 clinical HDR and 243 clinical LDR plans.

RESULTS

For HDR brachytherapy, the mean absolute difference between the estimated and calculated integral dwell time was 0.8% ± 1.0% (n = 30) with a single-source path and 2.7% ± 1.1% (n = 25) for multiple source paths. The corresponding value for LDR brachytherapy was 1.8% ± 2.0% (n = 243). In HDR brachytherapy, the verification method depends slightly on the plan class when considering one or more than one source paths. Good agreement between the estimated and calculated integral dwell times was obtained based on the 2 Gy isodose. Unlike HDR brachytherapy, the parameters used in the verification method for LDR brachytherapy plan verification strongly depend on the type of seed distribution. So, we recommend using an isodose at the prescribed dose for prostate HDR therapy.

CONCLUSIONS

Isodose-based verification methods are precise, do not presuppose dedicated tools, and are simple to implement in clinical practice.

Combined brachytherapy and ultra-hypofractionated radiotherapy for intermediate-risk prostate cancer: Comparison of toxicity outcomes using a high-dose-rate (HDR) versus low-dose-rate (LDR) brachytherapy boost

PURPOSE/OBJECTIVE

To compare toxicity profiles of low-dose rate (LDR) and high-dose rate (HDR) brachytherapy boost combined with ultra-hypofractionated external beam radiation therapy (UH-EBRT).

MATERIALS/METHODS

99 patients with intermediate-risk prostate cancer underwent an HDR (n = 59) or LDR (n = 40) boost combined with UH-EBRT (5 Gy x 5) . HDR (Ir-192) was delivered a single dose (15 Gy) and LDR (Pd-103) prescription dose was 100 Gy. Median baseline IPSS was 5 for both cohorts. Median follow-up was 29.3mos. Cumulative incidences were calculated for toxicity. Fisher exact tests were used to evaluate associations.

RESULTS

Overall incidence of grade 2 genitourinary toxicity for the entire cohort at 12 and 24 months was 21% and 29%, respectively. The incidence of grade 2 genitourinary toxicity at 12 and 24 months was higher for LDR cohort compared with HDR cohort (45% vs 5.1% and 55% vs 11%; p<0.001). On MVA, only treatment regimen (LDR versus HDR) was associated with grade 2+ genitourinary toxicity (p<0.001). Two patients experienced grade 2 rectal toxicity in each cohort. No grade > 3 toxicities were observed.

CONCLUSIONS

Both LDR and HDR brachytherapy combined with UH-EBRT had favorable toxicity profiles, but significantly less grade 2+ genitourinary toxicity was observed in patients receiving HDR.

On the importance of quality assurance (QA) for COMS eye plaque Silastic inserts: A guide to measurement methods, typical variations, and an example of how QA intercepted a manufacturing aberration

PURPOSE

Eye plaques are widely used for ocular melanoma and provide an effective alternative to enucleation with adequate tumor control. A COMS plaque utilizes a Silastic insert for precise positioning of the radioactive seeds with respect to the scleral surface of the eye; however, due to manufacturing variability, the insert may unintentionally increase or decrease the distance between the sources and tumor. The purpose of this work is to provide guidance in measuring and identifying outliers in Silastic inserts. The importance of regular quality assurance (QA) is illustrated in an experience where a systematic problem was detected and the manufacturer's 22-mm mold was corrected.

METHODS

A detailed description of the molds and manufacturing process used to produce Silastic inserts is provided, including photographs of the process steps. The variability in Silastic insert production was evaluated by measuring the thickness of 124 Silastic inserts. An estimate of how the observed Silastic thickness discrepancies impact the dose to the tumor and critical eye structures was performed using homogeneous dose calculations. A standard QA protocol was developed to guide the clinical user.

RESULTS

Thickness of the measured Silastic inserts ranged from 1.22 to 2.67 mm, demonstrating variation from the 2.25 mm standard. Six of the 22-mm inserts were outliers (Δthickness >3 standard deviations) and were excluded from the statistics. The outliers were investigated with the help of the manufacturer, who discovered that a systematic error was accidentally introduced into the 22-mm mold.

CONCLUSIONS

Due to manufacturing errors or variability, the Silastic inserts used in COMS eye plaques may be thicker or thinner than the design standard. Such variations may impact tumor control or increase the risk of normal tissue side effects. A standardized QA program is recommended to detect variations and communicate unusual findings to the manufacturer.

Analysis of radioactive implant migration in patients treated with iodine-125 seeds for permanent prostate brachytherapy with MRI-classified median lobe hyperplasia

Purpose

Prostate cancer with median lobe hyperplasia (MLH) is a relative contraindication for permanent prostate brachytherapy (PPB) because of an increased risk of post-implant dysuria and technical difficulties associated with achieving stability while implanting within the intravesical tissue. We examined treatment outcome, seed migration, and urination disorders after treatment in MLH patients in order to determine to what degree MLH implants could be stabilized.

Material and methods

Between March 2007 and December 2016, 32 patients had MLH identified radiologically on magnetic resonance imaging, and 193 patients did not have MLH (non-MLH). All patients were treated with loose seeds. In this study, seed migration was defined as a seed distant from the target (≥ 1.5 cm) and/or with no dosimetric contribution to the target. The MLH patients were divided into 2 MLH groups of mild (< 10 mm) and severe (≥ 10 mm) MLH by measuring the distance between the posterior transitional zone and the prostatic tissue protruding into the bladder. We retrospectively analyzed seed migration, dose-volume histograms (DVH), and genitourinary toxicity.

Results

MLH was classified as mild in 24 patients and severe in 8. Seed migration occurred in 61 (31.6%) of 193 non-MLH patients and 10 (31.5%) of 32 MLH patients. Implant seed migration and low-dose level of median lobe tended to be high in severe MLH cases. International Prostate Symptom Score (IPSS) peaked one month after implantation, but then resolved slowly and returned to around the pre-treatment level after one year. There were no severe complications.

Conclusions

MLH does not appear to be a strong contraindication for low-dose-rate brachytherapy. However, we found that the seed migration and degree of cold spots tended to be higher in severe MLH cases than in others; therefore, close attention when treating severe MLH cases must be paid.

Live implant dosimetry may be an effective replacement for postimplant computed tomography in localized prostate cancer patients receiving low dose rate brachytherapy

PURPOSE

To determine if Live Implant Dosimetry (LIDO) utilizing intraoperative transrectal ultrasound (TRUS) is equivalent to postimplant CT dosimetry (either day 0 or day 30) in patients with localized prostate cancer (PC) treated with low dose rate (LDR) prostate seed brachytherapy.

METHODS AND MATERIALS

The treated population consisted of 628 men with localized (T1-T2) PC. All d'Amico risk categories (low, intermediate, and high) were included, and 437 patients were treated with monotherapy (160 Gy) [low and low tier intermediate], and the remainder (191) [high tier intermediate and high risk] with an implant boost (106 Gy) post external beam radiation, to a volume including the prostate and seminal vesicles (46 Gy). LIDO with intraoperative TRUS, postimplant CT (day 0 and day 30) were performed in all cases. Prostate volumes (V), V₁₀₀ (prostate) and dose (D) D₉₀ (prostate), D₃₀ (urethra), and Rectum D_2cc, were recorded. No urinary catheter was used on Day 30 CT.

RESULTS

More than 91.33% of monotherapy patients reached the target D₉₀ according to LIDO while only 82.99% of Day 0 CT and 92.82% of Day 30 CT achieved target D₉₀. When considering V₁₀₀, monotherapy patients recorded target dosimetry in 90.93%, 82.31%, and 92.02% of cases assessed by LIDO, Day 0 CT and Day 30 CT, respectively. Strong correlations are observed in D₉₀, Rectum D_2cc and Urethra D₃₀ across imaging modalities but V₁₀₀ and V₁₅₀ were poorly correlated due to the relative quantification of this parameter and high degree of error in measurement. Of all monotherapy patients with satisfactory dosimetry on LIDO, 94.82% reached target D₉₀ at day 30 CT and 94.19% reached target V₁₀₀.

CONCLUSIONS

LIDO and CT are both effective tools for assessing postimplant dosimetry. Patients with satisfactory LIDO dosimetry are highly likely to have equivalent dosimetry on CT at follow-up, indicating that postimplant CT may be eliminated in PC a patients implanted with this technique.

Focal low-dose-rate prostate brachytherapy for low- and intermediate-risk prostate cancer

Purpose

To prospectively investigate the efficacy and feasibility of focal low-dose-rate (LDR) prostate brachytherapy for low- and intermediate-risk prostate cancer.

Material and methods

Between October 2014 and May 2019, nineteen low- and intermediate-risk prostate cancer patients who presented with abnormality on both diffusion-weighted and T2-weighted magnetic resonance imaging (MRI) underwent focal LDR brachytherapy at our institution. Focal gross tumor volume (F-GTV) was delineated on transrectal ultrasound, based on abnormality seen on fused T2-weighted MRI. F-GTV was expanded by 5 mm, as a safety margin, to create focal clinical target volume (F-CTV). Prescribed dose to F-CTV was 145 Gy. Biochemical recurrence (BCR) was determined using Phoenix criterion (prostate specific antigen nadir + 2 ng/ml). Pre- and post-implant dosimetry data were compared using non-parametric Wilcoxon’s rank sum test. Treatment-related toxicities were evaluated using common terminology criteria for adverse events.

Results

Mean F-CTV D_90% was significantly lower in the post-implant evaluation than in intraoperative planning (p = 0.004). On post-implant dosimetry, the mean D_90% for F-GTV and mean V_100% for the entire prostate were 222 Gy and 35%, respectively. Median follow-up time for all patients was 31 months. BCR occurred in one patient after 23 months. Kaplan-Meier 2-year BCR-free rate was 92.9% (95% confidence interval [CI]: 79.4-100%). No patients had grade 1 or greater gastrointestinal toxicity. Three patients who were taking α-blockers to treat benign prostatic hyperplasia (present before brachytherapy), experienced no treatment-related genitourinary toxicities. Two patients suffered from temporary grade 2 urinary frequency. None of the remaining patients experienced grade 2 or higher genitourinary toxicity.

Conclusions

Focal LDR prostate brachytherapy appears acceptable for MRI-based index tumors, with a low cumulative incidence of BCR. Such brachytherapy might offer a feasible minimally invasive therapeutic option for localized prostate cancer.

The accuracy and safety of CT-guided iodine-125 seed implantation assisted by 3D non-coplanar template for retroperitoneal recurrent carcinoma

PURPOSE

To investigate the accuracy, dosimetric parameters, and safety of 3D-printing non-coplanar template (3D-PNCT)-assisted CT guidance for radioactive iodine-125 (125I) seed implantation brachytherapy (RSI-BT) for retroperitoneal recurrent carcinomas METHODS AND MATERIALS: We enrolled 15 patients with 17 retroperitoneal recurrent carcinomas after external beam radiotherapy (EBRT). All patients received CT-guided 125I RSI-BT assisted by 3D-PNCT successfully. We compared the original needle insertion position, angular, and the needle tip distance deviations of preoperative plan with that of intraoperative in brachytherapy treatment planning system (B-TPS). The dosimetric parameters of RSI-BT were evaluated on preoperative plan, intraoperative real-time plan, and postoperative plan, including D90, D100 (the dose to 90% and 100% of the target volume), V100, V150, and V200 (the volume receives 100%, 150%, and 200% of the prescribed doses). The quality assurance of RSI-BT evaluated on conformal index (CI), external index (EI), and homogeneity index (HI) of the targets were compared among preoperative plan, intraoperative real-time plan, and postoperative plan. The perioperation complications and RSI-BT-related toxicity were assessed.

RESULTS

The median follow-up was 8.2 months (range 1-18.5 months). One patient was lost to follow-up after RSI-BT. Fourteen patients were assessed for response rate and toxicity. The mean entrance point distance deviation for all 165 needles was 4.50 ± 4.10 mm (range, 0-30). The mean angular deviation was 2.70 ± 3.00° (range, 0-20). The needle tip distance deviation was 6.90 ± 6.00 mm (range, - 30-28). D90 for preoperative plan, intraoperative plan, and postoperative plan were 140.55 ± 23.93, 124.25 ± 28.04, and 128.98 ± 22.75, respectively. There was significant difference between D90 of preoperative plan with that of intraoperative plan (p = 0.036). Four lesions reached CR, six lesions reached PR, three lesions were SD, and three lesions were PD. Four patients with moderate pain became mild, and two with mild pain relieved completely after RSI-BT. The other parameters showed no differences among preoperative plan, intraoperative plan, and postoperative plan. The perioperative complications were observed in four patients, including three patients of grade 1 and one patient of grade 2. No ≥ grade 3 side effects were observed.

CONCLUSION

CT-guided 125I RSI-BT assisted by 3D-PNCT was a safe, accurate, and feasible strategy for recurrent carcinomas located in the retroperitoneal regions.

A novel and fast methodology to calculate doses in LDR brachytherapy

We present the concept of a new methodology for faster simulation of the doses in brachytherapy with permanent implants, based on the knowledge of the seeds arrangement, adding previously simulated doses in an equivalent medium in terms of the atomic composition of the organ in question. To perform the doses calculations we use Monte Carlo simulations. We simulated a cylindrical I-125 seed and compared our results against published data. Our proposal is to have the doses simulated previously in different arrangement of seed-absorbents, and then, considering the spacial positions of the seeds after the implants, these doses can be directly added, obtaining a very fast computation of the total dose. Two phantoms of prostates with permanent implant seeds in 2D and 3D arrangements were simulated. The results of the proposed methodology were compared with two complete Monte Carlo simulations in 2D and 3D designs. Differences in doses were analysed, obtaining statistical discrepancies of less than 1% and reducing the simulation time by more than 4 orders of magnitude. With the proposed methodology, it is possible to perform rapid dose calculations in brachytherapy, using laptop or desktop computers.

High biologically effective dose radiation therapy using brachytherapy in combination with external beam radiotherapy for high-risk prostate cancer

Purpose

To evaluate the outcomes of high-risk prostate cancer patients treated with biologically effective dose (BED) ≥ 220 Gy of high-dose radiotherapy, using low-dose-rate (LDR) brachytherapy in combination with external beam radiotherapy (EBRT) and short-term androgen deprivation therapy (ADT).

Material and methods

From 2005 to 2013, a total of 143 patients with high-risk prostate cancer were treated by radiotherapy of BED ≥ 220 Gy with a combination of LDR brachytherapy, EBRT, and androgen deprivation therapy (ADT). The high-risk patients in the present study included both high-risk and very high-risk prostate cancer. The number of high-risk features were: 60 patients with 1 high-risk factor (42%), 61 patients with 2 high-risk factors (43%), and 22 patients with 3 high-risk factors (15%) including five N1 disease. External beam radiotherapy fields included prostate and seminal vesicles only or whole pelvis depending on the extension of the disease. Biochemical failure was defined by the Phoenix definition.

Results

Six patients developed biochemical failure, thus providing a 5-year actual biochemical failure-free survival (BFFS) rate of 95.2%. Biochemical failure was observed exclusively in cases with distant metastasis in the present study. All six patients with biochemical relapse had clinical failure due to bone metastasis, thus yielding a 5-year freedom from clinical failure (FFCF) rate of 93.0%. None of the cases with N1 disease experienced biochemical failure. We observed four deaths, including one death from prostate cancer, therefore yielding a cause-specific survival (CSS) rate of 97.2%, and an overall survival (OS) rate of 95.5%.

Conclusions

High-dose (BED ≥ 220 Gy) radiotherapy by LDR in combination with EBRT has shown an excellent outcome on BFFS in high-risk and very high-risk cancer, although causal relationship between BED and BFFS remain to be explained further.

Focal partial salvage low-dose-rate brachytherapy for local recurrent prostate cancer after permanent prostate brachytherapy with a review of the literature

Purpose

To investigate the treatment results for focal partial salvage re-implantation against local recurrence after permanent prostate brachytherapy.

Material and methods

Between January 2010 and September 2015, 12 patients were treated with focal partial salvage re-implantation for local recurrence after low-dose-rate brachytherapy using ¹²⁵I seeds. The focal clinical target volume (F-CTV) was delineated on positive biopsy areas in a mapping biopsy, combining the cold spots on the post-implant dosimetry for initial brachytherapy. The F-CTV was expanded by 3 mm to create the planning target volume (PTV) as a margin to compensate for uncertainties in image registration and treatment delivery. The prescribed dose to the PTV was 145 Gy. The characteristics and biochemical disease-free survival (BdFS) rates were analyzed. Genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated using the Common Terminology Criteria for Adverse Events version 4.

Results

The median prostate-specific antigen (PSA) level at re-implantation was 4.09 ng/ml (range: 2.91-8.24 ng/ml). The median follow-up time was 56 months (range: 6-74 months). The median RD_2cc and UD₁₀ were 63 Gy and 159 Gy, respectively. The 4-year BdFS rate was 78%, which included non-responders. Biochemical recurrence occurred in two patients after 7 and 31 months, respectively. The former was treated with hormonal therapy after biochemical failure, and the latter underwent watchful waiting (PSA at the last follow-up of 53 months: 7.3 ng/ml) at the patient's request. No patients had grade 3 GU/GI toxicities or died after salvage re-implantation.

Conclusions

The partial salvage low-dose-rate brachytherapy used to treat local recurrence after permanent prostate brachytherapy is well-tolerated, with high biochemical response rates. This treatment can be not only a method to delay chemical castration but also a curative treatment option in cases of local recurrence of prostate carcinoma after seed implantation.

Safety and efficacy of salvage low-dose-rate brachytherapy for prostate bed recurrences following radical prostatectomy

Purpose

To report efficacy in our series of nodular recurrences in the post-surgical bed that underwent salvage low-dose-rate (LDR) brachytherapy.

Material and methods

Patients with radical prostatectomy (RP) who had biochemical failure with nodular recurrence detected by DRE, ultrasound, and pelvic CT and then salvaged with LDR ¹²⁵I brachytherapy were included. Nodular recurrences were biopsy confirmed adenocarcinoma, and patients had no evidence of nodal or distant metastasis on imaging including bone scan. Follow up was at least every 6 months with a serial prostate specific antigen (PSA).

Results

Twelve patients had salvage LDR brachytherapy with median age 69 years (range 59-86) and median pre-salvage PSA of 4.22 ng/ml. Nodule biopsy Gleason score was 7, 8, or undifferentiated. Median rectal V₁₀₀ was 0.00 cc. Compared to pre-salvage, patients reported no additional genitourinary (GU) toxicity. After a median 35 months post-salvage follow up (range 10-81 months), patients had a median PSA nadir of 0.72 ng/ml (range 0.01-22.4). At 6 months post salvage, 90% of patients had a PSA below pre-salvage levels. At last follow up, 4 patients had PSA control.

Conclusions

There was a trend to improved biochemical relapse free survival for lower Gleason score and pre-salvage PSA, which may be indicative of the lack of or only low volume metastatic disease. LDR brachytherapy is an effective salvage technique and can be considered in well selected patients allowing for dose escalation to the nodular recurrence.

Comparison of permanent (125)I seeds implants with two different techniques in 500 cases of prostate cancer

Purpose

To perform a comparative study of 500 consecutive ¹²⁵I seeds implants for intracapsular prostate carcinoma with two techniques differing in terms of both strand implantation and planning.

Material and methods

From 2002 to 2007 we performed 250 implants with fixed stranded seeds (RapidStrand™) and a preplanning system and from 2007 to 2010, 250 with real-time and ProLink™ system. Mean age was 68 and 66, respectively, median PSA (prostate-specific antigen) 7.3 and 7.2, stage T1-T2a in 98% and 94%, and Gleason ≤ 6 in 96% and 86%. Low risk cases were 81% and 71%. The prescribed dose was 145 Gy to the prostate volume, or 108 Gy plus EBRT 46 Gy in some intermediate risk cases. Hormonal treatment was given to 42% and 28%.

Results

Median follow-up was 48 and 47 months, respectively, 14 patients in the first group and 7 patients in the second developed biochemical failure (BF). Actuarial biochemical relapse-free survival (bRFS) at 5 years increased from 90.2% to 97.2% (low risk from 91.3% to 97.2%, intermediate risk from 84.2% to 97.1%). Biochemical failure was independent of hormone treatment. Rectal complications were G1-2 in 1.2% and 5.2%, respectively. A urinary catheter was necessary in 6.9% and 9.6%, and urethral resection in 1.9% and 4.4%. Genitourinary toxicity was G1-2 in 4.6% and 12%, G3-4 in 1.9% and 4.8%. An assessment of mean D₉₀ in a sample of patients showed that the dosimetry in postoperative planning based on CT improved from a mean D₉₀ of 143 Gy to 157 Gy.

Conclusions

The outcome of patients with low risk prostate carcinoma treated with ¹²⁵I seed is very good with low complications rate. The real-time approach in our hands achieved a more precise seed implantation, better dosimetry, and a statistically non-significant better biochemical control. We have made this our standard technique.

Urethral toxicity after LDR brachytherapy: experience in Japan

Urinary toxicity is common after low-dose-rate (LDR) brachytherapy, and the resolution of urinary toxicity is a concern. In particular, urinary frequency is the most common adverse event among the urinary toxicities. We have previously reported that approximately 70% of patients experience urinary frequency during the first 6 months after seed implantation. Most urinary adverse events were classified as Grade 1, and Grade 2 or higher adverse events were rare. The incidence of urinary retention was approximately 2-4%. A high International Prostate Symptom Score before seed implantation was an independent predictor of acute urinary toxicity of Grade 2 or higher. Several previous reports from the United States also supported this trend. In Japan, LDR brachytherapy was legally approved in 2003. A nationwide prospective cohort study entitled Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 Seed Implantation was initiated in July 2005. It is an important issue to limit urinary toxicities in patients who undergo LDR brachytherapy.

Pre-plan parameters predict post-implant D90 ≥ 140 Gy for (125)I permanent prostate implants

Purpose

To find permanent prostate implant (PPI) pre-plan dosimetric parameters that predict post-implant D₉₀ ≥ 140 Gy.

Material and methods

Pre-plans were evaluated for 504 patients undergoing PPI with ¹²⁵I seeds for low or intermediate risk prostate cancer. Baseline patient and disease factors, numbers of seeds, ratios of number of seeds to available positions (occupancy proportion), and distances between the 100% isodose line and edge of the prostate (margin) planned for the whole prostate (WP), superior (S), inferior (I), anterior (A), and posterior (P) halves, SA, SP, IA, and IP quarters, and superior (S_T), inferior (I_T), and middle (M_T) thirds, and anterior (A_T) and posterior (P_T) middle one-sixth segments were analyzed by post-implant D₉₀ subset (≥ 140 Gy vs. < 140 Gy).

Results

20% had post-implant D₉₀ < 140 Gy (mean: 128.0 Gy, range: 97.5-139.2) vs. ≥ 140 Gy (mean: 154.4 Gy, range: 140.0-193.5). The D₉₀ ≥ 140 Gy subset had larger A_T and IA segment mean numbers of seeds (p = 0.01, 0.046), larger WP, S, A, SA, S_T, A_T, and M_T segment mean margins (p = 0.01, 0.01, 0.001, 0.0001, 0.03, 0.005, 0.02), and lower P_T segment occupancy proportion (p = 0.004). On multivariate analysis, independent predictors of post-implant D₉₀ ≥ 140 Gy were increased SA mean margin, no pre-implant 5-α-reductase inhibitor, higher pre-plan D₉₀, decreased P occupancy proportion, no pre-implant hormone therapy, and decreased SP mean margin.

Conclusions

Higher occupancy proportion and larger margins anteriorly and reduced occupancy proportion, and smaller margins posteriorly on PPI pre-plans predict post-implant D₉₀ ≥ 140 Gy.

Brachytherapy in the therapy of prostate cancer - an interesting choice

Brachytherapy is a curative alternative to radical prostatectomy or external beam radiation [i.e. 3D conformal external beam radiation therapy (CRT), intensity-modulated radiation therapy (IMRT)] with comparable long-term survival and biochemical control and the most favorable toxicity. HDR brachytherapy (HDR-BT) in treatment of prostate cancer is most frequently used together with external beam radiation therapy (EBRT) as a boost (increasing the treatment dose precisely to the tumor). In the early stages of the disease (low, sometimes intermediate risk group), HDR-BT is more often used as monotherapy. There are no significant differences in treatment results (overall survival rate – OS, local recurrence rate – LC) between radical prostatectomy, EBRT and HDR-BT. Low-dose-rate brachytherapy (LDR-BT) is a radiation method that has been known for several years in treatment of localized prostate cancer. The LDR-BT is applied as a monotherapy and also used along with EBRT as a boost. It is used as a sole radical treatment modality, but not as a palliative treatment. The use of brachytherapy as monotherapy in treatment of prostate cancer enables many patients to keep their sexual functions in order and causes a lower rate of urinary incontinence. Due to progress in medical and technical knowledge in brachytherapy (“real-time” computer planning systems, new radioisotopes and remote afterloading systems), it has been possible to make treatment time significantly shorter in comparison with other methods. This also enables better protection of healthy organs in the pelvis. The aim of this publication is to describe both brachytherapy methods.

Three-dimensional dosimetric considerations from different point A definitions in cervical cancer low-dose-rate brachytherapy

Purpose

To investigate the dosimetric difference due to the different point A definitions in cervical cancer low-dose-rate (LDR) intracavitary brachytherapy.

Material and methods

Twenty CT-based LDR brachytherapy plans of 11 cervical patients were retrospectively reviewed. Two plans with point As following the modified Manchester system which defines point A being 2 cm superior to the cervical os along the tandem and 2 cm lateral (A_os), and the American Brachytherapy Society (ABS) guideline definition in which the point A is 2 cm superior to the vaginal fornices instead of os (A_ovoid) were generated. Using the same source strength, two plans prescribed the same dose to A_os and A_ovoid. Dosimetric differences between plans including point A dose rate, treatment volume encompassed by the prescription isodose line (TV), and dose rate of 2 cc of the rectum and bladder to the prescription dose were measured.

Results

On average A_ovoid was 8.9 mm superior to A_os along the tandem direction with a standard deviation of 5.4 mm. With the same source strength and arrangement, A_os dose rate was 19% higher than A_ovoid dose rate. The average TV(A_ovoid) was 118.0 cc, which was 30% more than the average TV(A_os) of 93.0 cc. D_2cc/D(A_prescribe) increased from 51% to 60% for rectum, and increased from 89% and 106% for bladder, if the prescription point changed from A_os to A_ovoid.

Conclusions

Different point A definitions lead to significant dose differences. Careful consideration should be given when changing practice from one point A definition to another, to ensure dosimetric and clinical equivalency from the previous clinical experiences.

Positional variation of applicators during low dose rate intracavitary brachytherapy for cervical cancer: a prospective study

Purpose

In order to know the effect of variation in position of applicators to the dose received by the tumor volume, critical organs such as rectum and bladder and the correlation of variation on the clinical outcome.

Material and methods

36 patients with histologically proven cervical cancer, undergoing intracavitary brachytherapy (ICBT) from October 2005 to December 2006 were the subjects of the study. Two pairs of orthogonal X-ray films were taken: one prior to loading of sources and the other after removal of sources. These patients were followed up as per the RTOG criteria.

Results

The median duration of insertion was 25 hours with a median follow up period of 6.7 months. The translational variation of the applicator position for all patients was 3 mm and 1 mm (2 SD), respectively, in the patient’s lateral and antero-posterior direction. The rotational variation was 3 and 4 degrees (2 SD) in the patient’s transverse and sagittal planes. Detailed analysis of source movement showed following changes in median dose: point A: 14%, point B: 2%, point P: 1%, Rectum 1: 3.5%, Rectum 2: 4% and Bladder: 9.1%. The incidence of rectal toxicity was 6/36 (16.7%) and that of bladder was 1/36 (2.8%). When the variables were grouped to evaluate the relationship, our study showed statistically significant relationship between: R2 and rectal toxicity (p value: 0.002), point A and rectal toxicity (Pearson: 0.792), lateral displacement/anteroposterior displacement and rectal toxicity (p value: 0.012/0.003), beta angle and R2 (p value: 0.002).

Conclusions

The geometric relationships between the ICBT applicators and the critical structures vary during the course of low dose rate brachytherapy. Source movement does result in significant dose alterations in terms of increased rate of complications, but its impact on cure rates needs to be studied in the future.

Is there any place for LDR brachytherapy for head and neck carcinomas in HDR era?

In Poland, the classical LDR brachytherapy for head and neck carcinomas with Ir-192 wires or hairpins has completely disappeared some time ago after 30 years of successful clinical use. Can this technique be fully and safely replaced by HDR or PDR application? This option seems attractive because of new possibilities of 3D reconstruction and computer real-time treatment planning and optimization. However, in my opinion, long time is needed to get a clinical and scientific experience that has been accumulated for decades with the use of LDR technique.