Acute urinary retention after I-125 prostate brachytherapy in relation to dose in different regions of the prostate

Associations of Clinical and Dosimetric Parameters with Urinary Toxicities after Prostate Brachytherapy: A Long-Term Single-Institution Experience

To examine the association of clinical, treatment, and dose parameters with late urinary toxicity after low-dose-rate brachytherapy (LDR-BT) for prostate cancer, we retrospectively studied patients with prostate cancer who underwent LDR-BT from January 2007 through December 2016. Urinary toxicity was assessed using the International Prostate Symptom Score (IPSS) and Overactive Bladder (OAB) Symptom Score (OABSS). Severe and moderate lower urinary tract symptoms (LUTS) were defined as IPSS ≥ 20 and ≥ 8, respectively; OAB was defined as a nocturnal frequency of ≥ 2 and a total OABSS of ≥ 3. In total, 203 patients (median age: 66 years) were included, with a mean follow-up of 8.4 years after treatment. The IPSS and OABSS worsened after 3 months of treatment; these scores improved to pretreatment levels after 18-36 months in most patients. Patients with a higher baseline IPSS and OABSS had a higher frequency of moderate and severe LUTS and OAB at 24 and 60 months, respectively. LUTS and OAB at 24 and 60 months were not correlated with the dosimetric factors of LDR-BT. Although the rate of long-term urinary toxicities assessed using IPSS and OABSS was low, the baseline scores were related to long-term function. Refining patient selection may further reduce long-term urinary toxicity.

Tensor Regression-based Model to Investigate Heterogeneous Spatial Radiosensitivity After I-125 Seed Implantation for Prostate Cancer

BACKGROUND/AIM

We established a data-driven method for extracting spatial patterns of dose distribution associated with radiation injuries, based on patients with prostate cancer who underwent iodine-125 (I-125) seed implantation.

PATIENTS AND METHODS

Seventy-five patients underwent I-125 seed implantation for prostate cancer. We modeled the severity of lower urinary tract symptoms (LUTS) to be estimated using a linear model, which is formulated as an inner product between the dose distribution D and voxel-wise radiosensitivity B inside the prostate. For the estimation, tensor regression based on a low-rank decomposition with generalized fused lasso penalty was applied.

RESULTS

The spatial distribution of B was visually assessed. Positive parameters appeared dominantly in the region close to the urethra and the prostate base.

CONCLUSION

Our tensor regression-based model can predict intra-organ radiosensitivity in a data-driven manner, providing a compelling parameter distribution associated with the development of LUTS after I-125 seed implantation for prostate cancer.

A Population-based Statistical Model for Investigating Heterogeneous Intraprostatic Sensitivity to Radiation Toxicity After 125I Seed Implantation

AIM

To develop a population-based statistical model in order to find a spatial pattern of dose distribution which is related to lower urinary tract symptoms (LUTS) after iodine-125 (¹²⁵I) seed implantation for prostate cancer.

PATIENTS AND METHODS

A total of 75 patients underwent ¹²⁵I seed implantation for prostate cancer. Principal component analysis was applied to the standardized dose array and for each patient dose distribution was uniquely characterized by a combination of weighted eigenvectors. The correlation between eigenvectors and the severity of LUTS was investigated with linear regression analysis.

RESULTS

Eight eigenvectors were identified as being significantly associated with the severity of LUTS (p<0.05). Multivariate regression model identified that intraprostatic parameters, which were positively associated with the severity of LUTS, were distributed around a portion of the urethral base and a peripheral region of the prostate.

CONCLUSION

We established a population-based statistical model that may indicate a significant dose pattern associated with the severity of radiation toxicity.

Dose to the bladder neck is the most important predictor for acute and late toxicity after low-dose-rate prostate brachytherapy: implications for establishing new dose constraints for treatment planning

PURPOSE

To identify an anatomic structure predictive for acute (AUT) and late (LUT) urinary toxicity in patients with prostate cancer treated with low-dose-rate brachytherapy (LDR) with or without external beam radiation therapy (EBRT).

METHODS AND MATERIALS

From July 2002 to January 2013, 927 patients with prostate cancer (median age, 66 years) underwent LDR brachytherapy with Iodine 125 (n=753) or Palladium 103 (n=174) as definitive treatment (n=478) and as a boost (n=449) followed by supplemental EBRT (median dose, 50.4 Gy). Structures contoured on the computed tomographic (CT) scan on day 0 after implantation included prostate, urethra, bladder, and the bladder neck, defined as 5 mm around the urethra between the catheter balloon and the prostatic urethra. AUT and LUT were assessed with the Common Terminology Criteria for Adverse Events, version4. Clinical and dosimetric factors associated with AUT and LUT were analyzed with Cox regression and receiver operating characteristic analysis to calculate area under the receiver operator curve (ROC) (AUC).

RESULTS

Grade ≥2 AUT and grade ≥2 LUT occurred in 520 patients (56%) and 154 patients (20%), respectively. No grade 4 toxicities were observed. Bladder neck D2cc retained a significant association with AUT (hazard ratio [HR], 1.03; 95% confidence interval [CI], 1.03-1.04; P<.0001) and LUT (HR, 1.01; 95% CI, 1.00-1.03; P=.014) on multivariable analysis. In a comparison of bladder neck with the standard dosimetric variables by use of ROC analysis (prostate V100 >90%, D90 >100%, V150 >60%, urethra D20 >130%), bladder neck D2cc >50% was shown to have the strongest prognostic power for AUT (AUC, 0.697; P<.0001) and LUT (AUC, 0.620; P<.001).

CONCLUSIONS

Bladder neck D2cc >50% was the strongest predictor for grade ≥2 AUT and LUT in patients treated with LDR brachytherapy. These data support inclusion of bladder neck constraints into brachytherapy planning to decrease urinary toxicity.

Effect of brachytherapy on NF-κB and VEGF in gastric carcinoma xenografts

Iodine-125 (125I) seed irradiation can be used as an important supplementary treatment for unresectable advanced gastric cancer. However, the radiobiological mechanism underlying brachytherapy remains unclear. Therefore, we investigated the influence of continuous and low-energy 125I irradiation on the cell cycle distribution, apoptosis, expression of NF-κB and VEGF and tumor growth in a human gastric cancer xenograft model. To create an animal model of gastric cancer, SGC-7901 cells were surgically implanted into mice. The 60 mice bearing SGC-7901 gastric cancer xenografts were randomly separated into 2 groups. Sham seeds (0 mCi) were implanted into the control group (n=30); 125I seeds (0.6 mCi) were implanted into the treatment group (n=30). At 28 days after irradiation, apoptosis was detected by flow cytometry. fluorescence micrograph detected intense VEGF and NF-κB immunofluorescence in the tumor samples, and changes in NF-κB and VEGF mRNA and protein expression were assessed by real-time PCR and western blot analysis, respectively. The tumor volume and weight were measured 0-28 days after 125I seed implantation. 125I seed irradiation induced significant apoptosis and G2/M phase arrest. Reduction in the intensities of VEGF and NF-κB immunofluorescence in tumor vessels was observed after treatment. NF-κB and VEGF mRNA and protein expression levels were substantially lower in the implantation treatment group than in the control group. Consequently, 125I seed implantation inhibited cancer growth and reduced cancer volume. The present study revealed that 125I seed irradiation significantly induced apoptosis and cell cycle arrest in the human gastric cancer xenografts. 125I-induced changes in NF-κB and VEGF expression are suggested as potential mechanisms underlying effective brachytherapy.

Obstructive voiding symptoms following stereotactic body radiation therapy for prostate cancer

Background

Obstructive voiding symptoms (OVS) are common following prostate cancer treatment with radiation therapy. The risk of urinary retention (UR) following hypofractionated radiotherapy has yet to be fully elucidated. This study sought to evaluate OVS and UR requiring catheterization following SBRT for prostate cancer.

Methods

Patients treated with SBRT for localized prostate cancer from February 2008 to July 2011 at Georgetown University were included in this study. Treatment was delivered using the CyberKnife® with doses of 35 Gy-36.25 Gy in 5 fractions. UR was prospectively scored using the CTCAE v.3. Patient-reported OVS were assessed using the IPSS-obstructive subdomain at baseline and at 1, 3, 6, 9, 12, 18 and 24 months. Associated bother was evaluated via the EPIC-26.

Results

269 patients at a median age of 69 years received SBRT with a median follow-up of 3 years. The mean prostate volume was 39 cc. Prior to treatment, 50.6% of patients reported moderate to severe lower urinary track symptoms per the IPSS and 6.7% felt that weak urine stream and/or incomplete emptying were a moderate to big problem. The 2-year actuarial incidence rates of acute and late UR ≥ grade 2 were 39.5% and 41.4%. Alpha-antagonist utilization rose at one month (58%) and 18 months (48%) post-treatment. However, Grade 3 UR was low with only 4 men (1.5%) requiring catheterization and/or TURP. A mean baseline IPSS-obstructive score of 3.6 significantly increased to 5.0 at 1 month (p < 0.0001); however, it returned to baseline in 92.6% within a median time of 3 months. Late increases in OVS were common, but transient. Only 7.1% of patients felt that weak urine stream and/or incomplete emptying was a moderate to big problem at two years post-SBRT (p = 0.6854).

Conclusions

SBRT treatment caused an acute increase in OVS which peaked within the first month post-treatment, though acute UR requiring catheterization was rare. OVS returned to baseline in > 90% of patients within a median time of three months. Transient Late increases in OVS were common. However, less than 10% of patients felt that OVS were a moderate to big problem at two years post-SBRT.

Regulation of autophagy via PERK-eIF2α effectively relieve the radiation myelitis induced by iodine-125

Radiation myelitis is the most serious complication in clinical radiotherapy for spinal metastases. We previously showed that ¹²⁵I brachytherapy induced apoptosis of spinal cord neurons accompanied by autophagy. In this study, we further investigated the mechanism by which ¹²⁵I radiation triggered autophagy in neural cells. We found that autophagy induced by ¹²⁵I radiation was involved in endoplasmic reticulum (ER) stress and mainly dependent on PERK-eIF2α pathway. The expressions of LC3II, ATG12 and PI3K were significantly suppressed in PERK knockout neural cells. Meanwhile, the expressions of phosphorylated-Akt s473 and caspase3/8 all significantly increased in neural cells transfected with a PERK siRNA and which enhanced apoptosis of neurons after ¹²⁵I radiation. The results were consistent with that by MTT and Annexin-FITC/PT staining. In annimal model of banna pigs with radiation myelitis caused by ¹²⁵I brachytherapy, we have successfully decreased PERK expression by intrathecal administration of the lentivirus vector. The apoptosis rate was significantly higher than that in control group and which deteriorated radiation myelitis of banna pigs. Thus, autophagy caused by ¹²⁵I radiation was mainly as an attempt of cell survival at an early stage, but it would be a self-destructive process and promoted the process of apoptosis and necrosis radiated by ¹²⁵I for more than 72 hours. The study would be useful and helpful to maximize efficiency of radiation therapy in clinical therapy.

Percutaneous vertebroplasty combined with interstitial implantation of 125I seeds in banna mini-pigs

BACKGROUND

Although brachytherapy is one of the most effective ways to treat metastatic spinal tumor with little damage to surrounding healthy tissue, it may cause radiation myelopathy if an overdose occurs. Establishing a valuable animal model can help to find a method to overcome its complications. In the current study, we set up a banna mini-pig model to mimic percutaneous vertebroplasty with 125I seed implantation.

METHODS

Percutaneous vertebroplasty (PVP) combined with interstitial implantation of 125I seeds, 125I seeds were transplanted into the vertebral body at the T13 level of the spine in banna mini-pigs. After raising them for up to eight months, the spinal cord and vertebral body were collected for pathological analysis.

RESULTS

A potential animal model had been successfully established, no case of radiation myelopathy was found in any of the treated banna pigs, and no significant cellular impairment was noted by pathological analysis.

CONCLUSIONS

It proves that PVP with 125I brachytherapy is an effective method to treat metastasis spinal tumor, and that the banna mini-pig can be a suitable model to investigate the mechanism of brachytherapy complications.

Pathological impairments induced by interstitial implantation of 125I seeds in spinal canal of banna mini-pigs

BACKGROUND

Use a banna mini-pig to set up 125I implantation model, and investigate the consequence of radiation-related impairments.

METHODS

In present study, 125I seeds were implanted into spinal canal of T13 level of spine in banna mini-pigs. After operation, the pigs were raised up to 8 months, behavior changes were recorded within this period. After 8 months, spinal cords were collected for pathological analysis.

RESULTS

In this study, a 125I brachytherapy animal model had been successfully established, in the model group, the banna pigs' Tarlov scale decreased from 5 to 2.57 ± 0.36, significant cellular impairments were noted by pathological analysis.

CONCLUSIONS

Without any protection and operation improvement, 125I implantation can cause serious histological impairments and moving difficulty for banna mini-pigs; this present research provides an alternative tool to study spinal 125I brachytherapy.

Changes in cell cycle, apoptosis and necrosis following the establishment of a (125)I brachytherapy model in the spinal cord in Banna mini-pigs

Brachytherapy is regarded as the most effective method in the treatment of metastatic spinal tumors since little damage is caused to surrounding healthy tissue. However, this method may cause radiation myelopathy if an overdose occurs. In the present study, we established a Banna mini-pig (125)I spinal cord implantation model to provide a tool for the study of how to reduce these types of side effects. Cell cycle alteration, apoptosis and necrosis of spinal cord neurons in the presence of various doses and durations of (125)I brachytherapy were also investigated. The pigs were randomly divided into four groups, A, B, C and D. In group A, four (125)I seeds (total radioactivity, 4.0 mCi) were implanted into the dura mater of the spinal canal at the level of T13. In groups B and C, eight (125)I sources (total radioactivity, 8.0 mCi) were inserted at the same location. Groups A and C were raised for up to 8 months and group B for only 2 months. Neurons from the swine spinal cord at the T13 level were collected and cell cycle analysis was performed. Apoptosis and necrosis were tested by a terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay. The Banna mini-pig brachytherapy model was successfully established. Radiation myelopathy was closely associated with radiation dose and duration, more neurons were blocked in the G2 and S phases as dose and time increased, and an increase in apoptosis and necrosis was detected. Ratios of apoptosis and necrosis were reduced as lower doses and shorter durations of radiation were applied. Our results demonstrate that the Banna mini-pig is an ideal animal to study (125)I brachytherapy. Low-dose and short-term brachytherapy may effectively decrease apoptosis and necrosis in spinal cord cells in Banna mini-pigs.