Brachytherapy for prostate cancer: Present and future

Prior MRI-imaging impact of patients submitted to brachytherapy for prostate cancer

INTRODUCTION

Brachytherapy for the treatment of prostate cancer is a well-established option. Use of Multiparametric Magnetic Resonance Imaging (mpMRI) for staging and diagnosis of prostate cancer has come to change the current paradigm. In this study we aim to assess the impact of performing mpMRI to evaluate the presence of extracapsular lesions before brachytherapy in patients with prostate cancer concerning biochemical recurrence and time to nadir.

METHODS

Review data from 73 patients submitted to brachytherapy. The following factors were evaluated: age, initial PSA, MRI local staging results, ISUP, nadir, time to nadir, PSA at one-year, biochemical recurrence, and time to recurrence.

RESULTS

Median age was 68 years (51-72) and median follow-up 53 months (30-72). Concerning imaging modality 30,1% (n = 22) patients performed mpMRI. In the mpMRI group, 90.9% (n = 20) had at least one suspect lesion on mpMRI. Time to nadir was 27 months (3-64) in patients where mpMRI was not performed and 23.5 months (2-48) in patients submitted to mpMRI (P = .244). The median value of nadir was 0.42 ng/mL (<0.001-2) in patients submitted to mpMRI and vs 0.28 ng/mL (<0.001-4) in patients without MRI (P = .062) Recurrence utilizing Phoenix criteria was 9% (n = 2) in patients with MRI and 9.2% (n = 5) without mpMRI (P = .456), median follow-up of 43 months (12-72) for the MRI group with 58 months (30-78) for the non-mpMRI group. Both groups were statistically similar.

CONCLUSION

Our results allow us to conclude that in our series MRI did not influence biochemical recurrence, time to nadir, or nadir value.

Comparison of the Oncological and Functional Outcomes of Brachytherapy and Radical Prostatectomy for Localized Prostate Cancer

Background and Objectives: To compare the oncological and functional outcomes of brachytherapy (BT) and radical prostatectomy (RP) in patients with localized prostate cancer (PCa). Materials and Methods: We retrospectively analyzed data from 557 patients with localized PCa who were treated with BT (n = 245) or RP (n = 312) at Northern Jiangsu People's Hospital between January 2012 and December 2017. Biochemical relapse-free survival (bRFS) and cancer-specific survival (CSS) were compared by treatment modality. Multivariate Cox regression analysis was used to evaluate bRFS. Health-related quality of life (HRQoL) was measured using the Expanded Prostate Cancer Index Composite (EPIC) questionnaire. Results: The BT group was older and had a higher initial PSA (iPSA). The 5-year bRFS was 82.9% in the BT group versus 80.1% in the RP group (p = 0.570). The 5-year CSS was 96.4% in the BT group versus 96.8% in the RP group (p = 0.967). Based on multivariate Cox regression analysis, Gleason score ≥ 8 was the main independent prognostic factor for bRFS. Regarding the HRQoL, compared with the baseline, both treatments produced a significant decrease in different aspects of HRQoL at 3, 6, and 12 months after treatment. Patients in the BT group had lower HRQoL with regard to urinary irritation/obstruction and bowel function or bother, while patients in the RP group had lower HRQoL concerning urinary incontinence and sexual function or bother. There was no significant difference in HRQoL aspects between the two groups after follow-up for 2 years compared with the baseline. Conclusions: BT provides equivalent oncological control outcomes in terms of bRFS and CSS for patients with localized PCa compared with RP. Gleason score ≥ 8 was the main independent prognostic factor for bRFS. BT had better HRQoL compared with RP, except for urinary irritation/obstruction and bowel function or bother, but returned to baseline after 2 years.

Bone Health Management in the Continuum of Prostate Cancer Disease

Prostate cancer (PCa) is the second-leading cause of cancer-related deaths in men. PCa cells require androgen receptor (AR) signaling for their growth and survival. Androgen deprivation therapy (ADT) is the preferred treatment for patients with locally advanced and metastatic PCa disease. Despite their initial response to androgen blockade, most patients eventually will develop metastatic castration-resistant prostate cancer (mCRPC). Bone metastases are common in men with mCRPC, occurring in 30% of patients within 2 years of castration resistance and in >90% of patients over the course of the disease. Patients with mCRPC-induced bone metastasis develop lesions throughout their skeleton; the 5-year survival rate for these patients is 47%. Bone-metastasis-induced early changes in the bone that proceed the osteoblastic response in the bone matrix are monitored and detected via modern magnetic resonance and PET/CT imaging technologies. Various treatment options, such as targeting osteolytic metastasis with bisphosphonates, prednisone, dexamethasone, denosumab, immunotherapy, external beam radiation therapy, radiopharmaceuticals, surgery, and pain medications are employed to treat prostate-cancer-induced bone metastasis and manage bone health. However, these diagnostics and treatment options are not very accurate nor efficient enough to treat bone metastases and manage bone health. In this review, we present the pathogenesis of PCa-induced bone metastasis, its deleterious impacts on vital organs, the impact of metastatic PCa on bone health, treatment interventions for bone metastasis and management of bone- and skeletal-related events, and possible current and future therapeutic options for bone management in the continuum of prostate cancer disease.

Epidemiology, Staging and Management of Prostate Cancer

Prostate cancer is the second most common and fifth most aggressive neoplasm among men worldwide. It is particularly incident in high human development index (HDI) nations, with an estimated one in seven men in the US receiving a prostate cancer diagnosis in their lifetime. A rapid rise and then fall in prostate cancer incidence in the US and Europe corresponded to the implementation of widespread prostate specific antigen (PSA) testing in 1986 and then subsequent fall from favor due to high rates of false positives, overdiagnosis, and overtreatment (as many as 20-50% of men diagnosed could have remained asymptomatic in their lifetimes). Though few risk factors have been characterized, the best known include race (men of African descent are at higher risk), genetics (e.g., BRCA1/2 mutations), and obesity. The Gleason scoring system is used for histopathological staging and is combined with clinical staging for prognosis and treatment. National guidelines have grown more conservative over the past decades in management, recommending watchful waiting and observation in older men with low to intermediate risk disease. Among higher risk patients, prostatectomy (robotic is preferred) and/or external beam radiotherapy is the most common interventions, followed by ADT maintenance. Following progression on androgen deprivation therapy (ADT) (known as castration-resistance), next generation endocrine therapies like enzalutamide, often in combination with cytotoxic agent docetaxel, are standard of care. Other promising treatments include Radium-223 for bone metastases, pembrolizumab for programmed death ligand-1 (PDL1) and microsatellite instability (MSI) high disease, and poly ADP ribose polymerase (PARP) inhibitors for those with mutations in homologous recombination (most commonly BRCA2).

Design and Challenges of Radiopharmaceuticals

This review describes general concepts with regard to radiopharmaceuticals for diagnostic or therapeutic applications that help to understand the specific challenges encountered during the design, (radio)synthesis, in vitro and in vivo evaluation and clinical translation of novel radiopharmaceuticals. The design of a radiopharmaceutical requires upfront decisions with regard to combining a suitable vector molecule with an appropriate radionuclide, considering the type and location of the molecular target, the desired application, and the time constraints imposed by the relatively short half-life of radionuclides. Well-designed in vitro and in vivo experiments allow nonclinical validation of radiotracers. Ultimately, in combination with a limited toxicology package, the radiotracer becomes a radiopharmaceutical for clinical evaluation, produced in compliance with regulatory requirements for medicines for intravenous (IV) injection.

Investigating the role of constrained CVT and CVT in HIPO inverse planning for HDR brachytherapy of prostate cancer

PURPOSE

The purpose of this study is to investigate the role of the centroidal Voronoi tessellation (CVT) and constrained CVT (CCVT) in inverse planning in combination with the Hybrid Inverse Planning Optimization (HIPO) algorithm in HDR brachytherapy of prostate cancer. HIPO implemented in Oncentra© Prostate treatment planning system, is used for three-dimensional (3D)-ultrasound-based intraoperative treatment planning in high dose rate brachytherapy. HIPO utilizes a hybrid iterative process to determine the most appropriate placement of a given number of catheters to fulfil predefined dose-volume constraints. The main goals of the current investigation were to identify a way of improving the performance of HIPO inverse planning; accelerating the HIPO, and to evaluate the effect of the two CVT-based initialization methods on the dose distribution in the sub-region of prostate that is not accessible by catheters, when trying to avoid perforation of urethra.

METHODS

We implemented the CVT algorithm to generate initial catheter configurations before the initialization of the HIPO algorithm. We introduced the CCVT algorithm to improve the dose distribution to the sub-volume of prostate within the bounding box of the urethra contours including its upper vertical extension (U-P). For the evaluation, we considered a total of 15 3D ultrasound-based HDRBT prostate implants. Execution time and treatment plan quality were evaluated based on the dose-volume histograms of prostate (PTV), its sub-volume U-P, and organs at risk (OARs). Furthermore, the conformity index COIN, the homogeneity index HI and the complication-free tumor control probability (P₊ ) were used for our treatment plan comparisons. Finally, the plans with the recommended HIPO execution mode were compared to the clinically used intraoperative pre-plans.

RESULTS

The plan quality achieved with CCVT-based HIPO initialization was superior to the default HIPO initialization method. Focusing on the U-P sub-region of the prostate, the CCVT method resulted in a significant improvement of all dosimetric indices compared to the default HIPO, when both were executed in the adaptive mode. For that recommended HIPO execution mode, and for U-P, CCVT demonstrated in general higher dosimetric indices than CVT. Additionally, the execution time of CCVT initialized HIPO was lower compared to both alternative initialization methods. This is also valid for the values of the aggregate objective function with the differences to the default initialization method being highly significant. Paired non-parametric statistical tests (Wilcoxon signed-rank) showed a significant improvement of dose-volume indices, COIN and P₊ for the plans generated by the CCVT-based catheter configuration initialization in HIPO compared to the default HIPO initialization process. Furthermore, in ten out of 15 cases, the CCVT-based HIPO plans fulfilled all the clinical dose-volume constraints in a single trial without any need for further catheter position adaption.

CONCLUSION

HIPO with CCVT-based initialization demonstrates better performance regarding the aggregate objective function and convergence when compared to the CVT-based and default catheter configuration initialization methods. This improved performance of HIPO inverse planning is clearly not at the cost of the dosimetric and radiobiologically evaluated plan quality. We recommend the use of the CCVT method for HIPO initialization especially in the adaptive planning mode.

125I low-dose-rate prostate brachytherapy and radical prostatectomy in patients with prostate cancer

Radical prostatectomy (RP) and low-dose-rate prostate brachytherapy (LDR) are two widely used treatment options for patients with T1c-T3a prostate cancer. In the present study, the efficacy of the two treatments was compared. A total of 429 patients who underwent either LDR (n=218) or RP (n=211) between January 2010 and June 2015 were retrospectively reviewed. Biochemical relapse-free survival time (bRFS) and clinical relapse-free survival time (cRFS) were assessed. The log-rank test compared bRFS between the two modalities, and Cox regression identified factors associated with bRFS. The median follow-up time and patient age were 46.6 months and 71 years, respectively. The bRFS at 1, 2 and 5 years was 89.4, 87.2 and 79.9% for LDR, respectively, and 91.0, 82.8 and 72.2% for RP, respectively (P=0.077). The cRFS at 1, 2 and 5 years was 99.1, 97.7 and 94.9% for LDR, respectively, and 99.0, 96.2 and 94.5% for RP, respectively (P=0.630). It was indicated that LDR produced equivalent bRFS and cRFS rates compared with RP. The risk of biochemical failure (bF) was higher for the RP group compared with the LDR group in patients with a Gleason score ≤3+4 (P=0.022) or initial prostate specific antigen ≤10 ng/ml (P=0.002). Based on the univariate and multivariate logistic regression analysis of all 429 patients, T stage ≥T2b was an independent predictor for bF.

Improving rectal dosimetry for patients with intermediate and high-risk prostate cancer undergoing combined high-dose-rate brachytherapy and external beam radiotherapy with hydrogel space

Purpose

To report on rectal dosimetric and toxicity outcomes of intermediate and high-risk prostate cancer patients undergoing combined high-dose-rate (HDR) brachytherapy and external beam radiotherapy (EBRT) with or without hydrogel spacer (HS) insertion.

Material and methods

A total of 97 patients were analyzed in this study, with 32 patients (33%) who had HS insertion compared with a preceding group of 65 patients (67%) without HS. HS safety, the dosimetric effects on organs at risk (rectal, urethral, penile bulb, and bladder) as well as gastrointestinal (GI) and genitourinary toxicity were evaluated and compared between the two groups.

Results

The median prostate-rectal separation achieved with HS was 10 mm (range, 5-14 mm). There were no post-operative complications following HS insertion. Patients with HS had significantly lower radiation dose to the rectum across all rectal dose volumes from rV₃₀ to rV₈₀, whether in absolute volume (cc) or as percentage of contoured OAR (p < 0.001). There was also significantly less acute > grade 1 GI toxicity (12.5% vs. 30.8%, p = 0.05) and a trend towards less late grade 1 GI toxicity (0% vs. 7.7%; p = 0.11) in the HS group compared to the non-HS group.

Conclusions

Insertion of HS in prostate cancer patients receiving combined HDR and EBRT is safe and has resulted in a significant radiation dose reduction to the rectum, resulting in significantly less acute GI toxicity and a trend towards less late GI toxicity.

[Prostate brachytherapy: New techniques, new indications]

Prostate brachytherapy has been for a long time one of the standard treatments for low risk prostate cancer, with high rates of biochemical control and low levels of urinary and sexual late toxicity compared to other available techniques, namely external beam radiotherapy and radical prostatectomy. The aim of this article is to review the recent innovations of prostate brachytherapy, which suggest a bright future for the technique. We will discuss the extension of indications of permanent implant brachytherapy to favorable intermediate-risk patients, the use of novel isotopes such as Palladium 103 and Cesium 131, and the benefit of brachytherapy as a boost following external beam radiotherapy for intermediate and high-risk patients. We will also discuss the rise of high dose rate brachytherapy, as a boost or monotherapy, the increasing use of MRI for patient selection and treatment planning, as well as the development of brachytherapy as a means of focal therapy.