Advances in the treatment of prostate cancer with radiotherapy

Long term update on toxicity and survival of a phase II trial of linac-based stereotactic body radiation therapy for low-intermediate risk prostate cancer

BACKGROUND

In 2016 we published a phase II study exploring safety and efficacy of Stereotactic Body Radiation Therapy (SBRT) delivered with Volumetric Modulated Arc Therapy (VMAT) and Flattening Filter Free (FFF) beams techniques in prostate cancer (PC) patients. We present herein the updated results on late toxicity and long-term survival.

METHODS

Patients enrolled in the study had a biopsy-confirmed localized PC and the features of a low- or intermediate-risk disease (National Comprehensive Network Criteria). The radiotherapy (RT) schedule consisted of 35 Gy delivered in five fractions every other day. Toxicities were registered according to the common toxicity adverse events v4.0. Biochemical recurrence was defined as an increase of prostate specific antigen after nadir, confirmed at least once. Local recurrence (LR) and distant metastases were detected either with Choline- or PSMA-PET/CT scans. Kaplan-Meier curves for Biochemical Recurrence-Free Survival (BFS), Local Control (LC), Distant Metastasis Free Survival (DMFS) and Cancer Specific Survival, were calculated by using MedCalc.

RESULTS

Ninety patients were submitted to SBRT between February 2012 and March 2015. Fifty-eight patients (64.5%) had a Gleason Score of 6, while 32 (35.5%) had a Gleason Score of 7. A late grade 1 Genito-Urinary toxicity was observed in 54.5% of patients while a grade 2 in 3.3%. A late Gastro-intestinal grade 1 toxicity was reported in 18.9% of patients, while a grade 2 in 2.2%. Erectile dysfunction was reported by 13% of patients No heavier toxicities were observed. At a median follow-up of 102 months, 5- and 8-year BFS were 93.0% and 84.4% respectively, 5- and 8-year LC were 95.2% and 87.0% respectively, 5- and 8-year DMFS were 95.3% and 88.4%, respectively.

CONCLUSIONS

This long-term update confirms that SBRT is a valid therapeutic strategy for low-intermediate risk PC. RT with VMAT and FFF warrants optimal results in terms of toxicity and disease control.

Esophagus segmentation from planning CT images using an atlas-based deep learning approach

BACKGROUND AND OBJECTIVE

One of the main steps in the planning of radiotherapy (RT) is the segmentation of organs at risk (OARs) in Computed Tomography (CT). The esophagus is one of the most difficult OARs to segment. The boundaries between the esophagus and other surrounding tissues are not well-defined, and it is presented in several slices of the CT. Thus, manually segment the esophagus requires a lot of experience and takes time. This difficulty in manual segmentation combined with fatigue due to the number of slices to segment can cause human errors. To address these challenges, computational solutions for analyzing medical images and proposing automated segmentation have been developed and explored in recent years. In this work, we propose a fully automatic method for esophagus segmentation for better planning of radiotherapy in CT.

METHODS

The proposed method is a fully automated segmentation of the esophagus, consisting of 5 main steps: (a) image acquisition; (b) VOI segmentation; (c) preprocessing; (d) esophagus segmentation; and (e) segmentation refinement.

RESULTS

The method was applied in a database of 36 CT acquired from 3 different institutes. It achieved the best results in literature so far: Dice coefficient value of 82.15%, Jaccard Index of 70.21%, accuracy of 99.69%, sensitivity of 90.61%, specificity of 99.76%, and Hausdorff Distance of 6.1030 mm.

CONCLUSIONS

With the achieved results, we were able to show how promising the method is, and that applying it in large medical centers, where esophagus segmentation is still an arduous and challenging task, can be of great help to the specialists.

Long non-coding RNA LINC00673 silencing inhibits proliferation and drug resistance of prostate cancer cells via decreasing KLF4 promoter methylation

Prostate cancer is one of the major causes of cancer‐related mortality in men across the world. Recently, long non‐coding RNAs (lncRNAs) and Kruppel‐like factor 4 (KLF4) have been reported to participate in the biology of multiple cancers including prostate cancer. Here, this study aimed to explore the possible role of LINC00673 in prostate cancer via KLF4 gene promoter methylation. Microarray‐based gene expression profiling of prostate cancer was employed to identify differentially expressed lncRNAs and genes, after which the expression of LINC00673 and KLF4 in prostate cancer tissues was determined using RT‐qPCR. Next, the relationship between LINC00673 and KLF4 was evaluated using in silico analysis. Further, the effect of LINC00673 and KLF4 on cell proliferation and drug resistance of transfected cells was examined with gain‐ and loss‐of‐function experimentation. It was found that LINC00673 was highly expressed, while KLF4 was poorly expressed in prostate cancer tissues. Additionally, LINC00673 could bind to KLF4 gene promoter region and recruit methyltransferase to the KLF4 gene promoter region. Moreover, LINC00673 silencing was demonstrated to reduce methylation of the KLF4 gene promoter to elevate the expression of KLF4, thus suppressing the proliferation and drug resistance of prostate cancer cells. In summary, LINC00673 silencing could drive demethylation of the KLF4 gene promoter and thus inhibit the proliferation and drug resistance of prostate cancer cells, suggesting that silencing of LINC00673 and elevation of KLF4 could serve as tumour suppressors in prostate cancer.

Spinal cord detection in planning CT for radiotherapy through adaptive template matching, IMSLIC and convolutional neural networks

BACKGROUND AND OBJECTIVE

The spinal cord is a very important organ that must be protected in treatments of radiotherapy (RT), considered an organ at risk (OAR). Excess rays associated with the spinal cord can cause irreversible diseases in patients who are undergoing radiotherapy. For the planning of treatments with RT, computed tomography (CT) scans are commonly used to delimit the OARs and to analyze the impact of rays in these organs. Delimiting these OARs take a lot of time from medical specialists, plus the fact that involves a large team of professionals. Moreover, this task made slice-by-slice becomes an exhaustive and consequently subject to errors, especially in organs such as the spinal cord, which extend through several slices of the CT and requires precise segmentation. Thus, we propose, in this work, a computational methodology capable of detecting spinal cord in planning CT images.

METHODS

The techniques highlighted in this methodology are adaptive template matching for initial segmentation, intrinsic manifold simple linear iterative clustering (IMSLIC) for candidate segmentation and convolutional neural networks (CNN) for candidate classification, that consists of four steps: (1) images acquisition, (2) initial segmentation, (3) candidates segmentation and (4) candidates classification.

RESULTS

The methodology was applied on 36 planning CT images provided by The Cancer Imaging Archive, and achieved an accuracy of 92.55%, specificity of 92.87% and sensitivity of 89.23% with 0.065 of false positives per images, without any false positives reduction technique, in detection of spinal cord.

CONCLUSIONS

It is demonstrated the feasibility of the analysis of planning CT images using IMSLIC and convolutional neural network techniques to achieve success in detection of spinal cord regions.

A comparison of treatment outcome between fiducial-based and bone-based image guided radiotherapy in prostate cancer patients

BACKGROUND AND PURPOSE

To compare the clinical outcome in prostate cancer patients treated with radiotherapy using two forms of image guidance: bone-based (BB) or fiducial-based (FB).

MATERIAL AND METHODS

This retrospective study consisted of 180 patients treated with kV-kV image-guided radiotherapy (IGRT) between the years 2008 and 2011. A total of 89 patients were aligned to pelvic bone (Group BB) and 91 patients to the fiducial implanted into prostate for image guidance (Group FB). Patients were treated to a total dose of 76 Gy in 38 fractions. The Cox Regression Model was used to evaluate the influence of clinical and treatment-related parameters on overall survival, biochemical progression and progression-free survival. Acute and late toxicity were evaluated based on the RTOG/EORTC criteria. Sexual function was assessed with QLQ PR-25 (EORTC QLQ forms). An assessment of the differences in patient daily set-up from the time of simulation was performed.

RESULTS

The incidence of acute G2/G3 genitourinary (GU) and gastrointestinal (GI) toxicity was similar between groups. In the BB group, 34 patients had G2 and 5 had G3 GU acute toxicity - compared to 40 patients with G2 and 2 with G3 in the FB group. G2 and G3 GI acute toxicity was observed respectively in 24 patients and in 1 patient in the BB group compared to 18 patients with G2 and 1 patient with G3 toxicity in the FB group. The five-year incidence of late ≥G2 GU toxicity was 12% in both groups (p = 0.98) and ≥ G2 GI toxicity 19% (BB) vs 15% (FB, p = 0.55), respectively. The five-year progression-free survival rate was 87% in BB and 81% in the FB Group (p = 0.15). The 5-year Overall Survival rate (OS) was 80% (BB) vs 91% % (FB, p = 0.20), but the difference was most pronounced in the intermediate-risk group: 5-year OS of 93% (FB) and 75% (BB), respectively (p = 0.06). No significant changes were observed in sexual or erectile functioning as compared to that specified at the beginning of radiotherapy and between the FB and BB Groups.

CONCLUSION

When comparing bone-based to fiducial-based techniques, no differences in clinical outcomes or late toxicity were seen in this population. However, intermediate risk prostate cancer patients are those who might benefit most from implementation of fiducial-based IGRT.

Focal therapy for prostate cancer: concepts and future directions

PURPOSE OF REVIEW

To present a perspective on the current status and future directions of focal therapy for prostate cancer (PCa).

RECENT FINDINGS

Focal therapy for localized PCa is a rapidly evolving field. Various recent concepts - the index lesion driving prognosis, the enhanced detection of clinically significant PCa using multiparametric MRI and targeted biopsy, improved risk-stratification using novel blood/tissue biomarkers, the recognition that reducing radical treatment-related morbidity (along with reducing pathologic progression) is a clinically meaningful end-point - have all led to a growing interest in focal therapy. Novel focal therapy modalities are being investigated, mostly in phase 1 and 2 studies. Recently, level I prospective randomized data comparing partial gland ablation with a standard-of-care treatment became available from one study. Recent developments in imaging, including 7-T MRI, functional imaging, radiomics and contrast-enhanced ultrasound show early promise. We also discuss emerging concepts in patient selection for focal therapy.

SUMMARY

PCa focal therapy has evolved considerably in the recent few years. Overall, these novel focal therapy treatments demonstrate safety and feasibility, low treatment-related toxicity and acceptable short-term and in some cases medium-term oncologic outcomes. As imaging techniques evolve, patient selection, detection of clinically significant PCa and noninvasive assessment of therapeutic efficacy will be further optimized. The aspirational goal of achieving oncologic control while reducing radical treatment-related morbidity will drive further innovation in the field.

Focal therapy for prostate cancer: the technical challenges

Focal therapy for prostate cancer has been proposed as an alternative treatment to whole gland therapy, offering the opportunity for tumor dose escalation and/or reduced toxicity. Brachytherapy, either low-dose-rate or high-dose-rate, provides an ideal approach, offering both precision in dose delivery and opportunity for a highly conformal, non-uniform dose distribution. Whilst multiple consensus documents have published clinical guidelines for patient selection, there are insufficient data to provide clear guidelines on target volume delineation, treatment planning margins, treatment planning approaches, and many other technical issues that should be considered before implementing a focal brachytherapy program. Without consensus guidelines, there is the potential for a diversity of practices to develop, leading to challenges in interpreting outcome data from multiple centers. This article provides an overview of the technical considerations for the implementation of a clinical service, and discusses related topics that should be considered in the design of clinical trials to ensure precise and accurate methods are applied for focal brachytherapy treatments.

Dosimetric comparison of intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy in patients with prostate cancer: a meta-analysis

Intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) are two main radiotherapy techniques. The aim of this study is to explore which is the preferred technique in prostate treatment through the related publica-tions and meta-analysis. Two authors independently identified all relevant articles available regarding eligibility criteria on PubMed, Embase, and Cochrane Library databases until December 2015. Publication bias was evaluated with funnel plot, and statistical analyses were performed with Stata software. P < 0.05 was thought statistically significant. Ten studies comprised a total of 110 patients; in total 110 IMRT plans and 110 VMAT plans that were included in this study. V40, V60, and V70 of rectum were significantly decreased in VMAT than in IMRT. However, V50 of rectum and V40, V50, V60, V70 of bladder had no statistical differences between IMRI and VMAT plans. Compared with IMRT, the treatment time and MUs of VMAT were significantly lower. VMAT protects rectum better than IMRT and improves the delivery efficiency. VMAT may be the preferred modality for treating prostate cancer.

Active Surveillance for Intermediate Risk Prostate Cancer: Survival Outcomes in the Sunnybrook Experience

PURPOSE

To assess the applicability of active surveillance in patients with intermediate risk prostate cancer, we compared the survival outcomes of patients with low risk and intermediate risk disease.

MATERIALS AND METHODS

Active surveillance was offered to all patients with low risk (cT1-T2b and Gleason score 6 and prostate specific antigen 10 ng/ml or less) and select intermediate risk disease (age greater than 70 years with cT2c or prostate specific antigen 15 ng/ml or less, or Gleason score 3+4 or less). Data from November 1995 to May 2013 were extracted from a prospectively collected database. The primary outcome was metastasis-free survival, and secondary outcomes were overall survival, cause specific survival and treatment-free survival.

RESULTS

A total of 213 intermediate risk and 732 low risk cases were identified. Median age was 72 years (IQR 67.3, 76.8) in the intermediate risk cohort and 67 years (IQR 60.6, 71.9) in the low risk group. Median followup was comparable (6.7 years for intermediate risk vs 6.5 years for low risk). Gleason 7 disease comprised 60% of the intermediate risk cohort. The 15-year metastasis-free, overall, cause specific and treatment-free survival rates were inferior in the intermediate risk group (metastasis-free survival HR 3.14, 95% CI 1.51-6.53, p=0.001, 82% for intermediate risk vs 95% for low risk). On further evaluation the estimated 15-year metastasis-free survival for cases of Gleason 6 or less with prostate specific antigen less than 10 ng/ml was 94%, Gleason 6 or less with prostate specific antigen 10 to 20 ng/ml was 94%, Gleason 3+4 with prostate specific antigen 20 ng/ml or less was 84% and Gleason 4+3 with prostate specific antigen 20 ng/ml or less was 63%.

CONCLUSIONS

These data support the use of active surveillance in low risk and intermediate risk cases of Gleason 6 but not Gleason 7 prostate cancer. Multiparametric magnetic resonance imaging and novel biomarkers might be vital in detecting favorable Gleason 7 disease.

Use of stereotactic body radiotherapy for prostate cancer in the United States from 2004 through 2012

BACKGROUND

Stereotactic body radiotherapy (SBRT) is a newer treatment option for patients with localized prostate cancer. The rates of diffusion of this technology across the United States are unknown. The goal of the current study was to describe the use of SBRT among patients with prostate cancer based on different risk groups (low, intermediate, or high risk) and by type of facility (community cancer program, comprehensive community cancer program, or academic program) in which patients were treated.

METHODS

Using the National Cancer Data Base, a national registry that contains approximately 70% of patients with cancer in the United States, the authors identified 274,466 men between the ages of 40 to 80 years who were diagnosed from 2004 to 2012 with localized prostate cancer and received radiation therapy (RT) as their initial treatment. The authors described the prevalence of SBRT use each year, and multivariable analysis was used to examine factors associated with the receipt of SBRT.

RESULTS

In 2004, SBRT use was low (<1% in all patient groups), and was observed to increase steadily each year. By 2012, 8.8% of low-risk patients treated at academic centers with RT received SBRT. Uptake of SBRT was highest in patients with low-risk or intermediate-risk disease. Multivariable analysis demonstrated that year of diagnosis, type of center, risk group, and race were all significantly associated with the use of SBRT.

CONCLUSIONS

To the authors' knowledge, the current study is the first report of the adoption of SBRT for localized prostate cancer across the United States. Diffusion was noted to be slowest at community cancer programs, reflecting potential barriers of cost or expertise for this new technology. Adoption of SBRT was found to be highest among patients with low-risk or intermediate-risk disease, in accordance with the bulk of patients included in published SBRT studies. Cancer 2016;122:2234-41. © 2016 American Cancer Society.

Low temperature plasmas as emerging cancer therapeutics: the state of play and thoughts for the future

The field of plasma medicine has seen substantial advances over the last decade, with applications developed for bacterial sterilisation, wound healing and cancer treatment. Low temperature plasmas (LTPs) are particularly suited for medical purposes since they are operated in the laboratory at atmospheric pressure and room temperature, providing a rich source of reactive oxygen and nitrogen species (RONS). A great deal of research has been conducted into the role of reactive species in both the growth and treatment of cancer, where long-established radio- and chemo-therapies exploit their ability to induce potent cytopathic effects. In addition to producing a plethora of RONS, LTPs can also create strong electroporative fields. From an application perspective, it has been shown that LTPs can be applied precisely to a small target area. On this basis, LTPs have been proposed as a promising future strategy to accurately and effectively control and eradicate tumours. This review aims to evaluate the current state of the literature in the field of plasma oncology and highlight the potential for the use of LTPs in combination therapy. We also present novel data on the effect of LTPs on cancer stem cells, and speculatively outline how LTPs could circumvent treatment resistance encountered with existing therapeutics.

Radiosensitivity in HeLa cervical cancer cells overexpressing glutathione S-transferase π 1

The aims of the present study were to investigate the effect of overexpressed exogenous glutathione S-transferase π 1 (GSTP1) gene on the radiosensitivity of the HeLa human cervical cancer cell line and conduct a preliminarily investigation into the underlying mechanisms of the effect. The full-length sequence of human GSTP1 was obtained by performing a polymerase chain reaction (PCR) using primers based on the GenBank sequence of GSTP1. Subsequently, the gene was cloned into a recombinant eukaryotic expression plasmid, and the resulting construct was confirmed by restriction analysis and DNA sequencing. A HeLa cell line that was stably expressing high levels of GSTP1 was obtained through stable transfection of the constructed plasmids using lipofectamine and screening for G418 resistance, as demonstrated by reverse transcription-PCR. Using the transfected HeLa cells, a colony formation assay was conducted to detect the influence of GSTP1 overexpression on the cell radiosensitivity. Furthermore, flow cytometry was used to investigate the effect of GSTP1 overexpression on cell cycle progression, with the protein expression levels of the cell cycle regulating factor cyclin B1 detected using western blot analysis. Colony formation and G₂/M phase arrest in the GSTP1-expressing cells were significantly increased compared with the control group (P<0.01). In addition, the expression of cyclin B1 was significantly reduced in the GSTP1-expressing cells. These results demonstrated that increased expression of GSTP1 inhibits radiosensitivity in HeLa cells. The mechanism underlying this effect may be associated with the ability of the GSTP1 protein to reduce cyclin B1 expression, resulting in significant G₂/M phase arrest.