Prospective results for 5-year survival and toxicity of moderately hypofractionated radiotherapy with simultaneous integrated boost (SIB) in (very) high-risk prostate cancer

Purpose

High-risk (HR) prostate cancer patients usually receive high-dose radiotherapy (RT) using a two-phase sequential technique, but data on a simultaneous integrated boost (SIB) technique are lacking. We prospectively evaluated the long-term results of urinary (GU) and digestive (GI) toxicity and survival data for high-dose RT using a SIB technique in HR and very high-risk (VHR) prostate cancer.

Methods

Patients were treated using an SIB technique in 34 fractions, at a dose of 54.4 Gy to the pelvis and seminal vesicles and 74.8 Gy to the prostate, combined with 36 months of androgen-depriving therapy in a prospective multicenter study. Acute and late GU and GI toxicity data were collected. Overall survival (OS), biochemical-relapse-free survival (bRFS), loco-regional-relapse-free survival (LRRFS), metastasis-free-survival (MFS) and disease-free-survival (DFS) were assessed.

Results

We recruited 114 patients. After a median follow-up of 62 months, very few patients experienced acute (M0-M3) (G3-4 GU = 3.7 %; G3-4 GI = 0.9 %) or late (M6-M60) severe toxicity (G3-4 GU = 5.6 %; G3-4 GI = 2.8 %). The occurrence of acute G2 + GU or GI toxicity was significantly related to the consequential late G2 + toxicity (p < 0.01 for both GU and GI). Medians of OS, bRFS, LRRFS, MFS and DFS were not reached. At 60 months, OS, bRFS, LRRFS, MFS and DFS were 88.2 % [82.1; 94.7], 86.0 % [79.4 %;93.2 %], 95.8 % [91.8 %;99.9 %], 87.2 % [80.9 %;94.0 %] and 84.1 % [77.2 %;91.6 %] respectively.

Conclusion

SIB RT at a dose of 54.4 Gy to the pelvis and 74.8 Gy to the prostate is feasible, leading to satisfying tumor control and reasonable toxicity in HR and VHR prostate cancer.

[Intermediate-risk prostate cancer treated with exclusive external irradiation: Focus on anatomical sites of recurrence in two French trials]

PURPOSE

Retrospective description of anatomical sites of relapse based on (18F)-choline PET-CT, (68Ga)-prostatic specific-membrane antigen PET-CT, bone scan, and prostate magnetic resonance imaging (MRI) data.

MATERIALS AND METHODS

From two French prospective cohorts, patients treated with exclusive radiotherapy for an intermediate-risk cancer were identified during their follow-ups. They were included if they presented a rising of the prostate-specific antigen (PSA) associated with the realization of an imaging showing the sites of recurrences.

RESULTS

Two hundred and sixty-three patients were included. After a median follow-up of 76 months (interquartile range [IQR] 67-95), 65 patients had biochemical recurrence and positive imaging. The median nadir PSA was 0.6ng/mL and the median PSA at recurrence was 3.4ng/mL. A single lesion was found in 48% of cases, 2 to 4 lesions in 43% of cases and more than 4 lesions in 9% of cases. The sites of relapse identified were prostate (37/65), prostate only (19/65), seminal vesicles (9/65) Pelvic nodes (35/65), extrapelvic nodes (15/65) and bone (13/65).

CONCLUSIONS

The majority of relapses presented as a single lesion localized in the pelvis.

Cost and Toxicity Comparisons of Two IMRT Techniques for Prostate Cancer: A Micro-Costing Study and Weighted Propensity Score Analysis Based on a Prospective Study

BACKGROUND

Intensity modulated radiation therapy (IMRT) combined with androgen deprivation therapy (ADT) has become the standard treatment for patients with high-risk prostate cancer. Two techniques of rotational IMRT are commonly used in this indication: Volumetric Modulated Arc Therapy (VMAT) and helical tomotherapy (HT). To the best of our knowledge, no study has compared their related costs and clinical effectiveness and/or toxicity in prostate cancer. We aimed to assess differences in costs and toxicity between VMAT and HT in patients with high-risk prostate cancer with pelvic irradiation.

MATERIAL AND METHODS

We used data from the "RCMI pelvis" prospective multicenter study (NCT01325961) including 155 patients. We used a micro-costing methodology to identify cost differences between VMAT and HT. To assess the effects of the two techniques on total actual costs per patient and on toxicity we used stabilized inverse probability of treatment weighting.

RESULTS

The mean total cost for HT, €2019 3,069 (95% CI, 2,885-3,285) was significantly higher than the mean cost for VMAT €2019 2,544 (95% CI, 2,443-2,651) (p <.0001). The mean ± SD labor and accelerator cost for HT was €2880 (± 583) and €1978 (± 475) for VMAT, with 81 and 76% for accelerator, respectively. Acute GI and GU toxicity were more frequent in VMAT than in HT (p = .021 and p = .042, respectively). Late toxicity no longer differed between the two groups up to 24 months after completion of treatment.

CONCLUSION

Use of VMAT was associated with lower costs for IMRT planning and treatment than HT. Similar stabilized long-term toxicity was reported in both groups after higher acute GI and GU toxicity in VMAT. The estimates provided can benefit future modeling work like cost-effectiveness analysis.

Interaction Between Modern Radiotherapy and Immunotherapy for Metastatic Prostate Cancer

Prostate cancer is the most frequently diagnosed cancer in men and a leading cause of cancer-related death. In recent decades, the development of immunotherapies has resulted in great promise to cure metastatic disease. However, prostate cancer has failed to show any significant response, presumably due to its immunosuppressive microenvironment. There is therefore growing interest in combining immunotherapy with other therapies able to relieve the immunosuppressive microenvironment. Radiation therapy remains the mainstay treatment for prostate cancer patients, is known to exhibit immunomodulatory effects, depending on the dose, and is a potent inducer of immunogenic tumor cell death. Optimal doses of radiotherapy are thus expected to unleash the full potential of immunotherapy, improving primary target destruction with further hope of inducing immune-cell-mediated elimination of metastases at distance from the irradiated site. In this review, we summarize the current knowledge on both the tumor immune microenvironment in prostate cancer and the effects of radiotherapy on it, as well as on the use of immunotherapy. In addition, we discuss the utility to combine immunotherapy and radiotherapy to treat oligometastatic metastatic prostate cancer.

[Oligorecurrent prostate cancer: current management and perspectives]

Oligometastatic prostate cancer (PCa) is an intense area of research thanks to the development of novel PET tracers such as ¹⁸F-choline or ⁶⁸Ga-PSMA. Several retrospective studies in patients with hormone-sensitive oligorecurrent PCa (usually up to 5 metastases with a controlled primary tumor) showed PSA response and a low toxicity profile of metastasis-directed therapies (MDT) such as Stereotactic Body Radiation Therapy (SBRT) or salvage lymph node dissection. More recently, randomized phase 2 studies showed that SBRT can delay the introduction of androgen deprivation, decrease biochemical relapses and increase overall survival. Regarding oligoprogressive metastatic castration-resistant PCa, limited data is however available. Based on these studies the European Association of Urology and the American Society of Radiotherapy EAU now recommend using MDT instead of observation. Several studies are undergoing in France and worldwide in order to confirm the exact role of MDT.

Haute Couture or Ready-to-Wear? Tailored Pelvic Radiotherapy for Prostate Cancer Based on Individualized Sentinel Lymph Node Detection

Prostate cancer (PCa) pelvic radiotherapy fields are defined by guidelines that do not consider individual variations in lymphatic drainage. We examined the feasibility of personalized sentinel lymph node (SLN)-based pelvic irradiation in PCa. Among a SLN study of 202 patients, we retrospectively selected 57 patients with a high risk of lymph node involvement. Each single SLN clinical target volume (CTV) was individually segmented and pelvic CTVs were contoured according to Radiation Therapy Oncology Group (RTOG) guidelines. We simulated a radiotherapy plan delivering 46 Gy and calculated the dose received by each SLN. Among a total of 332 abdominal SLNs, 305 pelvic SLNs (beyond the aortic bifurcation) were contoured (mean 5.4/patient). Based on standard guidelines, CTV missed 67 SLNs (22%), mostly at the common iliac level (40 SLNs). The mean distance between iliac vessels and the SLN was 11mm, and despite a 15mm margin around the iliac vessels, 9% of SLNs were not encompassed by the CTV. Moreover, 42 SLNs (63%) did not receive 95% of the prescribed dose. Despite a consensus on contouring guidelines, a significant proportion of SLNs were not included in the pelvic CTV and did not receive the prescribed dose. A tailored approach based on individual SLN detection would avoid underdosing pelvic lymph nodes that potentially contain tumor cells.

microRNAs identified in prostate cancer: Correlative studies on response to ionizing radiation

As the most frequently diagnosed non-skin cancer in men and a leading cause of cancer-related death, understanding the molecular mechanisms that drive treatment resistance in prostate cancer poses a significant clinical need. Radiotherapy is one of the most widely used treatments for prostate cancer, along with surgery, hormone therapy, and chemotherapy. However, inherent radioresistance of tumor cells can reduce local control and ultimately lead to poor patient outcomes, such as recurrence, metastasis and death. The underlying mechanisms of radioresistance have not been fully elucidated, but it has been suggested that miRNAs play a critical role. miRNAs are small non-coding RNAs that regulate gene expression in every signaling pathway of the cell, with one miRNA often having multiple targets. By fine-tuning gene expression, miRNAs are important players in modulating DNA damage response, cell death, tumor aggression and the tumor microenvironment, and can ultimately affect a tumor's response to radiotherapy. Furthermore, much interest has focused on miRNAs found in biofluids and their potential utility in various clinical applications. In this review, we summarize the current knowledge on miRNA deregulation after irradiation and the associated functional outcomes, with a focus on prostate cancer. In addition, we discuss the utility of circulating miRNAs as non-invasive biomarkers to diagnose, predict response to treatment, and prognosticate patient outcomes.

Reoxygenation during radiotherapy in intermediate-risk prostate cancer

Hypoxia is a major risk factor of prostate cancer radioresistance. We evaluated hypoxia non-invasively, using ¹⁸F-Misonidazole PET/CT prior to radiotherapy and after a dose of 20 Gy in intermediate-risk prostate cancer patients. Decreased hypoxic volumes were observed in all patients, suggesting that radiotherapy induces early prostate tumor reoxygenation.

Moderately hypofractionated prostate external-beam radiotherapy: an emerging standard

Research over recent years has demonstrated that curative external-beam radiotherapy can be safely and efficaciously delivered with roughly half the number of treatments which was previously considered standard. We review the data supporting this change in practice, methods for implementation, as well as emerging future directions.

Combined abiraterone acetate plus prednisone, salvage prostate bed radiotherapy and LH-RH agonists (CARLHA-GEP12) in biochemically-relapsing prostate cancer patients following prostatectomy: A phase I study of the GETUG/GEP

Background

To establish the maximum tolerated dose of abiraterone acetate plus prednisone (AA) combined with salvage radiotherapy (SRT) and goserelin in a phase 1 study in men with rising PSA following radical prostatectomy.

Methods

AA was given during one month before SRT at 1000 mg PO once daily, then 750 mg (Dose Level 1, DL1) or 1000 mg (DL2) during 5 months combined with 6-months goserelin by injection on the first day of irradiation (scheme NEO) or one month before starting SRT (scheme CONCO).

Results

In scheme NEO at DL1, 2/9 patients did not achieve castration levels of testosterone. 4/9 patients (44%) presented with grade 3 liver enzyme elevation. In scheme CONCO testosterone dropped to undetectable levels. At DL1, 6 patients were recruited, with no dose limiting toxicities. At DL2, 2/3 patients presented with grade 3 liver enzyme elevation occurring during SRT.

Conclusions

When AA was administered without goserilin, only 78% achieved castration levels. AA combined with SRT and goserilin did not increase pelvic toxicity, but lead to an unsuspected high frequency of grade 3 liver toxicity. The phase II recommended dose of AA combined to goserelin and SRT is 750 mg.

Comprehensive Geriatric Assessment and quality of life after localized prostate cancer radiotherapy in elderly patients

Introduction

Radiotherapy can diminish quality of life (QoL) for prostate cancer patients. Our objective was to evaluate the effect of radiotherapy on QoL in men aged 75 years or older treated with radiotherapy for a localized prostate cancer, and to identify predictors of reduced QoL.

Patients and methods

We prospectively administered a battery of geriatric (MNA, GDS, Get up and Go Test, CIRS-G, ADL, IADL, MMSE), toxicity (IPSS; IIEF 5), and QoL (QLQ C30) screening tests in 100 elderly patients before and two months after prostate cancer radiotherapy (NCT 02876237). Patients ≥ 75 years undergoing radiotherapy with a curative intent for localized prostate cancer with or without androgen deprivation therapy (ADL) were eligible for study inclusion. Correlations between patient-assessed QoL and tumor characteristics, radiotherapy treatment or CGA parameters were sought using the Fisher or the Mann and Whitney tests. Changes in QoL parameters over time were analyzed using the Wilcoxon signed-rank test.

Results

At study entry, scores for IADL impairments were present in 51%, reduced autonomy in activities of daily living in 16%, cognitive impairment found in 20%, depression-related symptoms in 31%, and 66% of patients had significant co-morbidities. Eight percent were judged to be at risk of fall and 2% were found to be undernourished. Severely impaired (IPSS ≥ 20) urinary function was observed in 11.2% and 13.5% of patients before and two months after completion of radiotherapy respectively. Significantly decreased QoL (> 20 points) at two months after treatment was found in 13% of patients and a moderate but clinically relevant reduction (10 to 20 points) in 17% of patients. No tumor characteristic, treatment, or oncogeriatric parameter was predictive of reduced QoL following prostate cancer radiotherapy.

Conclusion

Despite sometimes markedly diminished oncogeriatric parameters, prostate cancer radiotherapy was generally well tolerated in these elderly patients. We found no predictive factor to determine which patients would experience impaired quality of life following radiotherapy.

A mini-review of quality of life as an outcome in prostate cancer trials: patient-centered approaches are needed to propose appropriate treatments on behalf of patients

Background

Patients with prostate cancer (PC) may be ready to make trade-offs between their quantity and their quality of life. For instance, elderly patients may prefer the absence of treatment if it is associated with a low-risk of disease progression, compared to treatments aiming at preventing disease progression but with a substantial deterioration of their Health-Related Quality of Life (HRQoL). Therefore, it seems relevant to compare the treatments by considering both survival and HRQoL. In this mini-review, the aim was to question whether the potential trade-offs between survival and HRQoL are considered in high impact factor journals.

Methods

The study was conducted from the PubMed database for recent papers published between May 01, 2013, and May 01, 2015. We also restricted our search to nine medical journals with 2013 impact factor > 15.

Results

Among the 30 selected studies, only six collected individual HRQoL as a secondary endpoint by using the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire. In four studies, the time to HRQoL change was analyzed, but its definitions varied. In two studies, the mean changes in HRQoL between the baseline and the 12- or 16-week follow-up were analyzed. None of the six studies reported in a single endpoint both the quantity and the quality of life.

Conclusions

Our mini-review, which only focused on recent publications in journals with high-impact, suggests moving PC clinical research towards patient-centered outcomes-based studies. This may help physicians to propose the most appropriate treatment on behalf of patients. We recommend the use of indicators such as Quality-Adjusted Life-Years (QALYs) as principal endpoint in future clinical trials.

Electronic supplementary material

The online version of this article (10.1186/s12955-018-0870-6) contains supplementary material, which is available to authorized users.

[Radiotherapy of oligometastatic pelvic node relapses in patients with prostate cancer]

The Oligopelvis 2 studies is based on the assumption that salvage pelvic radiotherapy may prolong the interval between the first and the second intermittent hormone therapy sequence in pelvic lymph node oligometastatic prostate cancer. This phase 3 study will compare intermittent hormone therapy (standard arm) alone or combined with salvage pelvic radiotherapy (experimental arm).

[Role of radiotherapy in the management of node-positive prostate cancer]

Node-positive prostate cancer patients represent a small proportion of all prostate cancers for whom limited prospective information is available. Most retrospective or cohort data strongly suggest however that radiotherapy combined with androgen-depriving therapies is the preferable treatment in this setting. Only randomized clinical trials would be able to better define both radiotherapy (dose? volume? fractionation?) and androgen-depriving therapies (duration? role of novel androgen-depriving therapy?) modalities.

Mechanistic Insights into Molecular Targeting and Combined Modality Therapy for Aggressive, Localized Prostate Cancer

Radiation therapy (RT) is one of the mainstay treatments for prostate cancer (PCa). The potentially curative approaches can provide satisfactory results for many patients with non-metastatic PCa; however, a considerable number of individuals may present disease recurrence and die from the disease. Exploiting the rich molecular biology of PCa will provide insights into how the most resistant tumor cells can be eradicated to improve treatment outcomes. Important for this biology-driven individualized treatment is a robust selection procedure. The development of predictive biomarkers for RT efficacy is therefore of utmost importance for a clinically exploitable strategy to achieve tumor-specific radiosensitization. This review highlights the current status and possible opportunities in the modulation of four key processes to enhance radiation response in PCa by targeting the: (1) androgen signaling pathway; (2) hypoxic tumor cells and regions; (3) DNA damage response (DDR) pathway; and (4) abnormal extra-/intracell signaling pathways. In addition, we discuss how and which patients should be selected for biomarker-based clinical trials exploiting and validating these targeted treatment strategies with precision RT to improve cure rates in non-indolent, localized PCa.

Integrating Geriatric Assessment into Decision-Making after Prostatectomy: Adjuvant Radiotherapy, Salvage Radiotherapy, or None?

Despite current advancements in the field, management of older prostate cancer patients still remains a big challenge for Geriatric Oncology. The International Society of Geriatric Oncology (ISGO) has recently updated its recommendations in this area, and these have been widely adopted, notably by the European Association of Urology. This article outlines the principles that should be observed in the management of elderly patients who have recently undergone prostatectomy for malignancy or with a biochemical relapse following prostatectomy. Further therapeutic intervention should not be considered in those patients who are classified as frail in the geriatric assessment. In patients presenting better health conditions, salvage radiotherapy is to be preferred to adjuvant radiotherapy, which is only indicated in certain exceptional cases. Radiotherapy of the operative bed presents a higher risk to the elderly. Additionally, hormone therapy clearly shows higher side effects in older patients and therefore it should not be administered to asymptomatic patients. We propose a decision tree based on the ISGO recommendations, with specific modifications for patients in biochemical relapse.

[What is the level of evidence of new techniques in prostate cancer radiotherapy?]

Prostate cancer radiotherapy has evolved from the old 2D technique to conformal, and then to intensity-modulated radiation therapy (IMRT) and stereotactic radiotherapy. At the same time, image-guidance (IGRT) is routinely used. New techniques such as protontherapy or carbontherapy are being developed with the objective of increased efficacy, decreased treatment duration, toxicity or cost. This review summarizes the evidence-based medicine of new technologies in the treatment of prostate cancer.

Improved functionality of the vasculature during conventionally fractionated radiation therapy of prostate cancer

Although endothelial cell apoptosis participates in the tumor shrinkage after single high-dose radiotherapy, little is known regarding the vascular response after conventionally fractionated radiation therapy. Therefore, we evaluated hypoxia, perfusion and vascular microenvironment changes in an orthotopic prostate cancer model of conventionally fractionated radiation therapy at clinically relevant doses (2 Gy fractions, 5 fractions/week). First, conventionally fractionated radiation therapy decreased tumor cell proliferation and increased cell death with kinetics comparable to human prostate cancer radiotherapy. Secondly, the injection of Hoechst 33342 or fluorescent-dextrans showed an increased tumor perfusion within 14 days in irradiated tumors, which was correlated with a clear reduction of hypoxia. Improved perfusion and decreased hypoxia were not explained by increased blood vessel density, size or network morphology. However, a tumor vascular maturation defined by perivascular desmin+/SMA+ cells coverage was clearly observed along with an increase in endothelial, zonula occludens (ZO)-1 positive, intercellular junctions. Our results show that, in addition to tumor cell killing, vascular maturation plays an uncovered role in tumor reoxygenation during fractionated radiation therapy.

[Hypofractionated radiotherapy in prostate cancer]

Radiotherapy plays a central role in the management of localized prostate cancer, but the total duration of treatment of nearly 2 months poses not only problems of fatigue related to repetitive transports, especially for older patients, but also increases the overall cost of treatment including linear accelerators occupancy and patient transportation. To address this problem, various teams have developed hypofractionated radiotherapy protocols seeking to maintain the same efficacy and toxicity while reducing the total duration of treatment. These hypofractionated protocols require recent techniques such as image-guided radiation therapy (IGRT) and intensity-modulated radiation therapy (IMRT). Single centre series have validated the feasibility of "light" hypofractionation schemes at doses per fraction less than 6 Gy Similarly, different teams have shown the possibility of stereotactic irradiation for delivering "severe" hypofractionation schemes at doses greater than 6 Gy per fraction. Whatever the dose per fraction, the current clinical data support the conclusion that hypofractionated radiotherapy does not increase mid-term toxicity and could even improve biochemical control. Studies with the objective of demonstrating non-inferiority are expected to definitively validate the role of hypofractionated irradiation in the treatment of prostate cancer.

Targeting cell cycle and hormone receptor pathways in cancer

The cyclin/cyclin-dependent kinase (CDK)/retinoblastoma (RB)-axis is a critical modulator of cell cycle entry and is aberrant in many human cancers. New nodes of therapeutic intervention are needed that can delay or combat the onset of malignancies. The antitumor properties and mechanistic functions of PD-0332991 (PD; a potent and selective CDK4/6 inhibitor) were investigated using human prostate cancer (PCa) models and primary tumors. PD significantly impaired the capacity of PCa cells to proliferate by promoting a robust G₁-arrest. Accordingly, key regulators of the G₁-S cell cycle transition were modulated including G1 cyclins D, E and A. Subsequent investigation demonstrated the ability of PD to function in the presence of existing hormone-based regimens and to cooperate with ionizing radiation to further suppress cellular growth. Importantly, it was determined that PD is a critical mediator of PD action. The anti-proliferative impact of CDK4/6 inhibition was revealed through reduced proliferation and delayed growth using PCa cell xenografts. Finally, first-in-field effects of PD on proliferation were observed in primary human prostatectomy tumor tissue explants. This study shows that selective CDK4/6 inhibition, using PD either as a single-agent or in combination, hinders key proliferative pathways necessary for disease progression and that RB status is a critical prognostic determinant for therapeutic efficacy. Combined, these pre-clinical findings identify selective targeting of CDK4/6 as a bona fide therapeutic target in both early stage and advanced PCa and underscore the benefit of personalized medicine to enhance treatment response.

Prospective evaluation of quality of life 54 months after high-dose intensity-modulated radiotherapy for localized prostate cancer

Objective

To determine late toxicity and quality of life (QoL) in patients with localized prostate cancer after high-dose intensity-modulated radiotherapy (IMRT).

Patient and methods

This was a prospective study in patients with localized prostate adenocarcinoma who had been treated by IMRT (76 Gy) between February and November 2006. Physicians scored acute and late toxicity using the Common Terminology Criteria for Adverse Events (version 3.0). Patients completed cancer and prostate-specific QoL questionnaires (EORTC QLQ-C30 and QLQ-PR25) before IMRT (baseline) and at 2, 6, 18 and 54 months.

Result

Data were available for 38 patients (median age, 73 years) (18% low risk; 60% intermediate risk; 32% high risk). The incidence of urinary and gastrointestinal toxicity was respectively: immediately post IMRT: 36.8% and 23.7% (grade 1), 5.3% and 5.3% (grade 2), 2.6% and 0% (grade 3); at 18 months: 23.7% and 10.3% (grade 1), 26.3% and 13.2% (grade 2), 0% and 2.6% (grade 3); at 54 months: 34.2% and 23.7% (grade 1), 5.3% and 15.8% (grade 2), 5.3% and 0% (grade 3). At 54 months, significant worsening was reported by patients for 11/19 QoL items but the worsening was clinically relevant (>10 points) for 7 items only: physical, role as well as social functioning, fatigue, pain, dyspnoea and constipation. There was no significant difference between 54-month and baseline QoL scores for global health, gastrointestinal symptoms, treatment-related symptoms and sexual function. However, there was significant - but clinically non-relevant (<10 points) - worsening of urinary symptom.

Conclusion

High-dose IMRT to the prostate with accurate patient positioning did not induce any clinically relevant worsening in late urinary and gastrointestinal QoL at 54 months. Impaired physical and role functioning may be related to age and comorbidities.

Radiosensitization of prostate cancer cells by the dual PI3K/mTOR inhibitor BEZ235 under normoxic and hypoxic conditions

BACKGROUND AND PURPOSE

Despite appropriate radiotherapy, high-risk prostate cancer patients often experience local relapse and progression to metastatic disease. Radioresistance may be due to tumor-hypoxia but also due to the PTEN mutation/deletion present in 70% prostate cancers. We investigated whether the novel PI3K/mTOR inhibitor BEZ235 might sensitize prostate cancer cells to radiation and reduce hypoxia-induced radioresistance.

MATERIALS AND METHODS

The potential radiosensitizing properties of BEZ235 were investigated in vitro and in vivo using two prostate cancer cell lines, PC3 (PTEN(-/-)) and DU145 (PTEN(+/+)), under normoxic (21% O(2)) and hypoxic (0.5% O(2)) conditions.

RESULTS

BEZ235 rapidly inhibited PI3K and mTOR signaling in a dose dependent manner and limited tumor cell proliferation and clonogenic survival in both cell lines independently of PTEN status. In vivo, BEZ235 pretreatment enhanced the efficacy of radiation therapy on PC3 xenograft tumors in mice without inducing intestinal radiotoxicity. In culture, BEZ235 radiosensitized both cell lines in a comparable manner. Moreover, BEZ235 inhibited PI3K/mTOR activation and radiosensitized both cell lines under normoxia and hypoxia. BEZ235 radiosensitizing effects correlated with a decrease in γH2AX foci repair and increased G2/M cell cycle arrest.

CONCLUSIONS

BEZ235 is a potent radiosensitizer of normoxic and hypoxic prostate cancer cells.

Sipuleucel-T (Provenge) autologous vaccine approved for treatment of men with asymptomatic or minimally symptomatic castrate-resistant metastatic prostate cancer

Sipuleucel-T (Provenge) (Sip-T) is first -in class as a therapeutic autologous vaccine approved for the treatment of men with asymptomatic or minimally symptomatic castrate-resistant metastatic prostate cancer. This product is the culmination of decades of basic immunological and prostate cancer investigations and 13 y of clinical trial investigations. Sip-T represents a paradigm shift in cancer therapeutics and represents the first approved autologous therapeutic cancer vaccine, which has demonstrated a survival benefit. The potential benefit of this product is the excellent risk to benefit ratio, which will allow for the combination of this approach with other more toxic therapies. The favorable risk to benefit will also afford the opportunity for trials investigating this product earlier in the disease state and in combination with local therapies. The ability to target more localized or lower volume disease will maximize the therapeutic benefit over a longer period of time. The novelty of the platform of this approach could be used to treat any cancer with a tumor-specific cell surface target. The main product of Sip-T is the re-infusion of a patient's antigen presenting cells from leukapheresis after ex-vivo exposure to a chimeric protein of human GM-CSF and PAP. In metastatic CRPC patients three infusions of these activated cells over a month lead to statistically significant 4.1 mo increase in median survival and a 22.5% reduction in risk of death. The main side effect from this re-infusion of activated immune cells is a "flu-like" syndrome that includes chills, fatigue, fevers, back pain, nausea, joints aches and headaches in decreasing order of frequency. Immune monitoring during the clinical trials also demonstrated a specific cellular and antibody immune response, suggesting the proposed mechanism of adoptive immunotherapy to PAP was behind this survival benefit. This product also serves as a proof of principle for targeted immunotherapy for others cancers with defined cell surface markers. In summary, the approval of Sip-T based on a survival benefit and very tolerable safety profile will 1) enhance our ability to care for men with advanced prostate cancer, 2) allow for further investigations of this approach in combination with others therapies with different mechanisms of action and non-overlapping toxicities, and 3) allow further investigations earlier in the course of the disease.