External Beam Radiation Therapy With or Without Brachytherapy Boost in Men With Very-High-Risk Prostate Cancer: A Large Multicenter International Consortium Analysis.

PURPOSE: Very-high-risk (VHR) prostate cancer (PC) is an aggressive subgroup with high risk of distant disease progression. Systemic treatment intensification with abiraterone or docetaxel reduces PC-specific mortality (PCSM) and distant metastasis (DM) in men receiving external beam radiation therapy (EBRT) with androgen deprivation therapy (ADT). Whether prostate-directed treatment intensification with the addition of brachytherapy (BT) boost to EBRT with ADT improves outcomes in this group is unclear. METHODS AND MATERIALS: This cohort study from 16 centers across 4 countries included men with VHR PC treated with either dose-escalated EBRT with ≥24 months of ADT or EBRT + BT boost with ≥12 months of ADT. VHR was defined by National Comprehensive Cancer Network (NCCN) criteria (clinical T3b-4, primary Gleason pattern 5, or ≥2 NCCN high-risk features), and results were corroborated in a subgroup of men who met Systemic Therapy in Advancing or Metastatic Prostate Cancer: Evaluation of Drug Efficacy (STAMPEDE) trials inclusion criteria (≥2 of the following: clinical T3-4, Gleason 8-10, or PSA ≥40 ng/mL). PCSM and DM between EBRT and EBRT + BT were compared using inverse probability of treatment weight-adjusted Fine-Gray competing risk regression. RESULTS: Among the entire cohort, 270 underwent EBRT and 101 EBRT + BT. After a median follow-up of 7.8 years, 6.7% and 5.9% of men died of PC and 16.3% and 9.9% had DM after EBRT and EBRT + BT, respectively. There was no significant difference in PCSM (sHR, 1.47 [95% CI, 0.57-3.75]; P = .42) or DM (sHR, 0.72, [95% CI, 0.30-1.71]; P = .45) between EBRT + BT and EBRT. Results were similar within the STAMPEDE-defined VHR subgroup (PCSM: sHR, 1.67 [95% CI, 0.48-5.81]; P = .42; DM: sHR, 0.56 [95% CI, 0.15-2.04]; P = .38). CONCLUSIONS: In this VHR PC cohort, no difference in clinically meaningful outcomes was observed between EBRT alone with ≥24 months of ADT compared with EBRT + BT with ≥12 months of ADT. Comparative analyses in men treated with intensified systemic therapy are warranted.

Comparison of Multimodal Therapies and Outcomes Among Patients With High-Risk Prostate Cancer With Adverse Clinicopathologic Features.

Importance: The optimal management strategy for high-risk prostate cancer and additional adverse clinicopathologic features remains unknown. Objective: To compare clinical outcomes among patients with high-risk prostate cancer after definitive treatment. Design, Setting, and Participants: This retrospective cohort study included patients with high-risk prostate cancer (as defined by the National Comprehensive Cancer Network [NCCN]) and at least 1 adverse clinicopathologic feature (defined as any primary Gleason pattern 5 on biopsy, clinical T3b-4 disease, ≥50% cores with biopsy results positive for prostate cancer, or NCCN ≥2 high-risk features) treated between 2000 and 2014 at 16 tertiary centers. Data were analyzed in November 2020. Exposures: Radical prostatectomy (RP), external beam radiotherapy (EBRT) with androgen deprivation therapy (ADT), or EBRT plus brachytherapy boost (BT) with ADT. Guideline-concordant multimodal treatment was defined as RP with appropriate use of multimodal therapy (optimal RP), EBRT with at least 2 years of ADT (optimal EBRT), or EBRT with BT with at least 1 year ADT (optimal EBRT with BT). Main Outcomes and Measures: The primary outcome was prostate cancer-specific mortality; distant metastasis was a secondary outcome. Differences were evaluated using inverse probability of treatment weight-adjusted Fine-Gray competing risk regression models. Results: A total of 6004 men (median [interquartile range] age, 66.4 [60.9-71.8] years) with high-risk prostate cancer were analyzed, including 3175 patients (52.9%) who underwent RP, 1830 patients (30.5%) who underwent EBRT alone, and 999 patients (16.6%) who underwent EBRT with BT. Compared with RP, treatment with EBRT with BT (subdistribution hazard ratio [sHR] 0.78, [95% CI, 0.63-0.97]; P = .03) or with EBRT alone (sHR, 0.70 [95% CI, 0.53-0.92]; P = .01) was associated with significantly improved prostate cancer-specific mortality; there was no difference in prostate cancer-specific mortality between EBRT with BT and EBRT alone (sHR, 0.89 [95% CI, 0.67-1.18]; P = .43). No significant differences in prostate cancer-specific mortality were found across treatment cohorts among 2940 patients who received guideline-concordant multimodality treatment (eg, optimal EBRT alone vs optimal RP: sHR, 0.76 [95% CI, 0.52-1.09]; P = .14). However, treatment with EBRT alone or EBRT with BT was consistently associated with lower rates of distant metastasis compared with treatment with RP (eg, EBRT vs RP: sHR, 0.50 [95% CI, 0.44-0.58]; P < .001). Conclusions and Relevance: These findings suggest that among patients with high-risk prostate cancer and additional unfavorable clinicopathologic features receiving guideline-concordant multimodal therapy, prostate cancer-specific mortality outcomes were equivalent among those treated with RP, EBRT, and EBRT with BT, although distant metastasis outcomes were more favorable among patients treated with EBRT and EBRT with BT. Optimal multimodality treatment is critical for improving outcomes in patients with high-risk prostate cancer.

Development and Validation of a Clinical Prognostic Stage Group System for Nonmetastatic Prostate Cancer Using Disease-Specific Mortality Results From the International Staging Collaboration for Cancer of the Prostate.

Importance: In 2016, the American Joint Committee on Cancer (AJCC) established criteria to evaluate prediction models for staging. No localized prostate cancer models were endorsed by the Precision Medicine Core committee, and 8th edition staging was based on expert consensus. Objective: To develop and validate a pretreatment clinical prognostic stage group system for nonmetastatic prostate cancer. Design, Setting, and Participants: This multinational cohort study included 7 centers from the United States, Canada, and Europe, the Shared Equal Access Regional Cancer Hospital (SEARCH) Veterans Affairs Medical Centers collaborative (5 centers), and the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry (43 centers) (the STAR-CAP cohort). Patients with cT1-4N0-1M0 prostate adenocarcinoma treated from January 1, 1992, to December 31, 2013 (follow-up completed December 31, 2017). The STAR-CAP cohort was randomly divided into training and validation data sets; statisticians were blinded to the validation data until the model was locked. A Surveillance, Epidemiology, and End Results (SEER) cohort was used as a second validation set. Analysis was performed from January 1, 2018, to November 30, 2019. Exposures: Curative intent radical prostatectomy (RP) or radiotherapy with or without androgen deprivation therapy. Main Outcomes and Measures: Prostate cancer-specific mortality (PCSM). Based on a competing-risk regression model, a points-based Score staging system was developed. Model discrimination (C index), calibration, and overall performance were assessed in the validation cohorts. Results: Of 19 684 patients included in the analysis (median age, 64.0 [interquartile range (IQR), 59.0-70.0] years), 12 421 were treated with RP and 7263 with radiotherapy. Median follow-up was 71.8 (IQR, 34.3-124.3) months; 4078 (20.7%) were followed up for at least 10 years. Age, T category, N category, Gleason grade, pretreatment serum prostate-specific antigen level, and the percentage of positive core biopsy results among biopsies performed were included as variables. In the validation set, predicted 10-year PCSM for the 9 Score groups ranged from 0.3% to 40.0%. The 10-year C index (0.796; 95% CI, 0.760-0.828) exceeded that of the AJCC 8th edition (0.757; 95% CI, 0.719-0.792), which was improved across age, race, and treatment modality and within the SEER validation cohort. The Score system performed similarly to individualized random survival forest and interaction models and outperformed National Comprehensive Cancer Network (NCCN) and Cancer of the Prostate Risk Assessment (CAPRA) risk grouping 3- and 4-tier classification systems (10-year C index for NCCN 3-tier, 0.729; for NCCN 4-tier, 0.746; for Score, 0.794) as well as CAPRA (10-year C index for CAPRA, 0.760; for Score, 0.782). Conclusions and Relevance: Using a large, diverse international cohort treated with standard curative treatment options, a proposed AJCC-compliant clinical prognostic stage group system for prostate cancer has been developed. This system may allow consistency of reporting and interpretation of results and clinical trial design.

Design and construction of a Maxwell-type induction coil for magnetic nanoparticle hyperthermia.

Purpose: We describe a modified Helmholtz induction coil, or Maxwell coil, that generates alternating magnetic fields (AMF) having field uniformity (≤10%) within a = 3000 cm3 volume of interest for magnetic hyperthermia research.Materials and methods: Two-dimensional finite element analysis (2D-FEA) was used for electromagnetic design of the induction coil set and to develop specifications for the required matching network. The matching network and induction coil set were fabricated using best available practices and connected to a 120 kW industrial induction heating power supply. System performance was evaluated by magnetic field mapping with a magnetic field probe, and tests were performed using gel phantoms.Results: Tests verified that the system generated a target peak AMF amplitude along the coil axis of ∼35 kA/m (peak) at a frequency of 150 ± 10 kHz while maintaining field uniformity to >90% of peak for a volume of ∼3000 cm3.Conclusions: The induction coil apparatus comprising three independent loops, i.e., Maxwell-type improves upon the performance of simple solenoid and Helmholtz coils by providing homogeneous flux density fields within a large volume while minimizing demands on power and stray fields. Experiments with gel phantoms and analytical calculations show that future translational research efforts should be devoted to developing strategies to reduce the impact of nonspecific tissue heating from eddy currents; and, that an inductor producing a homogeneous field has significant clinical potential for deep-tissue magnetic fluid hyperthermia.

Magnetic nanoparticle hyperthermia for treating locally advanced unresectable and borderline resectable pancreatic cancers: the role of tumor size and eddy-current heating.

PURPOSE: Tumor volume largely determines the success of local control of borderline resectable and locally advanced pancreatic cancer with current therapy. We hypothesized that a tumor-mass normalized dose of magnetic nanoparticle hyperthermia (MNPH) with alternating magnetic fields (AMFs) reduces the effect of tumor volume for treatment. METHODS: 18 female athymic nude mice bearing subcutaneous MiaPaCa02 human xenograft tumors were treated with MNPH following intratumor injections of 5.5 mg Fe/g tumor of an aqueous suspension of magnetic iron-oxide nanoparticles. Mice were randomly divided into control (n = 5) and treated groups having small (0.15 ± 0.03 cm3, n = 4) or large (0.30 ± 0.06 cm3, n = 5) tumors. We assessed the clinical feasibility of this approach and of pulsed AMF to minimize eddy current heating using a finite-element method to solve a bioheat equation for a human-scale multilayer model. RESULTS: Compared to the control group, both small and large MiaPaCa02 subcutaneous tumors showed statistically significant growth inhibition. Conversely, there was no significant difference in tumor growth between large and small tumors. Both computational and xenograft models demonstrated higher maximum tumor temperatures for large tumors compared to small tumors. Computational modeling demonstrates that pulsed AMF can minimize nonspecific eddy current heating. CONCLUSIONS: MNPH provides an advantage to treat large tumors because the MION dose can be adjusted to increase power. Pulsed AMF, with adjusted treatment time, can enhance MNPH in challenging cases such as low MION dose in the target tissue and/or large patients by minimizing nonspecific eddy current heating without sacrificing thermal dose to the target. Nanoparticle heterogeneity in tumors remains a challenge for continued research.

Reductions in prostatic doses are associated with less acute morbidity in patients undergoing Pd-103 brachytherapy: Substantiation of the rationale for focal therapy.

PURPOSE: Interest in prostate dose reduction or focal treatment exists due to expected reductions in treatment morbidity. Prior analyses have not generally corroborated relationships between prostate or urethral dose and urinary toxicity after brachytherapy, but such analyses have been performed on cohorts all receiving the same prescribed dose. We analyzed patients treated to differing prescription doses to assess acute urinary morbidity with dose reduction. METHODS AND MATERIALS: Patients treated with Pd-103 to either 125 Gy or 90-100 Gy were compared using the International Prostate Symptom Score (IPSS) at 1-month postimplant. Patients in the 90-100 Gy cohort began external beam radiation therapy after their 1-month assessment; thus, toxicities were measured before contribution from external beam radiation therapy. Patient/treatment characteristics were compared to verify subgroup homogeneity. Dose and change in IPSS 1 month after treatment were assessed using a multivariate linear regression model. RESULTS: One hundred ninety-one and 41 patients were treated with 125 Gy versus 90-100 Gy, respectively. Preimplant and postimplant prostate volumes and initial IPSS were similar between groups. Higher prescription dose and increased pretreatment IPSS were independent predictors of increased 1-month IPSS. In addition, every 10 percentage point additional prostate volume receiving a given dose was associated with increase in IPSS after treatment for the same level of pretreatment IPSS. CONCLUSION: Lower prescription dose and decreased volume of high-dose regions to the prostate correlated with reduced acute urinary morbidity after brachytherapy. Our findings suggest that focal treatment approaches with modest dose reductions to subregions of the prostate may reduce acute morbidity and potentially expand the number of patients eligible for brachytherapy.

Very High-Risk Localized Prostate Cancer: Outcomes Following Definitive Radiation.

PURPOSE: Existing definitions of high-risk prostate cancer consist of men who experience significant heterogeneity in outcomes. As such, criteria that identify a subpopulation of National Comprehensive Cancer Network (NCCN) high-risk prostate cancer patients who are at very high risk (VHR) for poor survival outcomes following prostatectomy were recently developed at our institution and include the presence of any of the following disease characteristics: multiple NCCN high-risk factors, primary Gleason pattern 5 disease and/or ≥5 biopsy cores with Gleason sums of 8 to 10. Whether these criteria also apply to men undergoing definitive radiation is unclear, as is the optimal treatment regimen in these patients. METHODS AND MATERIALS: All men consecutively treated with definitive radiation by a single provider from 1993 to 2006 and who fulfilled criteria for NCCN high-risk disease were identified (n=288), including 99 patients (34%) with VHR disease. Multivariate-adjusted competing risk regression models were constructed to assess associations between the VHR definition and biochemical failure (BF), distant metastasis (DM), and prostate cancer-specific mortality (PCSM). Multivariate-adjusted Cox regression analysis assessed the association of the VHR definition with overall mortality (OM). Cumulative incidences of failure endpoints were compared between VHR men and other NCCN high-risk men. RESULTS: Men with VHR disease compared to other NCCN high-risk men experienced a higher 10-year incidence of BF (54.0% vs 35.4%, respectively, P<.001), DM (34.9% vs 13.4%, respectively, P<.001), PCSM (18.5% vs 5.9%, respectively, P<.001), and OM (36.4% vs 27.0%, respectively, P=.04). VHR men with a detectable prostate-specific antigen (PSA) concentration at the end of radiation (EOR) remained at high risk of 10-year PCSM compared to VHR men with an undetectable EOR PSA (31.0% vs 13.7%, respectively, P=.05). CONCLUSIONS: NCCN high-risk prostate cancer patients who meet VHR criteria experience distinctly worse outcomes following definitive radiation and long-term androgen deprivation therapy, particularly if an EOR PSA is detectable. Optimal use of local therapies for VHR patients should be explored further, as should novel agents.

Magnetic nanoparticle hyperthermia enhances radiation therapy: A study in mouse models of human prostate cancer.

PURPOSE: We aimed to characterise magnetic nanoparticle hyperthermia (mNPH) with radiation therapy (RT) for prostate cancer. METHODS: Human prostate cancer subcutaneous tumours, PC3 and LAPC-4, were grown in nude male mice. When tumours measured 150 mm3 magnetic iron oxide nanoparticles (MIONPs) were injected into tumours to a target dose of 5.5 mg Fe/cm3 tumour, and treated 24 h later by exposure to alternating magnetic field (AMF). Mice were randomly assigned to one of four cohorts to characterise (1) intratumour MIONP distribution, (2) effects of variable thermal dose mNPH (fixed AMF peak amplitude 24 kA/m at 160 ± 5 kHz) with/without RT (5 Gy), (3) effects of RT (RT5: 5 Gy; RT8: 8 Gy), and (4) fixed thermal dose mNPH (43 °C for 20 min) with/without RT (5 Gy). MIONP concentration and distribution were assessed following sacrifice and tissue harvest using inductively coupled plasma mass spectrometry (ICP-MS) and Prussian blue staining, respectively. Tumour growth was monitored and compared among treated groups. RESULTS: LAPC-4 tumours retained higher MIONP concentration and more uniform distribution than did PC3 tumours. AMF power modulation provided similar thermal dose for mNPH and combination therapy groups (CEM43: LAPC-4: 33.6 ± 3.4 versus 25.9 ± 0.8, and PC3: 27.19 ± 0.7 versus 27.50 ± 0.6), thereby overcoming limitations of MIONP distribution and yielding statistically significant tumour growth delay. CONCLUSION: PC3 and LAPC-4 tumours represent two biological models that demonstrate different patterns of nanoparticle retention and distribution, offering a model to make comparisons of these effects for mNPH. Modulating power for mNPH offers potential to overcome limitations of MIONP distribution to enhance mNPH.

Magnetic resonance imaging contrast of iron oxide nanoparticles developed for hyperthermia is dominated by iron content.

PURPOSE: Magnetic iron oxide nanoparticles (MNPs) are used as contrast agents for magnetic resonance imaging (MRI) and hyperthermia for cancer treatment. The relationship between MRI signal intensity and cellular iron concentration for many new formulations, particularly MNPs having magnetic properties designed for heating in hyperthermia, is lacking. In this study, we examine the correlation between MRI T2 relaxation time and iron content in cancer cells loaded with various MNP formulations. MATERIALS AND METHODS: Human prostate carcinoma DU-145 cells were loaded with starch-coated bionised nanoferrite (BNF), iron oxide (Nanomag® D-SPIO), Feridex™, and dextran-coated Johns Hopkins University (JHU) particles at a target concentration of 50 pg Fe/cell using poly-D-lysine transfection reagent. T2-weighted MRI of serial dilutions of these labelled cells was performed at 9.4 T and iron content quantification was performed using inductively coupled plasma mass spectrometry (ICP-MS). Clonogenic assay was used to characterise cytotoxicity. RESULTS: No cytotoxicity was observed at twice the target intracellular iron concentration (∼100 pg Fe/cell). ICP-MS revealed highest iron uptake efficiency with BNF and JHU particles, followed by Feridex and Nanomag-D-SPIO, respectively. Imaging data showed a linear correlation between increased intracellular iron concentration and decreased T2 times, with no apparent correlation among MNP magnetic properties. CONCLUSIONS: This study demonstrates that for the range of nanoparticle concentrations internalised by cancer cells the signal intensity of T2-weighted MRI correlates closely with absolute iron concentration associated with the cells. This correlation may benefit applications for cell-based cancer imaging and therapy including nanoparticle-mediated drug delivery and hyperthermia.

Monitoring nanoparticle-mediated cellular hyperthermia with a high-sensitivity biosensor.

AIM: To develop and apply a heat-responsive and secreted reporter assay for comparing cellular response to nanoparticle (NP)- and macroscopic-mediated sublethal hyperthermia. MATERIALS & METHODS: Reporter cells were heated by water bath (macroscopic heating) or iron oxide NPs activated by alternating magnetic fields (nanoscopic heating). Cellular responses to these thermal stresses were measured in the conditioned media by secreted luciferase assay. RESULTS & CONCLUSION: Reporter activity was responsive to macroscopic and nanoparticle heating and activity correlated with measured macroscopic thermal dose. Significant cellular responses were observed with NP heating under doses that were insufficient to measurably change the temperature of the system. Under these conditions, the reporter response correlated with proximity to cells loaded with heated nanoparticles. These results suggest that NP and macroscopic hyperthermia may be distinctive under conditions of mild hyperthermia.

Molecularly targeted agents as radiosensitizers in cancer therapy--focus on prostate cancer.

As our understanding of the molecular pathways driving tumorigenesis improves and more druggable targets are identified, we have witnessed a concomitant increase in the development and production of novel molecularly targeted agents. Radiotherapy is commonly used in the treatment of various malignancies with a prominent role in the care of prostate cancer patients, and efforts to improve the therapeutic ratio of radiation by technologic and pharmacologic means have led to important advances in cancer care. One promising approach is to combine molecularly targeted systemic agents with radiotherapy to improve tumor response rates and likelihood of durable control. This review first explores the limitations of preclinical studies as well as barriers to successful implementation of clinical trials with radiosensitizers. Special considerations related to and recommendations for the design of preclinical studies and clinical trials involving molecularly targeted agents combined with radiotherapy are provided. We then apply these concepts by reviewing a representative set of targeted therapies that show promise as radiosensitizers in the treatment of prostate cancer.

Method to reduce non-specific tissue heating of small animals in solenoid coils.

PURPOSE: Solenoid coils that generate time-varying or alternating magnetic fields (AMFs) are used in biomedical devices for research, imaging and therapy. Interactions of AMF and tissue produce eddy currents that deposit power within tissue, thus limiting effectiveness and safety. We aim to develop methods that minimise excess heating of mice exposed to AMFs for cancer therapy experiments. MATERIALS AND METHODS: Numerical and experimental data were obtained to characterise thermal management properties of water using a continuous, custom water jacket in a four-turn simple solenoid. Theoretical data were obtained with method-of-moments (MoM) numerical field calculations and finite element method (FEM) thermal simulations. Experimental data were obtained from gel phantoms and mice exposed to AMFs having amplitude >50 kA/m and frequency of 160 kHz. RESULTS: Water has a high specific heat and thermal conductivity, is diamagnetic, polar, and nearly transparent to magnetic fields. We report at least a two-fold reduction of temperature increase from gel phantom and animal models when a continuous layer of circulating water was placed between the sample and solenoid, compared with no water. Thermal simulations indicate the superior efficiency in thermal management by the developed continuous single chamber cooling system over a double chamber non-continuous system. Further reductions of heating were obtained by regulating water temperature and flow for active cooling. CONCLUSIONS: These results demonstrate the potential value of a contiguous layer of circulating water to permit sustained exposure to high intensity alternating magnetic fields at this frequency for research using small animal models exposed to AMFs.

The effect of cell cluster size on intracellular nanoparticle-mediated hyperthermia: is it possible to treat microscopic tumors?

AIM: To compare the measured surface temperature of variable size ensembles of cells heated by intracellular magnetic fluid hyperthermia with heat diffusion model predictions. MATERIALS & METHODS: Starch-coated Bionized NanoFerrite (Micromod Partikeltechnologie GmbH, Rostock, Germany) iron oxide magnetic nanoparticles were loaded into cultured DU145 prostate cancer cells. Cell pellets of variable size were treated with alternating magnetic fields. The surface temperature of the pellets was measured in situ and the associated cytotoxicity was determined by clonogenic survival assay. RESULTS & CONCLUSION: For a given intracellular nanoparticle concentration, a critical minimum number of cells was required for cytotoxic hyperthermia. Above this threshold, cytotoxicity increased with increasing cell number. The measured surface temperatures were consistent with those predicted by a heat diffusion model that ignores intercellular thermal barriers. These results suggest a minimum tumor volume threshold of approximately 1 mm(3), below which nanoparticle-mediated heating is unlikely to be effective as the sole cytotoxic agent.

Perineural invasion affects biochemical recurrence-free survival in patients with prostate cancer treated with definitive external beam radiotherapy.

OBJECTIVES: To assess the prognostic effect of perineural invasion (PNI) for patients undergoing external beam radiotherapy for prostate cancer. METHODS: We evaluated 657 consecutive patients who had undergone external beam radiotherapy for clinically localized prostate cancer. The clinical/treatment parameters used for analysis included PNI, clinical stage, biopsy Gleason score, pretreatment prostate-specific antigen, radiation dose, and androgen deprivation. The primary endpoint was biochemical recurrence defined by the Radiation Therapy Oncology Group-American Society for Therapeutic Radiology Oncology Phoenix consensus; the secondary endpoint was prostate cancer death. RESULTS: Of 586 men with a minimum of 24 months of follow-up, 112 (19.1%) had PNI present in the biopsy specimen. When patients were stratified into risk groups using the National Comprehensive Cancer Network criteria, PNI was more prevalent in patients within higher risk groups (6.8% in low-risk versus 18.3% in intermediate-risk versus 30.1% in high-risk groups; P <0.001). The presence of PNI was associated with lower biochemical recurrence-free (P = 0.003) and cancer-specific (P = 0.040) survival rates by Kaplan-Meier analysis. Cox regression analysis showed that PNI was a statistically significant prognostic factor of biochemical recurrence on both univariate (hazard ratio [HR] 1.71, 95% confidence interval [CI] 1.19 to 2.46, P = 0.004) and multivariate (HR 1.57, 95% CI 1.06 to 2.32, P = 0.025) analyses. Regression analysis after stratification by risk group and adjustment for treatment covariates demonstrated a significant association between PNI and the risk of biochemical recurrence for low-risk (HR 4.14, 95% CI 1.55 to 11.02, P = 0.005) and intermediate/high-risk patients (HR 1.53, 95% CI 1.02 to 2.29, P = 0.040). CONCLUSIONS: The results of our study have shown that the presence of PNI is an independent risk factor associated with an increased risk of biochemical recurrence in patients with prostate cancer undergoing external beam radiotherapy.

Defective human MutY phosphorylation exists in colorectal cancer cell lines with wild-type MutY alleles.

Oxidative DNA damage can generate a variety of cytotoxic DNA lesions such as 8-oxoguanine (8-oxoG), which is one of the most mutagenic bases formed from oxidation of genomic DNA because 8-oxoG can readily mispair with either cytosine or adenine. If unrepaired, further replication of A.8-oxoG mispairs results in C:G to A:T transversions, a form of genomic instability. We reported previously that repair of A.8-oxoG mispairs was defective and that 8-oxoG levels were elevated in several microsatellite stable human colorectal cancer cell lines lacking MutY mutations (human MutY homolog gene, hmyh, MYH MutY homolog protein). In this report, we provide biochemical evidence that the defective repair of A.8-oxoG may be due, at least in part, to defective phosphorylation of the MutY protein in these cell lines. In MutY-defective cell extracts, but not extracts with functional MutY, A.8-oxoG repair was increased by incubation with protein kinases A and C (PKA and PKC) and caesin kinase II. Treatment of these defective cells, but not cells with functional MutY, with phorbol-12-myristate-13-acetate also increased the cellular A.8-oxoG repair activity and decreased the elevated 8-oxoG levels. We show that MutY is serine-phosphorylated in vitro by the action of PKC and in the MutY-defective cells by phorbol-12-myristate-13-acetate but that MutY is already phosphorylated at baseline in proficient cell lines. Finally, using antibody-isolated MutY protein, we show that MutY can be directly phosphorylated by PKC that directly increases the level of MutY catalyzed A.8-oxoG repair.