The Importance of Quality Assurance in Radiation Oncology Clinical Trials

Clinical trials have been the center of progress in modern medicine. In oncology, we are fortunate to have a structure in place through the National Clinical Trials Network (NCTN). The NCTN provides the infrastructure and a forum for scientific discussion to develop clinical concepts for trial design. The NCTN also provides a network group structure to administer trials for successful trial management and outcome analyses. There are many important aspects to trial design and conduct. Modern trials need to ensure appropriate trial conduct and secure data management processes. Of equal importance is the quality assurance of a clinical trial. If progress is to be made in oncology clinical medicine, investigators and patient care providers of service need to feel secure that trial data is complete, accurate, and well-controlled in order to be confident in trial analysis and move trial outcome results into daily practice. As our technology has matured, so has our need to apply technology in a uniform manner for appropriate interpretation of trial outcomes. In this article, we review the importance of quality assurance in clinical trials involving radiation therapy. We will include important aspects of institution and investigator credentialing for participation as well as ongoing processes to ensure that each trial is being managed in a compliant manner. We will provide examples of the importance of complete datasets to ensure study interpretation. We will describe how successful strategies for quality assurance in the past will support new initiatives moving forward.

Targeting VEGF/Neuropilin-2 as a Novel Approach to Induce Radiosensitivity in Triple Negative Breast Cancer

PURPOSE/OBJECTIVE(S)

Triple-negative breast cancer (TNBC) is an aggressive phenotype with patients having more limited survival compared with other breast cancer subtypes. The high rate of locoregional/distant recurrence after primary management implies that additional treatment is necessary to optimize the sensitivity of TNBC tumors to therapy including radiation. Our lab studies the role of VEGF/Neuropilin-2 (NRP2) in mediating cancer stem cell properties such as self-renewal and therapy resistance. We sought to identify a new therapeutic approach that can induce radiosensitization in TNBC.

MATERIALS/METHODS

Cell viability in response to radiotherapy in patient-derived organoids (PDO) and xenografts (PDX) was determined using CellTiter-Glo. The VEGF/NRP2 pathway was disrupted in human BT549 and murine 4T1 models using RNA interference and a function blocking antibody (aNRP2-10) provided by aTyr Pharma. Nitrite levels, a surrogate marker for NOS2 activity, were measured using Measure-IT Nitrite Assay Kit. H2DCFDA was used to measure intracellular reactive oxygen species (ROS). Clonogenic survival assays were used to calculate radiosensitivity enhancement ratios (rER) in TNBC cell lines. For our in vivo models, 4T1 xenografts were given antibody treatment every 48 hours starting a day prior to 10Gy irradiation.

RESULTS

We identified a novel radioresistant population expressing high levels of NRP2 and NOS2 and observed that NOS2 expression was dependent on VEGF/NRP2 via Gli1 transcription. Interestingly, reducing NRP2 expression increased radiation-induced ROS because of reduced NOS2/NO levels. The downstream consequence of higher NOS2/NO was increased Nrf2 activation via KEAP1 S-nitrosylation; thus, inducing expression of antioxidant response elements. TNBC cells were radiosensitized by knocking down NRP2 (rER 1.19 - 1.34). We saw similar results when using aNRP2-10 vs IgG (rER 1.30 - 1.37). Ectopic expression of NOS2 and constitutively active Nrf2 rescued the radioresistance phenotype in the NRP2 knock-down cells (rER 0.73 - 0.82). Consistent with the cell line data, the clinically relevant models (PDOs and PDXs) had a synergistic reduction in cell viability in response to aNRP2-10 prior to radiotherapy. We also observed a significant reduction in tumor volume and increase in necrosis in vivo in response to VEGF/NRP2 inhibition during radiotherapy.

CONCLUSION

Inhibiting VEGF/NRP2 induces radiosensitization of TNBC by decreasing NOS2/NO levels and, consequently, Nrf2-mediated antioxidant gene expression. The role of Gli1 as a transcription factor for NOS2 is a novel finding that provides an unexpected link between VEGF/NRP2 and redox homeostasis in response to radiation. Current Nrf2 inhibitors are non-specific and have high toxicity; thus, making VEGF/NRP2 inhibition more favorable. Our data provide a novel therapeutic strategy for targeting TNBC breast cancer.

Quality improvements in radiation oncology clinical trials

Clinical trials have become the primary mechanism to validate process improvements in oncology clinical practice. Over the past two decades there have been considerable process improvements in the practice of radiation oncology within the structure of a modern department using advanced technology for patient care. Treatment planning is accomplished with volume definition including fusion of multiple series of diagnostic images into volumetric planning studies to optimize the definition of tumor and define the relationship of tumor to normal tissue. Daily treatment is validated by multiple tools of image guidance. Computer planning has been optimized and supported by the increasing use of artificial intelligence in treatment planning. Informatics technology has improved, and departments have become geographically transparent integrated through informatics bridges creating an economy of scale for the planning and execution of advanced technology radiation therapy. This serves to provide consistency in department habits and improve quality of patient care. Improvements in normal tissue sparing have further improved tolerance of treatment and allowed radiation oncologists to increase both daily and total dose to target. Radiation oncologists need to define a priori dose volume constraints to normal tissue as well as define how image guidance will be applied to each radiation treatment. These process improvements have enhanced the utility of radiation therapy in patient care and have made radiation therapy an attractive option for care in multiple primary disease settings. In this chapter we review how these changes have been applied to clinical practice and incorporated into clinical trials. We will discuss how the changes in clinical practice have improved the quality of clinical trials in radiation therapy. We will also identify what gaps remain and need to be addressed to offer further improvements in radiation oncology clinical trials and patient care.

Radiation Oncology: Future Vision for Quality Assurance and Data Management in Clinical Trials and Translational Science

The future of radiation oncology is exceptionally strong as we are increasingly involved in nearly all oncology disease sites due to extraordinary advances in radiation oncology treatment management platforms and improvements in treatment execution. Due to our technology and consistent accuracy, compressed radiation oncology treatment strategies are becoming more commonplace secondary to our ability to successfully treat tumor targets with increased normal tissue avoidance. In many disease sites including the central nervous system, pulmonary parenchyma, liver, and other areas, our service is redefining the standards of care. Targeting of disease has improved due to advances in tumor imaging and application of integrated imaging datasets into sophisticated planning systems which can optimize volume driven plans created by talented personnel. Treatment times have significantly decreased due to volume driven arc therapy and positioning is secured by real time imaging and optical tracking. Normal tissue exclusion has permitted compressed treatment schedules making treatment more convenient for the patient. These changes require additional study to further optimize care. Because data exchange worldwide have evolved through digital platforms and prisms, images and radiation datasets worldwide can be shared/reviewed on a same day basis using established de-identification and anonymization methods. Data storage post-trial completion can co-exist with digital pathomic and radiomic information in a single database coupled with patient specific outcome information and serve to move our translational science forward with nimble query elements and artificial intelligence to ask better questions of the data we collect and collate. This will be important moving forward to validate our process improvements at an enterprise level and support our science. We have to be thorough and complete in our data acquisition processes, however if we remain disciplined in our data management plan, our field can grow further and become more successful generating new standards of care from validated datasets.

Practice patterns of pediatric total body irradiation techniques: A Children's Oncology Group survey

PURPOSE

The aim of this study was to examine current practice patterns in pediatric total body irradiation (TBI) techniques among xxx member institutions.

METHODS AND MATERIALS

Between Nov 2019 and Feb 2020 a questionnaire, containing 52 questions related to the technical aspects of TBI was sent to medical physicists at 152 xxx institutions. The questions were designed to obtain technical information on commonly used TBI treatment techniques. Another set of 9 questions related to the clinical management of patients undergoing TBI was sent to 152 xxx member radiation oncologists at the same institutions.

RESULTS

Twelve institutions were excluded because TBI was not performed in their institutions. A total of 88 physicists from 88 institutions (63% response rate) and 96 radiation oncologists from 96 institutions responded (69% response rate). The AP/PA technique was the most common (49 institutions - 56%); 44 institutions (50%) used the lateral technique and 14 institutions (16%) used volumetric modulated arc therapy (VMAT)/Tomotherapy. Mid-plane dose rates of 6-15 cGy/min were most commonly used. The most common specification for lung dose was the mid lung dose for both AP/PA (71%) and lateral (63%) techniques. All physician responders agreed with the need to refine current TBI techniques and 79% supported the investigation of new TBI techniques to further lower the lung dose.

CONCLUSION

There is no consistency in the practice patterns, methods for dose measurement and reporting of TBI doses among xxx institutions. The lack of a standardization precludes meaningful correlation between TBI doses and clinical outcomes including disease control and normal tissue toxicity. The xxx radiation oncology discipline is currently undertaking several steps to standardize the practice and dose reporting of pediatric TBI using detailed questionnaires and phantom-based credentialing for all xxx centers.

Quality assurance in radiation oncology

The Children's Oncology Group (COG) has a strong quality assurance (QA) program managed by the Imaging and Radiation Oncology Core (IROC). This program consists of credentialing centers and providing real-time management of each case for protocol compliant target definition and radiation delivery. In the International Society of Pediatric Oncology (SIOP), the lack of an available, reliable online data platform has been a challenge and the European Society for Paediatric Oncology (SIOPE) quality and excellence in radiotherapy and imaging for children and adolescents with cancer across Europe in clinical trials (QUARTET) program currently provides QA review for prospective clinical trials. The COG and SIOP are fully committed to a QA program that ensures uniform execution of protocol treatments and provides validity of the clinical data used for analysis.

Practice patterns and recommendations for pediatric image-guided radiotherapy: A Children's Oncology Group report

This report by the Radiation Oncology Discipline of Children's Oncology Group (COG) describes the practice patterns of pediatric image-guided radiotherapy (IGRT) based on a member survey and provides practice recommendations accordingly. The survey comprised of 11 vignettes asking clinicians about their recommended treatment modalities, IGRT preferences, and frequency of in-room verification. Technical questions asked physicists about imaging protocols, dose reduction, setup correction, and adaptive therapy. In this report, the COG Radiation Oncology Discipline provides an IGRT modality/frequency decision tree and the expert guidelines for the practice of ionizing image guidance in pediatric radiotherapy patients.

The VEGF receptor neuropilin 2 promotes homologous recombination by stimulating YAP/TAZ-mediated Rad51 expression

Vascular endothelial growth factor (VEGF) signaling in tumor cells mediated by neuropilins (NRPs) contributes to the aggressive nature of several cancers, including triple-negative breast cancer (TNBC), independently of its role in angiogenesis. Understanding the mechanisms by which VEGF-NRP signaling contributes to the phenotype of such cancers is a significant and timely problem. We report that VEGF-NRP2 promote homologous recombination (HR) in BRCA1 wild-type TNBC cells by contributing to the expression and function of Rad51, an essential enzyme in the HR pathway that mediates efficient DNA double-strand break repair. Mechanistically, we provide evidence that VEGF-NRP2 stimulates YAP/TAZ-dependent Rad51 expression and that Rad51 is a direct YAP/TAZ-TEAD transcriptional target. We also discovered that VEGF-NRP2-YAP/TAZ signaling contributes to the resistance of TNBC cells to cisplatin and that Rad51 rescues the defects in DNA repair upon inhibition of either VEGF-NRP2 or YAP/TAZ. These findings reveal roles for VEGF-NRP2 and YAP/TAZ in DNA repair, and they indicate a unified mechanism involving VEGF-NRP2, YAP/TAZ, and Rad51 that contributes to resistance to platinum chemotherapy.

αvβ3 Integrin Mediates Radioresistance of Prostate Cancer Cells through Regulation of Survivin

The α_vβ₃ integrin is involved in various physiologic and pathologic processes such as wound healing, angiogenesis, tumor growth, and metastasis. The impact of α_vβ₃ integrin on the radiosensitivity of prostate cancer cells and the molecular mechanism controlling cell survival in response to ionizing radiation (IR) was investigated. Both LNCaP cells stably transfected with α_vβ₃ integrin and PC-3 cells that contain endogenous β₃ integrin were used. This study demonstrated that α_vβ₃ integrin increases survival of α_vβ₃-LNCaP cells upon IR while small hairpin RNA (shRNA)-mediated knockdown of α_vβ₃ integrin in PC-3 cells sensitizes to radiation. Expression of α_vβ₃ integrin in LNCaP cells also enhances anchorage-independent cell growth while knockdown of α_vβ₃ integrin in PC-3 cells inhibits anchorage-independent cell growth. The α_vβ₃ antagonist, cRGD, significantly increases radiosensitivity in both α_vβ₃-LNCaP and PC-3 cells. Moreover, α_vβ₃ integrin prevents radiation-induced downregulation of survivin. Inhibition of survivin expression by siRNA or shRNA enhances IR-induced inhibition of anchorage-independent cell growth. Overexpression of wild-type survivin in PC-3 cells treated with α_vβ₃ integrin shRNA increases survival of cells upon IR. These findings reveal that α_vβ₃ integrin promotes radioresistance and regulates survivin levels in response to IR. IMPLICATIONS: Future translational research on targeting α_vβ₃ integrin and survivin may reveal novel approaches as an adjunct to radiotherapy for patients with prostate cancer.

Hodgkin Lymphoma: Differences in Treatment Between Europe and the United States/North America: Evolving Trends in Protocol Therapy

With continued progress and success in clinical care, the management of patients with Hodgkin lymphoma (HL) has undergone continuous revision to improve patient care outcomes and limit acute and late treatment effects on normal tissue imposed by therapy. Hodgkin lymphoma is a disease that affects children, adolescents, and adults. Clinical management strategies are influenced by the patient's age at diagnosis, tumor burden, response to induction therapy, and potential expectation of treatment impact on normal tissue. The approach to patient management varies in many parts of the world and is influenced by treatment availability, physician training, and medical culture. Differences in approach are important to understand for accurately comparing and contrasting outcome studies. In this article, we will identify current areas of common ground and points of separation in patient care management for HL. Opportunities for clinical trial strategies will be defined for future clinical trials.

Patterns of Involved-Field Radiation Therapy Protocol Deviations in Pediatric Versus Adolescent and Young Adults With Hodgkin Lymphoma: A Report From the Children's Oncology Group AHOD0031

PURPOSE

The presented protocol for pediatric intermediate-risk Hodgkin lymphoma evaluated the use of a dose-intensive chemotherapy regimen (ABVE-PC [doxorubicin, bleomycin, vincristine, etoposide, cyclophosphamide, prednisone]) with response-based therapy augmentation (addition of DECA [dexamethasone, etoposide, cisplatin, cytarabine]) or therapy reduction (elimination of radiation).

METHODS AND MATERIALS

A central review of the radiation therapy data for quality assurance was performed, and the association between radiation protocol deviation (RPD) and relapse was assessed in the pediatric group (age <15 years) and adolescent and young adult (AYA) group (age ≥15-21 years). Involved-field radiation therapy (IFRT) planning was reviewed before the start of treatment and at treatment completion. The records were reviewed through the Quality Assurance Review Center's central review to identify RPD, classified according to dose deviation (DD), volume deviation (VD), undertreatment (UT), and overtreatment (OT). DDs and VDs were further classified as major or minor.

RESULTS

Of the 1712 patients enrolled, 1155 received IFRT, of whom, 216 (18.7%) had RPDs. The DD and VD patterns were similar between the pediatric and AYA groups. Minor VDs were most common. UT RPDs accounted for 69% in the pediatric group and 75% in the AYA group. Of the 35 patients with relapse and a RPD, 29 had an undertreatment RPD. Among the patients who received IFRT, a significant difference was found in the cumulative incidence rates of relapse between the pediatric and AYA groups (P = .03); however, no significant difference was found between patients with and without RPD (P = .2).

CONCLUSIONS

Most RPDs were minor and consisted of UT in the AYA and pediatric populations both. No difference was observed in RPDs between the pediatric and AYA patients. Thus, in a well-defined and standardized protocol, the RPD distributions for AYA patients will be similar to those for pediatric population. However, the increased cumulative incidence of relapse in the AYA patients who had received IFRT compared with the pediatric population requires further exploration, given the potential differences in clinical outcomes in the AYA population.

Association between cumulative radiation dose, adverse skin reactions, and changes in surface hemoglobin among women undergoing breast conserving therapy

Introduction

Radiation therapy is crucial to effective cancer treatment. Modern treatment strategies have reduced possible skin injury, but few clinical studies have addressed the dose relationship between radiation exposure and skin reaction. This prospective clinical study analyzes skin oxygenation/perfusion in patients undergoing fractionated breast conserving therapy via hyperspectral imaging (HSI).

Methods

Forty-three women undergoing breast conserving therapy were enrolled in this study. Optically stimulated luminescent dosimeters (OSLDs) measured radiation exposure in four sites: treatment breast, lumpectomy scar, medial tattoo and the control breast. The oxygenation/perfusion states of these sites were prospectively imaged before and after each treatment fraction with HSI. Visual skin reactions were classified according to the RTOG system.

Results

2753 observations were obtained and indicated a dose-response relationship between radiation exposure and oxygenated hemoglobin (OxyHb) after a 600 cGy cumulative dose threshold. There was a relatively weak association between DeoxyHb and radiation exposure. Results suggest strong correlations between changes in mean OxyHb and skin reaction as well as between radiation exposure and changes in skin reaction.

Conclusion

HSI demonstrates promise in the assessment of skin dose as well as an objective measure of skin reaction. The ability to easily identify adverse skin reactions and to modify the treatment plan may circumvent the need for detrimental treatment breaks.

Effect of Standard Radiotherapy With Cisplatin vs Accelerated Radiotherapy With Panitumumab in Locoregionally Advanced Squamous Cell Head and Neck Carcinoma: A Randomized Clinical Trial

Importance

The Canadian Cancer Trials Group study HN.6 is the largest randomized clinical trial to date comparing the concurrent administration of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies with radiotherapy (RT) to standard chemoradiotherapy in locoregionally advanced squamous cell carcinoma of the head and neck (LA-SCCHN).

Objective

To compare progression-free survival (PFS) in patients with LA-SCCHN treated with standard-fractionation RT plus high-dose cisplatin vs accelerated-fractionation RT plus the anti-EGFR antibody panitumumab.

Design, Setting, and Participants

A randomized phase 3 clinical trial in 17 Canadian centers. A total of 320 patients were randomized between December 2008 and November 2011.

Interventions

Patients with TanyN+M0 or T3-4N0M0 LA-SCCHN were randomized 1:1 to receive standard-fractionation RT (70 Gy/35 over 7 weeks) plus cisplatin at 100 mg/m2 intravenous for 3 doses (arm A) vs accelerated-fractionation RT (70 Gy/35 over 6 weeks) plus panitumumab at 9 mg/kg intravenous for 3 doses (arm B).

Main Outcomes and Measures

Primary end point was PFS. Due to an observed declining event rate, the protocol was amended to a time-based analysis. Secondary end points included overall survival, local and regional PFS, distant metastasis-free survival, quality of life, adverse events, and safety.

Results

Of 320 patients randomized (268 [84%] male; median age, 56 years), 156 received arm A and 159 arm B. A total of 93 PFS events occurred. By intention-to-treat, 2-year PFS was 73% (95% CI, 65%-79%) in arm A and 76% (95% CI, 68%-82%) in arm B (hazard ratio [HR], 0.95; 95% CI, 0.60-1.50; P = .83). The upper bound of the HR 95% CI exceeded the prespecified noninferiority margin. Two-year overall survival was 85% (95% CI, 78%-90%) in arm A and 88% (95% CI, 82%-92%) in arm B (HR, 0.89; 95% CI, 0.54-1.48; P = .66). Incidence of any grade 3 to 5 nonhematologic adverse event was 88% in arm A and 92% in arm B (P = .25).

Conclusions and Relevance

With a median follow-up of 46 months, the PFS of panitumumab plus accelerated-fractionation RT was not superior to cisplatin plus standard-fractionation RT in LA-SCCHN and noninferiority was not proven. Despite having negative results, HN.6 has contributed important data regarding disease control and toxic effects of these treatment strategies.

Trial Registration

clinicaltrials.gov Identifier: NCT00820248.

αvβ6 Integrin Promotes Castrate-Resistant Prostate Cancer through JNK1-Mediated Activation of Androgen Receptor

Androgen receptor signaling fuels prostate cancer and is a major therapeutic target. However, mechanisms of resistance to therapeutic androgen ablation are not well understood. Here, using a prostate cancer mouse model, Pten(pc-/-), carrying a prostate epithelial-specific Pten deletion, we show that the αvβ6 integrin is required for tumor growth in vivo of castrated as well as of noncastrated mice. We describe a novel signaling pathway that couples the αvβ6 integrin cell surface receptor to androgen receptor via activation of JNK1 and causes increased nuclear localization and activity of androgen receptor. This downstream kinase activation by αvβ6 is specific for JNK1, with no involvement of p38 or ERK kinase. In addition, differential phosphorylation of Akt is not observed under these conditions, nor is cell morphology affected by αvβ6 expression. This pathway, which is specific for αvβ6, because it is not regulated by a different αv-containing integrin, αvβ3, promotes upregulation of survivin, which in turn supports anchorage-independent growth of αvβ6-expressing cells. Consistently, both αvβ6 and survivin are significantly increased in prostatic adenocarcinoma, but are not detected in normal prostatic epithelium. Neither XIAP nor Bcl-2 is affected by αvβ6 expression. In conclusion, we show that αvβ6 expression is required for prostate cancer progression, including castrate-resistant prostate cancer; mechanistically, by promoting activation of JNK1, the αvβ6 integrin causes androgen receptor-increased activity in the absence of androgen and consequent upregulation of survivin. These preclinical results pave the way for further clinical development of αvβ6 antagonists for prostate cancer therapy. Cancer Res; 76(17); 5163-74. ©2016 AACR.

A Comparative Evaluation of Normal Tissue Doses for Patients Receiving Radiation Therapy for Hodgkin Lymphoma on the Childhood Cancer Survivor Study and Recent Children's Oncology Group Trials

PURPOSE

Survivors of pediatric Hodgkin lymphoma (HL) are recognized to have an increased risk of delayed adverse health outcomes related to radiation therapy (RT). However, the necessary latency required to observe these late effects means that the estimated risks apply to outdated treatments. We sought to compare the normal tissue dose received by children treated for HL and enrolled in the Childhood Cancer Survivor Study (CCSS) (diagnosed 1970-1986) with that of patients treated in recent Children's Oncology Group (COG) trials (enrolled 2002-2012).

METHODS AND MATERIALS

RT planning data were obtained for 50 HL survivors randomly sampled from the CCSS cohort and applied to computed tomography planning data sets to reconstruct the normal tissue dosimetry. For comparison, the normal tissue dosimetry data were obtained for all 191 patients with full computed tomography-based volumetric RT planning on COG protocols AHOD0031 and AHOD0831.

RESULTS

For early-stage patients, the mean female breast dose in the COG patients was on average 83.5% lower than that for CCSS patients, with an absolute reduction of 15.5 Gy. For advanced-stage patients, the mean breast dose was decreased on average by 70% (11.6 Gy average absolute dose reduction). The mean heart dose decreased on average by 22.9 Gy (68.6%) and 17.6 Gy (56.8%) for early- and advanced-stage patients, respectively. All dose comparisons for breast, heart, lung, and thyroid were significantly lower for patients in the COG trials than for the CCSS participants. Reductions in the prescribed dose were a major contributor to these dose reductions.

CONCLUSIONS

These are the first data quantifying the significant reduction in the normal tissue dose using actual, rather than hypothetical, treatment plans for children with HL. These findings provide useful information when counseling families regarding the risks of contemporary RT.

Bending the cost curve: a unique collaboration between radiation oncologists and Blue Cross Blue Shield of Massachusetts to optimize the use of advanced technology

PURPOSE

Intensity-modulated radiation therapy (IMRT) limits the dose of radiation to critical normal tissue structures and can be applied to the management of most cancers treated with radiation therapy. Because of increased treatment planning time and quality assurance, IMRT is costly. Blue Cross Blue Shield of Massachusetts (BCBSMA) and the Massachusetts Radiation Oncology Physicians Advisory Council (PAC) developed a strategy to develop standards for the appropriate use of IMRT.

METHODS

Normal tissue volume guidelines were established in multiple oncology disease areas and body site regions. Guidelines were activated in September 2011, and the use of IMRT per case was tracked quarterly by BCBSMA staff.

RESULTS

During the first year of activation of the volume-based guidelines, use of IMRT decreased by 17% in Massachusetts, in contrast to a 20% increase during the previous year.

CONCLUSIONS

The normal tissue-based guidelines have decreased the use of IMRT in Massachusetts; increased the use of 3D treatment; continued communication between treating radiation oncologists and an insurance organization responsible for cost and quality in medicine; increased cost savings; enabled an efficient appeal process; and provided optimal, cost-effective patient care. This may prove to be an effective model for other disciplines and other developing and maturing radiation technologies.

Patterns of relapse from a phase 3 Study of response-based therapy for intermediate-risk Hodgkin lymphoma (AHOD0031): a report from the Children's Oncology Group

PURPOSE

The study was designed to determine whether response-based therapy improves outcomes in intermediate-risk Hodgkin lymphoma. We examined patterns of first relapse in the study.

PATIENTS AND METHODS

From September 2002 to July 2010, 1712 patients <22 years old with stage I-IIA with bulk, I-IIAE, I-IIB, and IIIA-IVA with or without doxorubicin, bleomycin, vincristine, etoposide, prednisone, and cyclophosphamide were enrolled. Patients were categorized as rapid (RER) or slow early responders (SER) after 2 cycles of doxorubicin, bleomycin, vincristine, etoposide, prednisone, and cyclophosphamide (ABVE-PC). The SER patients were randomized to 2 additional ABVE-PC cycles or augmented chemotherapy with 21 Gy involved field radiation therapy (IFRT). RER patients were stipulated to undergo 2 additional ABVE-PC cycles and were then randomized to 21 Gy IFRT or no further treatment if complete response (CR) was achieved. RER without CR patients were non-randomly assigned to 21 Gy IFRT. Relapses were characterized without respect to site (initial, new, or both; and initial bulk or initial nonbulk), and involved field radiation therapy field (in-field, out-of-field, or both). Patients were grouped by treatment assignment (SER; RER/no CR; RER/CR/IFRT; and RER/CR/no IFRT). Summary statistics were reported.

RESULTS

At 4-year median follow-up, 244 patients had experienced relapse, 198 of whom were fully evaluable for review. Those who progressed during treatment (n=30) or lacked relapse imaging (n=16) were excluded. The median time to relapse was 12.8 months. Of the 198 evaluable patients, 30% were RER/no CR, 26% were SER, 26% were RER/CR/no IFRT, 16% were RER/CR/IFRT, and 2% remained uncategorized. The 74% and 75% relapses involved initially bulky and nonbulky sites, respectively. First relapses rarely occurred at exclusively new or out-of-field sites. By contrast, relapses usually occurred at nodal sites of initial bulky and nonbulky disease.

CONCLUSION

Although response-based therapy has helped define treatment for selected RER patients, it has not improved outcome for SER patients or facilitated refinement of IFRT volumes or doses.

Radiotherapy quality assurance report from children's oncology group AHOD0031

PURPOSE

A phase 3 trial assessing response-based therapy in intermediate-risk Hodgkin lymphoma mandated real-time central review of involved field radiation therapy (IFRT) and imaging records by a centralized review center to maximize protocol compliance. We report the impact of centralized radiation therapy review on protocol compliance.

METHODS AND MATERIALS

Review of simulation films, port films, and dosimetry records was required before and after treatment. Records were reviewed by study-affiliated or review center-affiliated radiation oncologists. A deviation of 6% to 10% from protocol-specified dose was scored as "minor"; a deviation of >10% was "major." A volume deviation was scored as "minor" if margins were less than specified or "major" if fields transected disease-bearing areas. Interventional review and final compliance review scores were assigned to each radiation therapy case and compared.

RESULTS

Of 1712 patients enrolled, 1173 underwent IFRT at 256 institutions in 7 countries. An interventional review was performed in 88% of patients and a final review in 98%. Overall, minor and major deviations were found in 12% and 6% of patients, respectively. Among the cases for which ≥1 pre-IFRT modification was requested by the Quality Assurance Review Center and subsequently made by the treating institution, 100% were made compliant on final review. By contrast, among the cases for which ≥1 modification was requested but not made by the treating institution, 10% were deemed compliant on final review.

CONCLUSIONS

In a large trial with complex treatment pathways and heterogeneous radiation therapy fields, central review was performed in a large percentage of cases before IFRT and identified frequent potential deviations in a timely manner. When suggested modifications were performed by the institutions, deviations were almost eliminated.

The impact of protocol assignment for older adolescents with hodgkin lymphoma

BACKGROUND AND PURPOSE

Hodgkin lymphoma (HL) treatment has evolved to reduce or avoid radiotherapy (RT) dose and volume and minimize the potential for late effects. Some older adolescents are treated on adult protocols. The purpose of this study is to examine the protocol assignment of older adolescents and its impact on radiation dose to relevant thoracic structures.

MATERIALS AND METHODS

Cooperative group data were reviewed and 12 adolescents were randomly selected from a pediatric HL protocol. Treatment plans were generated per one pediatric and two adult protocols. Dose volume histograms for heart, lung, and breast allowed comparison of radiation dose to these sites across these three protocols.

RESULTS

A total of 15.2% of adolescents were treated on adult HL protocols and received significantly higher radiation dosage to heart and lung compared to pediatric HL protocols. Adolescents treated on either pediatric or adult protocols received similar RT dose to breast.

CONCLUSION

Older adolescents treated on adult HL protocols received higher RT dose to thoracic structures except breast. Level of nodal involvement may impact overall RT dose to breast. The impact of varying field design and RT dose on survival, local, and late effects needs further study for this vulnerable age group. Adolescents, young adults, Hodgkin lymphoma, RT, clinical trials.

Dose-intensive response-based chemotherapy and radiation therapy for children and adolescents with newly diagnosed intermediate-risk hodgkin lymphoma: a report from the Children's Oncology Group Study AHOD0031

PURPOSE

The Children's Oncology Group study AHOD0031, a randomized phase III study, was designed to evaluate the role of early chemotherapy response in tailoring subsequent therapy in pediatric intermediate-risk Hodgkin lymphoma. To avoid treatment-associated risks that compromise long-term health and to maintain high cure rates, dose-intensive chemotherapy with limited cumulative doses was used.

PATIENTS AND METHODS

Patients received two cycles of doxorubicin, bleomycin, vincristine, etoposide, cyclophosphamide, and prednisone (ABVE-PC) followed by response evaluation. Rapid early responders (RERs) received two additional ABVE-PC cycles, followed by complete response (CR) evaluation. RERs with CR were randomly assigned to involved-field radiotherapy (IFRT) or no additional therapy; RERs with less than CR were nonrandomly assigned to IFRT. Slow early responders (SERs) were randomly assigned to receive two additional ABVE-PC cycles with or without two cycles of dexamethasone, etoposide, cisplatin, and cytarabine (DECA). All SERs were assigned to receive IFRT.

RESULTS

Among 1,712 eligible patients, 4-year event-free survival (EFS) was 85.0%: 86.9% for RERs and 77.4% for SERs (P < .001). Four-year overall survival was 97.8%: 98.5% for RERs and 95.3% for SERs (P < .001). Four-year EFS was 87.9% versus 84.3% (P = .11) for RERs with CR who were randomly assigned to IFRT versus no IFRT, and 86.7% versus 87.3% (P = .87) for RERs with positron emission tomography (PET) -negative results at response assessment. Four-year EFS was 79.3% versus 75.2% (P = .11) for SERs who were randomly assigned to DECA versus no DECA, and 70.7% versus 54.6% (P = .05) for SERs with PET-positive results at response assessment.

CONCLUSION

This trial demonstrated that early response assessment supported therapeutic titration (omitting radiotherapy in RERs with CR; augmenting chemotherapy in SERs with PET-positive disease). Strategies directed toward improved response assessment and risk stratification may enhance tailoring of treatment to patient characteristics and response.

Integrin αvβ6 promotes an osteolytic program in cancer cells by upregulating MMP2

The molecular circuitries controlling osseous prostate metastasis are known to depend on the activity of multiple pathways, including integrin signaling. Here, we demonstrate that the αvβ6 integrin is upregulated in human prostate cancer bone metastasis. In prostate cancer cells, this integrin is a functionally active receptor for fibronectin and latency-associated peptide-TGF-β1; it mediates attachment and migration upon ligand binding and is localized in focal contacts. Given the propensity of prostate cancer cells to form bone metastatic lesions, we investigated whether the αvβ6 integrin promotes this type of metastasis. We show for the first time that αvβ6 selectively induces matrix metalloproteinase 2 (MMP2) in vitro in multiple prostate cancer cells and promotes osteolysis in vivo in an immunodeficient mouse model of bone metastasis through upregulation of MMP2, but not MMP9. The effect of αvβ6 on MMP2 expression and activity is independent of androgen receptor in the analyzed prostate cancer cells. Increased levels of parathyroid hormone-related protein (PTHrP), known to induce osteoclastogenesis, were also observed in αvβ6-expressing cells. However, by using MMP2 short hairpin RNA, we demonstrate that the αvβ6 effect on bone loss is due to upregulation of soluble MMP2 by the cancer cells, not due to changes in tumor growth rate. Another related αv-containing integrin, αvβ5, fails to show similar responses, underscoring the significance of αvβ6 activity. Overall, these mechanistic studies establish that expression of a single integrin, αvβ6, contributes to the cancer cell-mediated program of osteolysis by inducing matrix degradation through MMP2. Our results open new prospects for molecular therapy for metastatic bone disease.

A Phase II Trial of Cetuximab, Gemcitabine, 5-Fluorouracil, and Radiation Therapy in Locally Advanced Nonmetastatic Pancreatic Adenocarcinoma

BACKGROUND

Pancreatic cancer is the fourth leading cause of cancer deaths in the United States. A minority of patients present with localized disease and surgical resection still offers patients the only hope for long-term survival. Locally advanced pancreatic cancer is defined as surgically unresectable, but has no evidence of distant metastases. The purpose of this study is to evaluate the efficacy and safety of cetuximab in combination with gemcitabine and 5-FU along with radiation therapy in locally advanced non-resectable, pancreatic adenocarcinoma, using progression free survival as the primary end point.

METHODS

This was a prospective, single arm, open label pilot phase II study to evaluate the anti-tumor activity of gemcitabine (200 mg/m(2) per week) and cetuximab (250 mg/m(2) per week after an initial 400 mg/m(2) loading dose) with continuous infusion 5-FU (800 mg/m(2) over 96 hours) and daily concurrent external beam radiation therapy (50.4 Gy total dose) for six weeks (cycle 1) in patients with non-metastatic, locally advanced pancreatic adenocarcinoma. Following neoadjuvant treatment, subjects were re-evaluated for response and surgical candidacy with restaging scans. After resection, or also if not resected; subjects received further therapy with four 28-day cycles (cycles 2-5) of weekly gemcitabine (1000 mg/m(2)) and cetuximab (250 mg/m(2)) on days 1, 8, and 15.

RESULTS

Between 2006 and 2011, twenty-six patients were screened and eleven of them were enrolled in the study. Most common reasons for screen failures were having resectable disease, metastatic disease or co-morbidity. Ten patients were able to tolerate and complete cycle 1 of chemoradiotherapy. One patient stopped the study prematurely due to grade III diarrhea. All except this one patient received planned radiation therapy. The response evaluation after cycle 1 showed one Partial Response, eight Stable Disease and two Progressive Disease. Four patients subsequently underwent surgical resection of the tumor. All patients had R0 resections. There was one preoperative mortality due to multiple organ failure. Median progression free survival (PFS) for four resected patients was 9.0 months while for unresected patients median PFS was 7.1 months. Median overall survival (OS) for four resected patients was 47.4 months and for unresected patients median OS was 17.0 months. Most common adverse events were hematologic (27%). Only two patients developed grade 3 neutropenia. Most common treatment related non-hematologic adverse events were diarrhea (10 of 11), nausea (8 of 11) and skin rash (10 of 11 patients). Only 9.5% of all reported non-hematologic adverse events were grade 3 or higher.

CONCLUSIONS

The combination of cetuximab, weekly gemcitabine and continuous infusion of 5-FU with radiotherapy was quite well tolerated with intriguing clinical benefit and survival results in carefully selected patients with locally advanced pancreatic adenocarcinoma. A trial with larger sample size will be necessary to confirm these results.

Abstract C40: αvβ6 integrin promotes a TGFβ1-mediated cancer cell autonomous osteolytic program through upregulation of matrix metalloproteinase 2 (MMP2)

Metastatic prostate cancer to the bone is associated with considerable morbidity and mortality. Because the molecular basis of this process is not completely understood, current treatment is largely palliative, aiming at reducing severe bone pain, nerve compression and pathological fractures. The molecular circuitries controlling osseous prostate metastasis are known to depend on the activity of a pro-metastatic cytokine, TGFβ1, and of matrix metalloproteinases (MMPs). MMP2 is known to enhance prostate cancer-mediated bone degradation and has been reported to be induced by TGFβ1. Various studies show that the αvβ6 integrin activates and is induced by TGFβ1, thus potentiating TGFβ1 responses in the sites where it is expressed. However, a role for αvβ6 in regulating TGFβ1—induced MMP2 has not been described before. Here, we demonstrate that the αvβ6 integrin is upregulated in human prostate cancer bone metastasis and promotes osteolysis as observed by μ–computed tomography (μ–CT) in an in vivo model of metastatic bone disease. Using immunoblotting and real-time PCR analysis, we provide evidence that the αvβ6 integrin sustains TGFβ1—dependent upregulation of MMP2 mRNA and protein levels by associating with TGFβ receptor II. We also show that αvβ6 contributes to upregulation of MMP2 by TGFβ1 through a highly specific transcriptional program mediated by Smad3, and promotes osteolysis in vivo through upregulation of MMP2 in cancer cells. In conclusion, we have identified a novel role of the αvβ6 integrin in directing, in vivo, a cell-autonomous osteolytic program through activation of MMP2. These mechanistic studies will support the development of novel molecular strategies for prostate cancer bone metastasis through inhibition of the TGFβ1\αvβ6\MMP2 signaling pathway.

Acknowledgments: This work was supported by the following grants: NIH — RO1 CA89720 to Dr. Lucia R. Languino and NIH — PO1 CA140043 to Drs. Lucia R. Languino, Gary S. Stein, Jane B. Lian.

Drs. Dutta and Li share the first authorship.

Citation Format: Anindita Dutta, Jing Li, Huimin Lu, Jacqueline Akech, Jitesh Pratap, Tao Wang, Thomas J. FitzGerald, Zhong Jiang, Shelia M. Violette, Gary S. Stein, Jane B. Lian, Lucia R. Languino. αvβ6 integrin promotes a TGFβ1-mediated cancer cell autonomous osteolytic program through upregulation of matrix metalloproteinase 2 (MMP2). [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C40.

Credentialing for participation in clinical trials

The National Cancer Institute (NCI) clinical cooperative groups have been instrumental over the past 50 years in developing clinical trials and evidence-based clinical trial processes for improvements in patient care. The cooperative groups are undergoing a transformation process to launch, conduct, and publish clinical trials more rapidly. Institutional participation in clinical trials can be made more efficient and include the expansion of relationships with international partners. This paper reviews the current processes that are in use in radiation therapy trials and the importance of maintaining effective credentialing strategies to assure the quality of the outcomes of clinical trials. The paper offers strategies to streamline and harmonize credentialing tools and processes moving forward as the NCI undergoes transformative change in the conduct of clinical trials.

Response-dependent and reduced treatment in lower risk Hodgkin lymphoma in children and adolescents, results of P9426: a report from the Children's Oncology Group

BACKGROUND

Hodgkin lymphoma is highly curable but associated with significant late effects. Reduction of total treatment would be anticipated to reduce late effects. This aim of this study was to demonstrate that a reduction in treatment was possible without compromising survival outcomes.

METHODS

Protocol P9426, a response-dependent and reduced treatment for low risk Hodgkin lymphoma (stages I, IIA, and IIIA(1) ) was designed in 1994 based on a previous pilot project. Patients were enrolled from October 15, 1996 to September 19, 2000. Patients were randomized to receive or not receive dexrazoxane and received two cycles of chemotherapy consisting of doxorubicin, bleomycin, vincristine, and etoposide. After two cycles, patients were evaluated for response. Those in complete response (CR) received 2,550 cGy of involved field radiation therapy (IFRT). Patient with partial response or stable disease, received two more cycles of chemotherapy and IFRT at 2,550 cGy.

RESULTS

There were 294 patients enrolled, with 255 eligible for analysis. The 8-year event free survival (EFS) between the dexrazoxane randomized groups did not differ (EFS 86.8 ± 3.1% with DRZ, and 85.7 ± 3.3% without DRZ (P = 0.70). Forty-five percent of patients demonstrated CR after two cycles of chemotherapy. There was no difference in EFS by histology, rapidity of response, or number of cycles of chemotherapy. Six of the eight secondary malignancies in this study have been previously reported.

CONCLUSIONS

Despite reduced therapy and exclusion of most patients with lymphocyte predominant histology, EFS and overall survival are similar to other reported studies. The protocol documents that it is safe and effective to reduce therapy in low-risk Hodgkin lymphoma based on early response to chemotherapy with rapid responding patients having the same outcome as slower-responding patients when given 50% of the chemotherapy.

Redesigning radiotherapy quality assurance: opportunities to develop an efficient, evidence-based system to support clinical trials--report of the National Cancer Institute Work Group on Radiotherapy Quality Assurance

PURPOSE

In the context of national calls for reorganizing cancer clinical trials, the National Cancer Institute sponsored a 2-day workshop to examine challenges and opportunities for optimizing radiotherapy quality assurance (QA) in clinical trial design.

METHODS AND MATERIALS

Participants reviewed the current processes of clinical trial QA and noted the QA challenges presented by advanced technologies. The lessons learned from the radiotherapy QA programs of recent trials were discussed in detail. Four potential opportunities for optimizing radiotherapy QA were explored, including the use of normal tissue toxicity and tumor control metrics, biomarkers of radiation toxicity, new radiotherapy modalities such as proton beam therapy, and the international harmonization of clinical trial QA.

RESULTS

Four recommendations were made: (1) to develop a tiered (and more efficient) system for radiotherapy QA and tailor the intensity of QA to the clinical trial objectives (tiers include general credentialing, trial-specific credentialing, and individual case review); (2) to establish a case QA repository; (3) to develop an evidence base for clinical trial QA and introduce innovative prospective trial designs to evaluate radiotherapy QA in clinical trials; and (4) to explore the feasibility of consolidating clinical trial QA in the United States.

CONCLUSION

Radiotherapy QA can affect clinical trial accrual, cost, outcomes, and generalizability. To achieve maximum benefit, QA programs must become more efficient and evidence-based.

PSA regulates androgen receptor expression in prostate cancer cells

BACKGROUND

Prostate-specific antigen (PSA) is a pivotal downstream target gene of the androgen receptor (AR), and a serum biomarker to monitor prostate cancer (PrCa) progression. It has been reported that PSA transactivates AR, but the mechanistic requirements of this response have not been investigated.

METHODS

We studied the localization of PSA, AR, and Src in intracellular compartments of synthetic androgen (R1881)-stimulated LNCaP and C4-2B PrCa cells, using immunofluorescence and subcellular fractionation approaches. We also investigated the effect of downregulation of PSA on AR expression by immunoblotting and real-time PCR using short hairpin RNA (shRNA) and small interfering RNA (siRNA). Src activity was analyzed by immunoblotting.

RESULTS

R1881 stimulation induced nuclear localization of both PSA and AR in LNCaP and C4-2B PrCa cells as well as increased phosphorylation of Src. Stable shRNA or transient siRNA knockdown of PSA resulted in reduced AR protein levels as well as AR mRNA levels in C4-2B cells. Similar to C4-2B cells, ablation of AR levels upon silencing of PSA was also confirmed in VCaP cells, another androgen-independent cell line. Silencing of PSA did not cause significant changes in Src activation; besides, Src regulation by integrins did not appear to affect AR transcriptional activity.

CONCLUSIONS

PSA localizes to nuclei of androgen-stimulated PrCa cells, and controls AR mRNA and protein levels. This regulatory loop is specific for PSA, does not involve known AR activators such as Src and AKT, and may contribute to AR signaling under conditions of increasing PSA levels in patients.

What we have learned: the impact of quality from a clinical trials perspective

In this review article, we address the radiation oncology process improvements in clinical trials and review how these changes improve the quality for the next generation of trials. In recent years, we have progressed from a time of limited data acquisition to the present in which we have real-time influence of clinical trials quality. This enables immediate availability of the important elements, including staging, eligibility, response, and outcome for all trial investigators. Modern informatics platforms are well designed for future adaptive clinical trials. We review what will be needed in the informatics architecture of current and future clinical trials.

α(V)β(6) integrin expression is induced in the POET and Pten(pc-/-) mouse models of prostatic inflammation and prostatic adenocarcinoma

Chronic inflammation is proposed to prime the development of prostate cancer. However, the mechanisms of prostate cancer initiation and development are not completely understood. The α(v)β(6) integrin has been shown to play a role in epithelial development, wound healing and some epithelial cancers [1, 2]. Here, we investigate the expression of α(v)β(6) in mouse models of prostatic inflammation and prostate cancer to establish a possible relationship between inflammation of the prostate, α(v)β(6) expression and the progression of prostate cancer. Using immunohistochemical techniques, we show expression of α(v)β(6) in two in vivo mouse models; the Pten(pc)-/- model containing a prostate- specific Pten tumor suppressor deletion that causes cancer, and the prostate ovalbumin-expressing transgenic (POET) inflammation mouse model. We show that the α(v)β(6) integrin is induced in prostate cancer and inflammation in vivo in these two mouse models. α(v)β(6) is expressed in all the mice with cancer in the Pten(pc-/-) model but not in age-matched wild-type mice. In the POET inflammation model, α(v)β(6) is expressed in mice injected with activated T-cells, but in none of the control mice. In the POET model, we also used real time PCR to assess the expression of Transforming Growth Factor Beta 1 (TGFβ1), a factor in inflammation that is activated by α(v)β(6). In conclusion, through in vivo evidence, we conclude that α(v)β(6) integrin may be a crucial link between prostatic inflammation and prostatic adenocarcinoma.

The cancer-related Runx2 protein enhances cell growth and responses to androgen and TGFbeta in prostate cancer cells

Prostate cancer cells often metastasize to bone where osteolytic lesions are formed. Runx2 is an essential transcription factor for bone formation and suppresses cell growth in normal osteoblasts but may function as an oncogenic factor in solid tumors (e.g., breast, prostate). Here, we addressed whether Runx2 is linked to steroid hormone and growth factor signaling, which controls prostate cancer cell growth. Protein expression profiling of prostate cell lines (i.e., PC3, LNCaP, RWPE) treated with 5alpha-dihydrotestosterone (DHT) or tumor growth factor beta (TGFbeta) revealed modulations in selected cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors that are generally consistent with mitogenic responses. Endogenous elevation of Runx2 and diminished p57 protein levels in PC3 cells are associated with faster proliferation in vitro and development of larger tumors upon xenografting these cells in bone in vivo. To examine whether TGFbeta or DHT signaling modulates the transcriptional activity of Runx2 and vice versa, we performed luciferase reporter assays. In PC3 cells that express TGFbetaRII, TGFbeta and Runx2 synergize to increase transcription of synthetic promoters. In LNCaP cells that are DHT responsive, Runx2 stimulates the androgen receptor (AR) responsive expression of the prostate-specific marker PSA, perhaps facilitated by formation of a complex with AR. Our data suggest that Runx2 is mechanistically linked to TGFbeta and androgen responsive pathways that support prostate cancer cell growth.

Abstract LB-201: Nuclear localization of Src, androgen receptor and PSA in prostate cancer

Src signaling plays an important role in prostate cancer (PrCa) progression. Dasatinib, an oral src family kinase inhibitor, is being tested in patients with PrCa in several Phase II and III clinical trials. It has been shown that src interacts with androgen receptor (AR) and enhances AR transactivation. Although it has been shown that src promotes AR activity, the underlying pathway has not been defined.

To characterize the src-AR pathway, we first analyzed the localization of src, AR, and Prostate Specific Antigen (PSA, an AR target gene). Using sub-cellular fractionation and immunofluorescence, p-src and src were found in the nucleus, apart from their normal cytoplasmic localization, in androgen-dependent LNCaP cells upon androgen stimulation or deprivation conditions. Also, their localization was not affected by androgen stimulation. Similar to src and p-src, AR as well as pSer81-AR (an AR site indirectly phosphorylated by src) were found in the nucleus as well as in the cytoplasm. Unexpectedly, we found PSA localization in the nucleus upon androgen stimulation in LNCaP and C4-2B cells as well as in the nucleus of C4-2B cells upon androgen deprivation.

We further studied the effect of src on AR activity by transfection of dominant negative src (SrcK298M) in LNCaP and androgen-independent C4-2B cells. Transfection with SrcK298M did not affect PSA expression in LNCaP cells whereas in C4-2B cells SrcK298M transfection inhibited PSA expression.

These data show that src is required for AR activity and, consequently, PSA expression in androgen-independent prostate cancer cells, but not in androgen-dependent cells.

In conclusion, these data suggest that the nuclear co-localization of p-src, AR and PSA might allow macromolecular interactions which can further enhance AR transactivation and promote disease progression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-201.

Abstract 2332: Alphavbeta6 integrin, a downstream effector of TGFbeta, promotes prostate cancer osteolytic lesions

Integrins and their extracellular matrix ligands are crucial regulators of cancer progression. We show in the present study that the alphaVbeta6 integrin is abundantly expressed in human bone metastasis and enhances metastatic bone disease, which occurs frequently in prostate and breast cancer patients.

Our analysis shows that alphaVbeta6 is upregulated in prostate cancer cells via a pro-metastatic signaling pathway mediated by TGFbeta and SMAD3. Given alphaVbeta6 ability to act as a downstream effector of TGFbeta, we tested the ability of alphaVbeta6 to mediate metastatic cancer growth in bone in vivo. We injected PC3 cells stably transfected with alphaVbeta6 in the tibiae of SCID mice. Intraosseous growth of these cells results in extensive osteolytic lesions. Micro-computed tomographic reconstruction of the various bone lesions demonstrates that expression of alphaVbeta6 promotes the appearance of osteolytic lesions beginning at 2 weeks after injection of the tumor cells, further progressing to massive trabecular and cortical bone loss by 4 and 8 weeks. In contrast, intraosseous growth of cells expressing alphaVbeta5, another alphaV containing integrin known to promote metastasis, does not result in osteolytic lesions at the same time intervals and causes woven bone deposition in the medullary cavity. Intraosseous tumors produced by intratibial injection of alphaVbeta6- or alphaVbeta5-expressing prostate cancer cells grew with indistinguishable kinetics, thus ruling out that the enhanced formation of osteolytic lesions mediated by alphaVbeta6 was simply due to accelerated tumor growth. Further analysis shows that alphaVbeta6 contributes to osteolytic lesions by selective upregulation of MMP2 levels in PC3 tumors in vivo, which, in contrast, is not observed in alphaVbeta5- PC3 tumors.

These findings show for the first time a mechanism that promotes alphaV integrin-mediated osteolysis in prostate cancer metastatic growth and suggest that the players involved are targets for future personalized therapies of prostate cancer.

Grant support: NIH R01 CA089720 (LRL).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2332.

Bicalutamide inhibits androgen-mediated adhesion of prostate cancer cells exposed to ionizing radiation

BACKGROUND

Cell adhesion plays an important role in proliferation, metastasis, and tumor growth and may represent a potential vulnerability in treatment of prostate cancer patients. Bicalutamide (Casodex) has been used as an anti-androgen agent for prostate cancer patients during hormone ablation therapy. This study focuses on the effect of Bicalutamide on cell adhesion to fibronectin (FN) in prostate cancer cells.

METHODS

Androgen-dependent LNCaP prostate cancer cells were stimulated with androgen before being irradiated with doses of 0, 5, 10, or 15 Gy. Cell adhesion to fibronectin was then measured to ascertain androgen's role in integrin mediated prostate cancer cell adhesion. Flow cytometry was used to analyze surface expression of integrin subtypes in LNCaP cells.

RESULTS

LNCaP cell adhesion to FN was significantly increased by stimulation with androgen when treated with 10 or 15 Gy ionizing radiations but not at 0 or 5 Gy. This increase was inhibited by treatment with Bicalutamide. LNCaP cells exposed to high dose radiation showed an increased expression of alpha(V) and beta(1) integrins in response to androgen treatment while Bicalutamide abolished this effect.

CONCLUSIONS

Our data show that Bicalutamide inhibits the effect of androgen on cell adhesion to FN through changes of integrin subtypes in cells given high dose radiation. This suggests new molecular targets and possible treatment strategies for prostate cancer patients to improve the outcome during hormone ablation therapy and radiation therapy.

Processes for quality improvements in radiation oncology clinical trials

Quality assurance in radiotherapy (RT) has been an integral aspect of cooperative group clinical trials since 1970. In early clinical trials, data acquisition was nonuniform and inconsistent and computational models for radiation dose calculation varied significantly. Process improvements developed for data acquisition, credentialing, and data management have provided the necessary infrastructure for uniform data. With continued improvement in the technology and delivery of RT, evaluation processes for target definition, RT planning, and execution undergo constant review. As we move to multimodality image-based definitions of target volumes for protocols, future clinical trials will require near real-time image analysis and feedback to field investigators. The ability of quality assurance centers to meet these real-time challenges with robust electronic interaction platforms for imaging acquisition, review, archiving, and quantitative review of volumetric RT plans will be the primary challenge for future successful clinical trials.

The Effect of Radiation Therapy on Normal Tissue Function

As more patients are treated for their primary malignancy with cure or increased disease-free intervals, injury to normal tissues will become more detectable and an important endpoint for study. Future protocols will probably be modified based on toxicity endpoints. In Hodgkin's disease, current protocols use response-based treatment strategies to limit therapy. The objective is to provide the same level of tumor control and follow normal tissue endpoints for outcome analysis. DVH analysis has improved the ability to analyze endpoint data for normal tissues. These image-guided platforms will provide the infrastructure needed to continue efforts in improving the delivery of radiation therapy.

Prostate carcinoma: opportunities for translational research

Adenocarcinoma of the prostate continues to be a major health concern. Although modern screening techniques have increased the number of men presenting with early stage disease, a significant population of men will present with intermediate or advanced pathological risk factors for recurrence. There are defined limitations in outcome with traditional therapies including surgery, radiation therapy, and hormone manipulation. Patients with intermediate and high-risk factors for treatment failure are candidates for protocols using translational research strategies incorporated into studies currently in development. These strategies may be able to selectively treat expression products of tumor and thus be more selective in the target for treatment. Carefully designed studies using these translational strategies have great potential in improving clinical outcome, tumor kill, and normal tissue tolerance in the care of these patients.

Current calibration, treatment, and treatment planning techniques among institutions participating in the Children's Oncology Group

PURPOSE

To report current technology implementation, radiation therapy physics and treatment planning practices, and results of treatment planning exercises among 261 institutions belonging to the Children's Oncology Group (COG).

METHODS AND MATERIALS

The Radiation Therapy Committee of the newly formed COG mandated that each institution demonstrate basic physics and treatment planning abilities by satisfactorily completing a questionnaire and four treatment planning exercises designed by the Quality Assurance Review Center. The planning cases are (1) a maxillary sinus target volume (for two-dimensional planning), (2) a Hodgkin's disease mantle field (for irregular-field and off-axis dose calculations), (3) a central axis blocked case, and (4) a craniospinal irradiation case. The questionnaire and treatment plans were submitted (as of 1/30/02) by 243 institutions and completed satisfactorily by 233. Data from this questionnaire and analyses of the treatment plans with monitor unit calculations are presented.

RESULTS

Of the 243 clinics responding, 54% use multileaf collimators routinely, 94% use asymmetric jaws routinely, and 13% use dynamic wedges. Nearly all institutions calibrate their linear accelerators following American Association of Physicists in Medicine protocols, currently 16% with TG-51 and 81% with TG-21 protocol. Treatment planning systems are relied on very heavily for all calculations, including monitor units. Techniques and results of each of the treatment planning exercises are presented.

CONCLUSIONS

Together, these data provide a unique compilation of current (2001) radiation therapy practices in institutions treating pediatric patients. Overall, the COG facilities have the equipment and the personnel to perform high-quality radiation therapy. With ongoing quality assurance review, radiation therapy compliance with COG protocols should be high.

Miniature multileaf collimator as an alternative to traditional circular collimators for stereotactic radiosurgery and stereotactic radiotherapy

PURPOSE

To evaluate the miniature multileaf collimator (MMLC) as an alternative to traditional circular collimators for radiosurgery.

MATERIALS AND METHODS

'Circular' fields were created with the Radionics MMLC (leaf width 3.53 mm at isocenter). Beam data, including tissue maximum ratios, output factors, penumbrae and isodose distributions of these fields were measured. These were compared to the Radionics circular collimators traditionally used for radiosurgery. The MMLC data were input to the XKnife Treatment Planning System. Treatment plans were completed and evaluated using both the MMLC 'circular' fields and the circular collimators.

RESULTS

MMLC fields using 3, 5, 7, 9, 11, and 13 leaves on each side of the Radionics MMLC were created to approximate circular fields. The TMRs are essentially identical to those of comparable-size circular collimators. Measured at isocenter at 5-cm depth for 6 MV, the 80-20% penumbra widths are comparable to circular collimators, but are increased by as much as 1 mm at the leaf intersections (steps) where scalloping occurs. Isodose distributions were matched to those of circular collimators with comparable 50% isodose widths. Treatment plans for the MMLC 'circular' fields with four arcs (totaling 360 degrees) are essentially identical to those of comparable circular collimators. Dose-volume histograms revealed clinically insignificant differences between the two in doses to the target, to the volume surrounding the target, and to adjacent critical normal tissues. There is very little discrepancy between the dose distribution calculated with the approximated MMLC fields and with those of simulated arcs with the actual MMLC fields.

CONCLUSIONS

With the MMLC simulating circular fields, dose distributions may be obtained which are essentially identical to comparable-size circular collimators. The mechanical accuracy of the MMLC is as good as that of the circular collimators, and the leakage dose is less. The diameter of 'circular' fields is limited by the MMLC leaf width to 1 cm and greater in increments of 7 mm. Attention needs to be paid to mechanical collisions because the MMLC is bulkier than the circular collimators.

Differential expression of nitric oxide synthases in EGF-responsive mouse neural precursor cells

Nitric oxide (NO) is a gaseous, radical molecule that plays a role in various physiological processes in the nervous system such as learning and hippocampal plasticity. It is generated from l-arginine by nitric oxide synthases (NOS), which come in three isoforms depending on the tissue of origin, namely inducible-NOS (iNOS in macrophages), endothelial-NOS (eNOS in endothelial cells) and neural-NOS (nNOS in neural cells). We used epidermal growth factor (EGF)-responsive nestin-positive neural precursor cells originating from the mouse E16 embryonic striatum, and studied the relative expression of NOS isoforms probed with isoform-specific antibody using the avidin-biotin immunohistochemical method. Our data revealed both nNOS and eNOS to be expressed in both neurospheres and desegregated neural precursor cells. However, iNOS signals were virtually undetectable in both cell categories. When the neural precursor cells were carried in the presence of poly-l-ornithine (PLO), there was a strong induction of the expression of iNOS proteins, indicating the possibility that this isoform is amenable to modulation by extracellular cues. These preliminary results suggest both nNOS and eNOS to be important in the physiology of neural precursor cells, and that iNOS might also play a role at certain stages in the life of these cells.

In vivo study of stainless steel and Ti-13Nb-13Zr bone plates in a sheep model

A sheep study was performed to compare the in vivo performance of bone plates of 316L stainless steel and a new titanium alloy, titanium + 13% niobium + 13% zirconium (Ti-13Nb-13Zr), which had been subjected to a diffusion hardening treatment to produce a blue, wear resistant surface. Bone plates and screws of stainless steel and diffusion hardened Ti-13Nb-13Zr were implanted in adult sheep, in one group (with unosteotomized femurs) for 16 weeks, and in the other (with osteotomized femurs) for 8 weeks. At harvest, the diffusion hardened Ti-13Nb-13Zr devices had superior fixation strength, with greater screw torque out strength and fewer loose screws. In the osteotomized animals, the femurs with diffusion hardened Ti-13Nb-13Zr plates had higher torsional strength after removal of the implants; however, the difference was not statistically significant. In the unosteotomized animals, the torsional strength of the femurs was identical for both materials. There was a slightly reduced incidence of infection (bacterial adhesion) for the sheep with diffusion hardened Ti-13Nb-13Zr implants. In a parallel in vitro study, the magnetic resonance imaging compatibility of Ti-13Nb-13Zr was significantly superior to that of stainless steel. This indicates that diffusion hardened Ti-13Nb-13Zr may be an attractive alternative material for osteosynthesis.