S.C. Formenti

Cutaneous low-dose radiation increases tissue vascularity through upregulation of angiogenic and vasculogenic pathways

Background/Aims: Neovascularization involves angiogenesis and vasculogenesis mediated by cytokines and soluble chemokines. The predominant stimulus is ischemia, however, recent data suggest that ionizing radiation (IR) has angiogenic potential. In this study we evaluated whether IR increases vascularity and perfusion in vivo. Methods: In wild-type mice, a full-thickness, pedicled skin flap was created and isolated for localized irradiation at a dose of 5 Gy. Serial Doppler analysis of the flap was performed. The skin flaps were then harvested at various time points for vascularity and histologic analysis. Blood was concurrently harvested for serum and hematopoietic progenitor cell population analysis. Results: IR to an ischemic flap augmented the angiogenic cytokines SDF-1 and VEGF. Serum MMP-9 and s-kit levels, which are critical for progenitor cell mobilization, were also increased. When hematopoietic progenitor cells were evaluated by Sca1+/Flk1+ cells, a correlate 2-fold increase was seen compared to controls. When the flaps were examined, both vascularity and perfusion were increased. Conclusion: In this study we demonstrate that local, low-dose IR upregulates angiogenic chemokines and results in progenitor cell mobilization to the systemic circulation. There is a resultant increase in the vascularity of the irradiated flap, suggesting that the pro-angiogenic effects of IR can be harnessed locally.

Dose-dependent effect of radiation on angiogenic and angiostatic CXC chemokine expression in human endothelial cells

Blood vessel growth is regulated by angiogenic and angiostatic CXC chemokines, and radiation is a vasculogenic stimulus. We investigated the effect of radiation on endothelial cell chemokine signaling, receptor expression, and migration and apoptosis. Human umbilical vein endothelial cells were exposed to a single fraction of 0, 5, or 20 Gy of ionizing radiation (IR). All vasculogenic chemokines (CXCL1-3/5-8) increased 3-13-fold after 5 or 20 Gy IR. 20 Gy induced a marked increase (1.6-4-fold) in angiostatic CXC chemokines. CXCR4 expression increased 3.5 and 7-fold at 48 h after 5 and 20 Gy, respectively. Bone marrow progenitor cell chemotaxis was augmented by conditioned media from cells treated with 5 Gy IR. Whereas 5 Gy markedly decreased intrinsic cell apoptosis (0 Gy=16%+/-3.6 vs. 5 Gy=4.5%+/-0.3), 20 Gy increased it (21.4%+/-1.2); a reflection of pro-survival angiogenic chemokine expression. Radiation induces a dose-dependent increase in pro-angiogenic CXC chemokines and CXCR4. In contrast, angiostatic chemokines and apoptosis were induced at higher (20 Gy) radiation doses. Cell migration improved significantly following 5 Gy, but not 20 Gy IR. Collectively, these data suggest that lower doses of IR induce an angiogenic cascade while higher doses produce an angiostatic profile.

Preliminary clinical results of accelerated IMRT with concomitant boost after breast conserving therapy (BCT)

860 Background: Inspired by the Canadian prospective randomized trial that demonstrated comparable 5-year safety and efficacy of accelerated (16 fractions) whole breast RT versus standard RT (25 fractions), we have started a protocol of accelerated intensity-modulated radiation therapy (AIMRT) after BCT. METHODS A protocol of 15 fractions over 3 weeks is offered to Stage I-II patients who have undergone BCT. Patients are treated in the prone position, to reduce breathing motion and to enable treatment of the index breast while sparing the other breast, the lung and heart tissue. Dynamic intensity modulated multiple photon fields are used to deliver 15 daily fractions of 2.7 Gy (40.5 Gy total dose) to the index breast with a simultaneous in-field boost of 0.5 Gy (48 Gy total dose) to the tumor bed(PTV). At prone CT planning, the index breast is defined and is encompassed by beams placed tangentially to the anterior edge of the chest wall. The superior and inferior margins are clinically determined at the time of simulation. Similarly, the PTV is defined as the post-surgical cavity, plus a 1.0 cm margin. RESULTS Since September 2003, eleven patients with Stage I(n=7) and IIA(n=4) breast cancer entered the study and were treated with either 3 or 4 non-coplanar IMRT fields. DVH Analysis: The median % volume of breast tissue outside the PTV(Br-PTV) receiving 110% and 125% of the prescription dose(PD 40.5 Gy) was 37.6% (SD±10.87) and 4.04% (SD±3.77), respectively. The median % dose covering 95% of the PTV volume(D95) was 118.6 % of the PD (SD±1.93). Five % of the ipsilateral lung received 7.2%(SD±8.4) of the PD(291.6 cGy), while five % of the heart received 7.3%(SD±2.7) of the PD(295.7 cGy). CONCLUSIONS Preliminary data suggest that it is technically feasible to plan and treat by AIMRT the ipsilateral breast with a concomitant boost. Prone positioning reduces breathing movement and spares heart and lung tissue. [Figure: see text] No significant financial relationships to disclose.

SU-E-T-588: Characterization and Clinical Validation of the Varian Pivotal™ Treatment Solution for Prone Breast Care

PURPOSE To report on the clinical validation of the Varian Pivotal™ Treatment Solution for Prone Breast Care: a platform for prone breast radiation therapy. METHODS Patients treated using Breast Conserving Radiation Therapy may benefit from treatment in the prone position with the breast tissue falling freely away from the body. This geometry allows the breast tissue to be treated while avoiding the lung and heart tissue. Eighteen patients simulated and treated using the Varian Medical Systems Pivotal™ Treatment Solution for Prone Breast Care were monitored over the course of treatment for positioning integrity and reproducibility. As this carbon-fiber platform actually replaces a portion of the couch top, indexing is inherent to its design. Patients were positioned on the couch and aligned using fiducial markers and lateral SSD to the breast fiducial point. The daily couch coordinates then serves as indicators for positioning variability with this system. RESULTS The variations in couch vertical, longitudinal and lateral positions were centered on a mean value of zero with standard deviations of 0.44cm, 0.75cm and 0.79cm respectively. Other factors explored were variations in distance of mid-sternum to table edge and patient rotation into the opening. The median rotation of the chest wall was found to be 11.5 degrees at CT-Simulation with a median distance of 2.5cm from midsternum to support opening. Patient rotation was not associated with either breast size or distance from edge of platform. CONCLUSION The Pivotal™ Treatment solution consists of a couch top that replaces the standard top and as such is open from beneath without obstruction. This is a distinction from all other solutions which rely on a platform positioned above and indexed to the treatment couch. We found the reproducibility to be consistent with our historical measures while offering benefits of an integrated solution as stated above. supported by Professional Services Agreeement with Varian Medical Systems.

SU-E-T-378: Limits and Possibilities of a Simplistic Approach to Whole Breast Radiation Therapy Planning

PURPOSE Challenges for radiation therapy in developing countries include unreliable infrastructure and high patient load. We propose a system to treat whole breast in the prone position without computed tomography and/or planning software. METHODS Six parameters are measured using calipers and levels with the patient prone in the treatment position. (1) The largest separation; (2) the angle that separation makes with the horizontal; (3) the separation 2 cm posterior to the nipple; (4) the vertical distance between these two separations; (5) the sup/inf length and (6) angle of the desired posterior field edge. The data in (5) (6) and (2) provide field length, collimator and gantry angles. Isocenter is set to the midpoint of (1), anterior jaw setting is 20cm (half-beam setup), and the dose is prescribed to a point 1.5 cm anterior to isocenter. MUs and wedge angles are calculated using an MU calculator and by requiring 100% dose at that point and 100-105% at the midpoint of (3). Measurements on 30 CT scans were taken to obtain the data 1-6. To test the resulting MU/wedge combinations, they were entered into Eclipse (Varian) and dose distributions were calculated. The MU/wedge combinations were recorded and tabulated. RESULTS Performing a dose volume histogram analysis, the contoured breast V95 was 90.5%, and the average V90 was 94.1%. The maximum dose never exceeded 114.5%, (average 108%). The lung V20 was <5% for 96.7%, and the heart V5 was <10% for 93.3% of our sample. CONCLUSION A method to provide prone whole breast treatment without CT-planning was developed. The method provides reasonable coverage and normal tissue sparing. This approach is not recommended if imaging and planning capabilities are available; it was designed to specifically avoid the need for CT planning and should be reserved to clinics that need to avoid that step.

Abstract OT2-1-02: Novel combination of toll-like receptor (TLR)-7 agonist imiquimod and local radiotherapy in the treatment of breast cancer chest wall recurrences or skin metastases

Background/Rationale: To assess the immune and systemic anti-tumor effects of the novel combination of local radiotherapy combined with imiquimod applied topically to breast cancer metastatic to skin. Breast cancer is the most common tumor, excluding melanoma, to metastasize to the skin in women. Chest wall recurrence is debilitating for patients, substantially affecting quality of life. Current treatment modalities for unresectable lesions are rarely curative and patients ultimately die of visceral metastases, indicating the need for more effective therapies. Imiquimod (IMQ), a synthetic TLR-7 agonist has immunomodulatory activity with profound effects on the tumor environment and can lead to tumor regression of cutaneous breast cancer metastases (Adams et al, Clin Ca Res, Dec 15, 2012). Accumulating evidence indicates that the potential of local radiotherapy to convert the tumor into an in-situ vaccine can be enhanced by combination with immunotherapy to achieve a therapeutic synergy. We have previously shown in a mouse model of cutaneous breast cancer that topical IMQ synergizes with local RT to induce complete tumor regression (REF). Importantly, this approach used a local treatment to generate anti-tumor immune responses with ability to control the tumor systemically (Dewan et al, Clin Ca Res Dec 15, 2012). This trial was designed to test the feasibility of translating this therapeutic synergy in the clinic (clinicaltrials.gov [NCT01421017][1]). Methods: Eligibility includes patients with biopsy-confirmed breast cancer, measurable disease and skin metastases, ECOG PS 0-2 and adequate organ/marrow function. Radiation therapy is delivered to one area of skin metastases in five fractions of 6 Gy (days 1,3,5,8,10). IMQ 5% cream is applied topically to skin metastases overnight for 5 days/week for 8 weeks, beginning the evening of the first radiotherapy. Continuous imiquimod to all skin metastases even after completion of RT is based on our preclinical evidence of an improved effector phase of the immune response. Additional treatment cycles with IMQ/RT are permitted. Following a brief phase I portion to allow dose optimization in the event of unanticipated adverse events (3-3 design), the phase II study evaluates efficacy with a planned additional 25 patients. Primary endpoint is the response rate in untreated metastases, assessed by immune-related response criteria. Furthermore, the local tumor responses and safety of the combination will be determined; tumor FNA biopsies will be obtained to investigate signatures of immune-mediated rejection as recently described with IMQ mediated rejection of basal cell carcinomas; and peripheral lymphocytes will be examined for the induction/boosting of selected tumor antigen-specific T and B cell responses. The phase I portion has been successfully completed with 6 patients without DLT. Enrollment into the phase II portion has begun. At present, a total of 11 patients have been enrolled. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT2-1-02. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01421017&atom=%2Fcanres%2F73%2F24_Supplement%2FOT2-1-02.atom

P1-17-07: Phase II Trial of RAD001 Plus Carboplatin in Patients with Triple-Negative Metastatic Breast Cancer.

Background: RAD001 is an oral mTOR inhibitor that has exhibited activity in breast cancer. Triple negative breast cancer cells are unable to repair double stranded DNA breaks and hence have sensitivity to platinum agents that cause interstrand cross-links. Rapamycin acts synergistically with platinum agents to induce apoptosis and inhibit proliferation in at least two different breast cancer cell lines (including ER/PR negative cell lines). We propose that combination RAD001 and carboplatin may have activity in triple-negative breast cancer. Methods: The primary objective of the study is to determine clinical benefit (complete remission (CR) + partial remission (PR) + stable disease (SD)) and the toxicity of this combination in women with triple negative metastatic breast cancer who have had 0–3 prior chemotherapy regimens for metastatic disease. Secondary objectives are to determine progression free survival as well as investigating the relationship between pretreatment sensitivity (biopsy at baseline) and clinical response (biopsy post 2 cycles) using IHC staining for abundance of key proteins in the Akt-mTOR pathway and their activity using surrogate phosphorylation site-specific antibodies (Akt and phospho-serine 473, phospho-threonine and phospho-threonine 308 Akt; mTOR and phospho-serine 2448 mTOR; ribosome protein S6 kinase (S6K) and phospho-threonine 378 S6K; 4E-BP1 and phospho-serine 65 4E-BP1). Prior carboplatin is allowed. Women with treated brain metastasis are eligible. According to the original study plan, carboplatin AUC 6, was to be given intravenously every three weeks. Five mg of RAD001 was to be given daily with a 3 patient run-in and then 10 mg daily if there were no dose-limiting toxicities. Due to a unexpected amount of thrombocytopenia with this combination the dose of carboplatin was first amended to AUC 5 and most recently to AUC 4 with 5 mg of RAD001 (and no plan to escalate to 10 mg). Results: Fourteen patients of a planned 25 have been recruited thus far. Median age is 58.5. Median number of prior regimens is 2 (0-3). Of the 7 patients assessable for response at this time, there have been 2 PR9s and 5 patients with SD. One SD was achieved in a patient progressing on single agent carboplatin at study entry. Median duration of SD + PR is 28.5 weeks (5 patients have ongoing response ranging from 8–46.5 weeks). Five of 8 patients assessable for toxicity had grade 3 or 4 thrombocytopenia and 2 patients had grade 3 neutropenia. No cases of febrile neutropenia were observed. Four patients have required blood transfusion and one patient has required platelet transfusion. All patients have had treatment held and/or dose reductions secondary to hematological toxicity, however, since amended carboplatin dose the regimen has been very well tolerated with only one out of six patients) with grade 3 neutropenia and grade 3 thrombocytopenia. There have been no non-hematological grade 3 or 4 toxicities. Conclusions: Clinical benefit was observed in all 7 assessable patients. Dose limiting thrombocytopenia was an unexpected side effect requiring protocol amendment. We continue to accrue study subjects at the amended dosing. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-17-07.

Abstract P5-06-05: Catalytic mTOR Inhibition with pp242 but Not Allosteric Inhibition with Rapamycin RAD001 Enhances the Radiosensitivity of Inflammatory Breast Cancer in an Animal Model

Purpose/Objective(s): Inflammatory breast cancer (IBC) is a highly aggressive and radiation resistant cancer that continues to have a dismal prognosis despite aggressive multimodality therapy, which includes ionizing radiation (IR). The PI3K/Akt/mTOR pathway is frequently dysregulated in human cancers, including IBC. mTOR (mammalian target of rapamycin) is a central regulator of protein synthesis, linking mRNA translation to the metabolic state of the cell, playing a key role in the signaling of malignant cell growth, proliferation, differentiation, migration, and survival. We have shown that mTOR activation following treatment with DNA damaging agents such as ionizing radiation (IR) is a primary protector of advanced breast cancer cells, including IBC cells, through selectively increased translation of mRNAs for survival and DNA repair genes, including survivin, PARP, and DNA repair enzymes, among other radio-protective mRNAs. Thus, treatment with an mTOR inhibitor, coupled with IR, would be expected to provide a synergistic ability to control IBC. Therefore we compared the cytotoxic effects of combining mTOR inhibition and radiation in an IBC xenograft model, using either the selective mTORC1/2 inhibitor pp242, or the partial mTORC1 inhibitor RAD001 (Everlimus), a rapamcyin analog. Methods: Experiments were conducted using SUM149 cells, a well-established model for IBC. Cells were treated with RAD001 or TORC1/2 inhibitor pp242 alone or in combination with increasing doses of radiation from 0-8 Gy. In vitro studies preformed included; cell survival assays, immunoblot analysis of key proteins, and 35S-methionine labeling to evaluate protein synthesis. In vivo studies were performed in a SUM149 xenograft nude mouse model; animals were treated with RAD001 or pp242 alone or in combination with IR. Results: We found that only the combination of IR and catalytic mTOR inhibition by pp242 led to a number of striking additive/synergistic effects that were not observed with the combination of IR and the partial mTORC 1 inhibitor RAD001. These effects included; decreased clonogenic survival, inhibition of both endogenous and radiation-induced Akt activation, greater inhibition of mTOR signaling to its downstream effectors, efficient inhibition of protein synthesis, and greater induction of apoptotic cell death, as indicated by induction of caspase-3 cleavage. Importantly, SUM149 IBC xenografts treated with pp242 and concurrent radiation treatment exhibited significantly greater tumor control and survival compared to radiation treatment alone or RAD001 with radiation. Conclusions: These studies demonstrate that targeted inhibition of mTORC1/2 catalytic activity synergizes with radiation therapy in a model system of IBC. Mechanistically, mTORC1/2 inhibition likely prevents radiation induced pro-survival signals mediated through constitutively active Akt, which is not blocked by Rapamycin and its analogs. Experiments examining whether inhibition by pp242 prevents the selective increase in translation of prosurvival mRNAs in IBC as a result of IR treatment will be presented. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-06-05.

WE‐C‐BRB‐02: A Support Vector Machine (SVM) Classifier Identifies From Prone CT Simulation the Optimal Set Up for Breast Radiotherapy

Purpose: To determine optimal (prone vs. supine) treatment positions for breast radiotherapy by classifying geometric features extracted from proneCT scans.Method and Materials:CT scans from patients enrolled in NYU 05‐181 Protocol were studied to discern predicting factors for optimizing treatment positions for breast radiotherapy. Each of the 400 patients accrued for this protocol underwent CT simulation and planning in both supine and prone positions. The treatment set up was chosen based on maximum sparing of heart and lung. Since the results demonstrated that most patients were best treated prone, we studied whether a support vector machine (SVM) classifier could successfully predict optimal position based on a single prone CT scan and limit a second supine CT only to the minority of women best treated supine. To build this classifier, prone CT scans of NYU 05‐181 were de‐identified and exported in DICOM RT format. Three‐dimensional shape and distance features were computed from organs at risk and the planning target volume in the CT scans. We used a k‐fold cross validation procedure to test the performance of the SVM classifier. Results:Images of 36 patients (23 prone‐treated and 13 supine‐treated) were used. Preliminary results indicate that breast volume, heart and lung involvement in the treatment field are significant predicting factors. A weighting of 1:5 (prone‐treated: supine‐treated) was used when determining the soft margin hyper plane of the SVM classifier. The purpose is to increase the specificity [true‐supine/ (true‐supine+false‐prone)] of the classifier since patients classified as prone will not receive a validation supine CT scan. A sensitivity [true‐prone/(true‐prone+false‐supine)] of 87% and a specificity of 92% was achieved using 11 geometric features and the SVM classifier. Conclusion: Preliminary data support the use of a feature‐based classification to predict the optimal treatment position from prone CT scans.

Prone accelerated partial breast irradiation using cone-beam CT (CBCT) guidance.

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #5136 Introduction: Prone external beam partial breast irradiation when used for a carefully selected subset of patients has been shown to have excellent long term control and cosmesis (Formenti et al. IJROBP 60(2): 493-504 2004). We used Cone-beam CT (CBCT) to visualize the tumor bed target prior to each daily fraction of partial breast irradiation. The purpose of this study is to measure the residual error in soft tissue positioning after alignment based on skin marks and MV portal imaging for patients treated on a prospective prone APBI study (3000cGy in 5 fractions over 5 days). Methods: Twenty-five post-menopausal women with pT1 breast cancer have consented on our NYU partial breast protocol using CBCT. Twenty-three patients have been simulated and treated in the prone position on a specially designed mattress. After initial skin mark setup and alignment, MV portal imaging with shift using the tangent beams eye view was used to optimize setup for the first 6 patients (Group I). For all daily fractions, CBCT was performed with the Varian On-Board Imager kV imaging system with a 35cm field of view and a 2.5mm slice thickness. CBCT was compared with the planning CT to shift the patient and evaluate the residual error in setup. The residual error from CBCT setup after optimal portal imaging was recorded for each patient. For the subsequent 17 patients (Group II), portal imaging was performed without shift to calculate the residual error from CBCT setup representing skin mark setup. Results: At the time of this report, 23 patients have been treated with all 5 fractions. The values for the residual error detected after cone-beam CT for Group I (after skin mark set up and portal imaging) and for Group II (after skin mark setup alone) are compared and shown in Table 1. Conclusions: In this preliminary study with a small number of patients, the residual error was minimal, around 2 mm. Therefore, for patients immobilized on our customized mattress, a reproducible and accurate prone APBI setup can be achieved with use of CBCT. However, given the very small residual error detected clinicians should be weary of indiscriminant use of CBCT for PBI. Concerns over contralateral breast dose and carcinogenic risk should limit the routine use of CBCT imaging for breast radiotherapy unless larger studies demonstrate improved accuracy of treatment delivery with CBCT. ![][1] Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5136. [1]: /embed/graphic-1.gif