Transferring care to enhance access to early-phase cancer clinical trials: Protocol to evaluate a novel program

Involving diverse populations in early-phase (phase I and II) cancer clinical trials is critical to informed therapeutic development. However, given the growing costs and complexities of early-phase trials, trial activation and enrollment barriers may be greatest for these studies at healthcare facilities that provide care to the most diverse patient groups, including those in historically underserved communities (e.g., safety-net healthcare systems). To promote diverse and equitable access to early-phase cancer clinical trials, we are implementing a novel program for the transfer of care to enhance access to early-phase cancer clinical trials. We will then perform a mixed-methods study to determine perceptions and impact of the program. Specifically, we will screen, recruit, and enroll diverse patients from an urban, integrated safety-net healthcare system to open and active early-phase clinical trials being conducted in a university-based cancer center. To evaluate this novel program, we will: (1) determine program impact and efficiency; and (2) determine stakeholder experience with and perceptions of the program. To achieve these goals, we will conduct preliminary cost analyses of the program. We will also conduct surveys and interviews with patients and caregivers to elucidate program impact, challenges, and areas for improvement. We hypothesize that broadening access to early-phase cancer trials conducted at experienced centers may improve equity and diversity. In turn, such efforts may enhance the efficiency and generalizability of cancer clinical research.

Predicting treatment plan approval probability for high-dose-rate brachytherapy of cervical cancer using adversarial deep learning

Objective.Predicting the probability of having the plan approved by the physician is important for automatic treatment planning. Driven by the mathematical foundation of deep learning that can use a deep neural network to represent functions accurately and flexibly, we developed a deep-learning framework that learns the probability of plan approval for cervical cancer high-dose-rate brachytherapy (HDRBT).Approach.The system consisted of a dose prediction network (DPN) and a plan-approval probability network (PPN). DPN predicts organs at risk (OAR)D2ccand CTVD90%of the current fraction from the patient's current anatomy and prescription dose of HDRBT. PPN outputs the probability of a given plan being acceptable to the physician based on the patients anatomy and the total dose combining HDRBT and external beam radiotherapy sessions. Training of the networks was achieved by first training them separately for a good initialization, and then jointly via an adversarial process. We collected approved treatment plans of 248 treatment fractions from 63 patients. Among them, 216 plans from 54 patients were employed in a four-fold cross validation study, and the remaining 32 plans from other 9 patients were saved for independent testing.Main results.DPN predicted equivalent dose of 2 Gy for bladder, rectum, sigmoidD2ccand CTVD90%with a relative error of 11.51% ± 6.92%, 8.23% ± 5.75%, 7.12% ± 6.00%, and 10.16% ± 10.42%, respectively. In a task that differentiates clinically approved plans and disapproved plans generated by perturbing doses in ground truth approved plans by 20%, PPN achieved accuracy, sensitivity, specificity, and area under the curve 0.70, 0.74, 0.65, and 0.74.Significance.We demonstrated the feasibility of developing a novel deep-learning framework that predicts a probability of plan approval for HDRBT of cervical cancer, which is an essential component in automatic treatment planning.

Definitive radiation for advanced cervix cancer is not associated with vaginal shortening-a prospective vaginal length and dose correlation

PURPOSE

Prospectively measure change in vaginal length after definitive chemoradiation (C-EBRT) with Intracavitary Brachytherapy (ICBT) for locally advanced cervix cancer (LACC) and correlate with vaginal dose (VD).

MATERIALS AND METHODS

Twenty one female patients with LACC receiving C-EBRT and ICBT underwent serial vaginal length (VL) measurements. An initial measurement was made at the time of the first ICBT procedure and subsequently at 3 month intervals up to 1 year post radiation. The vagina was contoured as a 3-dimensional structure for each brachytherapy plan. The difference in VL before and at least 6 months after the last fraction of brachytherapy was considered as an indicator of toxicity.

RESULTS

The mean initial VL was 8.7 cm (6.5-12) with median value of 8.5 cm. The mean VL after 6 months was 8.6 cm (6.5-12) and VL change was not found to be statistically significant. The median values (interquartile ranges) for vaginal D0.1cc, D1cc, and D2cc were 129.2 Gy (99.6-252.2), 96.9 Gy (84.2-114.9), and 89.6 Gy (82.4-102.2), respectively. No significant correlation was found between vaginal length change and the dosimetric parameters calculated for all patients.

CONCLUSION

Definitive C-EBRT and ICBT did not significantly impact VL in this prospective cohort probably related to acceptable doses per ICRU constraints. Estimate of vaginal stenosis and sexual function was not performed in this cohort which is a limitation of this study and which we hope to study prospectively going forward.

Optimizing Online Adaptation Timing in the Treatment of Locally Advanced Cervical Cancer

PURPOSE

Online adaptive radiation therapy (ART) has emerged as a new treatment modality for cervical cancer. Daily online adapting improves target coverage and organ-at-risk (OAR) sparing compared with traditional image guided radiation therapy (IGRT); however, the required resources may not be feasible in a busy clinical setting. Less frequent adapting may still benefit cervical cancer patients due to large volume changes of the uterocervix of the treatment course. In this study, the dosimetry from different online adapt-on-demand schedules was compared.

MATERIALS AND METHODS

A retrospective cohort of 10 patients with cervical cancer treated with 260 fractions of definitive daily online ART was included. Plans with different adaptation schedules were simulated with adaptations weekly, every other week, once during treatment, and no adaptations (IGRT). These plans were applied to the synthetic computed tomography (CT) images and contours generated during the patient's delivered daily adaptive workflow. The dosimetry of the weekly replan, every-other-week replan, once replan, and IGRT plans were compared using a paired t test.

RESULTS

Compared with traditional IGRT plans, weekly and every-other-week ART plans had similar clinical target volume (CTV) coverage, but statistically significant improved sparing of OARs. Weekly and every-other-week ART had reduced bowel bag V40 by 1.57% and 1.41%, bladder V40 by 3.82% and 1.64%, rectum V40 by 8.49% and 7.50%, and bone marrow Dmean by 0.81% and 0.61%, respectively. Plans with a single adaptation had statistically significantly worse target coverage, and moderate improvements in OAR sparing. Of the 18-dose metrics evaluated, improvements were seen in 15 for weekly ART, 14 for every-other-week ART, and 10 for single ART plans compared with IGRT. When every-other-week ART was compared with weekly ART, both plans had similar CTV coverage and OAR sparing with only small improvements in bone marrow dosimetry with weekly ART.

CONCLUSIONS

This retrospective work compares different adapt-on-demand treatment schedules using data collected from patients treated with daily online adaptive radiation therapy. Results suggest weekly or every-other-week online ART is beneficial for reduced OAR dose compared with IGRT by exploiting the gradual changes in the uterocervix target volume.

Improved Dosimetry with Daily Online Adaptive Radiotherapy for Cervical Cancer: Waltzing the Pear

AIMS

Standard of care radiotherapy for locally advanced cervical cancer includes large margins to ensure the uterocervix remains within the treatment fields over the course of treatment. Daily online cone-beam adaptive radiotherapy corrects for interfractional changes by adjusting the plan to match the target position during each treatment session, thus allowing for significantly reduced clinical target volume (CTV) to planning target volume (PTV) margins. We hypothesise that reduced margins from daily online adaptive radiotherapy will reduce organ at risk dose without compromising target coverage.

MATERIALS AND METHODS

Ten patients with cervical cancer (stage IIB-IIIC2) were treated with definitive chemoradiation using daily online cone-beam adaptive radiotherapy in 25-27 fractions. Initial and all adapted treatment plans were generated with CTV to PTV margins versus standard of care image-guided radiotherapy (IGRT) plans as follows: cervix/uterus/gross tumour volume (0.5 versus 1.5 cm), parametria/vagina (0.5 versus 1.0 cm) and nodal chains and gross nodes (0.5 versus 0.5 cm). IGRT plans were created and copied to synthetic computed tomography scans and contours generated from each daily adapted fraction. The dosimetry of each clinically treated online adapted fraction was compared with emulated IGRT plans. Statistical significance was defined as P < 0.05.

RESULTS

Daily online cone-beam adaptive radiotherapy significantly improves bowel bag dosimetry compared with IGRT, with a reduction in V40 by an average of 91.3 cm3 [V40 (-6.2%) and V45 (-6.1%)]. The daily adapted plans showed significant improvements in bladder and rectum [V40 (-25.2% and -36.0%) and V30 (-9.7% and -17.1%), respectively]. Additionally, bone marrow had a significantly reduced dose [V10 (-2.7%) and V20 (-3.3%)]. Daily online cone-beam adaptive radiotherapy improved uterocervix CTV coverage and reduced hotspots compared with IGRT [D95% (+1.6%) and Dmax (-0.9%)].

CONCLUSIONS

Reduced CTV to PTV margins achievable with daily online adaptive radiotherapy improves organ at risk dosimetry and target coverage when compared with standard of care IGRT for locally advanced cervical cancer. The clinical impact of improved dosimetry is currently undergoing investigation.

A Tale of Two Hospitals: Effect of Access to Care Through a Safety Net Hospital on Adjuvant Therapy, Imaging Compliance and 5-Year Survival Rates Compared to the University Hospital Served by the Same Breast Cancer Clinical Teams

RATIONALE AND OBJECTIVES

To compare rates of guideline-concordant care, imaging surveillance, recurrence and survival outcomes between a safety-net (SNH) and tertiary-care University Hospital (UH) served by the same breast cancer clinical teams.

MATERIALS AND METHODS

647 women with newly diagnosed breast cancer treated in affiliated SNH and UH between 11.1.2014 and 3.31.2017 were reviewed. Patient demographics, completion of guideline-concordant adjuvant chemotherapy, radiation and hormonal therapy were recorded. Two multivariable logistic regression models were performed to investigate the effect of hospital and race on cancer stage. Kaplan-Meier log-rank and Cox-regression were used to analyze five-year recurrence-free (RFS) and overall survival (OS) between hospitals and races, (p < 0.05 significant).

RESULTS

Patients in SNH were younger (mean SNH 53.2 vs UH 57.9, p < 0.001) and had higher rates of cT3/T4 disease (SNH 19% vs UH 5.5%, p < 0.001). Patients in the UH had higher rates of bilateral mastectomy (SNH 17.6% vs UH 40.1% p < 0.001) while there was no difference in the positive surgical margin rate (SNH 5.0% vs UH 7.6%, p = 0.20), completion of adjuvant radiation (SNH 96.9% vs UH 98.7%, p = 0.2) and endocrine therapy (SNH 60.8% vs UH 66.2%, p = 0.20). SNH patients were less compliant with mammography surveillance (SNH 64.1% vs UH 75.1%, p = 0.02) and adjuvant chemotherapy (SNH 79.1% vs UH 96.3%, p < 0.01). RFS was lower in the SNH (SNH 54 months vs UH 57 months, HR 1.90, 95% CI: 1.18-3.94, p = 0.01) while OS was not significantly different (SNH 90.5% vs UH 94.2%, HR 1.78, 95% CI: 0.97-3.26, p = 0.06).

CONCLUSION

In patients experiencing health care disparities, having access to guideline-concordant care through SNH resulted in non-inferior OS to those in tertiary-care UH.

The accuracy of artificial intelligence deformed nodal structures in cervical online cone-beam-based adaptive radiotherapy

Background and Purpose

Online cone-beam-based adaptive radiotherapy (ART) adjusts for anatomical changes during external beam radiotherapy. However, limited cone-beam image quality complicates nodal contouring. Despite this challenge, artificial-intelligence guided deformation (AID) can auto-generate nodal contours. Our study investigated the optimal use of such contours in cervical online cone-beam-based ART.

Materials and Methods

From 136 adaptive fractions across 21 cervical cancer patients with nodal disease, we extracted 649 clinically-delivered and AID clinical target volume (CTV) lymph node boost structures. We assessed geometric alignment between AID and clinical CTVs via dice similarity coefficient, and 95% Hausdorff distance, and geometric coverage of clinical CTVs by AID planning target volumes by false positive dice. Coverage of clinical CTVs by AID contour-based plans was evaluated using D100, D95, V100%, and V95%.

Results

Between AID and clinical CTVs, the median dice similarity coefficient was 0.66 and the median 95 % Hausdorff distance was 4.0 mm. The median false positive dice of clinical CTV coverage by AID planning target volumes was 0. The median D100 was 1.00, the median D95 was 1.01, the median V100% was 1.00, and the median V95% was 1.00. Increased nodal volume, fraction number, and daily adaptation were associated with reduced clinical CTV coverage by AID-based plans.

Conclusion

In one of the first reports on pelvic nodal ART, AID-based plans could adequately cover nodal targets. However, physician review is required due to performance variation. Greater attention is needed for larger, daily-adapted nodes further into treatment.

Definitive ablative stereotactic partial breast irradiation in early stage inoperable breast cancer

PURPOSE

This case series and literature review aims to investigate the efficacy and safety of definitive ablative radiation therapy as a treatment modality for non-operable patients with early stage breast cancer. We present two cases demonstrating the potential of this approach to achieve durable responses.

METHODS

We assessed the long-term response of two non-operable patients diagnosed with Stage II (cT2N0M) and Stage IA (T1bN0M0) invasive ductal carcinoma (IDC), who were deemed unfit for surgery due to significant co-morbid conditions. Definitive ablative radiation therapy was administered using stereotactic partial breast irradiation with ablative doses delivered in either a single fraction or two fractions. Serial imaging was conducted to assess treatment response and monitor adverse events.

RESULTS

Both patients exhibited notable treatment responses following definitive ablative radiation therapy. The first patient, an 84-year-old woman, experienced a 69% reduction in tumor size over a follow-up period exceeding 2 years. The second patient, an 87-year-old woman, achieved complete resolution of disease on imaging, with no signs of progression even 26 month post-treatment. Both patients tolerated the treatment well, without significant treatment-related adverse events.

CONCLUSIONS

Our case series suggests that definitive ablative radiation therapy may serve as a safe and effective treatment option for non-operable patients with early stage breast cancer. The observed durable treatment responses and minimal toxicity support the potential of this approach. Furthermore, a longer interval between ablative radiation therapy and surgery may enhance treatment response, potentially leading to increased complete pathologic response rates.

Optimal sites for agricultural and forest residues energy conversion plant using geographic information system

The Federal Government of Nigeria (FGN) has committed to net-zero emission development pathways to respond to the Paris Agreement adopted in 2015. However, the country is in dire need of energy to support its developmental ambitions. Therefore, it is necessary to consider green energy technologies to support both socioeconomic development and to meet the FGN's emission reduction target. In view of this, the current work presents the optimal sites for bioenergy plants in a state in Nigeria using Geographic Information System (GIS). Key findings suggest that 62.03 PJ/yr and 4.12 PJ/yr of energy could be derived from crop residues and forest residues, respectively, to support the state's bioenergy development. The crop residues considered include plantain (stem), oil palm (shell and fibre), maize (stalks) and cassava (peel and stalks). Six criteria were used in selecting the optimal sites, and include biomass residue distribution, settlement, road accessibility, nearness to waterline, slope and aspect. These criteria were incorporated into the ArcGIS platform through the weighted overlay tool. Strategically, the analysis presents seven sites for biomass plants to sustainably meet part of the energy needs. The efforts of the current work which supports not less than three SDGs-SDG 7 (Clean and Affordable Energy), SDG 12 (Responsible Consumption and Production) and SDG 13 (Climate Action), will assist policymakers in Nigeria to make appropriate policies within the climate change space.

A deep learning approach for automatic delineation of clinical target volume in stereotactic partial breast irradiation (S-PBI)

Accurate and efficient delineation of the clinical target volume (CTV) is of utmost significance in post-operative breast cancer radiotherapy. However, CTV delineation is challenging as the exact extent of microscopic disease encompassed by CTV is not visualizable in radiological images and remains uncertain. We proposed to mimic physicians' contouring practice for CTV segmentation in stereotactic partial breast irradiation (S-PBI) where CTV is derived from tumor bed volume (TBV) via a margin expansion followed by correcting the extensions for anatomical barriers of tumor invasion (e.g. skin, chest wall). We proposed a deep-learning model, where CT images and the corresponding TBV masks formed a multi-channel input for a 3D U-Net based architecture. The design guided the model to encode the location-related image features and directed the network to focus on TBV to initiate CTV segmentation. Gradient weighted class activation map (Grad-CAM) visualizations of the model predictions revealed that the extension rules and geometric/anatomical boundaries were learnt during model training to assist the network to limit the expansion to a certain distance from the chest wall and the skin. We retrospectively collected 175 prone CT images from 35 post-operative breast cancer patients who received 5-fraction partial breast irradiation regimen on GammaPod. The 35 patients were randomly split into training (25), validation (5) and test (5) sets. Our model achieved mean (standard deviation) of 0.94 (±0.02), 2.46 (±0.5) mm, and 0.53 (±0.14) mm for Dice similarity coefficient, 95th percentile Hausdorff distance, and average symmetric surface distance respectively on the test set. The results are promising for improving the efficiency and accuracy of CTV delineation during on-line treatment planning procedure.

Aspirin use is associated with improvement in distant metastases outcome in patients with residual disease after neoadjuvant chemotherapy

PURPOSE

Aspirin (ASA) use has been correlated with improved outcomes in high-risk patients at risk for distant metastases. Breast cancer (BC) patients with residual disease, particularly nodal disease (ypN +) after neoadjuvant chemotherapy (NAC), are high-risk patients portending worse outcomes. We hypothesized that ASA use can reduce distant metastases and improve outcomes in these patients.

METHODS

Patients at our institutions from 2005 to 2018, with BC who did not achieve complete response (pCR) after NAC were reviewed (IRB protocol STU- 052012-019). Data, including evidence of ASA use, and clinico-pathologic parameters were analyzed. Survival outcomes were obtained (Kaplan Meier analysis) and univariate (UVA) and multivariable (MVA) Cox proportional hazards regression analyses were performed.

RESULTS

637 did not achieve pCR (ypN+ = 422). 138 were ASA users. Median follow-up for the control and ASA group were 3.8 (IQR 2.2-6.3) and 3.8 (IQR 2.5-6.4) years, respectively. Majority were stage II/III. 387 were hormone receptor positive, 191 HER2 +, and 157 triple negative. On UVA, ASA use, PR status, pathologic and clinical stage showed significance for DMFS, and disease-free survival (DFS). On MVA, ASA use associated with improved 5-year DFS (p = .01, 87.0% vs 79.6%, adjusted HR = 0.48) and improved 5-year DMFS (p = .04, 92.8% vs 89.2%, adjusted HR = 0.57). In the ypN + patients, ASA use associated with improved 5-year DMFS (p = .008, 85.7% vs 70.7%, adjusted HR = 0.43) and DFS (p = .02, 86.8% vs 74.3%, adjusted HR = 0.48).

CONCLUSION

For non-responders, particularly ypN + patients, ASA use associated with improved outcome. These hypotheses-generating results suggest for development of prospective clinical trials of augmented ASA use in selected very high-risk BC patients.

Spare the Bowel, Don't Spoil the Target: Optimal Margin Assessment for Online Cone Beam Adaptive Radiation Therapy (OnC-ART) of the Cervix

PURPOSE

The standard treatment for locally advanced cervical cancer involves pelvic chemoradiation. Intensity modulated radiation therapy planning requires expansion of the cervix and uterus clinical target volume (CTV) by 1.5 to 2 cm to account for motion. With online cone beam adaptive radiation therapy (OnC-ART), interfractional movement is accounted for, which can potentially lead to smaller CTV to planned target volume (PTV) margins. In this study, we attempted to determine the optimal CTV-to-PTV margin for adequate coverage with OnC-ART and factors that can affect CTV coverage.

METHODS AND MATERIALS

A retrospective cohort of 21 patients with cervical cancer treated with definitive chemoradiation was included. Nine patients treated with nonadaptive radiation had the uterocervix contoured on pretreatment cone beam computed tomography (CBCT) and end-treatment CBCTs. Anterior-posterior, lateral, and superior-inferior shifts and the average shift in all directions were calculated. A CTV-to-PTV expansion was determined and verified on a validation cohort of 12 patients treated with OnC-ART.

RESULTS

The average anterior-posterior, lateral, and superior-inferior shifts with standard deviation were 0.32 ± 1.55 cm, 0.12 ± 2.31 cm, and 1.67 ± 3.41 cm, respectively. A uniform 5-mm expansion around the pretreatment CTV covered 98.85% ± 1.23% of the end-treatment CTV. This 5-mm expansion was applied to our validation cohort treated with OnC-ART, and 98.39% ± 3.0% of the end-treatment CTV was covered. Time between CBCTs >30 minutes and change in bladder volume were significantly correlated to CTV coverage.

CONCLUSIONS

Based on our analysis, a CTV-to-PTV margin of 5 mm is adequate to encompass 98% of the CTV. A significantly reduced margin could potentially decrease the toxicities associated with radiation for patients with cervical cancer and lead to improved patient reported toxicity outcomes. We recommend physicians begin with a 5-mm margin and assess adequate coverage with image guidance during daily adaptation.

Aspirin Use Is Associated With Improved Outcomes in Inflammatory Breast Cancer Patients

PURPOSE

Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer and has a high propensity for distant metastases. Our previous data suggested that aspirin (acetylsalicylic acid, ASA) use may be associated with reduced risk of distant metastases in aggressive breast cancer; however, there are no reported studies on the potential benefit of ASA use in patients with IBC.

METHODS

Data from patients with non-metastatic IBC treated between 2000-2017 at two institutions, were reviewed. Overall survival (OS), disease-free survival (DFS), and distant metastasis-free survival (DMFS) were performed using Kaplan-Meier analysis. Univariate and multivariable logistic regression models were used to identify significant associated factors.

RESULTS

Of 59 patients meeting the criteria for analysis and available for review, 14 ASA users were identified. ASA users demonstrated increased OS (p = 0.03) and DMFS (p = 0.02), with 5-year OS and DMFS of 92% (p = 0.01) and 85% (p = 0.01) compared to 51% and 43%, respectively, for non-ASA users. In univariate analysis, pT stage, pN stage, and ASA use were significantly correlated (p < 0.05) with OS and DFS. On multivariable analysis, ASA use (hazard ratio [HR], 0.11; 95% confidence interval [CI], 0.01-0.8) and lymph node stage (HR, 5.9; 95% CI, 1.4-25.9) remained significant for OS and DFS ASA use (HR, 0.13; 95% CI, 0.03-0.56) and lymph node stage (HR, 5.6; 95% CI, 1.9-16.4).

CONCLUSION

ASA use during remission was associated with significantly improved OS and DMFS in patients with IBC. These results suggest that ASA may provide survival benefits to patients with IBC. Prospective clinical trials of ASA use in patients with high-risk IBC in remission should be considered.

On the feasibility of improved target coverage without compromising organs at risk using online adaptive stereotactic partial breast irradiation (A-SPBI)

PURPOSE

Describe an early-adopting institution's experience with online adaptive radiation for stereotactic partial breast irradiation.

METHODS AND MATERIALS

Retrospective review of 22 women treated between May 2021 and March 2022 with adaptive stereotactic partial breast irradiation. A total of 106 of 110 fractions were evaluated for dosimetric changes in target coverage and organ-at-risk (OAR) dose. Patient set up with stereotactic wooden frame and adapted per fraction. Treatment and planning times were collected prospectively by radiation therapists.

RESULTS

Scheduled PTV_30 Gy was <95% in 72.1% and <90% in 38.5% of fractions, and both PTV and CTV coverage were improved significantly after adaption, and 83.7% of fractions were delivered as adapted per physician choice. There was no difference in OAR coverage. Average adaptive treatment planning took 15 min and average time-on-couch was 34.4 min.

CONCLUSIONS

Adaptive stereotactic breast irradiation resulted in improved target coverage with equivalent dosing to OARs in an efficient and tolerated treatment time. Improved target coverage allowed for decreased PTV margins compared to prior trial protocols that may improve acute and late toxicities.

A How-To Compendium for GammaPod Treatments, Clinical Workflow, and Clinical Program at an Early Adopting Institution

Breast irradiation following breast-conserving surgery is an integral part of breast conserving therapy for curative treatment of early-stage breast cancer^1-7. With the recognition that the majority of ipsilateral local relapses following breast-conserving therapy occur at the site of the tumor bed, several trials have since investigated the efficacy of accelerated partial-breast irradiation (APBI)^8-10 as an alternative to the established but less convenient option of daily whole breast irradiation over several weeks. However, the setup uncertainty and inter-fraction movement expected with 3-dimensional conformal radiation therapy (3D-CRT) APBI has generally required the use of larger planning target volume margin expansions, which ultimately results in a larger dose to normal tissues, as well as an association with worsened cosmesis^11-13. A stereotactic partial breast irradiation (S-PBI) approach is needed to allow more precise radiation therapy to the region of the primary tumor. As the GammaPod uses a vacuum assisted breast cup and pump, it allows for smaller CTV margins than 3D-CRT. Here, we describe our methods and workflow for efficient GammaPod S-PBI, as the second institution in the world to go live with GammaPod.

Saliency-guided deep learning network for automatic tumor bed volume delineation in post-operative breast irradiation

Efficient, reliable and reproducible target volume delineation is a key step in the effective planning of breast radiotherapy. However, post-operative breast target delineation is challenging as the contrast between the tumor bed volume (TBV) and normal breast tissue is relatively low in CT images. In this study, we propose to mimic the marker-guidance procedure in manual target delineation. We developed a saliency-based deep learning segmentation (SDL-Seg) algorithm for accurate TBV segmentation in post-operative breast irradiation. The SDL-Seg algorithm incorporates saliency information in the form of markers' location cues into a U-Net model. The design forces the model to encode the location-related features, which underscores regions with high saliency levels and suppresses low saliency regions. The saliency maps were generated by identifying markers on CT images. Markers' location were then converted to probability maps using a distance transformation coupled with a Gaussian filter. Subsequently, the CT images and the corresponding saliency maps formed a multi-channel input for the SDL-Seg network. Our in-house dataset was comprised of 145 prone CT images from 29 post-operative breast cancer patients, who received 5-fraction partial breast irradiation (PBI) regimen on GammaPod. The 29 patients were randomly split into training (19), validation (5) and test (5) sets. The performance of the proposed method was compared against basic U-Net. Our model achieved mean (standard deviation) of 76.4(±2.7) %, 6.76(±1.83) mm, and 1.9(±0.66) mm for Dice similarity coefficient, 95 percentile Hausdorff distance, and average symmetric surface distance respectively on the test set with computation time of below 11 seconds per one CT volume. SDL-Seg showed superior performance relative to basic U-Net for all the evaluation metrics while preserving low computation cost. The findings demonstrate that SDL-Seg is a promising approach for improving the efficiency and accuracy of the on-line treatment planning procedure of PBI, such as GammaPod based PBI.

Retention and motivation of health workers in remote and rural areas in Cross River State, Nigeria: a discrete choice experiment

BACKGROUND

Cross River State is making investments geared towards ensuring equitable distribution and improved retention of its frontline health workforce in remote and rural areas. This informed the conduct of a discrete choice experiment to determine the motivating factors supporting the retention of healthcare workers.

METHODS

Study participants were 198 final year students of nursing, midwifery and community health and frontline health workers. Eight focus group discussions and 38 key informant interviews were conducted to obtain information about the dimensions of the work conditions that are important to frontline health workers when choosing to take up posting or stay in their rural work locations.

RESULTS

Health workers are 2.7 times more likely to take up a rural posting or continue to stay in their present rural duty posts if they receive a salary increment. They are also four times more likely to take a rural job posting if a basic housing or a housing allowance is provided.

CONCLUSION

Improving working conditions of frontline health workers in terms of adequate staff strength, good skills mix and equipment, etc., as well as improving opportunities for career advancement will support retention in rural health posts.

Recurrence risk factors in stage IA grade 1 endometrial cancer

OBJECTIVES

Patients with early-stage endometrial cancers (EC) with disease recurrences have worse survival outcomes. The purpose of this study was to identify clinical and pathologic factors that predict for all recurrences in stage IA grade 1 (IAG1) EC.

METHODS

Records from patients diagnosed with EC were retrospectively reviewed. Baseline characteristics of 222 patients with IAG1 EC who underwent surgical resection were analyzed. Cox proportional hazard analysis was used to identify univariate and multivariate risk factors that predict for recurrence.

RESULTS

Seventeen (7.65%) patients had recurrences. The 3-year cumulative incidence of recurrence were significantly higher for patients with time from biopsy to surgery ≥6 months (54% vs. 8%, p=0.003), simple hysterectomy with ovarian preservation vs. total hysterectomy and bilateral salpingo-oophorectomy (31% vs. 9%, p=0.032), any myometrial invasion vs. no invasion (18% vs. 2%, p=0.004), and tumor size ≥2 cm (15% vs. 2%, p=0.021). On, multivariate analysis, any myometrial invasion, increasing time from biopsy to surgery, and larger tumor size were independent predictors of any recurrence. Patients with recurrences had worse outcomes than those without (5-year overall survival [OS]=60%; 95% confidence interval [CI]=16%-86% vs. 5-year OS=95%; 95% CI=87%-99%, respectively, p=0.003).

CONCLUSION

Time from biopsy to surgery, larger tumors, and myometrial invasion are the most important predictors of recurrence. Though the recurrence rates are generally low in IAG1 EC, the survival rate for the patients with recurrences was worse than those without. Identification of additional recurrence risk factors can help select patients who may benefit from adjuvant treatment.

Updating and Optimizing Anatomic Atlases for Elective Radiation of Para-Aortic Lymph Nodes in Cervical Cancer

PURPOSE

Previous studies have proposed 2 different contouring guidelines for the prophylactic radiation of para-aortic lymph nodes (PANs) for locally advanced cervical cancer. Because PAN-mapping atlases in current literature are limited to small patient samples and nodal populations, we updated the PAN atlas with a large data set of positron emission tomography (PET)-positive PANs on PET/computed tomography (CT) from patients with cervical cancer.

METHODS AND MATERIALS

We identified 176 PET-positive PANs on pretreatment PET/CT of 47 patients with diagnosed International Federation of Gynecology and Obstetrics stage IB to IVA cervical cancer. PANs were classified as left-lateral para-aortic (LPA), aortocaval (AC), or right paracaval (RPC). PAN clinical target volume (CTV) contours were drawn for all patients based on previously published guidelines by Takiar (CTV-T) and Keenan (CTV-K) and nodal volumetric coverage was assessed.

RESULTS

We identified 94 LPA nodes (54%), 71 AC nodes (40%), and 11 (6%) RPC nodes. CTV-T had improved nodal center coverage of 97.6% compared with 85.0% for CTV-K (P < .001). Nodal center coverage for CTV-K and CTV-T (with corresponding PAN) were 79 (84.0%) and 93 (99.0%) LPA nodes (P = .001), 64 (90.1%) and 68 (95.8%) AC nodes (P = .221), and 5 (45.5%) and 9 (81.8%) RPC nodes (P = .134), respectively. Additionally, our updated PAN atlas identified nodal centers anterior to the aorta and inferior vena cava that are not covered by CTV-T but covered by CTV-K due to the 10 mm anterior aortic expansion of CTV-K.

CONCLUSIONS

We have updated the PAN anatomic map of 176 PET-positive nodes from 47 patients and demonstrated that CTV-T has significantly better PAN coverage over CTV-K for posterior LPA and retrocaval regions for our data set. Additionally, we suggest a modification that includes a blend of CTV-T and CTV-K to provide optimal coverage for the mapped nodes anterior to the great vessels in our data set.

Postoperative analgesic effect of intrathecal dexmedetomidine on bupivacaine subarachnoid block for open reduction and internal fixation of femoral fractures

Background

One of the drawbacks of subarachnoid block is the short duration of analgesia particularly when adjuvants are not added to local anesthetics agent used. However, dexmedetomidine an α_2-adrenergic agent has been found to possess analgesic effect.

Aims

This study seeks to determine the analgesic efficacy of intrathecal 7.5 μg of dexmedetomidine and its side effects when used for open reduction and internal fixation (ORIF) of femoral fractures.

Methodology

It is a prospective randomized, double-blinded study that was carried out in a Nnamdi Azikiwe University Teaching Hospital, Nnewi in Nigeria. Seventy American Society of Anesthesiologists I or II patients were randomized into two groups of 35 each to receive 3 ml of 0.5% hyperbaric bupivacaine combined with either 7.5 μg of dexmedetomidine in 0.3 ml of normal saline (Group D) or 0.3 ml of normal saline alone (Group S). Patient's outcome measures noted (time to first request of analgesia, proportion of patients with pain score <4 postoperatively using numerical rating scale [NRS], and total analgesic consumed in 24 h.).

Results

The patients in Group D had a longer time to first request of analgesia, larger proportion of patients with pain score <4 using NRS in the 2^nd h postoperatively and lower amount of total analgesic consumed compared to those in Group S. These differences between the two groups were all statistically significant. Furthermore, there was no difference in the incidences of side effects between the two groups (P > 0.05). However, the patient satisfaction was better in Group D.

Conclusion

The addition of 7.5 μg of dexmedetomidine to bupivacaine for subarachnoid block in the management of femoral fractures using ORIF provided better anesthetic profile, particularly prolonged duration of postoperative analgesia without significant side effects.

Workforce Capacity and Capability Building Through Metrics-Based Mentoring Partnerships

Background: Globally, cancer is the second leading cause of death. Low- and middle-income countries (LMICs) especially lack the sufficient healthcare and oncology workforces needed to screen, diagnose and treat individuals with cancer. While traditional academic and training programs designed to produce healthcare professionals in these countries fill a critical role, few programs exist that maintain, develop, and increase the knowledge, skills, and professional performance of current healthcare and oncology workforces. Mentoring partnerships and twinning programs can provide ongoing education and training that strengthen and build workforce capacity and capability for the full scope of cancer care. Aim: The goal is to achieve resource-appropriate multimodality cancer-care using guideline- and protocol-based education and training and also to develop the capability to conduct world quality research. The model utilizes in-person, in-country site visits lasting from several weeks to months and ongoing connectivity through weekly telemedicine video conferences. Methods: The International Cancer Expert Corps (ICEC) and partner organizations are establishing a network of global and multisectoral partnerships that builds human capacity and capability needed to establish sustainable cancer programs that function at world-class standards. The three-fold mentor-mentee approach ( www.iceccancer.org ) is built by 1) enlisting hubs of expertise to include academic medical centers/universities, private practices and an ICEC Central Hub, 2) enrolling the breadth of expert-mentors needed from a university, practice, professional society and interested individuals, and 3) identifying centers in LMICs - clinics/hospitals/and other care delivery sites in underserved areas, and associates - physicians/allied healthcare workers- seeking mentoring and education. Results: Recent implementation of the ICEC 5-Step Progression Plan provides guidance and serves as an assessment tool for measuring progress between the hubs-centers programs and expert-associate. Twinning programs (hubs-ICEC centers) have been established in multiple sites worldwide including in Africa, Asia and Eurasia. Conclusion: Implementation of the ICEC 5-Step Progression Plan provides a platform from which to track the current stages and progress of twinning mentor-mentee programs, and to evaluate new programs. This information guides the programs and also provides metric-based investment in global health. Critically as the skills in associates and ICEC centers grows, they achieve expert-mentor status and centers become hubs to serve the surrounding regions, thereby enabling geometric growth in cancer care to meet the needs of the growing global burden of cancer. The content is the personal opinion of the authors and not their organizations.

Sinoatrial node dysfunction after stereotactic ablative radiation therapy in the chest

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Background: Sinoatrial node (SAN) injury following stereotactic ablative radiation therapy (SABR) in the chest has not been reported in the literature. We report SAN dysfunction as a potential toxicity of SABR in the chest. Methods: We examined the clinical courses and SABR plans of 47 patients treated for T1 or T2 non-small cell lung cancer of the right upper lobe, middle lobe, lower lobe, or hilum. After developing a contouring atlas for the SAN, based upon the junction between the superior vena cava and the right atrium, dose to the SAN was retrospectively determined for each patient. We identified 13 patients whose treatment imparted significant dose to the SAN, as defined by the SAN encompassed within the 10% prescription isodose (IDL) line. Biologically effective doses (BED), acute and chronic, were correlated with SAN toxicity. Results: Patients underwent SABR to the right lung to a dose of 40-50 Gy in 4 or 5 fractions, with mean acute BED (alpha/beta ratio = 10) of 100.2 Gy and late BED (alpha/beta ratio = 3) of 222.7 Gy. Mean volume of the GTV and PTV were 26.1 and 75.1 mL, respectively. Mean follow-up was 25.5 months. The mean volume of the SAN was 0.37 mL. Average max dose and mean dose to the SAN were 24.7 and 70.7 Gy, respectively. Of the 13 patients whose treatment imparted significant dose to the SAN, one patient without prior arrhythmia developed symptomatic SAN dysfunction requiring pacemaker placement at 6 months after completion of treatment. The sinoatrial node of the patient received a maximum dose of 44.8 Gy in 4 fractions, correlated with an acute BED (alpha/beta ratio = 10) of 90 Gy and late BED (alpha/beta ratio = 3) of 194.1 Gy, and a mean dose of 35.5 Gy in 4 fractions, correlated with an acute BED (alpha/beta ratio = 10) of 71 Gy and late BED (alpha/beta ratio = 3) of 153.8 Gy. This was the third highest max dose and second highest mean dose to SAN in the cohort. Conclusions: We report sinoatrial node dysfunction as a potential toxicity of SABR in the chest for non-small cell lung cancer. Caution is advised when treatment imparts significant dose to the sinoatrial node.

Molecular Subtype-Specific Expression of MicroRNA-29c in Breast Cancer Is Associated with CpG Dinucleotide Methylation of the Promoter

Basal-like breast cancer is a molecularly distinct subtype of breast cancer that is highly aggressive and has a poor prognosis. MicroRNA-29c (miR-29c) has been shown to be significantly down-regulated in basal-like breast tumors and to be involved in cell invasion and sensitivity to chemotherapy. However, little is known about the genetic and regulatory factors contributing to the altered expression of miR-29c in basal-like breast cancer. We here report that epigenetic modifications at the miR-29c promoter, rather than copy number variation of the gene, may drive the lower expression of miR-29c in basal-like breast cancer. Bisulfite sequencing of CpG sites in the miR-29c promoter region showed higher methylation in basal-like breast cancer cell lines compared to luminal subtype cells with a significant inverse correlation between expression and methylation of miR-29c. Analysis of primary breast tumors using The Cancer Genome Atlas (TCGA) dataset confirmed significantly higher levels of methylation of the promoter in basal-like breast tumors compared to all other subtypes. Furthermore, inhibition of CpG methylation with 5-aza-CdR increases miR-29c expression in basal-like breast cancer cells. Flourescent In Situ Hybridization (FISH) revealed chromosomal abnormalities at miR-29c loci in breast cancer cell lines, but with no correlation between copy number variation and expression of miR-29c. Our data demonstrated that dysregulation of miR-29c in basal-like breast cancer cells may be in part driven by methylation at CpG sites. Epigenetic control of the miR-29c promoter by epigenetic modifiers may provide a potential therapeutic target to overcome the aggressive behavior of these cancers.

Evaluating dissection in the gross anatomy course: Correlation between quality of laboratory dissection and students outcomes

Anatomy learned by active exploration through dissection has many proven benefits including improvement of anatomic knowledge. Decreased laboratory time may affect the quality of dissection and ultimately lower student performance in anatomy translating to lower knowledge acquisition. The aim of this study was to determine whether the quality of students' dissection in teams correlates with their performance in the gross anatomy course. Quality of dissections for each team enrolled in a gross anatomy course at Mayo Medical School was evaluated biweekly using a five-point rubric based on course learning objectives. Assessment of anatomic knowledge was based on sequential laboratory practice practical examination scores, achievements on daily audience response system (ARS) quizzes, and final practical, written, and National Board of Medical Examiners(®) (NBME(®) ) Gross Anatomy and Embryology Subject Examinations. Twelve teams comprising 48 students were included in the study. There was a positive correlation between dissection quality and practice practical examination score (R = 0.83) and a negative correlation between dissection quality and ARS quizzes (R = -0.985). Dissection teams with a passing score on their dissection evaluations (>70%) performed better on their final examinations. Based on an end of course survey, students agreed that dissection evaluations should continue to be a part of the course. This study showed that better quality of dissection was associated with higher scores on practice practical examinations, final practical, written, and NBME examinations. The study demonstrated a positive correlation between dissection evaluations, accompanied by formative feedback during the course, and higher scores on final course assessments.

Differentiation and loss of malignant character of spontaneous pulmonary metastases in patient-derived breast cancer models

Patient-derived human-in-mouse xenograft models of breast cancer (PDX models) that exhibit spontaneous lung metastases offer a potentially powerful model of cancer metastasis. In this study, we evaluated the malignant character of lung micrometastases that emerge in such models after orthotopic implantation of human breast tumor cells into the mouse mammary fat pad. Interestingly, relative to the parental primary breast tumors, the lung metastasis (met)-derived mammary tumors exhibited a slower growth rate and a reduced metastatic potential with a more differentiated epithelial status. Epigenetic correlates were determined by gene array analyses. Lung met-derived tumors displayed differential expression of negative regulators of cell proliferation and metabolism and positive regulators of mammary epithelial differentiation. Clinically, this signature correlated with breast tumor subtypes. We identified hsa-miR-138 (miR-138) as a novel regulator of invasion and epithelial-mesenchymal transition in breast cancer cells, acting by directly targeting the polycomb epigenetic regulator EZH2. Mechanistic investigations showed that GATA3 transcriptionally controlled miR-138 levels in lung metastases. Notably, the miR-138 activity signature served as a novel independent prognostic marker for patient survival beyond traditional pathologic variables, intrinsic subtypes, or a proliferation gene signature. Our results highlight the loss of malignant character in some lung micrometastatic lesions and the epigenetic regulation of this phenotype.

Changes in presentation, treatment, and outcomes of adult low-grade gliomas over the past fifty years

BACKGROUND

To identify changes in patient presentation, treatment, and outcomes of low-grade gliomas (LGGs) over the past 50 years.

METHODS

Records of 852 adults who received a diagnosis at Mayo Clinic from 1960 through 2011 with World Health Organization grade II LGGs were reviewed and grouped by those who received a diagnosis before (group I: 1960-1989) and after (group II: 1990-2011) the routine use of postoperative MRI.

RESULTS

Median follow-up was 23.3 and 8.7 years for groups I and II, respectively. Patients in group I more often presented with seizures, headaches, sensory/motor impairment, and astrocytoma histology. Over time, more gross total resections (GTRs) were achieved, fewer patients received postoperative radiotherapy (PORT), and more received chemotherapy. Median progression-free survival (PFS) and overall survival (OS) were 4.4 and 8.0 years, respectively. Although PFS was similar, 10-year OS was better in group II (47%) than in group I (33%; P < .0001). Improved PFS in multivariate analysis was associated with group I patients, nonastrocytoma histology, small tumor size, successful GTR, or radical subtotal resection (rSTR), PORT, and postoperative chemotherapy. Factors associated with improved OS in multivariate analysis were younger age, nonastrocytoma histology, small tumor size, and GTR/rSTR.

CONCLUSIONS

OS for LGG has improved over the past 50 years, despite similar rates of progression. In the modern cohort, more patients are receiving a diagnosis of oligodendroglioma and are undergoing extensive resections, both of which are associated with improvements in OS. Because of risk factor stratification by clinicians, the use of PORT has decreased and is primarily being used to treat high-risk tumors in modern patients.

MicroRNA-30c inhibits human breast tumour chemotherapy resistance by regulating TWF1 and IL-11

Chemotherapy resistance frequently drives tumour progression. However, the underlying molecular mechanisms are poorly characterized. Epithelial-to-mesenchymal transition has been shown to correlate with therapy resistance, but the functional link and signalling pathways remain to be elucidated. Here we report that microRNA-30c, a human breast tumour prognostic marker, has a pivotal role in chemoresistance by a direct targeting of the actin-binding protein twinfilin 1, which promotes epithelial-to-mesenchymal transition. An interleukin-6 family member, interleukin-11 is identified as a secondary target of twinfilin 1 in the microRNA-30c signalling pathway. Expression of microRNA-30c inversely correlates with interleukin-11 expression in primary breast tumours and low interleukin-11 correlates with relapse-free survival in breast cancer patients. Our study demonstrates that microRNA-30c is transcriptionally regulated by GATA3 in breast tumours. Identification of a novel microRNA-mediated pathway that regulates chemoresistance in breast cancer will facilitate the development of novel therapeutic strategies.

Abstract 5337: MicroRNA-30c targets cytoskeleton genes involved in breast cancer cell invasion

Metastasis remains a significant challenge in treating cancer. MicroRNAs have emerged as important epigenetic regulators of various cellular processes during cancer development and progression. The goal of this study was to characterize signaling pathways for miRNA biomarkers that regulate breast cancer metastasis. Here we show that human breast tumor biomarker miR-30c regulates invasion by targeting the cytoskeleton network genes encoding Twinfilin 1 (TWF1) and Vimentin (VIM). Both VIM and TWF1 have been shown to regulate epithelial-to-mesenchymal transition (EMT). Similar to TWF1, VIM also regulates F-actin formation, a key component of cellular transition to a more invasive mesenchymal phenotype. To further characterize the role of the TWF1 pathway in breast cancer, we found that IL-11 is an important target of TWF1 that regulates breast cancer cell invasion and STAT3 phosphorylation. This miR-30c VIM/TWF1-IL11-pSTAT3 pathway will expedite the development of targeting strategies to prevent and treat breast tumor progression.

Citation Format: Jessica Bockhorn, Kathy Yee, Ya-Fang Chang, Aleix Prat, Dezheng Huo, Chika Nwachukwu, Rachel Dalton, Simo Huang, Kaitlin E. Swanson, Charles M. Perou, Olufunmilayo I. Olufunmilayo, Michael F. Clarke, Huiping Liu, Geoffrey Greene. MicroRNA-30c targets cytoskeleton genes involved in breast cancer cell invasion. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5337. doi:10.1158/1538-7445.AM2013-5337

Abstract 832: MicroRNA-30c inhibits human breast tumor chemo-resistance by regulating twinfinlin-1 (TWF1) and IL-11

Chemotherapy resistance remains a challenging problem in the clinic and the underlying molecular mechanisms are poorly characterized. We hypothesize that epithelial-to-mesenchymal transition (EMT) is involved in therapy resistance and cancer progression, but the functional link and signalling pathways need to be elucidated. Our work discovered that miR-30c, a human breast tumour prognostic marker, plays a pivotal role in chemo-resistance and apoptosis by a direct targeting of TWF1, which encodes an actin-binding protein and promotes EMT. We also identified IL-11 as a secondary target of TWF1 in the miR-30c signalling pathway. Expression of miR-30c inversely correlated with TWF1 and IL-11 levels in primary breast tumours and low IL-11 associated with relapse-free survival in breast cancer patients. Furthermore, our study demonstrates that miR-30c is transcriptionally regulated by GATA3 in breast tumours. Identification of a novel miRNA-mediated pathway that regulates chemo-resistance and apoptosis in breast cancer will facilitate the development of novel therapeutic strategies.

This study was supported in part by The University of Chicago Women's Board (J.B.) and Chicago Fellows Program (H.L.), DOD W81XWH-09-1-0331, NIH K12 CA139160-02, NCI K99 CA160638-01A1, CTSA UL1 RR024999 (H.L.), Segal Fund and Ludwig Fund (G.L.G.).

Citation Format: Huiping Liu, Jessica Bockhorn, Rachel Dalton, Chika Nwachukwu, Simo Huang, Aleix Prat, Kathy Yee, Ya-Fang Chang, Dezheng Huo, Jun Lu, Eileen Dolan, Charles M. Perou, Olufunmilayo I. Olopade, Michael F. Clarke, Geoffrey Greene. MicroRNA-30c inhibits human breast tumor chemo-resistance by regulating twinfinlin-1 (TWF1) and IL-11. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 832. doi:10.1158/1538-7445.AM2013-832

MicroRNA-30c targets cytoskeleton genes involved in breast cancer cell invasion

Metastasis remains a significant challenge in treating cancer. A better understanding of the molecular mechanisms underlying metastasis is needed to develop more effective treatments. Here, we show that human breast tumor biomarker miR-30c regulates invasion by targeting the cytoskeleton network genes encoding twinfilin 1 (TWF1) and vimentin (VIM). Both VIM and TWF1 have been shown to regulate epithelial-to-mesenchymal transition. Similar to TWF1, VIM also regulates F-actin formation, a key component of cellular transition to a more invasive mesenchymal phenotype. To further characterize the role of the TWF1 pathway in breast cancer, we found that IL-11 is an important target of TWF1 that regulates breast cancer cell invasion and STAT3 phosphorylation. The miR-30c-VIM/TWF1 signaling cascade is also associated with clinical outcome in breast cancer patients.

Basal-like Breast cancer DNA copy number losses identify genes involved in genomic instability, response to therapy, and patient survival

Breast cancer is a heterogeneous disease with known expression-defined tumor subtypes. DNA copy number studies have suggested that tumors within gene expression subtypes share similar DNA Copy number aberrations (CNA) and that CNA can be used to further sub-divide expression classes. To gain further insights into the etiologies of the intrinsic subtypes, we classified tumors according to gene expression subtype and next identified subtype-associated CNA using a novel method called SWITCHdna, using a training set of 180 tumors and a validation set of 359 tumors. Fisher's exact tests, Chi-square approximations, and Wilcoxon rank-sum tests were performed to evaluate differences in CNA by subtype. To assess the functional significance of loss of a specific chromosomal region, individual genes were knocked down by shRNA and drug sensitivity, and DNA repair foci assays performed. Most tumor subtypes exhibited specific CNA. The Basal-like subtype was the most distinct with common losses of the regions containing RB1, BRCA1, INPP4B, and the greatest overall genomic instability. One Basal-like subtype-associated CNA was loss of 5q11-35, which contains at least three genes important for BRCA1-dependent DNA repair (RAD17, RAD50, and RAP80); these genes were predominantly lost as a pair, or all three simultaneously. Loss of two or three of these genes was associated with significantly increased genomic instability and poor patient survival. RNAi knockdown of RAD17, or RAD17/RAD50, in immortalized human mammary epithelial cell lines caused increased sensitivity to a PARP inhibitor and carboplatin, and inhibited BRCA1 foci formation in response to DNA damage. These data suggest a possible genetic cause for genomic instability in Basal-like breast cancers and a biological rationale for the use of DNA repair inhibitor related therapeutics in this breast cancer subtype.

Abstract 3331: MicroRNAs regulate breast cancer stem cells and spontaneous metastases in orthotopic xenograft models

To examine the role of microRNAs (miRNAs) in breast cancer progression, we profiled miRNA and gene expression in both clinical breast tumors and human-in-mouse breast tumor models, where breast cancer stem cells (BCSCs) contribute to spontaneous metastasis. CD44+ cells from both primary tumors and lung metastases were highly enriched for tumor initiating cells. Based on the miRNA profile analyses, we identified a limited number of miRNAs that are differentially expressed in metastatic triple-negative breast tumors and regulate BCSCs and tumor invasion in vitro. To facilitate miRNA functional studies in vivo, we also developed tumor imaging approaches by transducing BCSCs with optical reporter fusion genes (Luc2-eGFP or -tdTomato), which enabled both bioluminescence imaging (BLI) and FACS-based analysis and sorting. With non-invasive BLI approaches, as few as 10 cells of stably labeled BCSCs can be tracked in vivo. When optical reporters are expressed along with miRNA precursors or inhibitors, the effects of introduced miRNA candidates can be evaluated by selective imaging of labeled tumor cells, thereby eliminating the noise of unlabeled cells. Using this model system and imaging technology, we have screened and identified miRNAs that regulate BCSCs and metastatic CSCs (MCSCs) by targeting polycomb repressors (BMI1 and the PC2 components) and cytoskeleton genes (TWF1 and VIM). Clinical studies demonstrated that the expression of candidate miRNAs was associated with and regulated by GATA3, suggesting a transcriptional regulation of aberrantly expressed miRNAs in breast tumors. The GATA3-miRNA-target genes signaling pathway was also strongly associated with relapse-free survival of breast cancer patients, indicating the clinical importance of the miRNA-gene network in breast cancer. Supported in part by the University of Chicago Women's Board Fellowship (J.B.), NIH T90 Fellowship DK070103-05, DOD Postdoctoral Fellowship W81XWH-09-1-0331, and Chicago Fellows Program and CTSA UL1 RR024999 at The University of Chicago (H.L.), University of Chicago Cancer Research Center Pilot Research Fund, UCMC/Northshore Collaborative Research Award and the Virginia and D.K. Ludwig Fund (G.L.G and H.L). NIH R01 and Breast Cancer Research Foundation (M.F.C. and H.L.).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3331. doi:1538-7445.AM2012-3331

Abstract 3004: Specific microRNAs associate with aggressive breast tumor phenotypes in an ethnically diverse patient cohort

Background: Sporadic basal like breast cancer (BLC), a subset of triple negative tumors with bad prognosis appears to be overrepresented in young women and women of African Ancestry. The molecular drivers of basal like and triple negative tumors have not been identified and there is a lack of targeted therapies for women with these tumor phenotypes. MicroRNAs (miRNAs), a new class of small non-coding RNAs, are known to regulate expression of genes important for several biological processes including stem cell division, apoptosis and cell proliferation. Thus, miRNAs have been linked to several diseases including cancer. To examine whether miRNAs play a role in the development and progression of breast cancer, we analyzed 47 primary breast tumors. We hypothesize that specific miRNAs will be associated with particular subtypes of breast cancer especially the biologically aggressive basal like subtype.

Materials and Methods: To test our hypothesis, we used a number of complementary approaches 1.) Using exiqon's miRNA microarray, we profiled 47 breast tumors enriched for African Americans and 4 adjacent normal samples for expression of all known miRNAs. Real time RT-PCR was used to validate the expression data 2.) All tumor samples were classified into the known molecular subtypes using DNA microarray and surrogate immunohistochemistry markers 3.) A subset of the patients with paired normal and tumor samples were analyzed for genomic alterations including deletions and amplifications using 100k Illumina SNP array to corroborate the expression data.

Results: The diverse patient cohort included 36 African Americans, 10 Whites, 1 Hispanic; median age was 51 years. The tumor subtypes included 13 basal like, 11 HER2, 9 Luminal A, 7 Luminal B and 5 normal like. We found 151 miRNA were differentially expressed between primary triple negative and non triple negative tumors. We also found 17 miRNAs that were down regulated in basal tumors. More importantly, some of the 17 microRNAs downregulated in primary BLCs were miRNAs already identified to play a role in de-differentiation or epithelial to mesenchymal transition, all characteristics of BLC. Lastly, some of the miRNAs downregulated in primary BLCs were located at chromosomal regions that are frequently deleted in basal like tumors.

Conclusion: Our data suggests that miRNAs downregulated in BLCs can be lost by several genomic mechanisms and more importantly loss of expression of specific miRNAs may play important roles in development of tumors with this phenotype. Ongoing work is aimed at examining the molecular mechanisms whereby specific miRNAs contribute to the development of basal like tumors.and in understanding the clinical implications of differentially expressed miRNAs in breast tumor progression. These studies underscore the need for an integrated genomic approach to understand breast cancer pathogenesis in diverse populations.

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 3004.