Comparative assessment of radiation therapy-induced vasculitis using [18F]FDG-PET/CT in patients with non-small cell lung cancer treated with proton versus photon radiotherapy

PURPOSE

To assess radiation therapy (RT)-induced vasculitis in patients with non-small cell lung cancer (NSCLC) by examining changes in the uptake of 18F-fluoro-D-deoxyglucose ([18F]FDG) by positron emission tomography/computed tomography (PET/CT) images of the ascending aorta (AA), descending aorta (DA), and aortic arch (AoA) before and after proton and photon RT.

METHOD

Thirty-five consecutive locally advanced NSCLC patients were definitively treated with proton (n = 27) or photon (n = 8) RT and concurrent chemotherapy. The patients were prospectively enrolled to undergo [18F]FDG-PET/CT imaging before and 3 months after RT. An adaptive contrast-oriented thresholding algorithm was applied to generate mean standardized uptake values (SUVmean) for regions of interest (ROIs) 3 mm outside and 3 mm inside the outer perimeter of the AA, DA, and AoA. These ROIs were employed to exclusively select the aortic wall and remove the influence of blood pool activity. SUVmeans before and after RT were compared using two-tailed paired t-tests.

RESULTS

RT treatments were associated with increased SUVmeans in the AA, DA, and AoA-1.9%, 0.3%, and 1.3% for proton and 15.8%, 9.5%, and 15.5% for photon, respectively. There was a statistically significant difference in the ∆SUVmean (post-RT SUVmean - pre-RT SUVmean) in patients treated with photon RT when compared to ∆SUVmean in patients treated with proton RT in the AA (p = 0.043) and AoA (p = 0.015). There was an average increase in SUVmean that was related to dose for photon patients (across structures), but that was not seen for proton patients, although the increase was not statistically significant.

CONCLUSION

Our results suggest that patients treated with photon RT for NSCLC may exhibit significantly more RT-induced inflammation (measured as ∆SUVmean) in the AA and AoA when compared to patients who received proton RT. Knowledge gained from further analyses in larger cohorts could aid in treatment planning and help prevent the significant morbidity and mortality associated with RT-induced vascular complications.

TRIAL REGISTRATION

NCT02135679.

Interpretable Machine Learning for Predicting Symptomatic Pneumonitis in Locally Advanced Non-Small Cell Lung Cancer Patients Treated with Concurrent Chemoradiotherapy and Immune Checkpoint Inhibitor Consolidation

PURPOSE/OBJECTIVE(S)

The rate of grade 2 and higher pneumonitis has increased with the use of immune checkpoint inhibitors (ICI) following chemoradiotherapy (CRT) for lung cancer, which may alter previously established dose-volume constraints (DVC). In this study, we used an interpretable machine learning model with clinical and dosimetric features to predict grade 2+ pneumonitis and determine DVC associated with pneumonitis for locally advanced non-small cell lung cancer (LA-NSCLC) radiotherapy (RT).

MATERIALS/METHODS

Between October 2017 and December 2021, 223 consecutively treated patients with LANSCLC treated with CRT and ICI were retrospectively reviewed. The dataset was split into training and test sets (n = 144/79). Clinical features included age, sex, smoking status, pack-years, BMI, ECOG PS, COPD, tumor location, delivered dose, RT technique, chemotherapy agent and volume of GTVp/GTVn. A total of 228 dosimetric features from the heart, contralateral/ipsilateral lung and lungs-IGTV were extracted, including the minimum/mean dose to the hottest x% volume (Dx%[Gy]/MOHx%[Gy]; x was 5-95 in 5% increments) and minimum/mean/maximum dose and percent volume receiving at least xGy (VxGy [%]; x was 5-60 in 5Gy increments), as well as the overlapping volume of each structure with PTV and the distance from each structure to GTVp/GTVn. Feature selection was performed using Boruta, followed by collinearity removal based on the variance inflation factor. The explainable boosting machine (EBM) was trained on the selected features. The performance of EBM on the test set was evaluated using the area under the receiver operating characteristic curve (AUC) and compared with that of blackbox (BB) models, including extreme gradient boosting (XGB), random forest (RF), and supporting vector machine (SVM). The global explanation of each feature's contribution to the predictions provided by the EBM was used to determine DVC. Shapley additive explanations (SHAP) were used to explain BB predictions.

RESULTS

Selected features, ranked in order of EBM's overall feature importance, were V25Gy [%] and MOH65%[Gy] in the ipsilateral lung, the maximum dose in the heart, MOH30%[Gy] in the contralateral lung, and BMI. No dosimetric features in the lungs-IGTV were selected. The SHAP values of three BB models showed similar trends to the feature importance of the EBM. The global explanations of the EBM suggested that to mitigate the risk of pneumonitis, the ipsilateral lung should have V25Gy [%] < 36.8% and MOH65%[Gy] < 39.5Gy, and the heart should have D0.03cc [Gy] < 66.0Gy. Furthermore, an increased risk of pneumonitis was indicated with an increase in BMI, and, surprisingly, a decrease in MOH30%[Gy] in the contralateral lung. The EBM showed the best performance for predicting grade 2+ pneumonitis (AUC = 0.739), followed by RF, SVM, and XGB (AUC = 0.735, 0.733, and 0.717).

CONCLUSION

EBM has the potential to predict grade 2+ pneumonitis in LA-NSCLC patients treated with CRT and ICI, while providing guidance on DVC.

Association of Cardiac Dose with Cardiac Events and Survival for Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) Treated with Concurrent Chemoradiotherapy (cCRT) in the Era of Immune Checkpoint Inhibitor (ICI) Consolidation

PURPOSE/OBJECTIVE(S)

To assess the association of cardiac dose with post-cCRT cardiac events and survival among patients (pts) with LA-NSCLC after adoption of ICI consolidation, modern radiotherapy (RT) techniques, and data-driven cardiac constraints.

MATERIALS/METHODS

This single-institution, multi-site retrospective study included 335 pts with LA-NSCLC treated with definitive cCRT (60-70 Gy) from October 2017 to December 2021. Pts were evaluated for ICI consolidation. Cardiac dose constraints included heart volume receiving ≥50 Gy (V50) <25% and mean heart dose (MHD) <20 Gy. Heart, left anterior descending artery (LAD), and left ventricle were autocontoured, manually reviewed, and edited. 21 dosimetric parameters (mean dose, max dose, and min dose to the hottest x% volume [Dx%(Gy); x from 5-95 in 5% intervals]) for each were extracted, as well as LAD V15. Baseline cardiovascular disease (bCVD) was defined as heart failure (HF), coronary artery disease, peripheral vascular disease, or cerebrovascular disease. Primary endpoint was post-cCRT major adverse cardiac events (MACE), defined as acute coronary syndrome, HF hospitalization/urgent visit, coronary revascularization, or cardiac death. Secondary endpoints were grade ≥3 cardiac events (CTCAE v5.0), overall survival (OS), cancer specific mortality (CSM), and other cause mortality (OCM). Competing risk regression was used for MACE and grade ≥3 cardiac events, and Cox regression for OS, CSM, and OCM.

RESULTS

Median age was 68 years, 139 (41%) had bCVD, and 225 (67%) received consolidation ICI. Proton therapy was used in 117 (35%), intensity-modulated RT in 199 (59%), and 3D conformal RT in 19 (6%). Median MHD was 8.7 Gy (IQR 4.6-14.4) and median LAD V15 1.4% (IQR 0-22). Median follow-up was 39.5 months. 35 MACE events occurred; 1- and 2-year cumulative incidence (CI) were 4.2% and 9.5%. No cardiac dosimetric parameter associated with MACE after adjusting for bCVD and age (e.g., MHD sHR 0.98/Gy, 95% CI 0.93-1.03, p = 0.43) or within the following 3 subgroups: no bCVD, photon therapy, and ICI consolidation. 87 grade ≥3 cardiac events occurred; 1- and 2- year CI were 12.6% and 20.4%. Heart dose was not associated with grade ≥3 cardiac events after adjusting for bCVD, ECOG, and BMI (e.g., MHD sHR 1.00/Gy, 95% CI 0.97-1.03, p = 0.85) or within the 3 aforesaid subgroups. 183 OS events occurred, including 125 CSM and 58 OCM events. Multiple cardiac dosimetric parameters associated with worse OS on multivariable analysis (e.g., LAD V15 HR 1.01/%, 95% CI 1.00-1.02, p = 0.003), driven by associations with CSM (LAD V15 HR 1.02/%, p<0.001) but not OCM (LAD V15 HR 1.00/%, p = 0.73). Median OS was worse for LAD V15 ≥10% (22.2 vs 35.1 months, p = 0.004).

CONCLUSION

Among pts with LA-NSCLC treated with cCRT after adoption of ICI consolidation, modern RT techniques, and cardiac constraints, post-cCRT cardiac events were common but showed no association with cardiac dose. Cardiac dose associated with OS, driven by an association with CSM and not OCM, which may not reflect cardiac toxicity.

Multitask AI Models for the Joint Prediction of Overall Survival, Progression-Free Survival, and Death without Progression as a Composite Endpoint for LA-NSCLC Patients Treated with Chemoradiotherapy

PURPOSE/OBJECTIVE(S)

Prior methods model the risk of endpoints separately. Herein, we construct a composite AI model that considers multiple endpoints jointly, including overall survival (OS), progression-free survival (PFS), and death without progression (DWP). Our hypothesis is that the composite model potentially improves predictive performance for patients with locally advanced non-small cell lung cancer (LANSCLC) treated with chemoradiotherapy (CRT).

MATERIALS/METHODS

A total of 335 LANSCLC patients treated with definitive CRT, including all evaluable patients accrued from Oct 2017 to Dec 2021, were randomly split into training/test subsets (n = 234/101). Cardio-pulmonary substructures (CPSs) were autocontoured, manually reviewed, and edited if necessary. A total of 1093 non-independent dosimetric parameters were extracted, including GTVp, GTVn, GTV, PTV, esophagus, lungs minus IGTV, left/right lung, 15 CPSs, and the overlapping volume of each OAR with PTV and the distance from each OAR to GTVp/GTVn. Other clinical parameters included age, consolidation immunotherapy (CI), ECOG score, Charlson comorbidity index, coronary heart disease, histology, PD-L1 expression, and clinical stage (AJCC 8). Within training, censored time-to-event data were imputed based on conditional event distributions derived from Kaplan-Meier estimators for casting survival analysis as a regression problem and training neural additive model (NAM) regressors. Features were selected by LASSO regression for a single endpoint (OS, PFS, DWP) and multi-task (MT) LASSO regression for four separate composite endpoints (OS-PFS, OS-DWP, PFS-DWP, OS-PFS-DWP). The performance of MT NAMs in the test set that jointly predicted the composite endpoints was evaluated using the C-index and compared to that of a single task (ST) NAM that predicted each endpoint separately.

RESULTS

The best testing performance in predicting OS and DWP was attained by the MT NAM that jointly predicted all endpoints (c-index = 0.65, 95% CI 0.58-0.71 for OS; c-index = 0.78, 95% CI 0.69-0.87 for DWP). The best model to predict PFS was also MT between PFS and DWP (c-index = 0.59, 95% CI 0.52-0.65). The c-indices of all ST NAMs were less than 0.56. The best MT NAMs significantly outperformed ST NAMs in predicting OS (p = 0.001) and DWP (p = 0.01) except for PFS (p = 0.32). The best MT NAM in predicting OS and DWP included ECOG score, atria-PTV overlap volume, D75% [Gy] to the left atrium (LA), pulmonary arterial volume, histology (adenocarcinoma), D65% [Gy] to the descending aorta (DA), V10 Gy [%] of the LA and CI in order of overall importance. ECOG score consistently ranked as the most important feature for all four MT NAMs. An increase of ECOG score from 0 to 2 indicated a 6-month earlier risk of mortality and DWP. Atria-PTV overlap volume and D65% [Gy] to the DA were included in all four MT NAMs.

CONCLUSION

MT AI models improved outcome prediction in patients with LANSCLC treated with CRT by jointly learning commonalities between the primary and auxiliary endpoints.

Interpretable Machine Learning Models for Severe Esophagitis Prediction in LA-NSCLC Patients Treated with Chemoradiation Therapy

PURPOSE/OBJECTIVE(S)

Radiation esophagitis is a common adverse event that may occur during chemoradiotherapy (CRT) that can adversely affect survival. This study aimed to develop interpretable machine learning (ML) models to predict grade 3 and higher radiation esophagitis in patients receiving definitive CRT therapy for locally advanced non-small cell lung cancer (LA-NSCLC).

MATERIALS/METHODS

A total of 335 patients with LA-NSCLC who received definitive concurrent CRT at a single institution from 2017 to 2021 were retrospectively identified. Patients with esophagitis were identified and graded according to CTCAE v5.0. For each patient, 31 clinical features and 1093 dose-volume histogram (DVH) parameters from 19 structures were collected. The data was then randomly split into training (n = 233) and testing (n = 102) datasets. Feature selection was performed on the training dataset using the minimum redundancy maximum relevance algorithm to find a set of relevant features while controlling for the redundancy within the selected features, which were then followed by the Boruta algorithm to remove unimportant features and make the ML model more accurate. Synthetic minority oversampling technique was used to handle class-imbalanced datasets by generating synthetic samples for the minority class. Four variants of the Generalized Additive Model (GAM), including Explainable Boosting Machine (EBM), neural GAM (NODE-GAM), eXtreme Gradient Boosting (XGB)-GAM, and Spline, were built with selected features. The models' performance in predicting esophagitis was evaluated using the area under the receiver operating characteristic curve (AUC) in the test dataset. Shape plots were used to interpret the models' output and explain the selected features' contribution to the prediction.

RESULTS

NODE-GAM yielded the highest performance (F1 score = 0.57, accuracy = 0.8, and AUC = 0.837), followed by EBM (F1 score = 0.43, accuracy = 0.8, and AUC = 0.7), Spline (F1 score = 0.42, accuracy = 0.74, and AUC = 0.737), and XGB-GAM (F1 score = 0.42, accuracy = 0.76, and AUC = 0.71). Selected features included D95%[Gy], D90%[Gy], D65%[Gy] and V40Gy [%] for the esophagus, V10Gy [%] for the pulmonary artery, and the distance from GTVn to the ascending aorta. The analysis of the selected features indicated that an increased radiation dose delivered to the esophagus and a shorter distance between the ascending aorta and GTVn were associated with a higher risk of developing esophagitis.

CONCLUSION

Our study demonstrates the feasibility of developing interpretable ML models to predict esophagitis in patients with LA-NSCLC patients treated with CRT. NODE-GAM provided the best accuracy while providing insights into the driving dosimetric factors that could be used to guide optimal RT planning.

Proton Beam Therapy (PBT) Versus Intensity-Modulated Radiotherapy (IMRT) for Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) in the Era of Immune Checkpoint Inhibitor (ICI) Consolidation: A Retrospective Cohort Study

PURPOSE/OBJECTIVE(S)

Patients (pts) with LA-NSCLC treated with concurrent chemoradiation (cCRT) and ICI consolidation are at high risk for treatment-related toxicities and subsequent hospitalization. We hypothesized that PBT is associated with a reduction in acute unplanned hospitalizations as compared to IMRT in the era of ICI consolidation.

MATERIALS/METHODS

This single institution, multi-site retrospective study included consecutive pts with LA-NSCLC treated with definitive cCRT with either PBT or IMRT from October 2017 to December 2021. Pts were evaluated for consolidative ICI. Primary endpoint was unplanned treatment-related hospitalization within 90 days of first radiation (RT) treatment. Secondary endpoints included grade 3+ pneumonitis, grade 3+ esophagitis, PFS and OS. Logistic regression was used to assess associations with 90-day hospitalization. Competing risk regression was used for grade 3+ pneumonitis and esophagitis, and Cox regression for PFS and OS.

RESULTS

A total of 316 pts were included: 117 (37%) received PBT and 199 (63%) IMRT. Median age was 68.5 yrs; median RT dose 66.6 Gy (IQR 65.9-70.0). PBT group was older (median 71.1 vs 67.2 yrs, p<0.005) and had a higher Charlson comorbidity index (CCI) (median 4 vs 3, p = 0.02). There was no significant difference in ECOG, smoking pack-years, T stage, N stage, target volume size, or receipt of ICI consolidation (66.7% vs 68.3%, p = 0.76). PBT group had lower mean heart dose (5.9 vs 10.8 Gy, p<0.001), LAD V15 (0 vs 6 %, p = 0.001), mean lung dose (14.7 vs 15.7 Gy, p <0.008) and effective dose to immune circulating cells (median 3.7 vs 4.9 Gy, p<0.001) but not mean esophagus dose. PBT was associated with fewer unplanned 90-day hospitalizations (23.9% vs 34.7%); which persisted on multivariable analysis (OR 0.52, 95% CI 0.30-0.90, p = 0.02) after adjusting for CCI, smoking pack-years, T4 tumors and target volume. Reasons for hospitalization in PBT and IMRT groups included progression (1.7% vs 1.5%), definite/probable toxicity from cCRT (11.1% vs 18.6%), possible toxicity from cCRT (7.7% vs 12.6%) or unrelated to cCRT (3.4% vs 2.0%). There was no significant difference between PBT or IMRT groups in G3+ pneumonitis (1-year 6.0% vs 9.1%, p = 0.49), G3+ esophagitis (1-year 6.0% vs 6.5%, p = 0.71), PFS (median 14.4 vs 15.1 months, p = 0.69), or OS (median 34.2 vs 29.4 months, p = 0.41).

CONCLUSION

Among pts with LA-NSCLC treated with cCRT in the era of ICI consolidation, PBT was associated with fewer acute unplanned hospitalizations compared to IMRT. There was no difference in G3+ pneumonitis, G3+ esophagitis, PFS or OS.

Patterns of Failure, Volume of Disease Progression, and Subsequent Ablative Management in Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) Treated with Definitive Chemoradiation and Consolidation Immune Checkpoint Inhibitors (ICI)

PURPOSE/OBJECTIVE(S)

For patients (pts) with LA-NSCLC treated with chemoradiation and consolidation ICI (CRT+ICI), the patterns of failure (POF) and volume of disease progression (PD) are not well characterized. The primary objective of this study was to classify POFs, the frequency of low volume relapse (LVR), and identify pts eligible for further ablative therapy.

MATERIALS/METHODS

We retrospectively identified pts with unresectable stage III NSCLC treated with CRT+ICI between October 2017 and December 2021 at a single institution. Site of first failure was classified as locoregional (LRF), distant (DF), or synchronous LRF + DF. Any LRF was subclassified as in field (IFF; PD within 90% isodose line), marginal (MF; within 50% isodose line) or out of field (OOF; outside of 50% isodose line). LVR was defined as < 3 discrete sites of PD in any number or location of organs. Pts with distant LVR were considered to have oligometastatic relapse. Ablative candidates were defined as pts with < 3 discrete sites of PD amenable to further RT or surgery. Cumulative incidence of PD was calculated with death as a competing risk. Progression free survival (PFS) and overall survival (OS) were calculated from the end of RT and assessed via Kaplan Meier. Multivariable Cox modeling was used to assess correlation of pt characteristics and time-to-event outcomes. Logistic regression was used to predict variables associated with LVR.

RESULTS

A total of 229 pts received CRT+ICI. Median follow up was 39 months and 119 pts experienced PD. Median PFS and OS were 18.4 and 34.5 months, respectively. Of pts with PD, 71 (60%) had DF, 28 (24%) had LRF+DF, and 20 (17%) had LRF. Of pts with any LRF, 28 (57%) had IFF, 10 (21%) had MF, and 10 (21%) had OOF. Estimated 1-year cumulative incidence of LRF, DF, and LRF+DF were 9.3% (95% CI 4.5-16), 39% (95% CI 31-48), and 19% (95% CI 12-27), respectively. A total of 63 (53%) pts had LVR. In pts with LVR, 19 (30%) had isolated thoracic relapse and 44 (69%) had oligometastatic relapse. Most oligometastatic disease was intracranial (22 metastases, 44%). Pts with LVR had a longer median OS vs pts with high volume relapse (37.4 vs 15.2 months, p<0.001). At time of PD, 56 (47%) pts were candidates for further ablative therapies. Subsequent anticancer therapies were local therapy alone (35%), local and systemic therapy (16%), systemic therapy alone (36%), or no therapy (13%). On multivariable analysis, LVR (HR 0.39; 95% CI 0.21-0.73, p = 0.003) and longer receipt of ICI (HR 0.96; 95% CI 0.95-0.98; p<0.001) were associated with improved survival while squamous histology (HR 2.26; 95% CI 1.18-4.32; p = 0.039) was associated with worse survival. Longer receipt of ICI was the only variable predictive for the development of LVR (OR 1.03; 95% CI 1.01-1.05; p = 0.004).

CONCLUSION

This is the largest real-world series reporting POF after CRT+ICI for stage III NSCLC. Approximately half of pts experience LVR and are candidates for further ablative therapy. Further data are needed to define optimal treatment strategies for pts with LVR after CRT+ICI.

Pneumonitis after Palliative Thoracic Radiotherapy +/- Immunotherapy: A Retrospective Propensity-Matched Cohort Study

PURPOSE/OBJECTIVE(S)

Patients (pts) with advanced lung cancer often receive combined palliative thoracic radiotherapy (RT) and immune checkpoint inhibitors (ICI). There are limited data assessing the toxicities of combined ICI-RT in this setting. We sought to compare the rates of clinically significant pneumonitis among pts with lung cancer receiving palliative thoracic RT with or without recent or concomitant ICI. We hypothesized there would be a higher rate of grade 2+ pneumonitis among RT pts who received recent or concomitant ICI compared to those who did not.

MATERIALS/METHODS

We retrospectively identified consecutive pts with advanced/recurrent lung cancer from a tertiary academic center who received palliative thoracic RT with recent (defined as within 95 days of RT start) or concomitant ICI (ICI-RT group) between January 2014 and February 2020. Pts were propensity matched in a 1:1 manner (by age, sex, ECOG, RT modality, and RT dose) to lung cancer pts who received palliative thoracic RT without any history of ICI receipt (RT-only group). The presence and grade (CTCAE v5.0) of pneumonitis were independently assessed by two investigators. The primary endpoint was grade 2+ pneumonitis, estimated using the cumulative incidence function and compared between the ICI-RT and RT-only groups using Gray's test. The secondary endpoint was overall survival, estimated using the Kaplan-Meier method and compared between groups using the log-rank test.

RESULTS

A total of 146 pts were included in the study (73 in each group). There were no statistically significant differences between the ICI-RT and RT-only groups with respect to age (median 67.7 vs. 67.6, p = 0.97), sex (52% vs. 52% female, p = 1.00), pre-treatment ECOG 0-1 (74% vs 75%, p = 0.85), or biologically effective dose greater than 45 (48% vs. 48%, p = 1.00). The most common RT regimens were 30 Gy in 10 fractions (33 pts, 23%) and 20 Gy in 5 fractions (18 patients, 12%). A plurality of cases utilized 3DCRT (67 pts, 46%). In the ICI-RT group, the median time from last dose of ICI to the start of palliative RT was 16 days; three pts in this group-initiated ICI while receiving RT treatment. The most common ICI was pembrolizumab (36 pts, 49%). A total of eleven grade 2+ pneumonitis events (nine grade 2 and two grade 3 events) were observed. The ICI-RT group had a higher cumulative incidence of grade 2+ pneumonitis compared with the RT-only group (1-year rate, 12.3% vs. 2.7%, p = 0.029); grade 3 pneumonitis occurred in 1/73 (1.4%) in each group. There was no difference in overall survival between groups (median 239 vs. 218 days, p = 0.76).

CONCLUSION

In pts with advanced lung cancer treated with palliative thoracic RT, recent or concomitant ICI use was associated with a higher cumulative incidence of grade 2+ pneumonitis. However, the incidence of grade 3+ pneumonitis was low (1.4%) regardless of ICI receipt.

Abstract OT2-03-03: Delivery of a single fraction lumpectomy cavity boost using a novel immobilization device and treatment delivery system

Background: The lumpectomy cavity (LPC) boost has been shown in 2 randomized studies to improve local control in breast cancer. Hypofraction is now being used for delivery of the LPC boost in some early-stage patients. This trial delivers the LPC boost in a single fraction using a novel breast immobilization device/treatment delivery system.

Trial design: Patients are enrolled in this trial after standard resection with lumpectomy/sentinel lymph node biopsy (as appropriate) and chemotherapy (as indicated per standard of care). At the time of CT simulation for whole-breast radiation therapy (RT), the radiation oncologist evaluates breast size and LPC position. If consented for treatment, the patient receives a single fraction “boost” treatment of 8 Gy in 1 fraction followed by standard whole-breast RT to start within 7 days of completion of the boost. Whole-breast radiation is delivered in the supine or prone position with the following fractionation schemes: 4005 cGy in 15 fractions or 5000 cGy in 25 fractions.

On the day of the boost treatment, the patient is fitted with the breast immobilization device, with a plastic inner cup that is fitted so that the breast fills all or most of the cup. A rigid outer cup with a built-in stereotactic fiducial system is attached. Moderate negative pressure is applied to immobilize the breast within the cup system. Patients then undergo CT simulation in the prone position. Clip placement and LPC cavity location must meet eligibility criteria before proceeding with treatment planning and delivery.

Eligibility criteria:

Eligibility criteria: age &gt;60 yo; female only; dx of invasive ductal or lobular carcinoma or ductal carcinoma in situ; estrogen receptor positive; successful completion of lumpectomy ± sentinel lymph node biopsy with negative margins for invasive or noninvasive cancer; greatest tumor dimension &lt;4 cm before surgery; weight &lt;330 lb; height &lt;76 inches; nonlactating and nonpregnant. Various additional dosimetric factors must be met prior to treatment. If these are unable to be met, the patient will become ineligible for treatment.

Specific aims: The aim of this study is to demonstrate the feasibility and safety of delivering the LPC boost RT using a single fraction with a novel immobilization device/treatment delivery system while ensuring coverage of the target volume with appropriate dose homogeneity and conformity. Secondary aims are evaluation of patient comfort, acute toxicity (1 month), and late toxicity (1 year).

Statistical methods: A Simon 2-stage design is utilized for this trial. After evaluating the device and treatment on 8 patients in the first stage, the trial was designed to be terminated and device rejected if the dose distribution was acceptable for ≤5 patients. The first stage was completed in spring 2017 and progressed to the second stage, designed to include a total of 17 patients.

Accrual and target accrual: Target accrual for this study is 14 patients successfully treated while meeting all protocol constraints. As of 6/2017, 16 patients have been enrolled, of whom 13 have been successfully treated while meeting all protocol constraints.

Citation Format: Nichols EM, Becker S, Hong J, Cohen RJ, Mishra MV, Citron W, Cheston SB, Niu Y, Mutaf Y, Yu CX, Feigenberg SJ. Delivery of a single fraction lumpectomy cavity boost using a novel immobilization device and treatment delivery system [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-03-03.

Abstract OT3-03-03: A prospective study of glycoprotein 88 (GP-88) blood test in healthy women undergoing screening for breast cancer (BC) with mammography (MM)

Background: Population based BC screening with XRAY mammography (MM) has been widely accepted as standard of care for women aged 40+ with average risk of developing BC. Sensitivity and specificity of MM is dependent on breast tissue density and up to ∼20% of BC are undetected by MM. The development of a dependable, low cost blood-based BC screening test to increase the sensitivity and specificity of currently existing BC screening methods is needed.

Rationale: GP88 is expressed & secreted by BC cells & is not expressed by normal mammary epithelial cells, 2 retrospective randomized multi-site trials (a training study & a validation study of 300 cases each) demonstrated that elevated GP88 expression in estrogen positive (ER+) invasive BC was statistically correlated with a 4-fold increase in the risk of 5-yr BC recurrence. GP88 was an independent predictor of BC recurrence in multivariate analysis of other factors such as PR expression, tumor size, grade, lymph node status & stage. The quantitative GP88 EIA was developed to determine the amount of GP88 in biological fluids. The blood based EIA assay is highly specific for GP88 & both sensitive & linear over a wide dynamic range, i.e. detection of GP88 concentrations from 0.1 to 20ng/ml. A baseline GP-88 level of28.4 ± 5 ng/ml was established by us for healthy volunteers (HV). In BC pts a statistically significant increase of serum GP88 was observed in early stage pts (40.7 ± 16 ng/ml; p=0.007). Stratification of BC pts according to their clinical outcomes shows that pts having no evidence of disease (NED) have serum GP88 levels within the range of HV. These data suggest that pts with breast tumors express & secrete high levels of GP88.

Objectives: 1. To determine prospectively GP-88 blood levels in HV at average risk of developing BC screened by MM & in women with recently biopsy-confirmed BC. 2. To establish the statistical distribution of GP88 serum levels in subjects by baseline BIRAD classification (1-6). 3. To determine if the initial GP88 level is predictive of change in BIRADS classification from baseline to 12-mos follow-up. 4. To determine if baseline GP88 level is predictive of the appearance of BC at 12 mos follow-up in HV who were cancer-free at study entry.

Inclusion Criteria: Female, aged &gt;=40 yrs old, presenting for screening or diagnostic MM or diagnostic workup and/or biopsy due to abnormal MM &lt;= to 12 wks before study entry.

Study procedures: Serum levels of GP88 in subjects with average BC risk factors will be measured prospectively at baseline; 3-6 mos & 6-12 mos & correlated with BIRADS reading of the screening MM, BIRADS 1-6; GP88 serum level will be correlated with pathologic results of breast biopsies performed on subjects with suspicious BIRADS (4 & 5) MM & final pathologically confirmed diagnosis of breast cancer as BIRADS 6.

Study Progress: The study is ongoing; currently we have 308 subjects enrolled, the total number of subjects will be up to 725 & screened up to 1400. Study is UM IRB approved & is conducted at the University od Maryland Medical Center (UMMC) and UM Baltimore Washington Medical Center (BWMC). Funding is provided by Maryland Industry Partnership Grant (MIPS)& Avon Grant No. 02-2013-018.

Citation Format: Tkaczuk KHR, Campassi C, Kesmodel S, Bellavance E, Rosenblatt P, Nichols E, Feigenberg SJ, Coughlin P, Drogula C, Urban B, Galandak J, Dromi S, Kuo L, Yue B, Hicks D, Serrero G. A prospective study of glycoprotein 88 (GP-88) blood test in healthy women undergoing screening for breast cancer (BC) with mammography (MM). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-03-03.

Abstract OT3-01-07: Phase II study of trastuzumab and pertuzumab alone and in combination with hormonal therapy or chemotherapy with eribulin in women aged ≥60 with HER2/neu overexpressed locally advanced and/or metastatic breast cancer

Her2 overexpression is both a predictive and prognostic marker with tumors overexpressing Her2 having an aggressive natural history, but also responding to targeted therapy. The standard of care for Her2 positive metastatic cancer is docetaxel paired with combined antibody therapy of pertuzumab (P) and trastuzumab (T). Older patients are known to have more difficulty tolerating traditional cytotoxic chemotherapy. Neoadjuvant studies have shown a proportion of patients have pathologic complete responses (pCR) with dual Her2 targeted therapy without chemotherapy. The NEOSPHERE trial demonstrated at 17% pCR after 3 cycles of T+P. The Translational Breast Cancer Research Consortium has shown 12-28% pCR with the combination of estrogen deprivation, trastuzumab, and lapatinib (TBCRC 006 and 023). We have designed a phase II study of T+P alone and then in combination with hormonal or chemotherapy after progression in women age ≥ 60 with Her2 overexpressed locally advanced or metastatic breast cancer (BC). As a primary endpoint, this study seeks to evaluate the overall response rate (ORR) of dual Her2 targeted therapy with T+P without chemotherapy in older patients with locally advanced or metastatic Her2 positive BC (cohort 1). At progression,depending on tumor characteristics and disease status, chemotherapy with eribulin or hormone therapy with anastrozole plus fulvestrant will be added (cohort 2 – A and B). ORR for cohorts 1, 2A and 2B will be determined. Secondary end points will evaluate clinical benefit, progression free survival, overall survival, tolerability, safety, and quality of life. Translational studies involving circulating tumor cells identified through OncoCEE – Biocept system and glycoprotein 88 expression will be performed. Eligibility includes patients' age ≥60 with locally advanced or metastatic Her2 positive BC treated with 0-3 lines of chemotherapy. Patients must have an ejection fraction &gt;50% and meet set hematologic and metabolic lab criteria. Her2 status is per ASCO/ACP guidelines. Excluded patients include patients with active brain metastasis, second malignancies, anticancer treatment &lt;3 weeks prior to the start of therapy. Patients must have not received pertuzumab, eribulin, anastrozole, or fulvestrant in the metastatic setting. A true ORR of 40% will be considered active. The study was designed assuming 25% of patients initially respond to T+P and 75% progress to cohort 2. With a type I error rate of 0.05 and power of 0.90, 40 patients will need to enroll in order to have 30 patients in cohort 2 (15 per arm). Data will be analyzed after eight patients are enrolled. If there are no responders in cohort 1 and 2, the accrual will be stopped and declared inefficient. After 15 patients are enrolled, if no more than 3 of the 15 respond, the therapy will be considered not promising and halted. Currently there are two patients enrolled at the University of Maryland. We are in negotiations to expand to additional sites. Questions can be directed to prosenblatt@umm.edu.

Citation Format: Rosenblatt PY, Kesmodel SD, Bellavance E, Nichols EM, Feigenberg SJ, Tait N, Lewis J, Sivisailam SS, Couzi R, Goloubeva O, Tkaczuk KHR. Phase II study of trastuzumab and pertuzumab alone and in combination with hormonal therapy or chemotherapy with eribulin in women aged ≥60 with HER2/neu overexpressed locally advanced and/or metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-01-07.

Pre-Chemoradiotherapy FDG PET/CT cannot Identify Residual Metabolically-Active Volumes within Individual Esophageal Tumors

Objective

To study whether subvolumes with a high pre-chemoradiotherapy (CRT) FDG uptake could identify residual metabolically-active volumes (MAVs) post-CRT within individual esophageal tumors. Accurate identification will allow simultaneous integrated boost to these subvolumes at higher risk to improve clinical outcomes.

Methods

Twenty patients with esophageal cancer were treated with CRT plus surgery and underwent FDG PET/CT scans before and after CRT. The two scans were rigidly registered. Seven MAVs pre-CRT and four MAVs post-CRT within a tumor were defined with various SUV thresholds. The similarity and proximity between the MAVs pre-CRT and post-CRT were quantified with three metrics: fraction of post-CRT MAV included in pre-CRT MAV, volume overlap and centroid distance.

Results

Eight patients had no residual MAV. Six patients had local residual MAV (SUV ≥2.5 post-CRT) within or adjoining the original MAV (SUV ≥2.5 pre-CRT). On average, less than 65% of any post-CRT MAVs was included in any pre-CRT MAVs, with a low volume overlap <45%, and large centroid distance >8.6 mm. In general, subvolumes with higher FDG-uptake pre-CRT or post-CRT had lower volume overlap and larger centroid distance. Six patients had new distant MAVs that were determined to be inflammation from radiation therapy.

Conclusions

Pre-CRT PET/CT cannot reliably identify the residual MAVs within individual esophageal tumors. Simultaneous integrated boost to subvolumes with high FDG uptake pre-CRT may not be feasible.

P1-12-20: The Safety and Tolerability of Vorinostat in Combination with Lapatinib in Advanced Solid Tumors

Background: Lapatinib has been previously shown to markedly decrease cancer stem cells (CSC) in HER2−positive breast cancer. In preclinical models, we have demonstrated that histone deacetylase inhibitors (HDACi) such as vorinostat can induce differentiation and decrease CSC. The combination of vorinostat and lapatinib is synergistic with a combination index of 0.32 (synergism if CI &lt;1). We therefore undertook a pilot study to evaluate the combination of these two drugs in advanced solid tumors.

Method: Patients were eligible if they were: age ≥ 18 years with incurable solid tumors, ECOG PS 0–2, adequate organ function, and no prior exposure to HDACi. The first 3 patients received lapatinib at the dose of 1,250 mg continuous daily and vorinostat 300 mg 4 days on 3 days off. The second dose level with lapatinib 1,250 mg continuous daily and vorinostat 400 mg 4 days on 3 days off were administered in 6 patients. Cycles were repeated every 21 days until disease progression. Echocardiogram and radiologic evaluation were performed every 12 weeks. During the first cycle, pharmacokinetic (PK) evaluation was performed on days 18 and 21.

Results: Nine consented patients (7 with metastatic breast cancer, 1 with non-small cell lung cancer, and 1 with thyroid cancer) have been enrolled with the median age of 52 (range 25–66). Patients received an average of 6 prior treatments (range 2–10). No dose limiting toxicity or drug related death have been observed. Grade 1–2 toxicities including diarrhea, fatigue, muscle cramps and stomatitis were observed. No grade 3 or 4 hepatic, renal or cardiac toxicity were observed (including no QTc prolongation and no significant reduction in the left ventricular ejection fraction). Patients have received the maximum of 7 cycles (median 3 cycles, range 2–7). Response: as of June 2011, 2 patients are still on treatment. Two patients achieved stable disease (triple negative metastatic breast cancer and HER2−positive breast cancer), 6 patients with progressive disease, and 1 patient is too early to evaluate for response. PK analysis will be presented at the time of the meeting.

Conclusions: The combination of vorinostat and lapatinib is tolerable and has some antitumor activity in heavily pretreated advanced solid tumors. A phase II study in HER2−positive metastatic breast cancer is underway with lapatinib 1,250 mg continuous daily and vorinostat 400 mg 4 days on 3 days off.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-12-20.

Early evidence of increasing national mastectomy rates for the treatment of breast cancer

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Background: The use of mastectomy for the treatment of breast cancer has declined since initial randomized trials demonstrated equivalent survival with breast conservation therapy. Recent single institution series, however, have reported increasing mastectomy rates within the past decade.

Methods: In order to verify these findings at the national level, we analyzed data from the Surveillance, Epidemiology, and End Results database, including women diagnosed with T1-2 N0-3 M0 breast cancer from 2000 to 2007. We evaluated therapeutic mastectomy rates by the year of diagnosis and performed a multivariable logistic regression analysis to determine predictors of mastectomy as the treatment choice.

Results: A total of 228,240 patients met the entry criteria. The proportion of women treated with mastectomy decreased from 40.3% to 35.6% between 2000 and 2005. Subsequently, the mastectomy rate increased to 37.9% in 2007 (p < 0.0001). The mastectomy rate in 2007 was the highest since 2002 (38.6%). A reversal in previously declining mastectomy rates was noted in nearly all cohorts, but was most pronounced among younger women. Multivariable analysis found that age, race, marital status, geographic location, involvement of multiple regions of the breast, lobular histology, increasing tumor size, lymph node positivity, increasing grade, negative hormone receptor status, and synchronous diagnosis of an ipsilateral or contralateral breast cancer were independent predictors of mastectomy. Additionally, multivariable analysis confirmed that women diagnosed in 2007 were more likely to undergo mastectomy than women diagnosed in 2005 (HR = 1.14, CI: 1.09 to 1.18, p < 0.0001).

Conclusions: There is evidence of a reversal in the previously declining national mastectomy rates, with the mastectomy rate reaching a nadir in 2005 and subsequently rising. Further follow-up to confirm this trend and investigation to determine the underlying cause of this trend and its impact on outcomes are warranted.

Risk of breast fibrosis following irradiation using a breast-specific SBRT system compared with conventional APBI

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Background: To determine the dosimetric characteristics and risk of breast fibrosis using a normal tissue complication probability (NTCP) model in conjunction with a novel preoperative stereotactic radiotherapy system called the GammaPod. Results are compared with linac based post-lumpectomy APBI plans for the same cohort.

Methods: The GammaPod breast SBRT system consists of a Co-60 irradiation unit in combination with an immobilization device with embedded fiducials. Eight patients were enrolled in an IRB-approved protocol and underwent CT scans in the prone position with breast immobilization. A preoperative target (GTV) was synthesized to match the tumor location and volume reported in imaging studies obtained prior to surgery (0.3-2.4 cc). The GTV was expanded by 1.5 cm to create a CTV, and a PTV was created using an additional 0.3 cm margin. The PTV was prescribed 25.5 Gy in 3 fx, which is radiobiologically equivalent to conventional APBI doses of 38.5 Gy in 10 fx. Following the radioablative experience in NSCLC, we also planned to deliver 60.0 Gy to the GTV+0.3 cm as a simultaneous boost in conjunction with the 25.5 Gy PTV prescription dose. For comparison, linac-based treatment plans were created for the same cohort following NSABP B-39 guidelines. Whole breast dosimetry was analyzed in terms of biologically equivalent dose (BED) and Lyman NTCP analysis was performed.

Results: The volume of ipsilateral breast receiving 10, 20, 50, and 100% of the prescribed dose was substantially smaller in GammaPod vs. APBI plans, with cohort averages of 19.3, 13.0, 7.1 and 4.0% vs. 75.8, 67.3, 48.1 and 27.6% respectively (p<0.001). Even though the PTV equivalent uniform BED (EUD) was substantially higher in GammaPod plans (87.9 Gy vs. 57.3 Gy), the ipsilateral breast EUD was still smaller in these plans, 18.9 ± 5.0 Gy vs. 47.2 ± 3.2 Gy (p<0.001). Corresponding NTCP predictions for breast fibrosis rates following GammaPod and APBI treatments were 0.2 ± 0.1% vs. 2.8 ± 0.8% (p<0.001), respectively.

Conclusions: The GammaPod system improves upon traditional post-lumpectomy linac-based APBI by decreasing dose to the ipsilateral breast as well as the predicted rates of breast fibrosis.

Comparing survival with breast-conservation therapy or mastectomy in the management of young women with early-stage breast cancer

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Background: Previous studies have shown that young women with breast cancer treated with breast-conservation therapy (BCT) experience higher local recurrence rates. Whether such patients are better treated with mastectomy is unclear. The purpose of this study was to evaluate survival outcomes of young women with early-stage breast cancer treated with BCT or mastectomy using a large, population-based database.

Methods: Using the Surveillance, Epidemiology, and End Results (SEER) database, information was obtained for all female patients age 20 to 39 diagnosed with T1-2 N0-1 M0 breast cancer between 1990 and 2007 who underwent either BCT (lumpectomy and radiation treatment) or mastectomy. Multivariable analysis as well as a matched pair analysis were performed to compare overall survival (OS) and cause-specific survival (CSS) of patients undergoing BCT and mastectomy.

Results: 14,760 women were identified, of whom 45% received BCT and 55% received mastectomy. Median follow-up was 5.7 years (range: 0.5 to 17.9 years). Multivariable analysis revealed year of diagnosis, age, race/ethnicity, grade, PR status, tumor size, number of lymph nodes positive, and number of lymph nodes examined were independent predictors of OS and CSS while ER status was of borderline significance. After accounting for all patient and tumor characteristics, multivariable analysis found that BCT resulted in similar OS (HR: 0.93; CI: 0.83-1.04; p = 0.16) and CSS (HR: 0.93, CI: 0.83-1.05; p = 0.26) as mastectomy. Matched pair analysis, including 4,644 BCT and mastectomy patients, confirmed no difference in OS or CSS: the 5/10/15-year OS for BCT and mastectomy were 92.5%/83.5%/77.0% and 91.9%/83.6%/79.1%, respectively (p = 0.99) and the 5/10/15-year CSS for BCT and mastectomy were 93.3%/85.5%/79.9% and 92.5%/85.5%/81.9%, respectively (p = 0.88).

Conclusions: Young women with early-stage breast cancer have equivalent survival whether treated with BCT or mastectomy. These patients should be counseled appropriately regarding their treatment options, and should not choose a mastectomy based on the assumption of improved survival.

Stereotactic radiosurgery for early-stage breast cancer: A new paradigm

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Background: Stereotactic radiosurgery (SRS) has not been widely used for breast cancer partly due to: 1) the lack of a suitable immobilization device; and 2) the lack of a delivery system that can concentrate a high radiation dose noninvasively. We have developed a SRS system that effectively addresses these obstacles and demonstrated the dosimetric feasibility of simultaneously ablating the intact tumor and sterilizing the tumor bed.

Methods: A breast immobilization device consists of a solid outer cup with embedded stereotactic frame and a porous inner cup; the two cups join at the chest wall side by a soft goggle-like lip for comfort. A negative pressure is applied to the space between the two cups to immobilize the breast tissues. 15 patients with surgical clips in their breast underwent a geometric reproducibility trial, in which the patients received two CT scans spaced 10-60 minutes while wearing the cup. A SRS delivery system uses 36 Co-60 sources that rotate around a focal point to produce 36 non-coplanar arcs. The breast cup is locked on the treatment couch with the patient in prone position. The couch moves dynamically during treatment, allowing the focal spots to “paint” the desired 3D dose distribution.

Results: The reproducibility of the 42 available clips was 1.83 mm ± 1.08 mm (2 std) and patients reported good comfort. 8 treatment plans simultaneously delivering an ablative dose of 18Gy to an intact tumor plus a 3mm margin (CTV1) and 10Gy to the tumor bed (CTV2 = CTV1+1cm) have been developed and verified with measurements. The dose-volume histograms showed very uniform dose coverage with 98% of CTV1 receiving 18Gy and 100% of tumor bed receiving 10Gy. On average, only 21% of the normal breast receives greater than 5Gy, safe to deliver 3 fractions of such doses.

Conclusions: A breast-specific SRS system has been developed. Dosimetric studies illustrated the feasibility of managing early-stage breast cancer with SRS. Clinical studies that will identify patients in whom current forms of surgery and postoperative radiation may be eliminated are planned, allowing completion of local therapies noninvasively within a few days rather than months.

Abstract P4-10-10: The Gammapod TM: A Novel Breast Specific Stereotactic Body Radiation Therapy (SBRT) for Small Breast Cancers

Introduction: SBRT is a novel approach to precisely deliver high doses of radiation therapy to a define target, while normal tissues immediately surrounding the tumor receives a significantly lower (i.e. tolerable) dose. This technique has revolutionized the management of small medically inoperable lung cancer with local control rates recently reported in the co-operative setting of 98% now setting the stage for challenging surgery as the standard of care for select patients with lung cancer. SBRT has not been used in the breast, since the breast is a pliable organ without a suitable immobilization device and the lack of an SBRT system that can create the rapid fall off in dose necessary to deliver ablative doses of radiation safely in the breast. The purpose of this NIH funded project is to develop a dedicated SBRT system for early breast cancer which could eventually lead paradigm shift in the management of breast cancer similar to lung cancer.

Materials and Methods: The SBRT system was developed such that dose distributions produced would be similar to stereotactic radiosurgery in the brain where the the drop off of the prescription isodose to 50% of the prescription dose was less than 5 mm. The device uses 36 non-coplanar Co-60 sources which rotate around a focal point to produce 36 non-coplanar arcs. The system incorporates the use of a floating/dynamic table which together with the rotatable sources enables differential dosing of target volumes similar to intensity modulated RT allowing higher ablative doses to the gross tumor and a lower sub clinical dose to treat microscopic tumor foci. In addition the SBRT system, a breast specific immobilization device was developed. This system consists of 2 layers with an air tight seal in between. Once placed on the breast a small negative pressure secures it to the breast. A prospective trial tested the reproducibility of the breast cup using the centroid of the post-operative clips on 2 consecutive CT simulations separated by 10 to 60 minutes simulating the treatment planning scenerio in the prone position. During this time, patients were also asked to fill out a questionaire regarding the comfort of this approach. Results: The issues within the specific aims of the grant have been effectively solved and have led to a breast specific immobilization device and a breast specific SBRT system — The Gammapod TM. The immobilization device demonstrated a set up error of less than 3 mm a significant decrease from the 10 mm planning target volume expansion as recommended in NSABP B39 for patients undergoing 3 dimensional conformal partial breast radiotherapy. All patients described this experience as more comfortable in comparison to a biopsy and similar to the experience of a mammogram.Dosimetric studies using Monte Carlo simulation demonstrate that tumors up to 5 cm in diameter, and 5 mm from the chest wall, lung/heart receive &lt; 10% of the maximum dose. Conclusions: A breast specific immobilization device and SBRT system has been developed produces dose distributions similar to stereotactic radiosurgery in the brain. The first prospective studies testing this device clinically through a multi-institutional consortium are expected to open in early 2011.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-10-10.

Abstract P4-11-11: Preoperative Radiotherapy Increases Eligibility for Partial Breast Irradiation by Significantly Reducing Normal Tissue Exposure

Introduction: External-beam accelerated partial breast irradiation (EB-APBI) is the most common technique used on NSABP B-39 primarily due to the non-invasive nature of the treatment. Many patients thought to be eligible for EB-APBI become ineligible at the time of planning due to inability to meet dose-volumetric constraints. EB-APBI in the preoperative setting will reduce the volume of normal tissue treated potentially increasing the number of patients eligible for APBI. This study tested the hypothesis that pre-operative EB-APBI will not only decrease target volumes but will decrease normal tissue exposure significantly increasing eligibility for APBI.

Materials and Methods: Forty patients with 41 previously treated early stage breast cancers (tumors ≥4 cm) were retrospectively analyzed from a prospective cohort. Imaging studies (MRI, US and mammogram) were utilized to create a spherical pre-op tumor volume using the largest reported dimension centered within the previously contoured lumpectomy cavity (LPC). Plans were created and optimized for each patient using the pre-operative tumor volume (pre-op) and LPC (post-op) using NSABP B-39 guidelines. Dose-volumetric constraints were analyzed between the cohorts using a t-test analysis. The primary end-point was to evaluate for differences in patient eligibility and normal tissue exposure.

Results: The median tumor volume was 93 cc (range 24-570 cc) and 250 cc (range 46-879 cc) in the pre-and post-operative setting respectively. This reduction in tumor volume translated into an increase in patient eligibility for EB-APBI with 35/41 (85%) cases being eligible for EB-APBI in the preop setting versus 18/41 (44%) cases in the post-op setting (p=0.0002). In the pre-op setting 6 cases were ineligible due to violation of one constraint by 5% and no case violated multiple constraints. In the post-op setting, 12 cases had 1 and 11 cases multiple reasons for ineligibility due to exceeding dose constraints by 5%. The most common reason for ineligibility in both groups was &gt; 60% of the ipsilateral breast volume receiving 50% of the dose. The mean volume of ipsilateral breast receiving 50% of the dose was 42% and 63% in the pre-and post-op groups respectively. The mean contralateral breast dose and ipsilateral lung V20 in the pre-and post-op groups were 1 versus 4% and 3 versus 9%. All DVH criteria were statistically significantly improved in the pre-op setting including heart V5 and V40, ipsilateral breast V5, V20, V50 and V80, contralateral breast dose, chest wall V5, V10 and V20; ipsilateral lung V5, V10, V20 and volume of skin receiving 50% of the dose. Contralateral lung dose and thyroid max dose were not significantly different between plans.

Conclusions: Administration of EB-APBI in the pre-op setting decreases the size of the target volume which significantly increases the utility of APBI nearly doubling the eligibility for APBI in this cohort. The largest benefit is seen by reducing the volume of breast receiving 50% of the dose. This decreased dose to normal tissues will potentially result in decreased morbidity and improved cosmesis.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-11-11.

PET response following stereotactic body radiotherapy for non-small cell lung carcinoma correlates with local control

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Background: Given the success of Stereotactic Body Radiotherapy (SBRT) for Non-Small Cell Lung Carcinoma (NSCLC), early surrogates of local failure (LF) are necessary to allow timely surgical salvage. This study tries to determine the utility of PET response as an early surrogate for LF. Methods: Eligible patients(pts) had biopsy proven NSCLC < 5 cm in size who underwent a pre- and post- SBRT PET scans. Pts treated at Fox Chase Cancer Center were either: 1. early stage (10 pts), 2. biopsy-proven local recurrences (4 patients) or 3. oligometastases (3 patients). Eleven of the 17 pts were treated on a prospective phase I dose escalation protocol and received either 40 Gy or 48 Gy in 4 fractions over 8 days. Non-protocol pts generally received 48 Gy in 4 fractions (5 of 6 pts). Treatment volumes were individualized for each pt using either 4 D or multi-phase CT simulation. As part of the prospective study design, PETs scan was obtained pre- and post-SBRT to correlate metabolic response with LF based on the work by MacManus. The post-SBRT PET scan was obtained at a median of 3 months following treatment (range, 2 to 6 months). LF was defined by my an increase in size on CT on serial imaging. Results: With a median follow up of 14 months (range 4 to 31 months), 3 LF have been documented. The median SUV max pre-SBRT was 4.7 (range 1.32 to 18.2) and 1.9 (range 0.9 to 7.0) post-SBRT. Only four pts had a post-SBRT SUV max > 2.5 (2.8, 5.1, 5.3 and 7). Overall, twelve pts had a drop in their SUV max following SBRT, while 1 pt had stabilization and 4 had an increase . Of these last 5 pts, 3 developed LF. The other two have been followed without any intervention and remain free of recurrence for > 2 years, respectively. No pt with an initial drop in post SBRT PET scan SUV has had LF. Conclusions: PET response (defined as a drop in the SUV max by 3 months) correlates with LF, and appears to be a good early surrogate of outcomes following SBRT. Larger studies are required to confirm this finding.

No significant financial relationships to disclose.

Investigation of optimal beam margins for stereotactic radiotherapy of lung-cancer using Monte Carlo dose calculations

This work investigated the selection of beam margins in lung-cancer stereotactic body radiotherapy (SBRT) with 6 MV photon beams. Monte Carlo dose calculations were used to systematically and quantitatively study the dosimetric effects of beam margins for different lung densities (0.1, 0.15, 0.25, 0.35 and 0.5 g cm(-3)), planning target volumes (PTVs) (14.4, 22.1 and 55.3 cm3) and numbers of beam angles (three, six and seven) in lung-cancer SBRT in order to search for optimal beam margins for various clinical situations. First, a large number of treatment plans were generated in a commercial treatment planning system, and then recalculated using Monte Carlo simulations. All the plans were normalized to ensure that 95% of the PTV at least receives the prescription dose and compared quantitatively. Based on these plans, the relationships between the beam margin and quantities such as the lung toxicity (quantified by V20, the percentage volume of the two lungs receiving at least 20 Gy) and the maximum target (PTV) dose were established for different PTVs and lung densities. The impact of the number of beam angles on the relationship between V20 and the beam margin was assessed. Quantitative information about optimal beam margins for lung-cancer SBRT was obtained for clinical applications.

Neck dissection following organ preservation protocols prolongs feeding tube dependence in patients with advanced head and neck cancer

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Background: Organ preserving strategies employed in the treatment of advanced stage head and neck cancer frequently result in significant organ dysfunction including dysphagia and feeding tube dependence. While the acute and chronic effects of radiation and chemotherapy are known to contribute to swallowing impairment, the effect of a neck dissection, performed 6–8 weeks following the completion of treatment is unknown. Methods: Retrospective review of Stage III/IV squamous carcinoma patients treated with primary radiation with/without chemotherapy and a post-treatment neck dissection, who remain free of locoregional or distant failure for a minimum of two years. Predictors of prolonged feeding tube dependence (>24 months following the completion of treatment) were evaluated using univariate and multivariate analysis. To determine the independent effect of neck dissection on length of feeding tube dependence, patients matched for covariates were also compared. Results: 79 patients treated at the Fox Chase Cancer Center between 1992 to 2003 were included in this study. 61 (77.2%) received chemotherapy and 37 (46.8%) underwent a neck dissection. The surgical specimen was positive for residual carcinoma in 12 patients (33%). 57 patients (71.3%) underwent placement of a feeding tube. The median time to removal of feeding tubes was 12 months [7–17 months, 95% CI]. Feeding tube-free status at 24 months was associated with use of standard radiotherapy (p = 0.031), N0 vs N+ neck stage (p = 0.041) and management without a neck dissection (p = 0.003). There was no association with age, T-stage, tumor site or use of chemotherapy. On multiple regression, only neck dissection remained a predictor of retained feeding tube at 24 months (p = 0.013). In patients matched for N-stage and treatment selection, those who underwent a neck dissections required a feeding tube a median of 36 months compared with 10 months for those without a neck dissection [32–57 months versus 7–13 months, 95% CI, p = 0.021]. The two year frequency of feeding tube dependence was 14/34 (41%) versus 3/30 (10%), respectively (p = 0.005). Conclusions: Neck dissection may contribute dysphagia experienced by head and neck cancer patients treated with organ preservation protocols.

No significant financial relationships to disclose.

The treatment of non-metastatic prostate cancer with external beam radiation therapy

Multiple treatment options exist for men with non-metastatic prostate cancer. For nearly 50 years, external beam radiation therapy (EBRT) has been an important means of treating men with this disease. Improvements in technology and better use of pre-treatment variables including prostate specific antigen (PSA), Gleason score and prediction nomograms have steadily improved biochemical and clinical outcomes. This article reviews the current status of EBRT in the treatment of prostate cancer. Differences in technique as well as clinical results using conventional, 3D conformal and intensity modulated radiation therapy are compared and contrasted. The appropriate use of adjuvant hormones as well as the complications of these treatments will also be discussed.

Megavoltage radiotherapy for aneurysmal bone cysts

PURPOSE

An aneurysmal bone cyst (ABC) is a rapidly expansile and destructive benign tumor of bone that is usually treated by curettage and bone graft, with or without adjuvant treatment. For recurrent tumors, or tumors for which surgery would result in significant functional morbidity, does radiotherapy (RT) provide a safe and effective alternative for local control?

PATIENTS AND METHODS

Nine patients with histologically diagnosed aneurysmal bone cysts without other associated benign or malignant tumors were treated at the University of Florida with megavoltage RT between February 1964 and June 1992. The patients received local radiotherapy doses between 20 and 60 Gy, with 6 patients receiving 26--30 Gy. In 6 patients the diagnosis was made by biopsy alone; 3 underwent intralesional curettage before RT. Minimum follow-up was 20 months; 7 of 9 patients (77%) had follow-up greater than 11 years.

RESULTS

No patient experienced a local recurrence (median follow-up, 17 years). One patient required stabilization of the cervical spine 10 months after RT because of dorsal kyphosis from vertebral body collapse. No other significant side effects were experienced, and no patients developed secondary malignancies. Four patients were lost to follow-up: at 20 months, 11.5 years, 17 years, and 20 years after the initiation of treatment, none with any evidence of local recurrence. All of the patients who had significant pain before RT had relief of their symptoms within 2 weeks of completion of therapy.

CONCLUSIONS

Using modern-day RT, patients with recurrent or inoperable aneurysmal bone cysts can be treated effectively (with minimal toxicity) using a prescribed tumor dose of 26--30 Gy.