Citations

Abstract Rationale Lymphangioleiomyomatosis (LAM) is a rare, progressive, cystic lung disease affecting women. Sirolimus has been shown to stabilize lung function in women with LAM, but real-world data on long-term safety and efficacy are limited. Methods The NIH Multicenter Safety and Durability of Sirolimus for LAM (MIDAS, NCT02432560) observational registry was launched in 2015. All adult (≥18 years) women with LAM (treated or untreated) were eligible to enroll at any of the 20 U.S. sites and followed longitudinally with serial assessments of lung function, health-related quality of life, and treatment related adverse event (TRAEs). Baseline cohort characteristics and TRAEs are summarized using descriptive analyses. Marginal structural models (MSMs) with inverse probability of treatment weighting estimated the causal effect of sirolimus on annualized forced expiratory volume in one-second (FEV1) decline, adjusting for age at LAM diagnosis, prior treatment with sirolimus, menopausal status, race, presence of angiomyolipomas, supplemental oxygen use; time-varying covariates included diffusing capacity for carbon monoxide (DLCO) and serum vascular endothelial growth factor-D (VEGF-D) levels. Results Longitudinal data was available in 350 LAM patients, most of whom (246, 70.3%) had sporadic LAM. The median age at the baseline pulmonary function test (PFT) measurement was 46 years (range: 19 - 74) and the median (IQR) number of serial PFTs obtained per patient was 3 (1 - 5). The average follow-up duration per patient was 2.8 years. Over half of the patients (196, 56%) were treated with sirolimus during the MIDAS observation period for a median (IQR) treatment duration of 4.9 (2.4 - 7.5) years. MSM analysis demonstrated that sirolimus treatment was durably effective and reduced FEV₁ decline by 74.36 mL/year (95% CI: 15.87 - 132.85) compared with no treatment (-85.31 mL/year for the untreated group vs. -10.95 mL/year for the treated group, p = 0.01). Sirolimus was generally well tolerated; treatment interruption ≥3 months was observed in 38 (19.4%) of the 196 sirolimus treated patients. Logistic regression analysis showed that higher levels of FEV1 (odds ratio: OR = 3.12 [1.45 - 7.11], p = 0.005), VEGF-D (OR = 1.0007 [1.0004 - 1.001], p < 0.001), and DLCO (OR = 1.023 [1.0053 - 1.0413, p = 0.01]), were associated with treatment interruption. Conclusions In the MIDAS cohort, sirolimus treatment resulted in durable stabilization of lung function with a favorable safety profile over a 5-year period. These real-world data support sirolimus as a chronic suppressive therapy for LAM, demonstrating durable efficacy in slowing lung disease progression and tolerability with long-term use. This abstract is funded by: National Institutes of Health

Abstract Introduction: Radiotherapy (RT)-induced acute esophagitis (AE) is a common side effect in lung cancer patients receiving RT, which can significantly impact their quality of life. This highlights the need for a predictive model that can estimate AE risk in advance using pretreatment imaging data. However, collecting sufficient data for model development is often resource-intensive and costly. Additionally, acquiring a homogeneous training dataset (e.g., from a single center or modality) is not always feasible. This study aimed to develop an automated artificial intelligence-based 3D vision foundation model (VFM) combining standard-of-care planning computed tomography (pCT) and planned radiation dose maps to predict grade II or higher AE. Materials and methods: This study included 246 patients with non-small cell lung cancer who underwent either image-guided radiation treatment (IMRT) or proton-beam radiation therapy. The endpoint was grade two or higher AE (33% positive and 67% negative). The IMRT group consisted of 182 patients from a single center, whereas the proton therapy group included 64 patients from the Proton Collaborative Group trial from 11 different institutions. For each patient, pCT, dose maps, and radiotherapy segmentations were available. The VFM was created using a transformer pretrained using a large number of unlabeled volumetric 3D CTs from patients with varied diseases through a self-supervised learning approach, which extracts useful features directly from images. Next, the pretrained encoder was combined with fully connected classification layers and fine-tuned using stratified 5-fold cross-validation with 20 patients set aside for testing. We developed two models: a CT only and CT + dose model. Model performance was assessed using the area under the curve (AUC), specificity, and sensitivity. Results: In cross-validation, adding dose information to CT (CT+Dose) improved model performance, increasing AUC from 0.72 ± 0.08 to 0.76 ± 0.10 and specificity from 0.82 ± 0.09 to 0.87 ± 0.04, while sensitivity remained the same. On the independent test set, CT+Dose showed a marked improvement over CT only (AUC: 0.82 vs. 0.59; sensitivity: 0.57 vs. 0.14), with a slight decrease in specificity (0.77 vs. 1.00). Conclusion: A VFM model combining CT and radiation dose showed the capability to predict AE more accurately with higher specificity. Further studies on larger cohorts of testing patients are planned to assess model generalization. Citation Format: Chloe Min Seo Choi, Jue Jiang, Nikhil Mankuzhy, John Chang, Jing Zeng, Carlos Vargas, James Urbanic, Isabella Choi, Mark Mcdonald, James Gray, Joseph Deasy, Maria Thor, Charles Simone, Harini Veeraraghavan. Prediction of radiotherapy-Induced esophagitis in non-small cell lung cancer using a 3D vision foundation model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Artificial Intelligence and Machine Learning; 2025 Jul 10-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(13_Suppl):Abstract nr B022.

Abstract Purpose: Clinical trials reported 25% to 30% pathologic complete response (pCR) rates in HER2+ patients with breast cancer treated with anti-HER2 therapies without chemotherapy. We hypothesize that a multiparameter classifier can identify patients with HER2-“addicted” tumors who may benefit from a chemotherapy-sparing strategy. Experimental Design: Baseline HER2+ breast cancer specimens from the TBCRC023 and PAMELA trials, which included neoadjuvant treatment with lapatinib and trastuzumab, were used. In the case of estrogen receptor–positive (ER+) tumors, endocrine therapy was also administered. HER2 protein and gene amplification (ratio), HER2-enriched (HER2-E), and PIK3CA mutation status were assessed by dual gene protein assay (GPA), research-based PAM50, and targeted DNA-sequencing. GPA cutoffs and classifier of response were constructed in TBCRC023 using a decision tree algorithm, then validated in PAMELA. Results: In TBCRC023, 72 breast cancer specimens had GPA, PAM50, and sequencing data, of which 15 had pCR. Recursive partitioning identified cutoffs of HER2 ratio ≥ 4.6 and %3+ IHC staining ≥ 97.5%. With PAM50 and sequencing data, the model added HER2-E and PIK3CA wild-type (WT). For clinical implementation, the classifier was locked as HER2 ratio ≥ 4.5, %3+ IHC staining ≥ 90%, and PIK3CA-WT and HER2-E, yielding 55% and 94% positive (PPV) and negative (NPV) predictive values, respectively. Independent validation using 44 PAMELA cases with all three biomarkers yielded 47% PPV and 82% NPV. Importantly, our classifier's high NPV signifies its strength in accurately identifying patients who may not be good candidates for treatment deescalation. Conclusions: Our multiparameter classifier differentially identifies patients who may benefit from HER2-targeted therapy alone from those who need chemotherapy and predicts pCR to anti-HER2 therapy alone comparable with chemotherapy plus dual anti-HER2 therapy in unselected patients.

522 Background: Our preclinical findings suggest a role for the mevalonate pathway (MVA) in treatment resistance in HER2+ BC by providing alternative growth and survival signaling to bypass potent HER2 blockade, which could be overcome by the MVA inhibitors statins and nitrogen-containing bisphosphonates (NBs). Here we explored the effect of MVA inhibitors’ use on pts’ outcomes in the ALTTO trial (BIG2-06; NCT00490139). Methods: In the ALTTO trial, 8381 pts with HER2+ BC were randomized to 1 year of adjuvant lapatinib (L), trastuzumab (T), L+T, or T→L. All pts with documented treatment start with statins or NBs < 1 year after randomization were considered as MVA inhibitors users. Survival curves, with a median follow-up of 6.9 years, for disease-free survival (DFS), distant relapse-free interval (DRFI), BC-specific survival (BCSS), and overall survival (OS) according to MVA inhibitors use were estimated by the Kaplan Meier method and Log-rank test. All multivariate survival analyses employed a Cox proportional hazards regression model, adjusting for tumor size, nodal status, hormonal receptor (HoR), menopausal status, BMI, timing of chemo, and randomization arm. We considered interactions terms in Cox’s model between MVA inhibitors use and randomization arm, hormonal status, and BMI group. Results: Among the 8381 pts included in this study, 493 and 299 were statins or NBs users, respectively. Table 1 summarizes the significant differences in pts’ characteristics according to MVA inhibitors use ( P <.005). In multivariate survival analyses, only NBs use was associated independently with better BCSS (HR, 0.44; 95% CI, 0.23 - 0.84; P = 0.014). Statin use was not independently associated with prognosis but only in interaction with pts characteristics: worse DFS, BCSS and OS in pts treated with L+T, worse DRFI and OS in pts treated with HoR+ BC (respective interaction P-values <0.05 in the Cox’s model). Conclusions: NBs independently predicted improved BC-specific outcome in pts with HER2+ BC treated with adjuvant anti-HER2 therapy. Statin use was associated with an inferior outcome in pts with HoR+ disease and/or those treated with L+T. Whether this inferior association in statin users may reflect the underlying predisposition factors that can weaken the efficacy of anti-HER2 treatments and whether this effect was observed only in the L+T arm due to the more potent inhibition of the HER2 signaling pathway remain open questions. Further clinical investigations on the impact of MVA inhibitors on the outcome of pts with HER2+ BC are warranted. [Table: see text]

1011 Background: Several trials have shown 25-30% pathologic complete response (pCR) rates in patients with HER2+ BC treated with LT therapy (+ endocrine therapy if ER+), but no chemotherapy (CTX). We hypothesize that a multiparameter classifier, comprised of HER2 gene and protein levels, intratumor heterogeneity (ITH), HER2-enriched (E) subtype, and PIK3CA mutation status can identify patients whose tumors are “addicted” to HER2 signaling and are likely to achieve pCR from a CTX-sparing de-escalation strategy. Methods: Baseline specimens from 2 trials (TBCRC023 [NCT00999804] and PAMELA [NCT01973660]) of neoadjuvant CTX-sparing LT (+ endocrine therapy if ER+) in HER2+ BC were used. HER2 protein and ITH (scored for % 3+ by IHC), and gene amplification (HER2:CEP17 ratio and copy number (CN) by CISH) were measured on the same slide by the dual gene protein assay (GPA). HER2-E and PIK3CA mutation status were assessed by research-based PAM50 and MSK-IMPACT platforms, respectively. A decision tree algorithm was used to determine the GPA cutoffs and to construct the classifier of response (by pCR) in TBCRC023, which was then validated in PAMELA. Results: Of the evaluable patients from TBCRC023 (N = 130) and PAMELA (N = 151), GPA data were available for 121 and 94 cases, respectively. Both cohorts exhibited similar distributions for HER2 ratio, CN, and % 3+, and a strong correlation between HER2 ratio and CN (R > 0.92). In TBCRC023, 73 cases had data from GPA, PAM50, and IMPACT, of which 15 had pCR. Recursive partitioning identified cutoffs of HER2 ratio > 4.6 and % 3+ > 97.5% in both the GPA data cohort (N = 121) and complete data cohort (N = 73). With PAM50 and IMPACT data, the model added HER2-E and PIK3CA wild-type (wt). For practical reasons, the classifier was locked as HER2 ratio ≥ 4.5 AND % 3+ ≥ 90% AND PIK3CA-wt AND HER2-E, which yielded a PPV of 55% and NPV of 94%. Validation in PAMELA using 45 cases with data for all 3 assays yielded PPV of 44% and NPV of 82%. 29 TBCRC023 cases without IMPACT data could be predicted to be non-pCR, of which 26 were correct (NPV = 89%). In PAMELA, 66 additional cases could be predicted to be non-pCR, of which 54 were correct (NPV = 81%). Conclusions: We have constructed a multiparameter classifier that can predict pCR with targeted therapy alone that compare to pCR rates of CTX + dual anti-HER2 in unselected patients. Prospective validation in a clinical trial is warranted. [Table: see text]

Abstract Purpose: Prior neoadjuvant trials with 12 weeks of dual anti-HER2 therapy without chemotherapy demonstrated a meaningful pathologic complete response (pCR) in patients with HER2-positive breast cancer. In this trial, we sought to determine whether longer treatment would increase the rate of pCR. Patients and Methods: TBCRC023 (NCT00999804) is a randomized phase II trial combining a Simon phase II design in the experimental arm with a pick-the-winner design, not powered for direct comparison. Women with HER2-positive breast tumors measuring ≥2 cm (median = 5 cm) were randomized in a 1:2 ratio to 12 versus 24 weeks of lapatinib and trastuzumab. Letrozole (along with ovarian suppression if premenopausal) was administered in patients whose tumors were also estrogen receptor (ER) positive. All evaluable patients were assessed for in-breast pCR. Results: Ninety-seven patients were enrolled (33 in 12-week arm and 64 in 24-week arm), of whom 94 were evaluable. Median age was 51 years, and 55% were postmenopausal. Median tumor size was 5 cm, and 65% were ER-positive. The rate of pCR in the 24-week arm was 28% and numerically superior to the 12-week arm (12%). This was driven by increased pCR in the ER-positive subgroup (33% vs. 9%). Study treatment was well tolerated, with grade 1–2 diarrhea and acneiform rash being the most common toxicities. Conclusions: Treatment with dual anti-HER2 therapy for 24 weeks led to a numeric increase in pCR rate in women with HER2-positive breast cancer, without using chemotherapy. If validated, this approach may help identify patients who may benefit from deescalation of therapy.

Abstract Rationale Lymphangioleiomyomatosis (LAM) is a progressive cystic lung disease that predominantly affects women and can worsen with pregnancy, estrogen treatment, and the menstrual cycle, suggesting an important role for estrogen in disease pathogenesis. Objectives To assess the efficacy and safety of the aromatase inhibitor letrozole in the treatment of LAM. Methods Seventeen postmenopausal women with LAM were enrolled in this phase II trial and randomized to receive letrozole 2.5 mg daily (n = 9) or placebo (n = 8) for a period of 12 months. Five patients in each group were also taking sirolimus at baseline and remained on the drug throughout the treatment period. Lung function, exercise capacity, quality of life, and serum vascular endothelial growth factor D (VEGF-D) were measured at baseline and at 3-month intervals. Results Fifteen patients completed the study. Two patients withdrew. There were no differences in adverse events in the letrozole and placebo groups. The target enrollment of 25 patients per arm was not met, so the efficacy of letrozole could not be assessed as planned. After adjusting for sirolimus use, we found that the rate of change in FEV1 for all subjects was −3 ± 3 ml/mo (P = 0.4), and for serum VEGF-D, the rate of change was −0.024 ± 0.009 pg/ml/mo (P = 0.015), showing a steeper decline in the letrozole group (−0.029 ± 0.013; P = 0.025). All patients who were taking sirolimus had a reduction in VEGF-D levels from baseline to the last visit, compared with only half of the patients who were not taking sirolimus. In a post hoc analysis, eight matched letrozole-treated–placebo-treated pairs were constructed, six of which demonstrated better FEV1 improvement for the letrozole-treated patients. Conclusions Letrozole treatment appears to be safe and well tolerated in postmenopausal patients with LAM, including those taking sirolimus. Enrollment in this trial was compromised by the publication of an effective treatment (sirolimus) in the same month as the study opened, resulting in limited power to detect treatment effects. Post hoc matched pairs exploration studies provide tentative support for additional studies of letrozole in LAM. Considering the reduced rate of lung function decline in postmenopausal patients, future studies will likely require enhanced study designs, such as selective enrollment of those with prognostic biomarkers predictive of decline. Clinical trial registered with www.clinicaltrials.gov (NCT01353209).

Abstract Survival is linked to the histopathologic distinction between usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP), the most commonly encountered fibrotic idiopathic interstitial pneumonia. We retrospectively compared the prognostic significance of histopathologic diagnoses, baseline pulmonary function indices, and serial trends in pulmonary function indices (diffusing capacity, FVC, FEV1, the recently defined composite physiologic index) at 6 and 12 months in 104 patients (UIP, n = 63; fibrotic NSIP, n = 41). Survival was lower in UIP than in fibrotic NSIP (p = 0.001) but not in patients with severe functional impairment; mortality during the first 2 years was linked solely to the severity of functional impairment at presentation. The composite physiologic index was the strongest determinant of outcome (p &lt; 0.001). At 6 months, serial diffusing capacity levels (p = 0.003) and histopathologic diagnosis (p = 0.002) were prognostically equivalent. At 12 months, serial pulmonary function trends were the only major prognostic determinant (p &lt; 0.0005 for all variables), with no independent significance associated with the distinction between UIP and fibrotic NSIP. We conclude that at 12 months, serial pulmonary function trends have considerable prognostic value in UIP and NSIP. Their histologic distinction provides no additional prognostic information when pulmonary function trends are clear cut or when functional impairment is severe.