Prospective Pilot Study of 18F-Fluoroestradiol PET/CT in Patients With Invasive Lobular Carcinomas.

BACKGROUND. PET/CT with 18F-fluoroestradiol (FES) (FDA-approved in 2020) depicts tissues expressing estrogen receptor (ER). Invasive lobular carcinoma (ILC) is commonly ER positive. OBJECTIVE. The primary aim of this study was to assess the frequency with which sites of histologically proven ILC have abnormal uptake on FES PET/CT. METHODS. This prospective single-center pilot study, conducted from December 2020 to August 2021, enrolled patients with histologically confirmed ILC to undergo FES PET/CT; patients optionally underwent FDG PET/CT. Two nuclear radiologists assessed FES PET/CT and FDG PET/CT studies for abnormal uptake corresponding to known ILC sites at enrollment and for additional sites of abnormal uptake, resolving differences by consensus. The primary endpoint was percentage of known ILC sites showing abnormal FES uptake. The alternative to the null hypothesis was that more than 60% of sites would have abnormal FES uptake, exceeding the percentage of ILC with abnormal FDG uptake described in prior literature. A sample size of 24 biopsied lesions was preselected to provide 81% power for the alternative hypothesis (one-sided α = .10). Findings on FES PET/CT and FDG PET/CT were summarized for additional secondary endpoints. RESULTS. The final analysis included 17 patients (mean age, 59.1 ± 13.2 years) with 25 sites of histologically confirmed ILC at enrollment (22 breast lesions, two axillary lymph nodes, one distant metastasis). FES PET/CT showed abnormal uptake in 22 of 25 (88%) lesions, sufficient to reject the null hypothesis (p = .002). Thirteen patients underwent FDG PET/CT. Four of 23 (17%) sites of histologically confirmed ILC, including additional sites detected and confirmed after enrollment, were identified with FES PET/CT only, and 1 of 23 (4%) was identified only with FDG PET/CT (p = .18). FES PET/CT depicted additional lesions not detected with standard-of-care evaluation in 4 of 17 (24%) patients (two contralateral breast cancers and two metastatic axillary lymph nodes, all with subsequent histologic confirmation). Use of FES PET/CT resulted in changes in clinical stage with respect to standard-of-care evaluation in 3 of 17 (18%) patients. CONCLUSION. The primary endpoint of the trial was met. The frequency of abnormal FES uptake among sites of histologically known ILC was found to be to be significantly greater than 60%. CLINICAL IMPACT. This pilot study shows a potential role of FES PET/CT in evaluation of patients with ILC. TRIAL REGISTRATION. ClinicalTrials.gov NCT04252859.

Response to post-axitinib treatment in patients with metastatic renal cell carcinoma.

BACKGROUND: Axitinib is a potent inhibitor of the vascular endothelial growth factor (VEGF) receptor family with clinical activity in patients with metastatic renal cell carcinoma (mRCC). Given this biochemical potency, the clinical activity of subsequent treatment with targeted therapies in patients progressing on axitinib is of interest. METHODS: Patients with advanced renal cell carcinoma of any pathologic subtype treated with at least one cycle (four weeks) of axitinib followed by at least one subsequent targeted therapy were investigated in a retrospective analysis. Patient characteristics, duration of treatment and clinical outcomes were analyzed for axitinib and each subsequent line of therapy by Response Evaluation Criteria in Solid Tumors (RECIST). RESULTS: Twenty-five mRCC patients who received at least one approved targeted agent following axitinib were identified. Eight percent of patients achieved a partial response (one patient each to sunitinib and pazopanib) and 42 % had a best response of stable disease to the first therapy after axitinib. The estimated median duration of therapy was 4.4 months (range, 0.2-27.5+). Twelve patients received a second post-axitinib targeted therapy. Six out of 11 evaluable patients (55 %) had a best response of SD. The estimated median duration of treatment was 4.8 months (range, 0.7-19.1+). CONCLUSION: Objective responses and stable disease is observed to post-axitinib targeted therapies and prospective studies are needed for validating role of predictive biomarkers.

TOWARDS Study: Patient-Derived Xenograft Engraftment Predicts Poor Survival in Patients With Newly Diagnosed Triple-Negative Breast Cancer.

PURPOSE: Assessing risk of recurrence for nonmetastatic triple-negative breast cancer (TNBC) is a key determinant of therapeutic strategy. The best predictor of recurrence risk is failure to achieve a pathologic complete response after preoperative chemotherapy, but it imperfectly correlates with the definitive end points of relapse-free and overall survival (OS). The inability to accurately predict recurrence has led to increasingly toxic treatment regimens for patients with early-stage TNBC. Better assays for recurrence risk are needed to tailor aggressive therapy for patients who need it and avoid overtreatment and unnecessary toxicity for those at low risk. The purpose of this study was to determine if patient-derived xenograft (PDX) engraftment of newly diagnosed breast tumors can serve as an accurate predictor of recurrence and death from breast cancer. METHODS: This study was a blinded noninterventional trial comprising 80 patients with newly diagnosed, nonmetastatic, estrogen receptor (ER)-negative or ER-low breast cancer. RESULTS: PDX engraftment was strongly associated with relapse in 1 year: 8 of 18 (44.4%) patients whose tumors engrafted relapsed versus 1 of 62 (1.6%) patients whose tumors did not engraft (P < .0001). Patients whose tumors engrafted had a hazard ratio (HR) for relapse of 17.5. HRs for OS and breast cancer-specific survival in PDX+ patients were 21.1 and 39.5, respectively. CONCLUSION: We report that the ability of a tumor to engraft as a PDX predicts early recurrence by serving as a functional readout of aggressiveness and prospectively identifies the most devastating tumors. This provides new opportunity to develop surrogate assays, such as biomarkers of engraftment, which will extend the clinical feasibility of this finding.

Time from definitive therapy to onset of metastatic disease predicts outcomes in men with metastatic hormone sensitive prostate cancer.

PURPOSE: Contemporary treatment for metastatic hormone sensitive prostate cancer (mHSPC) includes androgen deprivation therapy (ADT) plus abiraterone or docetaxel. While these intensified regimens have improved efficacy, they are also associated with increased cost and toxicities. Not all men with mHSPC may be candidates for these intensified regimens, yet there are no clinical models or biomarkers used to optimize treatment selection. Herein, we hypothesized that longer time from prior definitive therapy (DT), either radical prostatectomy, definitive radiotherapy, or both, to onset of metastatic disease is associated with improved survival outcomes in men with newly diagnosed mHSPC. METHODS: This multicenter retrospective study included men initiating systemic therapy with ADT for new mHSPC. Kaplan-Meier and COX proportional hazard models assessed time to metastatic castration-resistant prostate cancer (mCRPC) and overall survival (OS) by receipt of prior DT. RESULTS: Of the 253 men with new mHSPC, 115 (45%) had received prior DT. In a multivariate analysis, increasing years from DT to the start of ADT was an independent predictor of time to mCRPC (per year: hazard ratio 0.91 95% confidence interval 0.84-0.99, P = 0.020) and improved OS (per year: hazard ratio 0.87, 95% confidence interval 0.74-0.99, P = 0.0025) in patients with new mHSPC, and may assist with risk stratification in these patients at time of mHSPC. CONCLUSION: Time from DT to start of ADT is an independent predictor of time to mCRPC and OS in men with new mHSPC, and may assist with risk stratification of these patients for systemic therapy selection.

Outcome of patients with metastatic sarcomatoid renal cell carcinoma: results from the International Metastatic Renal Cell Carcinoma Database Consortium.

BACKGROUND: Sarcomatoid renal cell carcinoma is associated with poor prognosis. Data regarding outcome in the targeted therapy era are lacking. PATIENTS AND METHODS: Clinical, prognostic, and treatment parameters in metastatic renal cell carcinoma patients with and without sarcomatoid histology treated with targeted therapy were retrospectively analyzed. RESULTS: Two thousand two hundred eighty-six patients were identified (sRCC: n = 230 and non-sRCC: n = 2056). sRCC patients had significantly worse IMDC prognostic criteria compared with non-sRCC (11% vs. 19% favorable risk; 49% vs. 57% intermediate risk, and 40% vs. 24% poor risk; P < .0001). Time from original diagnosis to relapse (excluding synchronous metastatic disease) was shorter in the sRCC group (18.8 vs. 42.9 months; P < .0001). There was no significant difference in the incidence of central nervous system metastases (6%-8%) or underlying clear cell histology (87%-88%). More than 93% of patients received VEGF inhibitors as first-line therapy; objective response was less common in sRCC whereas primary refractory disease was more common (21% vs. 26% and 43% vs. 21%; P < .0001, for both). sRCC patients had significantly less use of second- (P = .018) and third-line (P < .0001) systemic therapy. The median progression-free survival (PFS)/overall survival (OS) was 4.5/10.4 months in sRCC patients and 7.8/22.5 months in non-sRCC patients (P < .0001 for both). Sarcomatoid histology was associated with a significantly worse PFS and OS after adjusting for individual IMDC risk factors in multivariable analysis (hazard ratio, 1.5; P < .0001 for both). CONCLUSION: Patients with sRCC have a shorter time to relapse, worse baseline prognostic criteria, and worse clinical outcome with targeted therapy. Additional insight into the biology of sRCC is needed to develop alternative therapeutics.