Tumor Shrinkage Research Articles

Abstract C034: Investigating residual disease in its spatial context in BRCA1 p53-deficient mammary tumors

Abstract Although various effective anti-cancer treatments have become available over the last decades, resistance to all available therapies remains the major cause of death of cancer patients with disseminated tumors. Striking examples are patients with triple-negative breast cancer (TNBC), which are frequently defective in the repair of DNA double strand breaks, e.g. due to loss of BRCA1 function. Because of this defect, the patients initially respond very well to DNA damage-inducing chemotherapy. Unfortunately, disseminated tumors are usually not eradicated and resistant tumor cells are eventually selected from residual primary or metastatic tumor sites. It is therefore crucial to understand the molecular mechanisms underlying the drug tolerance of the residual tumor cells. To study residual disease, we used the K14cre;Brca1 F/F ;p53 F/F (KB1P) mouse model for hereditary breast cancer, which provides the unique opportunity to explore and target those mechanisms in a fully immunocompetent model. The mammary tumors that spontaneously develop highly resemble their human counterparts, both morphologically and in their therapy response. For example, tumors shrink in response to poly(ADP-ribose) polymerase inhibition, platinum-based treatment or the commonly used doxorubicin, docetaxel and cyclophosphamide (TAC) combination therapy. But despite repeated drug sensitivity, the KB1P mammary tumors are not eradicated, not even by a frequent dosing schedule. By combining single-cell RNA sequencing, spatial transcriptomics and imaging mass cytometry, we dissected the intratumoral heterogeneity and alterations in the tumor microenvironment of residual disease. We identified specific subpopulations of tumor cells that have a survival benefit after treatment, and these occurred together with an altered microenvironment characterized by a highly reactive stroma infiltrated with both anti-inflammatory and pro-tumoral immune cells. Interestingly, those structural and transcriptional changes are reversed in the relapsed tumors, highlighting the plasticity of drug tolerance. To investigate the mechanisms of the altered tumor-stroma interactions that are relevant for drug tolerance, we have designed a custom-made CRISPR/Cas9 library based on differential gene expression of the residual tumor cells. This library enables us to functionally test relevant mechanisms of drug tolerance in vivo and we expect that these analyses will provide useful insights into the tumor-stroma interactions that contribute to residual disease. Taken together, our detailed analyses demonstrate the substantial remodeling of tumor cells in their microenvironment upon treatment. To develop new therapeutic approaches to eradicate drug-tolerant tumor cells and thereby circumvent tumor relapse, it is essential to better understand the heterogeneous cellular composition of residual tumors in its spatial context. With this project, we hope to provide comprehensive data to develop better therapeutic strategies that target the tumor-stroma interaction and eradicate residual tumors. Citation Format: Morgane Decollogny, Demeter Túrós, Astrid Chanfon, Myriam Siffert, Ismar Klebic, Sven Rottenberg. Investigating residual disease in its spatial context in BRCA1 p53-deficient mammary tumors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C034.

Abstract B023: Cell-free HPV-DNA dynamics during induction chemotherapy and response-stratified de-escalation in viral-mediated oropharyngeal cancer

Abstract Background: Cell-free HPV-DNA (cfHPV-DNA) in plasma represents a promising biomarker to grade treatment response and monitor for persistence/recurrence. We evaluated the dynamic changes of cfHPV-DNA during induction chemotherapy followed by response-stratified de-escalation in HPV associated (HPV+) oropharyngeal squamous cell cancer (OPSCC). Methods: A prospective biomarker clinical trial of response-stratified de-escalation therapy was conducted. Eligible patients had loco-regional HPV+ OPSCC and received induction chemotherapy with carboplatin and paclitaxel for three cycles followed by risk and response-stratified de-escalation with transoral robotic surgery (TORS), de-escalated radiation (RT) to 50Gy with or without cisplatin, or standard RT to 70Gy with cisplatin. Patients with deep response (>=50% tumor shrinkage per RECIST 1.1) qualified for de-escalated therapy. Cell-free HPV-DNA was measured using a CLIA-certified HPV-SEQ assay that utilizes NGS technology to detect and quantify HPV16 and HPV18 DNA in plasma at baseline, after each cycle of induction chemotherapy, during radiation, and post-treatment surveillance at 3, 6, 9, 12, 18, and 24 months following treatment. Results: Forty-six eligible patients were enrolled, with 464 cfHPV-DNA plasma samples analyzed (median 10 samples per patient). There were five recurrences (10.9%), all detected by HPV-SEQ. Baseline cfHPV-DNA was detected in 44/46 patients (96%). Patients with rapid early cfHPV-DNA clearance after one 3-week cycle of induction (>=95% clearance) predicted deep radiographic response following induction therapy (p=0.003). The detection of cfHPV-DNA at 3 months or later after treatment was associated with worse progression free survival (PFS), with 2-year PFS of 25% (95% CI 0.012-0.65) compared with patients without detectable cfHPV-DNA of 100% (95% CI 1.0-1.0); p<0.001). The longest lead-time from positive cfHPV-DNA to developing recurrent disease was 25 months. Conclusion: Rapid early clearance of cfHPV-DNA during induction has utility in predicting response to treatment. Detectable cfHPV-DNA following treatment is strongly associated with worse PFS. A subsequent trial using cfHPV-DNA to select patients for treatment de-escalation is ongoing. Clinicaltrials.gov ID: NCT04572100 Citation Format: Ari Rosenberg, Evgeny Izumchenko, John Cursio, Augustin Vannier, Aditya Juloori, Rohan Katipally, Rifat Hasina, Frederick Jones, Anna Starus, Elizabeth Blair, Daniel J. Haraf, Alexander T. Pearson, Everett E. Vokes, Nishant Agrawal. Cell-free HPV-DNA dynamics during induction chemotherapy and response-stratified de-escalation in viral-mediated oropharyngeal cancer [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B023.

Real-world evidence of effectiveness and safety of pasireotide in the treatment of acromegaly: a systematic review and meta-analysis.

Pasireotide long-acting release (PAS-LAR) is a second-generation somatostatin receptor ligand (SRL) approved for acromegaly treatment. This meta-analysis aimed to evaluate the real-world effectiveness and safety of PAS-LAR in patients with acromegaly resistant to first-generation somatostatin receptor ligands (fgSRL). A systematic literature search was conducted in PubMed and Web of Science for real-world studies on PAS-LAR in acromegaly published between 2014 and 2023. Random-effects meta-analyses were performed on biochemical control rates, tumor shrinkage, and metabolic parameters. Twelve studies comprising 409 patients were included. The pooled rate of insulin-like growth factor 1 (IGF-1) control was 57.9% [95% CI: 48.4-66.8] and the percentage of patients with tumor shrinkage was 33.3% [95%CI: 19.7-50.4]. Significant reductions were observed in growth hormone standardized mean difference (SMD) 0.6 ng/mL [95% CI: 0.3 to 1.0] and IGF-1 levels SMD 0.9 ULN [95% CI: 0.4 to 1.4]. However, as expected, a worsening in glucose metabolism was noted as an increase in fasting glucose SMD - 0.8mg/dL [95% CI: -1.0 to -0.5, p < 0.01], glycated hemoglobin SMD - 0.5% [95% CI: -0.7 to -0.2]. and type 2 diabetes mellitus prevalence SMD - 11.5% (95% CI: -17.5 to -5.5). PAS-LAR demonstrated higher effectiveness in real-world settings, with over 60% of patients achieving IGF-1 control compared to the around 30% efficacy observed in clinical trials. These findings suggest that PAS-LAR is an effective option for acromegaly patients resistant to fgSRL, but careful monitoring of glucose levels is essential. The high heterogeneity observed across studies emphasizes the need for identifying PAS-LAR response biomarkers to set-up individualized treatment approaches for optimizing patient outcomes.

Complete response to immunotherapy in a metastatic lymphoepithelioma-like bladder carcinoma: a case report

BackgroundLymphoepithelioma-like carcinoma of the bladder (LELC-B) is a very rare variant of bladder carcinoma, has a good prognosis, and possibly a high response to platinum-based chemotherapy (ChT) and immune-checkpoint inhibitors (ICI).Case presentationThis is the case of a male patient that presented a metastatic relapse of a LELC-B, the disease progressed after platinum based first line ChT. Second line with atezolizumab was initiated with progressive tumor shrinking until complete response was achieved. Final atezolizumab discontinuation was decided in agreement with the patient after 3 years of maintenance of complete response.ConclusionAfter the experience of this case and the few cases of neoadjuvant treatment with pembrolizumab of localized disease, it seems that immunotherapy may play a main role in the treatment of this variant of bladder carcinoma.

Surgical resection following chemoradiotherapy for thoracic SMARCA4-deficient undifferentiated tumor: a report of two cases

BackgroundThoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a high-grade malignant neoplasm with a poor prognosis. Most cases of SMARCA4-UT have extensive chest wall and mediastinum involvement. The efficacy of surgical resection has not been clearly established. Here, we report two surgical cases of SMARCA4-UT with chest wall invasion after chemoradiotherapy.Case presentationThe first patient was a 40-year-old man with back pain. Computed tomography revealed a 6.8 cm mass in contact with the thoracic vertebrae near the intervertebral foramen, which was suspected to involve the third to fifth ribs. The patient was diagnosed with SMARCA4-UT with clinical T3N0M0 stage IIB. The tumor shrank after chemoradiotherapy, and conversion surgery combined with partial vertebrectomy was performed. Histopathological findings revealed 30% residual tumor in the tumor bed. Thirty-six days after surgery, the patient developed multiple liver metastases and peritoneal dissemination. Chemotherapy combined with immune checkpoint inhibitor treatment was performed, resulting in tumor shrinkage. However, peritoneal dissemination recurred within a short interval. The patient died 5 months postoperatively. The second patient was a 74-year-old man with chest pain. Computed tomography revealed a 7.4-cm mass in the left upper lobe with invasion of the third and fourth ribs. The patient was initially diagnosed with non-small cell lung cancer with clinical T4N1M0 stage IIIA. The tumor shrank after induction chemoradiotherapy, and a left upper lobectomy combined with the chest wall resection was performed. Based on histopathological findings, the patient was diagnosed with SMARCA4-UT. The residual tumor percentage was 3%. The patient was followed up for 12 months postoperatively without recurrence.ConclusionsWe performed the complete resection of SMARCA4-UT following chemoradiotherapy. The two surgical cases had different postoperative courses. Radical surgery after chemoradiotherapy is effective for local control. However, its long-term prognostic efficacy remains unclear. Multidisciplinary approaches and further investigations of novel therapeutic options are required.

075. The Use of Tyrosine Kinase Inhibitor as Neoadjuvant Therapy in Patients with Thyroid Carcinoma: A Literature Review

Background: Papillary thyroid carcinoma (PTC) and medullary thyroid cancer (MTC) are the most common thyroid cancers in Indonesia, with an increasing incidence in recent years. The primary treatment for PTC is surgery, but it often faces challenges in managing invasive tumors. Tyrosine kinase inhibitors (TKI) have shown potential as neoadjuvant therapy to shrink tumors before surgery, though their use remains experimental. This study aims to evaluate the effectiveness of TKI as neoadjuvant therapy in patients with unresectable thyroid carcinoma, specifically PTC and MTC. Methods: Following PRISMA 2020 guidelines, a literature review was conducted using databases such as Cochrane, PubMed, EMBASE, and Scopus. The study selection was based on inclusion and exclusion criteria, with a risk of bias assessment performed using Joanna Briggs Institute tools. Data from case reports were extracted and analyzed qualitatively. Results: Eight case reports demonstrated that TKI, including Sunitinib, Lenvatinib, and Sorafenib, effectively reduced tumor size, allowing previously unresectable tumors to be surgically removed. Despite showing significant tumor shrinkage, adverse effects such as hypertension and gastrointestinal issues were noted, requiring careful management during treatment. Additionally, the duration of TKI therapy varied among the cases, but all showed notable improvements in tumor resectability. Conclusion: TKI shows promise as an effective neoadjuvant therapy for reducing tumor size in invasive PTC and MTC, making surgery more feasible. However, evidence is still limited to case reports, and further research is required to confirm the safety and effectiveness of TKI in this setting and to determine the appropriate patient selection criteria.

A comprehensive luminal breast cancer patient-derived xenografts (PDX) library to capture tumor heterogeneity and explore the mechanisms of resistance to CDK4/6 inhibitors.

Breast cancer (BC) is marked by significant genetic, morphological and clinical heterogeneity. To capture this heterogeneity and unravel the molecular mechanisms driving tumor progression and drug resistance, we established a comprehensive patient-derived xenograft (PDX) biobank, focusing particularly on luminal (estrogen receptor, ER+) and young premenopausal patients, for whom PDX models are currently scarce. Across all BC subtypes, our efforts resulted in an overall success rate of 17% (26 established PDX lines out of 151 total attempts), specifically 15% in luminal, 12% in human epidermal growth factor receptor 2 positive (HER2+) and 35% in triple negative BC. These PDX mirrored morphologic and genetic features of BC from which they originated, serving as a reliable tool to investigate drug resistance and test therapeutic strategies. We focused on understanding resistance to CDK4/6 inhibitors (CDK4/6i), which are crucial in the treatment of patients with advanced luminal BC. Treating a sensitive luminal BC PDX with the CDK4/6i palbociclib revealed that, despite initial tumor shrinkage, some tumors might eventually regrow under drug treatment. RNA sequencing, followed by gene set enrichment analyses, unveiled that these PDXs have become refractory to CDK4/6i, both at biological and molecular levels, displaying significant enrichment in proliferation pathways, such as MTORC1, E2F and MYC. Using organoids derived from these PDX (PDxO), we observed that acquisition of CDK4/6i resistance conferred cross-resistance to endocrine therapy and that targeting MTORC1 was a successful strategy to overcome CDK4/6i resistance. Considered together, these results indicate that our PDX models may serve as robust tools to elucidate the molecular basis of BC disease progression and, by providing the possibility to simultaneously test different therapies on the same tumor, to surmount treatment resistance. While this approach is of course not feasible in the clinic, its exploitation in PDX may expedite the identification and development of more successful therapies for patients with advanced luminal BC. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Design of Murine Double Minute 2 Proteolysis Targeting Chimera Degraders with a Built-In Tumor-Targeting Ability.

Proteolysis targeting chimeras (PROTACs) are heterobifunctional molecules to induce the proteasomal degradation of target proteins. Currently, there are no tumor-targeting PROTACs for modulating oncogenic murine double minute 2 (MDM2). AS1411 is a tumor-targeting aptamer that specifically recognizes nucleolin (NCL) overexpressed on the surface of tumor cells. We recently repurposed AS1411 as an MDM2 recruiter since it could form an NCL-bridged ternary complex with MDM2. In this study, we design a PROTAC molecule AS1411-VH032 via conjugating AS1411 with a recruiter of von Hippel-Lindau (VHL) ligase VH032. AS1411-VH032 facilitates tumor-selective degradation of MDM2, leading to tumor shrinkage with no detectable toxicity. Besides being a molecular target, MDM2 also serves as an E3 ligase harnessed by PROTACs. Thus, we developed an AS1411-based homo-PROTAC homoAS1411, which induces tumor-specific suicide degradation of MDM2 and prevents tumor progression without causing side effects. Both AS1411-VH032 and homoAS1411 are promising MDM2 degraders with built-in tumor-targeting ability, which balances the antitumor efficacy with a favorable safety profile.

Residual Vestibular Schwannomas: Proposed Age-Tumor-Residual (ATR) Staging System to Predict Future Growth.

To assess growth rates of residual vestibular schwannoma after subtotal and near-total surgical resection and establishing staging system for risk of residual tumor growth. Retrospective cohort study. Tertiary referral center. Patients with residual vestibular schwannoma after surgical resection from 2011 to 2023 identified on postoperative MRI defined as near-total resection (NTR, less than 5 mm of remaining tumor), subtotal resection (STR; 5-10 mm) and debulking (>10 mm). Tumor growth of 2 mm or more after subtotal or near-total surgical resection of vestibular schwannoma. A total of 56 patients (54% female; mean, standard deviation [SD] age 51 [17] yr) had residual tumor. Mean preoperative tumor size was 3.0 (1.1) cm, and residual tumors involved both sides with similar frequency (right: 52%). Quantitatively, 29% were NTR, 32% were STR, and 39% were debulking. With an average follow-up of 27 (SD 31) months, tumor growth occurred in 11 (20%), tumor shrinkage occurred in 16 (29%), and tumors were unchanged in 29 (51%) cases. Growing residual tumors were treated with radiation (7 patients) or a second surgical resection (4 patients). Multivariable analysis identified lower patient age, larger preoperative tumor size, and larger residual tumor size in risk of residual growth. A residual VS tumor staging system (Age, Tumor, Residual [ATR]) is proposed with most tumors in stage II (22, 42%) or stage III (23, 44%), whereas 7 (14%) tumors are stage I. Approximately 80% of residual VS are stable or shrink in size. Initial observation is advocated after incomplete resection and long-term follow up is needed. Patient age less than 55 years, larger preoperative tumor size, and larger postoperative residual tumor size appear predictive of residual tumor growth.Level of Evidence: 4.

Sustained Clinical Benefit and Intracranial Activity of Tarlatamab in Previously Treated Small Cell Lung Cancer: DeLLphi-300 Trial Update.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Tarlatamab, a bispecific T-cell engager immunotherapy targeting delta-like ligand 3, has shown durable anticancer activity and manageable safety in previously treated small cell lung cancer (SCLC) in DeLLphi-300 phase I and DeLLphi-301 phase II trials. Here, we report extended follow-up of DeLLphi-300 (median follow-up, 12.1 months [range, 0.2-34.3]) in fully enrolled cohorts treated with tarlatamab ≥10 mg dose administered once every two weeks, once every three weeks, or once on day 1 and once on day 8 of a 21-day cycle (N = 152). Overall, the objective response rate (ORR) was 25.0%; the median duration of response (mDOR) was 11.2 months (95% CI, 6.6 to 22.3), and the median overall survival (mOS) was 17.5 months (95% CI, 11.4 to not estimable [NE]). Among 17 patients receiving 10 mg tarlatamab once every two weeks, the ORR was 35.3%, the mDOR was 14.9 months (95% CI, 3.0 to NE), the mOS was 20.3 months (95% CI, 5.1 to NE), and 29.4% had sustained disease control with time on treatment ≥52 weeks. No new safety signals were identified. In modified Response Assessment in Neuro-Oncology Brain Metastases analyses, CNS tumor shrinkage of ≥30% was observed in 62.5% of patients (10 of 16) who had a baseline CNS lesion of ≥10 mm, including in a subset of patients with tumor shrinkage long after previous brain radiotherapy. In DeLLphi-300 extended follow-up, tarlatamab demonstrated unprecedented survival and potential findings of intracranial activity in previously treated SCLC.

Treatment of malignant primary cardiac tumors requires attention to cardiovascular complications: a single-center, retrospective study.

Malignant primary cardiac tumors require multimodal approaches including surgery, chemotherapy and radiotherapy, but these treatments can be associated with cardiovascular complications. However, few reports have described the cardiovascular complications related to primary cardiac tumor treatment because of their rarity. Clinical records of patients with primary cardiac tumors treated at Kyushu University Hospital from January 2010 to August 2021 were retrospectively examined. Of the 47 primary cardiac tumor patients, 13 (28%) were diagnosed with malignancy, including 5 angiosarcomas, 3 intimal sarcomas, 3 diffuse large B-cell lymphomas, 1 Ewing's sarcoma and 1 fibrosarcoma. Cardiovascular events were observed in 10 patients (77%), including cardiac dysfunction in 6 patients, arrhythmias in 5 patients, right heart failure in 2 patients, and excessively prolonged prothrombin time due to the combination of warfarin and chemotherapy in 1 patient. Two patients who showed notable cardiac complications are described. Case A involved a 69-year-old woman who underwent surgery for a left atrial intimal sarcoma, followed by postoperative chemotherapy with doxorubicin plus ifosfamide and radiotherapy. After three cycles of chemotherapy and sequential radiotherapy, her left ventricular ejection fraction decreased to 34%, and ongoing heart failure therapy was required. Case B involved a 66-year-old man who received chemotherapy for primary cardiac lymphoma, resulting in tumor shrinkage. However, due to tumor involvement of the intraventricular septum, atrioventricular block developed, requiring cardiac pacemaker implantation. High incidences of cardiac failure and arrhythmias were observed during multimodal treatments for malignant primary cardiac tumors. Proper management of complications may lead to a favorable prognosis in patients with malignant primary cardiac tumors.

Vimseltinib versus a placebo in patients with tenosynovial giant cell tumor: a plain language summary of the MOTION phase 3 trial.

This article presents a patient-friendly summary of the MOTION phase 3 clinical trial results, which were published in The Lancet in June 2024.The primary goal of the MOTION trial was to understand if treatment with a drug called vimseltinib shrank tumors more than a placebo in participants with symptomatic tenosynovial giant cell tumor, also known as TGCT, for which surgery was unlikely to provide benefit. A placebo is something that looks like the treatment being studied but does not contain any medicine.The MOTION trial compared the effects of vimseltinib versus a placebo using several different outcomes associated with TGCT. These outcomes included tumor size, active range of motion of the affected joint, and several patient-reported quality-of-life measures including physical function, stiffness, overall health, and pain. The trial showed that more participants treated with vimseltinib experienced significant tumor shrinkage, as defined by a 30% or greater reduction in tumor size, compared with those receiving a placebo. Participants receiving vimseltinib had improved active range of motion, and they reported improved physical function, stiffness, overall health, and pain, regardless of the amount of tumor shrinkage, compared with participants receiving a placebo. Most side effects in participants treated with vimseltinib were not severe and were manageable. Vimseltinib was better at shrinking tumors and improving active range of motion, stiffness, pain, and other health measures than the placebo for participants with TGCT. Vimseltinib has the potential to become a new treatment option for patients with TGCT for whom surgery may not provide benefit.

Proapoptotic activity of JNK-sensitive BH3-only proteins underpins ovarian cancer response to replication checkpoint inhibitors.

Recent studies indicate that replication checkpoint modulators (RCMs) such as inhibitors of CHK1, ATR, and WEE1 have promising monotherapy activity in solid tumors, including platinum-resistant high grade serous ovarian cancer (HGSOC). However, clinical response rates are generally below 30%. While RCM-induced DNA damage has been extensively examined in preclinical and clinical studies, the link between replication checkpoint interruption and tumor shrinkage remains incompletely understood. Here we utilized HGSOC cell lines and patient-derived xenografts (PDXs) to study events leading from RCM treatment to ovarian cancer cell death. These studies show that RCMs increase CDC25A levels and CDK2 signaling in vitro, leading to dysregulated cell cycle progression and increased replication stress in HGSOC cell lines independent of homologous recombination status. These events lead to sequential activation of JNK and multiple BH3-only proteins, including BCL2L11/BIM, BBC3/PUMA and the BMF, all of which are required to fully initiate RCM-induced apoptosis. Activation of the same signaling pathway occurs in HGSOC PDXs that are resistant to poly(ADP-ribose) polymerase inhibitors but respond to RCMs ex vivo with a decrease in cell number in 3-dimensional culture and in vivo with xenograft shrinkage or a significantly diminished growth rate. These findings identify key cell death-initiating events that link replication checkpoint inhibition to antitumor response in ovarian cancer.

Effect of replanning boost radiotherapy plan in locally advanced unresectable middle to lower thoracic esophageal cancer

Thoracic bulky esophageal cancer shrinks during radiotherapy, changing the location and shape of the surrounding heart and lungs. The current study aimed to explore how replanning by volumetric-modulated arc radiotherapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) influences the target coverage and dose to organs at risk in locally advanced unresectable middle to lower thoracic esophageal cancer. We retrospectively collected CT simulation images of initial and boost radiotherapy plans for locally advanced unresectable thoracic esophageal cancer in 17 consecutive patients. First, we created boost plans of 20 Gy using 3DCRT and VMAT on the initially acquired CT images. Second, we replicated the process on CT images acquired after 20–40 Gy of radiotherapy. We then compared non-replanned boost radiotherapy plans with replanned boost plans. Replanned radiotherapy delivered more conformal doses to the target and reduced heart and lung doses. VMAT reduced more irradiated mean doses to the heart than 3DCRT in the case of replanning (1.7 and 1.1 Gy, p < 0.001). Replanning to accommodate tumor shrinkage during radiotherapy effectively lowers the irradiated doses to the heart and lungs in patients with locally advanced unresectable middle to lower thoracic esophageal cancer, especially those treated with VMAT.

8617 Gender Differences In The Course Of Giant Prolactinomas - Single-Centre Case Series

Abstract Disclosure: M.A. Komisarz-Calik: None. A. Boguslawska: None. K. Ciszek: None. G. Zieliński: None. A. Hubalewska-Dydejczyk: None. A. Gilis-Januszewska: None. Introduction: Giant prolactinomas are the specific subtype of lactotroph PitNET, and are classified, according to their maximum diameter (≥40 mm). They constitute about 3% of prolactinomas. The prevalence is more common in men, however, the differences in the course of the disease between the genders remain unclear. Aim: The purpose of our study was to analyse gender differences in the course of giant prolactinomas. Materials and Methods: We analysed the data of consecutive patients with giant prolactinomas treated in the tertiary clinical center in the years 2022-2023. Results: There were 12 patients with giant prolactinoma (10 men and 2 women).Men and women were of similar age (32 vs 36 years). The maximum dimensions of the pituitary tumour in men were 56x70x67 mm, in women 60x55x55 mm. In all cases, treatment included dopamine agonists (cabergoline in 11 patients (all male patients and one female patient) and bromocriptine in one woman. Combined treatment with temozolomide and pasireotide were implemented in two male patients. In three men (30%) a surgical treatment was performed due to the visual field disturbances and severe headaches. Multiple surgeries were performed in two patients due to recurrence of symptoms and tumour progression (surgery was performed twice, and three times). One male patient received radiotherapy.The most frequent symptoms were associated with insufficiency of the adrenal, thyroid, and gonadal axis (80% vs 50%), visual field deficits (50% vs 50%) and headache (80% vs 0%), respectively in men and women. In men, the most common symptom was hypofunction of the gonadal axis (8 cases - 4 isolated gonadal axis hypofunction and 4 cases - hypofunction of the adrenal, thyroid and gonadal axis). In one woman, hypofunction of the three pituitary axes was present. Serum prolactin was higher in men than in women (6576 - 284232 ulU/ml vs 2000 - 5659 ulU/ml). In total, after treatment, prolactin concentration decreased in 7 cases, 5 men (50%) and 2 women (100%). The decrease in prolactin levels in men was by 80,4-99,9%, while in women it was by 83,9-86,7%. Tumour shrinkage was observed in 7 cases - 6/10 men and 1/2 woman. In men, tumour size was reduced by 27,5-64,4%. Tumour progression was observed in three cases, in 1 case the dimensions were stable. In two cases due to a recent diagnosis, follow-up MRI has not been yet performed. In women, tumour reduction by 99,8% was observed; in second the size of the tumour remained stable. Conclusions: The prevalence of giant prolactinomas is higher in men. The most frequent symptoms in both genders are visual field disturbances. The prevalence of tumour shrinkage is similar in both sexes, however giant prolactinomas require surgery more often in men. Further multicenter projects are needed to study the course of giant prolactinomas and to improve the outcomes of care. Presentation: 6/3/2024

7911 High Dose Serial Radioactive Iodine Therapies Facilitated byAutologous Stem Cell Cryopreservation in a Patient with Exceptionally Avid Metastatic FTC

Abstract Disclosure: S. Paknikar: None. D. Toro Tobon: None. J. Durski: None. H. Alkhateeb: None. M.M. Ryder: None. Introduction: Radioactive iodine (RAI) therapy-induced myelosuppression is a dose-limiting toxicity for RAI avid metastatic differentiated thyroid cancers. We describe a patient with exceptionally RAI avid metastatic follicular thyroid cancer (FTC) who underwent autologous stem cell cryopreservation (ASCC) to enable high dose I-131 treatments. Case: A 60-year-old woman with T1bN0M0 FTC underwent two-stage thyroidectomy and three doses of I-131 between 2002-2007 (434 mCi cumulative activity) due to incomplete biochemical response. She presented to our institution in 2015 with rising thyroglobulin (Tg) levels and lung nodules that were intensely RAI avid. She enrolled in a clinical trial of selumetinib versus placebo (for 1 month) followed by 150 mci I-131. She had a profound response with an 80% reduction in Tg and 50% tumor shrinkage. The following year her Tg rose to 8381 ng/mL and she developed biopsy proven, well differentiated metastatic FTC in the hip and liver. Lenvatinib treatment resulted in partial tumor and Tg response but was halted due to grade 3/4 toxicities. Tumor genomic interrogation revealed NRAS, PIK3CA, and TSH-R activating mutations, providing a causal explanation of her intensely RAI avid and responsive disease. Repeat I-131 therapy was facilitated by GM-CSF stimulated ASCC (8.57 x10(6) CD34+ cells/kg for two cycles) as a tool to help mitigate future potential RAI-induced myelosuppression. The patient received 295 mci I-131 followed by a 98% decrease in Tg and 20-25% shrinkage of liver metastases. Transient pancytopenia ensued but did not require autologous stem cell transplantation (ASCT). Due to insurance issues, the patient was lost to follow-up for two years. She returned with cachexia from severe, untreated thyrotoxicosis due to widespread functional, thyroxine producing metastatic disease. Anti-thyroid drug therapy (ATD) restored euthyroid status with significant clinical improvement. A non-stimulated I-123 whole body scan showed diffuse RAI avid disease with 88% whole body radioiodine retention at 48h. She received 125 mci I-131 with initial tumor response but with progression of bone marrow, calvaria, and retinal metastases. Six months later, a final dose of 253 mCi I-131 (cumulative activity 1,370 mCi) resulted in mixed tumor responses. Unfortunately, resection of a RAI refractory calvaria lesion postoperatively resulted in serious complications. ASCT and salvage treatments could not be pursued due to her impaired functional status. The patient pursued hospice care and passed away 20 years after her diagnosis. Conclusion: We characterize a patient with NRAS, PIK3CA and TSH-R mutant metastatic, thyroxine-producing FTC whose recurrences over 20 years retained intense RAI avidity and response to I-131 therapy. In cases with potential benefit from multiple high dose RAI therapies, ASCT may be a tool to mitigate I-131-induced myelosuppression. Presentation: 6/1/2024

7145 Enhanced Ability of the Small Peptide GH Receptor Antagonist, AZP-3813, to Decrease IGF1 When Combined with the Somatostatin Analog, Octreotide

Abstract Disclosure: G. Ravel: None. C. Berardet: Employee; Self; Amolyt Pharma. C. Chalmey: Employee; Self; Amolyt Pharma. H. Kurasaki: Employee; Self; Peptidream Inc. T. Tomiyama: Employee; Self; Peptidream Inc. P. Reid: Employee; Self; Peptidream Inc. D. Duracher: Employee; Self; Amolyt Pharma. R. Datta: Consulting Fee; Self; Amolyt Pharma. M. Aouadi: Employee; Self; Amolyt Pharma. M.D. Culler: Employee; Self; Amolyt Pharma. There is a strong rationale for combining a growth hormone (GH) receptor antagonist (GHRA) with somatostatin analog (SSA) therapy for acromegalic patients. While SSAs are the primary medical therapy for treatment of acromegaly, insulin-like growth factor 1 (IGF1) levels fail to normalize with SSA monotherapy in most patients. Even in patients with controlled IGF1, GH levels can remain elevated and induce symptoms by interacting with GH receptors throughout the body. In addition, while GHRAs have no significant effect on the causative pituitary tumor, SSAs can often induce tumor stabilization or shrinkage. AZP-3813 is a 16-amino acid, bicyclic peptide GHRA which has been demonstrated to potently decrease IGF1 in both rats and dogs. In order to examine the effect of combining AZP-3813 with a SSA in decreasing IGF1, 8-week old, male, Sprague Dawley rats were implanted subcutaneously with Alzet model 2002 minipumps containing either vehicle or the SSA, octreotide (OCT), at concentrations required to deliver either 20 or 40μg OCT/kg/day. Blood samples for IGF1 measurement were collected before, and 48 and 72 hours after pump implantation. Immediately following the 72-hour blood collection, rats from each infusion group were injected subcutaneously with either vehicle or AZP-3813 at 0.3, 1, 3, 10 or 30mg/kg (n=7/group). A subsequent blood sample was collected 24 hours after the injection of vehicle or AZP-3813, which also corresponded to 96 hours after pump implantation. Plasma levels of IGF1 were assessed by radioimmunoassay. In rats infused with vehicle, the 0.3mg/kg dose of AZP-3813 had no effect on IGF1 as compared with baseline; however, with higher doses a clear, dose-related decrease in IGF1 was observed ranging from -7 ± 3.0% with 1mg/kg AZP-3813 to -29 ± 2.0% with 30mg/kg. OCT infusion alone at 20μg/kg/day produced a -10 ± 3.6% decrease in IGF1, while injection of AZP-3813 into rats infused with 20μg/kg/day OCT, produced an enhanced, dose-related decrease, ranging from -7 ± 3.8% with 0.3mg/kg AZP-3813 to -38 ± 3.4% with 30mg/kg. A clear additive relationship was observed by focusing on the 3mg/kg dose of AZP-3813, which, alone, decreased IGF1 by -13 ± 2.8% in vehicle-infused rats. When injected into rats infused with OCT, which alone decreased IGF1 by -10 ± 3.6%, a combined decrease of -23 ± 3.3% was observed. The magnitude of the combined decrease was not statistically different from the decrease obtained with 30mg/kg AZP-3813 alone in vehicle-infused rats; thus, demonstrating a 10-fold increase in the effectiveness of AZP-3813 when combined with OCT. Similar results were observed with 40μg/kg/day OCT infusion. These results demonstrate the enhanced efficacy of AZP-3813 in decreasing IGF1 when combined with the SSA, OCT, and support the development of AZP-3813 as an add-on therapy in patients inadequately controlled with SSA treatment. Presentation: 6/3/2024

12612 Chiasmal Herniation - A Rare Complication Of Prolactinoma Treatment

Abstract Disclosure: A. Syeda: None. V. Kantorovich: None. Introduction: Primary treatment of symptomatic prolactinomas is medical therapy with dopamine agonists (DA). Herniation of optic chiasm is a rare complication of tumor shrinkage induced by DA therapy which causes secondary deterioration in visual fields. Case:A 26-year-old man presented to our hospital after a syncopal episode. He had headaches and blurry vision in the left eye for the past 4 months. He was diagnosed with a 4 cm x 3.6 cm x 2.6 cm pituitary macroprolactinoma compressing the optic chiasm, his prolactin (PRL) was 4700 ng/mL (N: 4.0-15.2 ng/mL) and testosterone was suppressed to 10 ng/dL (N: 249-836 ng/dL). Other hormonal workup was unremarkable. Ophthalmologic evaluation was consistent with left optic nerve pallor and neural rim thinning suggestive of a guarded prognosis. Immediate neurosurgical intervention was deemed unnecessary. Cabergoline 0.25 mg twice a week was initiated. Subsequently, the PRL levels improved but remained elevated to 414.2 ng/mL and cabergoline dose was increased to 0.5 mg twice a week. MRI Brain after 10 months revealed significant tumor reduction to 2.1 cm x 2.1cm x 1.2 cm. He was inconsistent with his endocrinology follow up appointments and was also non-adherent to cabergoline intermittently. After 14 months of starting DA therapy, he presented with worsening blurriness in his left eye. A repeat brain MRI showed stable appearance of the large pituitary macroadenoma with inferior bowing of the optic chiasm. Significant distortion, tented appearance, and attenuation of the left prechiasmatic optic nerve was also noted. He was evaluated by neuro ophthalmology and a diagnosis of secondary visual deterioration due to optic chiasmal herniation was made. Cabergoline therapy was promptly discontinued. Two weeks post-cabergoline cessation, he underwent trans-sphenoidal resection reporting vision improvement pre-surgery. Post-operative MRI depicted changes with no residual tumor and improved optic chiasm position. Discussion:Various theories explain chiasmal herniation with dopamine agonist (DA) treatment for prolactinomas. Pre-existing chiasm-tumor tethering may exacerbate downward pull during tumor reduction caused by DA therapy. Some case series have suggested that not all patients with chiasmal herniation have visual field defects and that despite improvement in visual fields with decrease in DA dosage, there are no appreciable radiographic changes/reversal of chiasmal herniation. One of the explanations for this lack of correlation is that visual impairment is rather a consequence of vascular compression. This case underscores the need for regular perimetry in macroprolactinoma patients on medical treatment. Adjusting dopamine agonist dosage to allow controlled tumor regrowth, monitored closely with frequent visual field and prolactin assessments, is crucial for relieving optic chiasm tension. Presentation: 6/3/2024

8594 Pasireotide and Pasireotide Combined Treatment in Aggressive, Giant Pituitary Neuroendocrine Tumours

Abstract Disclosure: K. Ciszek: None. A. Bogusławska: None. M. Komisarz-Calik: None. J. Kunicki: None. A. Hubalewska-Dydejczyk: None. A. Gilis-Januszewska: None. Pasireotide is a second-generation somatostatin analogue that gained recognition as a treatment option for acromegaly and Cushing disease. Recently, there are single reports of pasireotide treatment in other subtype of pituitary neuroendocrine tumours (PitNETs).We present a case series of aggressive, giant PitNETs which were treated with pasireotide alone or as combined multimodal treatment. Case 1: A 59-year-old male presented in our Unit due to severe headaches and visual field deficits. The patient underwent transsphenoidal surgery (TSS) ten years ago. Histopathology results showed partially acidophilic adenoma (FSH- LH- GH- ACTH- PRL-). Control MRI showed tumour regrowth - 56x56x89mm and invasion of local structures. The patient was qualified for radiotherapy, to which he did not consent. Due to the progression of symptoms, temozolomide and pasireotide were introduced. After 5 months, significant improvement in headaches and vision was observed. In MRI stable pituitary mass was noted. Case 2: A 17-year-old male presented in our clinic due to daily severe headaches and peripheral vision loss who underwent two non-radical surgeries for dopamine-resistant giant prolactinoma. In control MRIs progressing mass 38x34x33mm invading local structures was observed. Due to resistance to dopamine agonists and worsening of the symptoms, pasireotide was introduced resulting in a decrease of headaches and improvement in vision. The tumour size remained stationary. Case 3: A 59-year-old male presented with severe headaches and life threatening tumour mass effect.In MRI a 48x48x33mm mass was observed. The patient underwent two non-radical TSS, 4 cycles of pasireotide, and cyberknife treatment. Histopathology showed gonadotroph PitNET. MRI showed tumour shrinkage to 45x46x29mm, with persistent severe headaches. The patient was re-qualified for pasireotide treatment. Case 4: A 33-year-old male reported to the Clinic due to severe headaches and vomiting. In MRI pituitary mass 33x39x55mm and a cerebral oedema were revealed. TSS with external ventricular drainage was performed -histopathology results showed densely granulated silent corticotroph adenoma subtype 1, Ki67&amp;lt;1%. After 3 months, MRI showed tumour progression to 39x40x30mm. Two emergency TSS followed by stereotactic radiotherapy were performed. Combined therapy with pasireotide, cabergoline and temozolomide was introduced. After 18 months, stabilization of the disease was observed with the complete disappearance of headaches. Conclusions: Our study demonstrates the clinical potential of pasireotide treatment in aggressive, giant PitNETs. The therapy alone, or in combination has a potential role in reducing the tumour size, and allows the stabilization of the disease. The analgesic and anti-inflammatory effect of pasireotide could potentially alleviate headaches in this subset of patients. Presentation: 6/2/2024

7778 Factors Predicting Recovery of Hypogonadism in Men with Prolactinoma Treated with Dopamine Agonists

Abstract Disclosure: S. Constantinescu: None. O. Alexopoulou: None. D.M. Maiter: None. Introduction: Recovery of hypogonadism is an important objective of dopamine agonist (DA) treatment in men with prolactinoma. However, the extent, timeline, and predictive factors of gonadotrope axis recovery are still unclear. Methods: We report data from a large cohort of 89 men with prolactinoma, looking at the evolution of testosterone levels after 6 and 12 months of treatment with DA. We excluded patients with peripheral hypogonadism, surgical treatment performed less than 12 months after onset of DA treatment, and patients with small tumors (≤ 5 mm and prolactin ≤ 50 µg/l) who did not achieve tumor shrinkage during treatment. We defined low testosterone as a morning value &amp;lt; 10 nmol/l. Patients who had started testosterone supplementation were considered as having persistent hypogonadism. Results: Among the 89 men (mean age ± SD: 44 ± 14 years; 65/89 with a macroprolactinoma), 14 (16%) had normal initial testosterone levels (NT) and 75 (84%) had low testosterone at diagnosis (LT). Compared to LT, NT patients had significantly lower PRL (median 53 µg/l versus 490 µg/l, p=0.009) and smaller tumors (median 6.5 mm versus 21.2 mm, p=0.013). In the NT group, after 6 (n=11) and 12 months (n=10), testosterone rose from a median of 13.4 to 16.6 (p=0.266) and 17.9 nmol/l (p=0.012), respectively. In LT patients, after 6 (n=56) and 12 months (n=42), testosterone rose significantly from a median of 5.8 to 10.7 (p&amp;lt;0.001) and 12.5 nmol/l (p&amp;lt;0.001).In the LT group, 45% (32/71) had recovered eugonadism at 6 months and 57% (40/70) at 12 months. These proportions rose to 61% (22/36) and 67% (n=26/39) at 6 and 12 months when prolactin concentrations were normalized. Factors associated with persistent hypogonadism after one year were chiasmal compression at diagnosis (p=0.05), cavernous sinus invasion (p=0.042), cystic tumoral component (p=0.038), a greater tumoral diameter (mean 25 mm vs 15 mm, p&amp;lt;0.01), lower testosterone concentrations at diagnosis (mean 3.6 nmol/l vs 6.8 nmol/l, p&amp;lt;0.001) and at 6 months (mean 6.0 nmol/l vs 13.0 nmol/l, p&amp;lt;0.03), and higher prolactin levels at one year (median 17.15 µg/l vs 8.4 µg/l, p=0.064). Testosterone &amp;lt; 6.7 nmol/l at 6 months predicted the long-term persistence of hypogonadism with 72% sensitivity and 92% specificity. Conclusion: The sensitivity of the gonadotrope axis to high prolactin levels is highly variable in men with prolactinoma and 16% of them retain normal testosterone concentrations. However, this finding does not exclude partial inhibition of the gonadotrope axis that will improve with DA treatment. In patients with low testosterone levels, the recovery rate of hypogonadism is 45% at 6 months and 57% at 12 months, increasing to 67% if prolactin is normalized. Testosterone supplementation could be started early in patients with large, invasive, cystic and/or compressive tumors, with a testosterone concentration lower than 6.7 nmol/L after 6 months of treatment. Presentation: 6/3/2024