177Lu-DOTATOC Peptide Receptor Radionuclide Therapy in a Patient With Neuroendocrine Breast Carcinoma and Breast Invasive Ductal Carcinoma

Neuroendocrine neoplasms of the breast: a review of literature

Primary neuroendocrine neoplasms (NENs) of the breast are characterized by neuroendocrine architectural and cytological features, which must be supported by immunohistochemical positivity for neuroendocrine markers (such as Chromogranin and Synaptophysin). According to the literature, making a diagnosis of primary neuroendocrine breast cancer always needs to rule out a possible primary neuroendocrine neoplasm from another site. Currently, the latest 2022 version of the WHO of endocrine and neuroendocrine neoplasms has classified breast NENs as well-differentiated neuroendocrine tumours (NETs) and aggressive neuroendocrine carcinomas (NECs), differentiating them from invasive breast cancers of no special type (IBCs-NST). with neuroendocrine features. The current review article describes six cases from our series and a comprehensive review of the literature in the field of NENs of the breast.

Case report: Neuroendocrine breast carcinoma with a germline EGFR T790M mutation

Background

The epidermal growth factor receptor (EGFR) p.Thr790Met (T790M) mutation was discovered as a resistance mechanism in patients with lung cancer treated with first- and second-generation tyrosine kinase inhibitors. Further studies revealed the EGFR T790M mutation in treatment-naive non-small cell lung carcinoma (NSCLC) and as a rare germline mutation strongly associated with NSCLC. Somatic EGFR T790M mutations have been reported in a limited population of patients with triple-negative breast cancer. There are no previous reports of a germline EGFR T790M mutation found in a patient with breast cancer.

Case presentation

We present a rare case of a 42-year-old woman with a rapidly progressing 8 cm mass in the right lateral breast. An additional right breast mass with multiple lymph nodes characteristic or suspicious of metastasis was found. Ultrasound-guided biopsy showed high-grade, poorly differentiated invasive neuroendocrine carcinoma of the right breast and metastatic carcinoma of a right axillary lymph node. Genetic testing revealed a germline EGFR T790M mutation. The patient underwent neoadjuvant chemotherapy, right mastectomy with lymph node dissection, adjuvant radiation to the right chest wall and axilla, and adjuvant chemotherapy.

Conclusion

This is the first reported case of a patient with high-grade neuroendocrine carcinoma, triple-negative breast cancer and a germline EGFR T790M mutation. Further investigation is needed to find a possible correlation between the cancer in this patient and her mutation. Since there are no current guidelines, further research is also needed to define screening protocols for patients with germline EGFR T790M mutations. Additional treatment options and cancer risk could also be found with further research, which would benefit all patients with a germline EGFR T790M mutation.

Primary Neuroendocrine Tumor of the Breast: Current Understanding and Future Perspectives

Primary neuroendocrine carcinoma of the breast (NECB) is characterized with heterogeneity, rarity, and poor differentiation, which is probably an underestimated subtype of breast cancer, including small cell NECs and large cell NECs. The diagnostic criteria for NECB have been constantly updated as the disease changes and the understanding increases. According to the latest WHO Classification, primary neuroendocrine neoplasm (NEN) of the breast consists of well-differentiated neuroendocrine tumors (NET), extremely aggressive neuroendocrine carcinomas (NEC) as well as invasive breast cancers of no special type (IBCs-NST) with neuroendocrine differentiation. The accurate diagnosis of NECB remains a challenge for its low incidence, which needs multi-disciplinary methods. For the rarity of the disease, there is a lack of large samples and prospective clinical research. For these invasive tumors, there are no standardized therapeutic guidelines or norms, and the treatment often refers to nonspecific breast cancer. In addition, the prognosis of such patients remains unknown. In 2003, the World Health Organization (WHO) listed NECB as an independent entity for the first time, while few features of NECB were clarified. In this review, it presents the WHO Classification, clinicopathologic characteristics, diagnosis, treatment, and prognosis of these patients. In addition, it summarizes the latest studies on molecular features of NECB, aiming to provide new therapeutic perspectives for the disease.

Clinical Evaluation of Nuclear Imaging Agents in Breast Cancer

Precision medicine is the customization of therapy for specific groups of patients using genetic or molecular profiling. Noninvasive imaging is one strategy for molecular profiling and is the focus of this review. The combination of imaging and therapy for precision medicine gave rise to the field of theranostics. In breast cancer, the detection and quantification of therapeutic targets can help assess their heterogeneity, especially in metastatic disease, and may help guide clinical decisions for targeted treatments. Positron emission tomography (PET) or single-photon emission tomography (SPECT) imaging has the potential to play an important role in the molecular profiling of therapeutic targets in vivo for the selection of patients who are likely to respond to corresponding targeted therapy. In this review, we discuss the state-of-the-art nuclear imaging agents in clinical research for breast cancer. We reviewed 17 clinical studies on PET or SPECT agents that target 10 different receptors in breast cancer. We also discuss the limitations of the study designs and of the imaging agents in these studies. Finally, we offer our perspective on which imaging agents have the highest potential to be used in clinical practice in the future.

Head to head: Do neuroendocrine tumours in the breast truly exist?

Breast cancer (BC) is a heterogeneous disease with a spectrum of morphological features. Concepts of histogenesis and differentiation in BC remain controversial. Recent evidence supports differentiation rather than histogenesis as the underlying mechanism for the myriad morphological appearances of BC. Prognosis and response to therapy are determined by a combination of factors including tumour grade, stage and receptor status whereas tumour histological types play an independent role in only limited examples. Neuroendocrine tumours (NETs) comprise one of the most debated entities in the breast since their first description. Apart from the rare small cell NE carcinoma (NEC) which has well-characterised features similar to their counterparts in other organs, the true existence, diagnostic criteria and clinical significance of NE neoplasms (NENs) in the breast are shrouded in controversy. At the core of this discussion is whether normal NE cells exist in the breast, and if breast NETs have distinct morphology and clinical behaviour. When NETs are encountered in the breast, metastatic origin has to be excluded. The more frequent situation in which NE differentiation is observed in breast cancers is in the context of recognisable, morphologically well described special type neoplasms like the hypercellular mucinous carcinoma and solid papillary carcinoma. In this review, arguments for and against maintaining the category of NENs in the breast are articulated in relation to existing literature on this group of unusual tumours.

Neuroendocrine Neoplasms of the Breast: The Latest WHO Classification and Review of the Literature

Simple Summary

Breast tumors exhibiting neuroendocrine differentiation are a heterogeneous group of tumors that have been variously defined in previous World Health Organization (WHO) classifications. In the WHO Classification of Tumours, 5th edition, neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs) of the breast, both of which are invasive cancers, are classified as neuroendocrine neoplasms (NENs) of the breast. However, the clinical significance of NE differentiation in breast cancers, especially in NETs of the breast, is not yet fully understood, and a large overlap appears to exist between breast cancers showing NE differentiation and invasive breast cancer of no special type (IBC-NST). While breast NECs show distinct clinical and morphological features, diagnosis of NETs based on the morphological characteristics alone can be challenging; one reason is that breast NETs do not necessarily have the same morphological characteristics as those of NENs arising in other organs. Thus, the heterogeneity of breast tumors with neuroendocrine differentiation and the changes in their classifications over the years have left many open issues that still need to be resolved. In this review, we shall summarize the history of breast “NENs,” including of mixed types of tumors and the characteristics of these tumors, and discuss their differences from NENs arising in other organs.

Abstract

Breast tumors with neuroendocrine (NE) differentiation comprise an uncommon and heterogeneous group of tumors, including invasive breast cancer of no special type (IBC-NST) with NE features, neuroendocrine tumors (NETs), and neuroendocrine carcinoma (NEC). The most recent World Health Organization (WHO) classification in 2019 defined neuroendocrine neoplasms (NENs) of the breast (Br-NENs) as tumors in which >90% of cells show histological evidence of NE differentiation, including NETs (low-grade tumors) and NEC (high-grade). Due to the low prevalence of these tumors and successive changes in their diagnostic criteria over the years, only limited evidence of these tumors exists, derived mainly from case reports and retrospective case series. Breast tumors with NE differentiation are usually treated like the more commonly occurring IBC-NSTs. Immunohistochemistry (IHC) of breast tumors with NE differentiation usually shows a hormone receptor (HR)-positive and human epidermal growth factor type 2 (HER2)-negative profile, so that hormonal therapy with cyclin-dependent kinase (CDK)4/6 inhibitors or other targeted agents would be reasonable treatment options. Herein, we present a review of the literature on breast tumors with NE differentiation as defined in the latest WHO 2019 classification, and discuss the clinical management of these tumors.

Theranostic Approach in Breast Cancer: A Treasured Tailor for Future Oncology

ABSTRACT

Breast cancer is the most frequent invasive malignancy and the second major cause of cancer death in female subjects mostly due to the considerable diagnostic delay and failure of therapeutic strategies. Thus, early diagnosis and possibility to monitor response to the treatment are of utmost importance. Identification of valid biomarkers, in particular new molecular therapeutic targets, that would allow screening, early patient identification, prediction of disease aggressiveness, and monitoring response to the therapeutic regimen has been in the focus of breast cancer research during recent decades. One of the intensively developing fields is nuclear medicine combining molecular diagnostic imaging and subsequent (radio)therapy in the light of theranostics. This review aimed to survey the current status of preclinical and clinical research using theranostic approach in breast cancer patients with potential to translate into conventional treatment strategies alone or in combination with other common treatments, especially in aggressive and resistant types of breast cancer. In addition, we present 5 patients with breast cancer who were refractory or relapsed after conventional therapy while presumably responded to the molecular radiotherapy with 177Lu-trastuzumab (Herceptin), 177Lu-DOTATATE, and 177Lu-FAPI-46.

EpCAM-Targeting Aptamer Radiotracer for Tumor-Specific PET Imaging

Noninvasive in vivo imaging to measure the expression of EpCAM, a biomarker overexpressed in the majority of carcinoma tumors and metastatic lesions, is highly desirable for accurate tumor staging and therapy evaluation. Here, we report the use of an aptamer radiotracer to enable tumor-specific EpCAM-targeting PET imaging. Oligonucleotide aptamers are small molecular ligands that specifically bind with high affinity to their target molecules. For specific tumor imaging, an aptamer radiotracer was formulated by chelating a ⁶⁴Cu isotope and DOTA-PEGylated aptamer sequence to target EpCAM. In vitro cell uptake assays demonstrated that the aptamer radiotracer specifically bound EpCAM-expressing breast cancer cells but did not react with off-target tumor cells. For in vivo tumor imaging, aptamer radiotracer was systemically administered into xenograft mice. MicroPET/CT scans revealed that the aptamer radiotracer rapidly highlighted xenograft tumors derived from MDA-MB-231 breast cancer cells (EpCAM positive) as early as 2 h postadministration with a gradually increasing tumor uptake signal that peaked at 24 h but not in lymphoma 937 tumors (EpCAM negative). In contrast, nonspecific background signals in the liver and kidneys were rapidly decreased postadministration. This proof-of-concept study demonstrates the utility of aptamer radiotracers for tumor-specific PET imaging.