Identification of Driver Mutations in Rare Cancers: The Role of SMARCA4 in Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT)

A Rare Case of Advanced-Stage Small Cell Carcinoma of the Ovary Identified During the Third Trimester of Pregnancy

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare form of aggressive ovarian malignancy linked with mutations in the SMARCA4 gene. This disease predominantly affects young women within the first five decades of life and is associated with poor overall long-term survival, particularly when diagnosed in the advanced stage of the disease. Due to the low incidence of the condition and limited literature, current clinical decision-making is based on a small number of case series and case reports. We present an extremely rare case of SCCOHT diagnosed in a young female during her third trimester of pregnancy, requiring preterm delivery via cesarean section with simultaneous unilateral oophorectomy and salpingectomy.

Prognosis comparison between small cell carcinoma of ovary and high-grade serous ovarian cancer: A retrospective observational cohort study

BACKGROUND

Small cell carcinoma of ovary (SCCO) is a rare and aggressive cancer primarily reported in the form of case reports. Due to limited epidemiological and prognostic analyses based on large populations, SCCO has varied considerably without prognostic models and a recognized first-line treatment strategy. The study aimed to compare the clinical characteristics, treatment methods, and prognosis of SCCO and high-grade serous ovarian cancer (HGSOC), the most prevalent subtype of ovarian cancer, in a large sample and develop a predictive model for these two subtypes.

METHODS

Data from the Surveillance, Epidemiology, and End Results program were analyzed for patients with SCCO or HGSOC from 2000 to 2017. Clinical, demographic, and treatment characteristics were compared between the two groups. Propensity-score matching, Cox risk regression analysis, and Kaplan-Meier survival curves were used to assess the data. Finally, a nomogram was developed to predict the patient survival time.

RESULTS

A total of 32,185 women, including 31,979 (99.4%) diagnosed with HGSOC and 206 (0.6%) diagnosed with SCCO, were identified. Age ≤ 51 years, single, median house income less than $70,000, early stage, and unilateral disease were more common characteristics of patients with SCCO than those with HGSOC. Patients with SCCO were more likely to receive radiotherapy (6.8% vs. 0.8%, p <0.001) and have tumors ≥ 141 mm (38.3% vs. 9.7%, p <0.001) than patients with HGSOC. The independent risk factors for SCCO patients included older age at diagnosis, advanced stage, surgery, radiotherapy, chemotherapy, larger tumor size, and bilateral tumor. Overall and cancer-specific survival rates were significantly lower for SCCO than more malignant HGSOC. Prognostic models and nomograms had been constructed to predict the individual survival rates of patients with SCCO and HGSOC.

CONCLUSION

Patients with SCCO presented with the early-stage disease more frequently than patients with HGSOC and had decreased overall and cancer-specific survival rates.

Simultaneous Brg1 Knockout and MYCN Overexpression in Cerebellar Granule Neuron Precursors Is Insufficient to Drive Tumor Formation but Temporarily Enhances their Proliferation and Delays their Migration

Medulloblastoma (MB) is the most common malignant brain tumor in childhood. According to the World Health Organization (WHO) classification of central nervous system (CNS) tumors, this embryonal tumor is divided into a wingless (WNT)-activated, Sonic hedgehog (SHH)-activated, and non-WNT/non-SHH entity. The latter is poorly defined but frequently carries mutations in Brahma-related gene 1 (BRG1) or amplifications of MYCN. Here, we investigated whether a combination of a Brg1 knockout and an overexpression of MYCN in cerebellar granule neuron precursors or multipotent neural stem cells is sufficient to drive brain tumor formation in mice. To this end, we generated Math1-creERT2::Brg1fl/fl::lslMYCN and hGFAP-cre::Brg1fl/fl::lslMYCN mice, respectively. We did not observe brain tumor formation in any of these models. hGFAP-cre::Brg1fl/fl::lslMYCN mice revealed severe CNS abnormalities with short survival, similar to the situation with a sole loss of Brg1, as we previously described. Investigation of Math1-creERT2::Brg1fl/fl::lslMYCN mice with a tamoxifen induction at postnatal day 3 revealed a regular survival but significant increase in cerebellar granule neuron precursor proliferation, followed by a delayed inward migration of these cells. This is in stark contrast to the hypoplastic cerebellum that we previously observed after embryonic deletion of Brg1 in Math1 positive cerebellar granule neurons. Our results indicate a time-specific function of Brg1 in cerebellar granule neuron precursors. Yet, the exact temporal and spatial origin of non-WNT/non-SHH MB remains unclear.

Brahma-related gene 1 has time-specific roles during brain and eye development

During development, gene expression is tightly controlled to facilitate the generation of the diverse cell types that form the central nervous system. Brahma-related gene 1 (Brg1, also known as Smarca4) is the catalytic subunit of the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex that regulates transcription. We investigated the role of Brg1 between embryonic day 6.5 (E6.5) and E14.5 in Sox2-positive neural stem cells (NSCs). Being without major consequences at E6.5 and E14.5, loss of Brg1 between E7.5 and E12.5 resulted in the formation of rosette-like structures in the subventricular zone, as well as morphological alterations and enlargement of neural retina (NR). Additionally, Brg1-deficient cells showed decreased survival in vitro and in vivo. Furthermore, we uncovered distinct changes in gene expression upon Brg1 loss, pointing towards impaired neuron functions, especially those involving synaptic communication and altered composition of the extracellular matrix. Comparison with mice deficient for integrase interactor 1 (Ini1, also known as Smarcb1) revealed that the enlarged NR was Brg1 specific and was not caused by a general dysfunction of the SWI/SNF complex. These results suggest a crucial role for Brg1 in NSCs during brain and eye development.

A Phase II Study of Durvalumab in Combination with Tremelimumab in Patients with Rare Cancers

LESSONS LEARNED

Disease control with signals of response were demonstrated, which should lead to future validating clinical trials using checkpoint inhibitors in this underserved rare malignancy population. Although the study of single types of rare cancers is practically challenging, clinical trial designs that aggregate such patients into cohorts treated similarly are feasible, even in the community setting.

BACKGROUND

Patients with rare cancers are an underserved population with limited access to clinical trials aside from phase I trials in the refractory setting. Treatment of these patients is often based on collections of anecdotes and small denominator review articles. Despite broad evidence of efficacy of combined immune checkpoint blockade across multiple tumor types, patients with rare tumors have not been afforded the opportunity for these therapies.

METHODS

A phase II, investigator-initiated, single institution trial using durvalumab (1,500 mg every [Q]4 weeks × 13) and tremelimumab (75 mg Q4 weeks × 7, then Q12 weeks × 2) is reported. The population included 50 patients with advanced rare solid tumors (incidence <6/100,000 per year). The phase II dose and safety profile were defined in prior phase I trials. All patients had exhausted standard therapy options and all had received at least one prior line of systemic therapy (n = 49) unless a standard treatment option did not exist (n = 1).

RESULTS

A complete response was demonstrated in one patient with anal cancer. Striking partial responses were seen in four patients. Prolonged disease stability was noted in 18 patients. Thirteen patients experienced disease progression. Patients were considered unevaluable if unable to initiate therapy (n = 6) or unable to complete two cycles of therapy (n = 8). In all cases, patients were unevaluable because of clinical deterioration. The toxicity profile paralleled prior published studies. Toxicities were manageable and without new signals. There were two events of grade 4 immune-mediated hepatitis and one death from pneumonitis.

CONCLUSION

This single-cohort basket trial demonstrated clinical activity from combined checkpoint blockade in 23 of the 36 evaluable patients. Patients with rare cancers, not eligible for immunotherapy via conventional clinical trial mechanisms, should be considered for this therapy through compassionate use, further clinical trials, and national registry programs.

Primary ovarian small cell carcinoma of hypercalcemic type in a pregnant woman: A case report

RATIONALE

Ovarian small cell carcinoma of hypercalcemic type (OSCCHT) is a relatively rare and highly fatal gynecological malignancy of unknown histogenesis, affecting mainly girls and young women. OSCCHT occurring during pregnancy is an uncommon event, and preoperative diagnosis of this malignancy is much more difficult in pregnant than non-pregnant women. The aim of this study was to describe a rare case of primary OSCCHT in a pregnant woman and to review the current literature.

PATIENT CONCERNS

Here we present a case of OSCCHT in a 21-year-old patient in the 32nd week of gestation, who had abdominal pain and irregular vaginal bleeding for 5 hours. Because placental abruption, stillbirth, and hemorrhagic shock were suspected, she subsequently underwent diagnostic laparotomy. During the hysterotomy delivery and exploratory laparotomy, we found a dead fetus in the uterus and a large tumor mass arising from her left ovary. Plasma-based detection showed that the patient had a slightly elevated parathyroid hormone (PTH) level and normal serum calcium. After surgery, her serum PTH levels returned to normal.

DIAGNOSIS AND INTERVENTIONS

The patient was initially treated with surgery. She underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy, as well as the following additional procedures: appendectomy, sigmoidectomy, debulking of extra-ovarian tumor, lymph node dissection, and peritoneal biopsies. The patient, who was in the third trimester of pregnancy, was diagnosed with OSCCHT that was confirmed to be Stage III. She was recommended chemotherapy after surgery, but she declined chemotherapy.

OUTCOMES

Unfortunately, the patient died 5 months after surgery.

LESSONS

OSCCHT is a very rare and highly aggressive tumor type. The clinical symptoms of this tumor are nonspecific, and pathological examination remains the gold standard for diagnosis. Most patients are diagnosed with advanced stage disease and do not respond to chemotherapy. The prognosis of OSCCHT is generally poor, and no treatment guidelines are available as yet. For pregnant woman, OSCCHT is especially harmful to the mother and may indirectly lead to the death of the fetus.

An In-Depth Look at Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT): Clinical Implications from Recent Molecular Findings

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a highly aggressive cancer in young women. The histogenesis remains unclear although a potential origin of germ cells has been suggested recently. The high throughput next generation sequencing techniques have facilitated the identification of inactivating SMARCA4 mutations as the driver of SCCOHT. These findings may greatly impact on the prevention, diagnosis, molecular classification and treatment of SCCOHTs. The SMARCA4 mutations, typically associated with dual loss of BRG1 and BRM expression, are highly sensitive and specific for the diagnosis of SCCOHT. Germline mutations of SMARCA4 support familial SCCOHT with a critical requirement of genetic counseling and possible prophylactic surgery for carriers. SCCOHT, malignant atypical teratoid/rhabdoid tumors, thoracic sarcomas and some undifferentiated carcinomas harbor rhabdoid morphology and mutations in the SMARC genes, generating an emerging molecular classification of SMARC-mutated tumors. A multi-modality treatment approach consisting of surgery and high dose multi-agent chemotherapy in atypical teratoid/rhabdoid tumors may have potential benefits for SCCOHT patients. Preliminary studies have implicated that the inhibitors targeting EZH2 and the receptor tyrosine kinase, and anti-PD-L1 immunotherapy might be potentially effective for SCCOHT patients. These recent advances on molecular genetics, diagnosis and treatment of SCCOHT address the necessity of multiple institutional collaboration work among oncologist, pathologist, genomic scientist, geneticist, molecular biologist, and pharmacologist.