Mechanisms of Intrinsic Tumor Resistance to Immunotherapy.

An increased understanding of the interactions between the immune system and tumors has opened the door to immunotherapy for cancer patients. Despite some success with checkpoint inhibitors including ipilimumab, pembrolizumab, and nivolumab, most cancer patients remain unresponsive to such immunotherapy, likely due to intrinsic tumor resistance. The mechanisms most likely involve reducing the quantity and/or quality of antitumor lymphocytes, which ultimately are driven by any number of developments: tumor mutations and adaptations, reduced neoantigen generation or expression, indoleamine 2,3-dioxygenase (IDO) overexpression, loss of phosphatase and tensin homologue (PTEN) expression, and overexpression of the Wnt⁻β-catenin pathway. Current work in immunotherapy continues to identify various tumor resistance mechanisms; future work is needed to develop adjuvant treatments that target those mechanisms, in order to improve the efficacy of immunotherapy and to expand its scope.

Objective Responses in Metastatic Pleomorphic Rhabdomyosarcoma Treated with Combination of Doxorubicin and Pembrolizumab: A Case Series.

Introduction: Pleomorphic rhabdomyosarcoma is a rare subtype of rhabdomyosarcoma, a soft tissue sarcoma with skeletal muscle differentiation. Although rhabdomyosarcoma is typically seen in the pediatric population, the pleomorphic variant most frequently presents in adulthood and is characteristically aggressive with no currently established treatment regimen in the setting of metastatic disease. There has been growing interest in the application of immune checkpoint inhibitors alongside conventional chemotherapeutic agents in the treatment of pleomorphic rhabdomyosarcoma. Case Presentation: In the present case series, we report 2 patients with metastatic pleomorphic rhabdomyosarcoma treated with combination doxorubicin and pembrolizumab who had confirmed objective responses. Of note, these 2 patients had variable PD-L1 status - negative and low positive. Duration of treatment response was notable at 14 months and 9 months, respectively, with the first patient remaining on maintenance pembrolizumab therapy and the second patient subsequently achieving complete response with third-line trabectedin. Both patients are currently undergoing routine interval imaging with no evidence of disease at this time. Conclusion: This report highlights and discusses the potential role of PD-1 blockade in the treatment of pleomorphic rhabdomyosarcoma and also discusses burgeoning immunological data that may explain the clinical responses seen in these 2 cases.

Pembrolizumab plus Pharmacologic Ascorbate in the Treatment of Leiomyosarcoma.

Introduction: Leiomyosarcoma (LMS) is a malignancy with smooth muscle differentiation. Metastatic LMS is associated with poor prognosis and limited efficacy of systemic treatment. Novel treatment modalities are desperately needed for this entity. Case Presentation: We report the first use of pembrolizumab plus pharmacologic ascorbate in 3 patients with metastatic LMS. All cases resulted in persistent objective responses and disease control significantly better than has been reported with chemotherapy or other immunotherapeutic approaches. Three patients with metastatic LMS, one each of uterine, vascular, and soft tissue origin, were treated with pembrolizumab plus pharmacologic ascorbate. The patient with uterine LMS received combination therapy at presentation and had persistent response for 12 months, which is ongoing. The patient with metastatic LMS of the inferior vena cava received combination therapy at presentation and had persistent response for 12 months, at which time new metastases were found. The patient with soft tissue LMS had disease progression on pembrolizumab monotherapy prior to the addition of ascorbate, after which she had a 17-month response, which is ongoing. No side effects attributed to treatment were reported. Conclusion: Pembrolizumab plus pharmacologic ascorbate is a novel immunotherapeutic approach and warrants further study in LMS.

A Case of Erdheim-Chester Disease Causing Secondary Sclerosing Cholangitis.

Erdheim-Chester disease (ECD) is an exceedingly rare and aggressive disease characterized by foamy CD68 + CDa-histiocytic infiltration into multiple tissues and organs. Only 1,500 cases have been diagnosed since 1930 when ECD was first described. Biliary tract involvement of ECD has only been reported in the literature once. We report a case of ECD causing extrahepatic biliary obstruction without significant bile duct dilation, mimicking primary sclerosing cholangitis or IgG4 disease.

Spontaneous regression of choroidal metastasis from renal cell carcinoma.

Purpose: To report a case of an elderly man who presented with a choroidal metastasis from renal cell carcinoma that spontaneously regressed prior to any local or systemic treatment. Observations: An 82-year-old man without a history of metastatic cancer was referred to the ocular oncology service for evaluation of a newly noted amelanotic choroidal lesion. Examination and imaging findings were concerning for choroidal metastasis. Systemic workup revealed previously undiagnosed widely metastatic renal cell carcinoma. The lesion spontaneously regressed prior to the initiation of any treatment for his tumor. Conclusions and importance: This is a unique case of choroidal metastases from renal cell carcinoma that spontaneously regressed prior to medical or surgical treatment of the primary tumor.

Sustained response to imatinib in patient with extraskeletal myxoid chondrosarcoma and novel KIT mutation.

A 55-year-old woman presented with a 3-month history of right groin swelling, discomfort and impaired mobility. On examination, a palpable mass was noted both to the right of midline in the lower abdomen and in the right groin. MRI of the pelvis showed two masses involving the anterior abdominal wall and right groin, as well as lymph node involvement. CT imaging revealed multiple bilateral pulmonary metastases. Pathology demonstrated a myxohayline stroma morphology. Tumour was also notable for NR4A3 gene region rearrangement and mutation in KIT exon 11 at position c.1669 T>G. Based on these findings, she was diagnosed with extraskeletal myxoid chondrosarcoma (EMC). The patient has been on imatinib, a tyrosine kinase inhibitor with activity against KIT, for 3 years with stable disease. Metastatic EMC is generally treated with surgical resection and perioperative radiation therapy with adjuvant chemotherapy and is associated with poor prognosis.

Presumed Melanoma of Unknown Primary Origin Metastatic to the Choroid Mimics Primary Uveal Melanoma.

We describe the case of a 69-year-old woman who presented with a decline in vision in the left eye and was found to have a choroidal lesion with clinical and echographic features concerning for primary uveal melanoma. Systemic imaging identified numerous metastases to the liver, kidneys, paratracheal lymph nodes, lung, and brain. The hepatic lesion was biopsied, and genetic analysis identified a Val600Glu (c.1799T>A) BRAF mutation, consistent with a cutaneous primary malignancy, although no primary tumor was identified. This case highlights that metastasis to the choroid is a rare presentation of nonuveal melanoma that can mimic primary uveal melanoma. Genetic analysis of tumor tissue can identify the origin of the melanoma and guide treatment options. Systemic imaging should be performed prior to intervention for choroidal neoplasms.

Melanoma Brain Metastases in the Era of Targeted Therapy and Checkpoint Inhibitor Therapy.

Brain metastases commonly develop in melanoma and are associated with poor overall survival of about five to nine months. Fortunately, new therapies, including immune checkpoint inhibitors and BRAF/MEK inhibitors, have been developed. The aim of this study was to identify outcomes of different treatment strategies in patients with melanoma brain metastases in the era of checkpoint inhibitors. Patients with brain metastases secondary to melanoma were identified at a single institution. Univariate and multivariable analyses were performed to identify baseline and treatment factors, which correlated with progression-free and overall survival. A total of 209 patients with melanoma brain metastases were identified. The median overall survival of the cohort was 5.3 months. On multivariable analysis, the presence of non-cranial metastatic disease, poor performance status (ECOG 2-4), whole-brain radiation therapy, and older age at diagnosis of brain metastasis were associated with poorer overall survival. Craniotomy (HR 0.66, 95% CI 0.45-0.97) and treatment with a CTLA-4 checkpoint inhibitor (HR 0.55, 95% CI 0.32-0.94) were the only interventions associated with improved overall survival. Further studies with novel agents are needed to extend lifespan in patients with brain metastases in melanoma.