Sirolimus for Vincristine-Resistant Kasabach-Merritt Phenomenon: Report of Eight Patients

Sirolimus for kaposiform hemangioendothelioma: Potential mechanisms of action and resistance

Kaposiform hemangioendotheliomas (KHEs) are vascular tumors that are considered borderline or locally aggressive and may lead to lethal outcomes. Traditional therapies, such as surgery and embolization, may be insufficient or technically impossible for patients with KHE. Sirolimus (or rapamycin), a specific inhibitor of mechanistic target of rapamycin, has recently been demonstrated to be very useful in the treatment of KHEs. Here, we highlight recent substantial progress regarding the effects of sirolimus on KHEs and discuss the potential mechanisms of action of sirolimus in treating this disease. The prevention of platelet activation and inflammation, along with antiangiogenic effects, the inhibition of lymphangiogenesis, the attenuation of fibrosis, or a combination of all these effects, may be responsible for the therapeutic effects of sirolimus. In addition, the mechanism of sirolimus resistance in some KHE patients is discussed. Finally, we review the somatic mutations that have recently been identified in KEH lesions, and discuss the potential of novel therapeutic targets based on these further understandings of the cellular and molecular pathogenesis of KHE.

Cost and effectiveness comparison of sirolimus versus standard treatment in Kasabach-Merritt phenomenon: a real-world evidence study in Thailand

The conventional treatment of Kasabach-Merritt Phenomenon (KMP) consists of corticosteroids with vincristine/vinblastine or others. The aim of the study is to compare the first-year direct costs and effectiveness between sirolimus and conventional treatment. A retrospective case-control study of KMP patients was conducted at a mean age of 9 months (1 day to 12 years) between 2000 and 2022 from four tertiary centers in Thailand. The direct costs, hematologic and clinical complete response (HCR, CCR), hospitalization, length of stay, and complications were compared. Of 29 patients, 13 underwent sirolimus (four upfront and nine were refractory to the conventional). The first-year total cost had no statistically significant difference between sirolimus VS conventional treatment (8,852.63 VS 9,083.56 USD: p value: 0.94). The therapeutics achievement was the same in both HCR (244.75 VS 168.94 days; p value: 0.60) and CCR (419.77 VS 399.87 days; p value: 0.90). The subgroup analysis of the first-line sirolimus (n = 4) compared with the conventional (n = 25) showed a more reduced total cost (4,907.84 VS 9,664.05 USD; p value: 0.26) rendered net total cost of -4,756.21 USD per patient (cost saving). A more significant contrast of therapeutic achievement by reduction of both HCR (11.67 VS 224.20 days; p value: 0.36) and CCR (38.50 VS 470.88 days; p value: 0.04) was shown. The sirolimus had no difference in hospitalization, length of stay, and complications. Even though, it was unable to identify significant differences in cost-effectiveness. Sirolimus is suitable for all patients who have diagnosis of KMP either for rescue therapy or first-line treatment.

Cocktail therapy with prednisolone, vincristine and sirolimus for Kasabach‑Merritt phenomenon in 10 infants

Kasabach-Merritt phenomenon (KMP) is a life-threatening condition caused by rare vascular tumors. To reduce drug resistance observed in monotherapy of KMP with prednisone, vincristine (VCR) or sirolimus, the present study evaluated the efficacy and safety of triad therapy in the treatment of KMP. A total of 10 KMP infants managed with prednisolone, VCR and sirolimus in The Second Affiliated Hospital of Xi'an Jiaotong University (Xi'an, China) between April 2017 and August 2021 were retrospectively reviewed. The three female and seven male infants with KMP underwent cocktail therapy with prednisone, VCR and sirolimus. At diagnosis, the infants, aged 49.1±41.0 days, showed laboratory test results with platelet counts 22±15.4x10⁹/l, fibrinogen 81.7±26.9 mg/dl and D-dimer 38649±13443.6 ng/ml. The average maximal diameter of the tumors at diagnosis was 84.5±25.1 mm. KMP risk is increased by large tumors with deep lesions infiltrating the muscle. Platelet counts normalized after a median 10 days (range, 5-69 days) of treatment. With combination therapy maintained for 46.8±24.4 days, ultrasound showed that the thickness of the tumors decreased by 51% from 28.9±12.1 to 13.9±6.2 mm. Neutropenia and gastrointestinal disorders were the most common adverse effects. The present study found that the cocktail therapy with prednisolone, VCR and sirolimus has favorable tolerance and efficacy for life-threatening KMP. Once a stable condition has been achieved, cocktail therapy should be replaced by sirolimus monotherapy to reduce potential side effects.

Effective low-dose sirolimus regimen for kaposiform haemangioendothelioma with Kasabach-Merritt phenomenon in young infants

AIMS

Management of kaposiform haemangioendotheliomas (KHE) with Kasabach-Merritt phenomenon is challenging in young infants who are subjected to developmental pharmacokinetic changes. Sirolimus, sometimes combined with corticosteroids, can be used as an effective treatment of KHE. Simultaneously, toxicities such as interstitial pneumonitis related to the use of sirolimus may be fatal. As infants have a very low CYP3-enzyme expression at birth, which rises during ageing, we hypothesize that a reduced metabolization of sirolimus might lead to high sirolimus serum levels and low dose may be sufficient without the side effects.

METHODS

A case series of 5 infants with kaposiform haemangioendothelioma with Kasabach-Merritt phenomenon was analysed retrospectively. All infants were treated with sirolimus 0.2 mg/m2 every 24 or 48 hours according to their age. Prednisone was added to the therapy for additional effect in 4 patients.

RESULTS

In all patients, low dose of sirolimus led to therapeutic sirolimus levels (4-6 ng/mL). All infants (aged 4 days-7 months) had a complete haematological response, without serious adverse events. In all patients, the Kasabach-Merritt phenomenon resolved, the coagulation profile normalized and tumour size reduction was seen.

CONCLUSION

Low-dose sirolimus treatment is safe for infants with kaposiform haemangioendothelioma and Kasabach-Merritt phenomenon. It is essential to realize that during the first months of life, metabolism is still developing and enzymes necessary to metabolise drugs like sirolimus still have to mature. To avoid toxic levels, the sirolimus dosage should be based on age and the associated pharmacological developments.

Sirolimus plus prednisolone vs sirolimus monotherapy for kaposiform hemangioendothelioma: a randomized clinical trial

The Kasabach-Merritt phenomenon (KMP) in kaposiform hemangioendothelioma (KHE) is characterized by life-threatening thrombocytopenia and consumptive coagulopathy. This study compared the efficacy and safety of sirolimus plus prednisolone vs sirolimus monotherapy as treatment strategies for KHE with KMP in the largest cohort to date. Participants were randomized to receive either sirolimus in combination with a short course of prednisolone or sirolimus monotherapy for at least 12 months. The primary outcome was defined as achievement of a durable platelet response (platelet count >100 × 109/L) at week 4. Participants completed efficacy assessments 2 years after the initial treatment. At week 4, a durable platelet response was achieved by 35 of 37 patients given sirolimus and prednisolone compared with 24 of 36 patients given sirolimus monotherapy (difference 27.9%; 95% confidence interval, 10.0-44.7). Compared with the sirolimus monotherapy group, the combination treatment group showed improvements in terms of measures of durable platelet responses at all points during the initial 3-week treatment period, median platelet counts during weeks 1 to 4, increased numbers of patients achieving fibrinogen stabilization at week 4, and objective lesion responses at month 12. Patients receiving combination therapy had fewer blood transfusions and a lower total incidence of disease sequelae than patients receiving sirolimus alone. The frequencies of total adverse events and grade 3-4 adverse events during treatment were similar in both groups. The responses seen in patients with KHE with KMP were profound and encouraging, suggesting that sirolimus plus prednisolone should be considered a valid treatment of KHE with KMP. This trial was registered at www.clinicaltrials.gov as #NCT03188068.

Indications and Limitations of Sirolimus in the Treatment of Vascular Anomalies-Insights From a Retrospective Case Series

BACKGROUND

Despite recent developments, the role of sirolimus in the heterogeneous spectrum of vascular anomalies is yet to be defined, in terms of indication, dosage, and therapy duration, recognizing both its potential and limitations.

METHODS

We retrospectively analyzed 16 children with vascular anomalies treated with sirolimus in two pediatric centers between 2014 and 2020 [male: n = 7, the median age at diagnosis: 4.6 months (range, 0-281.4)]. In addition, repetitive volumetric analyses of the vascular anomalies were performed when possible (11 cases).

RESULTS

Ten patients were diagnosed with vascular malformations and 6 with vascular tumors. The mean therapy duration was 27.2 months (range, 3.5-65). The mean sirolimus level was 8.52 ng/ml (range, 5.38-12.88). All patients except one with central conducting lymphatic anomaly responded to sirolimus, with the most noticeable volume reduction in the first 4-6 months. Additional administration of vincristine was needed in five patients with kaposiform hemangioendothelioma and yielded a response, even in cases, refractory to sirolimus monotherapy. As a single agent, sirolimus led to impressive improvement in a patient with another vascular tumor-advanced epithelioid hemangioendothelioma. Complicated vascular malformations required long-term sirolimus therapy. Side effects of sirolimus included mucositis and laboratory abnormalities. No major infectious episodes were recorded. An infant with COVID-19, diagnosed while on sirolimus therapy, presented with a mild course.

CONCLUSION

In the current series, we reported limitations of sirolimus as monotherapy, addressing the need to redefine its indications, and explore combination regimens and multimodal treatment strategies. Tools for objective evaluation of response trends over time could serve as a basis for the establishment of future therapeutic algorithms.

Effective surgical treatment of life-threatening huge vascular anomalies associated with thrombocytopenia and coagulopathy in infants unresponsive to drug therapy

BACKGROUND

Systemic drug therapy is generally recommended for infant huge vascular anomalies associated with thrombocytopenia and coagulopathy, but some patients are not suitable due to drug unresponsiveness or life threatening conditions before the drug works, who will need to receive surgical treatment. This study retrospectively analyzed the clinical features, imaging features, and surgical outcomes of these patients.

METHODS

The clinical data of 4 infants with huge vascular anomalies (2 vein malformations (VMs) and 2 kaposiform hemangioendothelioma (KHE)) associated with thrombocytopenia and coagulopathy treated from June 2016 to December 2017 were retrospectively analyzed. All patients received glucocorticoids, propranolol, vincristine or sirolimus treatment before admission, but the treatment was ineffective. Skin petechia, thrombocytopenia and coagulopathy were present at the time of admission. CT scanning was performed before operation. The patient's general clinical data, hematological examination results, operation time, surgical bleeding volume, blood transfusion volume and surgical complications were collected for analysis. The patients were followed up for 10-26 months.

RESULTS

CT scanning results of 2 patients showed special CT features without detectable enhancement within the lesion after CT enhanced scanning and multiple phleboliths formation. Four patients underwent surgical treatment successfully. Two patients underwent complete resection of the lesion, and 2 underwent cytoreductive surgery. Preoperative clinical symptoms such as skin petechia, thrombocytopenia and coagulopathy were normal at 1 week after surgery. Postoperative pathological results showed 2 cases of KHE and 2 cases of VMs. All patients were discharged from hospital without physical dysfunction, recurrence, or death.

CONCLUSIONS

Timely and appropriate surgical intervention can achieve satisfactory results for infants with huge VMs and KHE who were unresponsive to drug therapy or suffering from life-threatening occasion before the drug become effective.

Kaposiform hemangioendothelioma: current knowledge and future perspectives

Kaposiform hemangioendothelioma (KHE) is a rare vascular neoplasm with high morbidity and mortality. The initiating mechanism during the pathogenesis of KHE has yet to be discovered. The main pathological features of KHE are abnormal angiogenesis and lymphangiogenesis. KHEs are clinically heterogeneous and may develop into a life-threatening thrombocytopenia and consumptive coagulopathy, known as the Kasabach-Merritt phenomenon (KMP). The heterogeneity and the highly frequent occurrence of disease-related comorbidities make the management of KHE challenging. Currently, there are no medications approved by the FDA for the treatment of KHE. Multiple treatment regimens have been used with varying success, and new clinical trials are in progress. In severe patients, multiple agents with variable adjuvant therapies are given in sequence or in combination. Recent studies have demonstrated a satisfactory efficacy of sirolimus, an inhibitor of mammalian target of rapamycin, in the treatment of KHE. Novel targeted treatments based on a better understanding of the pathogenesis of KHE are needed to maximize patient outcomes and quality of life. This review summarizes the epidemiology, etiology, pathophysiology, clinical features, diagnosis and treatments of KHE. Recent new concepts and future perspectives for KHE will also be discussed.

Vincristine and sirolimus in the treatment of kaposiform haemangioendothelioma

AIM

Kaposiform haemangioendothelioma (KHE) is a rare, potentially life-threatening vascular tumour that is often associated with thrombocytopenia and coagulopathy, known as the Kasabach-Merritt phenomenon (KMP). Because of the rarity and complexity of KHE, the optimal paradigm for treating KHE has yet to be elucidated. We aim to assess the efficacy and safety of vincristine and sirolimus for the treatment of KHE.

METHODS

A comprehensive review of the literature was conducted from January 1993 to June 2018. A total of 15 studies were selected for the meta-analysis. Five studies included 75 individuals and reported the response and side effects to vincristine in the treatment of KHE with or without KMP. A total of 10 studies that included 127 individuals reported the response and safety of sirolimus for treating KHE with or without KMP.

RESULTS

The pooled odds ratio (OR) for the effectiveness of vincristine was 0.72. The pooled OR for the effectiveness of sirolimus was 0.91. The side effects associated with vincristine during the treatment included neuropathy, abdominal pain, loss of appetite and mild elevations of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). The side effects associated with sirolimus therapy included bronchitis; lymphopenia; elevated AST, ALT and platelets; hyperlipidaemia; opportunistic infection; mild reversible leukopenia; mucositis; fever; pain and skin rash/vomiting and diarrhoea.

CONCLUSIONS

This systematic review showed a high efficacy of vincristine and sirolimus in the treatment of KHE. Based on the available data in the literature, it appears that sirolimus is potentially an efficacious and safe treatment option for KHE. Further randomised, controlled trials are recommended.

The use of rapamycin to treat vascular tumours and malformations: A single-centre experience

Objectives

To assess the safety and efficacy of rapamycin in treating children with vascular tumours and malformations.

Study design

We performed a retrospective review at a large tertiary care paediatric centre to assess the efficacy and safety of using rapamycin to treat vascular tumours and malformations. Response to therapy was defined by patient-reported symptom improvement, radiological reduction in size of lesions, and/or improvement of laboratory parameters.

Results

Forty-two patients (7 with vascular tumours and 35 with vascular malformations) have been treated with rapamycin. Despite 33 of 42 patients being diagnosed in the first year of life, the median age of initiating rapamycin was 11 years. Of the 38 children treated for a minimum of 4 months, 29 (76%) exhibited a clinical response. Twenty-one patients had follow-up imaging studies and of these, 16 (76%) had radiographic decrease in lesion size. Median time to demonstration of response was 49 days. All five children with vascular tumours and all three children with vascular malformations under the age of 4 years showed a clinical response. Response rate was lower for children ≥ 4 years of age (0/2, 0% for vascular tumours; 21/28, 75% for vascular malformations). No patient experienced an infection directly related to rapamycin or discontinued rapamycin due to toxicity.

Conclusions

Rapamycin is safe and efficacious in most children with select vascular tumours and malformations. Young children appear to respond better, suggesting that early initiation of rapamycin should be considered.

A not so harmless mass: Kaposiform hemangioendothelioma complicated by a Kasabach-Merritt phenomenon

A vascular mass localized in the face and the neck was displayed by ultrasonography in a 38-week-old male fetus. At birth, the mass was bulky and purplish. The newborn breathed spontaneously but with severe desaturation. During laryngoscopy, we observed an obstruction of the larynx with a left-shift caused by the hemorrhagic mass. Blood analysis revealed anemia, severe thrombocytopenia, and coagulation disorders. The diagnosis of kaposiform hemangioendothelioma (KHE) complicated by a Kasabach-Merritt phenomenon (KMP) was put forward and treatment with propranolol, corticoids, and vincristine was initiated. Platelets were transfused daily for 8 days but did not resolve the thrombocytopenia. At day 8, we added sirolimus to the treatment and noted a rapid response with the normalization of the platelet count within 1 week and a significant regression of the mass. In this paper, we review the clinical and biological features of hemangioendothelioma associated with KMP and discuss its current and future treatment. Sirolimus seems to be very promising.

Abnormal hemostasis in children with vascular anomalies, part I: Thrombocytopenias among different vascular anomalies

Long before the classification of vascular anomalies from the International Society for the Study of Vascular Anomalies (ISSVA) provided a framework to differentiate vascular anomalies, otherwise known as vascular birthmarks, it was recognized that patients with such lesions can present with acute life-threatening hemostatic and/or thrombotic complications, as well as chronic long-standing bleeding or thrombotic issues. Scenarios such as a rapidly growing vascular lesion with severe acute thrombocytopenia, a visceral hemorrhagic lesion, a lesion associated with repetitive and painful superficial thrombosis, and cases of unprovoked or post-procedural fatal pulmonary embolism highlight the wide spectrum of manifestations of abnormal coagulation in patients with vascular anomalies. The separation of vascular anomalies into two distinct groups, vascular tumors and vascular malformations, was followed by the characterization that their respective coagulopathies were due to either a derangement of platelets or to a disequilibrium of the patient's coagulation/fibrinolytic process. This configuration of coagulopathies will be the foundation for this two-chapter review series. In the initial review, coagulopathies where thrombocytopenia is the main feature will be characterized, whereas the second review will focus on vascular malformations that have a coagulation disorder secondary to some degree of coagulation consumption and/or fibrinolytic pathway derangement.