MGMT protein expression is a reliable predictive biomarker for temozolomide-containing chemotherapy in osteosarcoma.

The prognosis of patients with osteosarcoma who experience recurrence or progression (R/P) is extremely poor, and more effective and less toxic therapies are needed. In the current study, the clinical data of osteosarcoma patients who experienced R/P were retrospectively analyzed to verify the reliability of O-6-methylguanine-DNA methyltransferase (MGMT) protein expression or MGMT promoter methylation for predicting the response to off-label temozolomide (TMZ)-containing chemotherapy. Of the 30 evaluable patients, 9 (30%) showed no/low MGMT protein expression, whereas all 16 evaluable patients had unmethylated MGMT promoter irrespective of MGMT protein expression levels. Twenty-three patients received TMZ-containing chemotherapy for measurable lesions (n = 14) or as adjuvant therapy following resection of recurrent lesions (n = 9). Among 14 patients with radiologically measurable lesions, the objective response rate was higher in the MGMT no/low-expression group (50.0%) than in the MGMT intermediate/high-expression group with borderline significance (0%, p = 0.066). The 6-month progression-free survival (PFS) rate in patients with radiologically measurable lesions was significantly higher in the MGMT no/low-expression group (50.0%) than in the MGMT intermediate/high-expression group (0%, p = 0.036). In the multivariate analysis of the 23 patients receiving TMZ-containing chemotherapy, MGMT expression and disease status before TMZ-containing chemotherapy were significantly associated with PFS. No severe adverse effects were observed during TMZ-containing chemotherapy. MGMT protein expression, but not MGMT promoter methylation, could predict a favorable outcome in patients receiving TMZ-containing chemotherapy.

[Experience with an international study on standard-risk relapsed childhood acute lymphoblastic leukemia (IntReALL SR 2010 study) in Japan].

Many effective new agents for relapsed childhood acute lymphoblastic leukemia (ALL) are now becoming available, and international standard chemotherapy should be developed to optimize use of these agents. Randomized controlled trials (RCTs) are needed to establish a standard treatment, but few have been conducted for relapsed childhood ALL in Japan due to the small patient population. Participation in international RCTs is necessary to access sufficient patients for informative study results, but differences in approved drugs and healthcare systems between countries make this challenging. In 2014, the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) participated in an international study on standard-risk relapsed childhood ALL (IntReALL SR 2010) involving two RCTs and multiple drugs not approved in Japan, which was addressed by replacing the unapproved drugs with alternative approved drugs with the same or similar efficacy. This article discusses the historical background of treatment development for relapsed childhood ALL, our experience in participating in the IntReALL SR 2010 trial, and prospects for treating relapsed childhood ALL.

Inversion of Central Venous Ports in Children Under Six Years Old: A Retrospective Analysis of 154 Oncology Patients.

Background Although some reports have evaluated the safety and efficacy of central venous port (CVP) placement in pediatric patients, the data about the inversion rate of the device and its risk factors are scarce. Therefore, this study aimed to evaluate the inversion rates of CVPs and their associated risk factors in pediatric patients. Methodology Between January 2010 and December 2021, 154 consecutive children (75 boys; median age, 28.5 months; range, 2-71 months) who underwent CVP placement at our center were included in this study. The primary outcome was the CVP inversion rate, and the secondary outcomes included technical success rate, intraoperative complications, and infectious complications. Intraoperative complications were evaluated according to the Society of Interventional Radiology guidelines. Patients under two years old were classified as the younger group and those aged ≥two years as the older group. Results The CVP inversion rate was 4.6% (n = 7/153), equivalent to 0.08 × 1,000 catheter-days. The inversion rate was significantly higher in the younger group (under two years old, 11.2%) than in the older group (≥two years old, 1.0%) according to the univariate analysis (p = 0.00576). The technical success rate was 99.4% (n = 153/154), and mild adverse events were observed during the procedure in three (1.9%) patients. Infectious complications were observed in 16 (10.5%) patients, equivalent to 0.19 × 1,000 catheter-days. Conclusions The CVP inversion rate was significantly higher in younger children (under two years old) than in older children (≥two years old).

Statistics of bone sarcoma in Japan: report from the population-based cancer registry in Japan.

BACKGROUND: No previous reports have characterized national bone sarcoma profiles overall. We examined the nationwide statistics for bone sarcoma in Japan using data from the National Cancer Registry (NCR), a population-based cancer registry. METHODS: We identified 3,755 patients with bone sarcomas entered in the NCR during 2016-2019 using International Classification of Diseases-Oncology, Third Edition codes for cancer topography and morphology. We extracted data on patient demographics, tumor details (reason for diagnosis, tumor location, histology, extent of disease), hospital volume/type, treatment, and prognosis for each patient. RESULTS: Bone sarcoma showed a slight male preponderance. The age distribution peaked at ages 10-20 and 60-80; approximately 44% of patients were aged over 60 years. Chordoma, chondrosarcoma, and malignant fibrous histiocytoma of bone peaked in the elderly, and Ewing's sarcoma peaked in children. Osteosarcoma had two peaks in Japan as well as in Western countries. The most frequent tumor locations were the limb (45%) and the pelvis (21%). Extent of disease was categorized as: "localized" (39%), "regional" (27%), and "distant" (11%). We found significant associations between overall survival and age, tumor location, facility type, hospital volume, histologic subtype, reason for diagnosis, and extent of disease. The latter had the poorest survival. CONCLUSIONS: This is the first study to outline the epidemiology, clinical features, treatment, prognosis, and significant factors affecting prognosis of bone sarcoma in Japan using the NCR. Documenting our data regarding elderly patients' outcomes is essential so other countries showing similar population-aging trends can learn from our experiences. LEVEL OF EVIDENCE: Prognostic studies, Level III.

Malignant melanoma in a 12-year-old boy 17 months after completing hepatoblastoma treatment.

BACKGROUND: Melanoma is rare as a secondary malignant neoplasm among childhood cancer survivors. CASE: We report a case of a 12-year-old boy who developed malignant melanoma with systemic metastases 17 months after completing treatment for hepatoblastoma. The diagnosis was made unexpectedly based on a bone marrow examination. The patient did not respond to immune checkpoint inhibitor therapy and died 6 weeks after being diagnosed with melanoma. Whole-exome sequencing to examine 103 genes associated with cancer predisposition did not identify any germ-line variants. CONCLUSION: This case study provides a unique example of melanoma in a childhood cancer survivor following hepatoblastoma treatment but does not identify any candidate variant to link hepatoblastoma and melanoma.

Incidence of skeletal-related events in patients with Ewing sarcoma: An observational retrospective study in Japan.

BACKGROUND: Skeletal-related events (SREs), including the pathological fracture, surgical treatment or radiation of bone lesions, malignant spinal cord compression, hypercalcemia, are important considerations when managing metastatic bone tumors; however, owing to their rarity, the incidence of SREs in patients with Ewing sarcoma remains unknown. METHODS: We retrospectively reviewed the clinical data from 146 patients with Ewing sarcoma treated at a single institution from 2005 to 2019. The median age at diagnosis was 22.7 years. Fifty patients (34.2%) had metastatic disease at diagnosis. The primary outcome was the SRE-free rate among patients with Ewing sarcoma. Moreover, we identified the risk factors for SREs using univariate or multivariate analyses. RESULTS: During the observational period (median, 2.6 years), SREs occurred in 23 patients. Radiation to the bone, malignant spinal cord compression, and hypercalcemia were documented as the initial SREs in 12 patients (52.2%), 10 patients (43.5%), and one patient (4.3%), respectively. The SRE-free rate was 94.2 ± 2.0, 87.3 ± 3.0, and 79.6 ± 3.8% at 1, 2, and 3 years after the initial visit, respectively. Multivariate analysis revealed bone metastasis at diagnosis (hazard ratio [HR] = 4.41, p = 0.007), bone marrow invasion (HR = 34.08, p < 0.001), and local progression or recurrence after definitive treatment (HR = 3.98, p = 0.012) as independent risk factors for SREs. CONCLUSIONS: SREs are non-rare events that can occur during the treatment course for Ewing sarcoma, with an especially high incidence of malignant spinal cord compression. Patients with metastatic disease at diagnosis, especially in the bone or bone marrow, or with local progression or recurrence after definitive treatment, should be carefully monitored for the occurrence of SREs. The most effective methods to monitor the occurrence of SREs and new preventative therapies for SREs should be investigated in the future.

Technical Feasibility and Safety of Central Venous Ports for Intravenous Chemotherapy in Infants With Retinoblastoma: A Retrospective Study.

PURPOSE: The central venous port (CVP) is widely used for intravenous chemotherapy (IVC) in adult patients because of its lower infection rates and easier management than that of a central venous catheter. However, the feasibility and safety of the CVP for IVC in infants remain unknown. This study evaluated the usefulness of CVP for IVC in infants with retinoblastoma. METHODS: The usefulness of CVP was retrospectively evaluated using technical success rates, the safety of CVP placement, and postoperative procedure-related complications in 18 infants with retinoblastoma. This study was conducted at the National Cancer Center Hospital, Chuo-Ku, Tokyo, Japan. RESULTS: The technical success rate was 100% (18/18) without any procedure-related complications. The sum duration of CVP implantation was 12,836 days (mean: 713 ± 453 days, range: 10-1,639 days). Postoperative complications were observed in two cases; one was a port reversal after 20 days, which was reversed by incisional surgery, and another was a catheter-related bloodstream infection after eight days, resulting in CVP removal. The total incidence of CVP-related infections was 5.6% (1/18) and 0.08/1000 catheter days. No other CVP-related complications were noted. CONCLUSION: The use of the CVP for IVC in infants with retinoblastoma was feasible with few complications.

Cross-individual cancer transmission to children during the gestational and perinatal periods.

Cancer transmission may rarely occur between individuals. Besides through allogenic transplantation, cancer transmission via the hemochorial placenta, which is permissive for cell traffic, has been described in a few reports. Three etiologies of transplacental cancer transmission include (1) maternofetal transmission of maternal cancer cells, (2) transmission of gestational choriocarcinoma to the fetus, and (3) transfer of preleukemic cells from one monozygotic twin to the other. Additionally, we recently reported two pediatric cases of lung tumors in which the lung-only distribution of tumors and genomic profiling of both the child's and mother's tumor samples suggested the airway/transbronchial transmission of maternal cervical cancer cells to the child by aspiration at birth. The immune system coordinates the hemostatic balance between effector and regulatory immunity, especially during fetal development. The immunoregulatory properties are shared in both physiological pregnancy-related and pathological cancer-related conditions. Mechanistically, the survival and colonization of transmitted cancer cells within a child are likely attributed to a combination of the child's immune tolerance and the cancer's immune escape. In this review, we summarize the current understanding of gestational/perinatal cancer transmission and discuss the possible mechanism-based immunotherapy for this rare form of pediatric cancer.

Promoter swapping of truncated PDGFRB drives Ph-like acute lymphoblastic leukemia.

Philadelphia chromosome (Ph)-like acute lymphoblastic leukemia (ALL) is a subset of ALL that demonstrated a high treatment failure rate. One of the hallmarks of Ph-like ALL is PDGFRB gene fusion, with fusion partner proteins often harboring dimerization domains and enhancing the kinase activity of PDGFRB. We determined a novel oncogenic PDGFRB fusion gene, NRIP1::PDGFRB, from a pediatric patient with ALL, encoding a protein with the carboxy-terminal kinase domain of PDGFRB, without the partner peptide. We confirmed the oncogenic potential of NRIP1::PDGFRB in vitro and the efficacy of all ABL1-specific inhibitor generations, including imatinib, dasatinib, nilotinib, and ponatinib, in suppressing this potential. PDGFRB activation mechanism may include juxtamembrane domain truncation in the predicted peptide. In conclusion, we determined a novel fusion gene pattern in Ph-like ALL.

KDM2B-Rearranged Soft Tissue Sarcomas Expand the Concept of BCOR-Associated Sarcoma.

Sarcomas with BCOR genetic alterations (BCOR-associated sarcomas) represent a recently recognized family of soft tissue and bone tumors characterized by BCOR fusion, BCOR internal tandem duplication, or YWHAE::NUTM2B fusion. Histologically, the tumors demonstrate oval to spindle cell proliferation in a variably vascular stroma and overexpression of BCOR and SATB2. Herein, we describe 3 soft tissue sarcomas with KDM2B fusions that phenotypically and epigenetically match BCOR-associated sarcomas. The cases included 1 infant, 1 adolescent, and 1 older patient. All tumors showed histologic findings indistinguishable from those of BCOR-associated sarcomas and were originally diagnosed as such based on the phenotype. However, none of the tumors had BCOR or YWHAE genetic alterations. Instead, targeted RNA sequencing identified in-frame KDM2B::NUTM2B, KDM2B::CREBBP, and KDM2B::DUX4 fusions. KDM2B fusions were validated using reverse-transcription PCR, Sanger sequencing, and in situ hybridization assays. Genome-wide DNA methylation analysis matched all 3 tumors with BCOR-associated sarcomas using the Deutsches Krebsforschungszentrum (DKFZ) classifier and t-distributed stochastic neighbor embedding analysis. One localized tumor showed a flat genome-wide copy number profile, and the patient remained disease-free after treatment. The other tumors showed multiple copy number alterations, including MDM2/CDK4 amplification and/or CDKN2A/B loss, and both tumors metastasized, leading to the patient's death in one of the cases. When tested using KDM2B immunohistochemistry, all 3 KDM2B-rearranged sarcomas showed diffuse strong staining, and all 13 sarcomas with BCOR genetic alterations also demonstrated diffuse, strong, or weak staining. By contrast, among 72 mimicking tumors, only a subset of synovial sarcomas showed focal or diffuse weak KDM2B expression. In conclusion, our study suggests that KDM2B-rearranged soft tissue sarcomas belong to the BCOR-associated sarcoma family and expand its molecular spectrum. This may be related to the known molecular relationship between KDM2B and BCOR in the polycomb repressive complex 1.1. Immunohistochemical analysis of KDM2B is a potentially valuable diagnostic tool for BCOR-associated sarcomas, including those with KDM2B rearrangement.

Pediatric Precision Medicine at the National Cancer Center Japan: Prospective Genomic Study of Pediatric Patients with Cancer as Part of the TOP-GEAR Project.

PURPOSE: This single-center, prospective molecular profiling study characterizes genomic alterations and identifies therapeutic targets in advanced pediatric solid tumors. METHODS: As part of the TOP-GEAR (Trial of Onco-Panel for Gene profiling to Estimate both Adverse events and Response by cancer treatment) project at the National Cancer Center (NCC), Japan, we enrolled pediatric patients with a refractory or recurrent disease during August 2016-December 2021 and performed genomic analysis of matched tumors and blood using originally developed cancer gene panels, NCC Oncopanel (ver. 4.0) and NCC Oncopanel Ped (ver. 1.0). RESULTS: Of 142 patients (age, 1-28 years) enrolled, 128 (90%) were evaluable for genomic analysis; 76 (59%) patients harbored at least one reportable somatic or germline alteration. The tumor samples were collected during the initial diagnosis in 65 (51%) patients, after treatment initiation in 11 (9%) patients, and upon either disease progression or relapse in 52 (41%) patients. The leading altered gene was TP53, followed by MYCN, MYC, CDKN2A, and CDK4. The commonly affected molecular processes were transcription, cell-cycle regulation, epigenetic modifiers, and RAS/mitogen-activated protein kinase signaling. Twelve (9%) patients carried pathogenic germline variants in cancer-predisposing genes. Potentially actionable findings were identified in 40 (31%) patients; to date, 13 (10%) patients have received the recommended therapy on the basis of their genomic profiles. Although four patients had access to targeted therapy through clinical trials, the agents were used in nine patients in an off-label setting. CONCLUSION: The implementation of genomic medicine has furthered our understanding of tumor biology and provided new therapeutic strategies. However, the paucity of proposed agents limits the full potential of actionability, emphasizing the significance of facilitating access to targeted cancer therapies.

Safety and efficacy of multiple tyrosine kinase inhibitors in pediatric/adolescent and young adult patients with relapsed or refractory osteosarcomas: A single-institution retrospective analysis.

BACKGROUND: The prognosis of relapsed or refractory osteosarcoma remains poor. Recent reports have stated that molecular targeting agents, including multiple tyrosine kinase inhibitors (MTKIs), are effective against adult osteosarcoma. To determine the safety and efficacy of MTKI therapy in children, adolescents and young adults (AYAs), we conducted a retrospective study on adverse events and treatment outcomes. METHODS: We retrospectively reviewed the medical records of patients with relapsed or refractory osteosarcoma who received MTKI therapy at the Department of Pediatric Oncology, National Cancer Center Hospital, from December 2013 to May 2021. RESULTS: The study included 31 patients (15 males and 16 females) who received MTKIs, including sorafenib monotherapy (seven patients), sorafenib and everolimus (14 patients), and regorafenib monotherapy (10 patients). Their median age was 17 years (range: 11-22 years). The incidence of treatment-related grade 3 nonhematological adverse events was 14.3% in the sorafenib monotherapy group, 21.4% in the sorafenib with everolimus group, and 20.0% in the regorafenib monotherapy group. No grade 4 nonhematological adverse events were observed. The median progression-free survival (PFS) was 51 days in the sorafenib monotherapy group, 101 days in the sorafenib with everolimus group, and 167 days in the regorafenib monotherapy group. CONCLUSION: The safety profile of MTKI therapies in pediatric and AYA patients was comparable to that in adult patients. MTKI therapies, particularly regorafenib, against pediatric relapsed osteosarcoma can suppress tumor growth and prolong PFS with tolerable adverse events.

Clinical characteristics of primary cutaneous and subcutaneous Ewing sarcoma.

OBJECTIVE: Given the rarity of cutaneous/subcutaneous Ewing sarcoma, their clinical characteristics remain poorly understood. In this study, we aimed to analyse the clinical characteristics of patients with cutaneous/subcutaneous Ewing sarcoma and review the treatment strategy. METHODS: We reviewed the clinical data of 154 patients with Ewing sarcoma who were treated at our hospital between 2005 and 2019. Amongst these patients, 21 patients with cutaneous/subcutaneous Ewing sarcoma were analysed. As a basic strategy, patients with localized disease received intensive chemotherapy (vincristine-doxorubicin-cyclophosphamide/ifosfamide-etoposide), followed by definitive surgery with or without radiotherapy. In total, 15 patients underwent pre-diagnostic resection with macroscopic residue (seven patients) or non-macroscopic residue (eight patients) before intensive chemotherapy. RESULTS: The median tumour length of the measurable lesions was 3.2 cm, and the ratio of metastasis was significantly lower than the Ewing sarcoma of other anatomical sites (10% vs. 37%, P = 0.013). Despite the pre-diagnostic resection, local recurrence after additional resection and/or adjuvant radiotherapy did not occur in any of the patients with localized disease. Overall survival was significantly higher in patients with cutaneous/subcutaneous Ewing sarcoma than in patients with Ewing sarcoma of other anatomical sites (hazard ratio = 0.33, P = 0.013). The event-free survival rate of cutaneous/subcutaneous Ewing sarcoma was also superior to that of Ewing sarcoma of other anatomical sites (hazard ratio = 0.35, P = 0.01). CONCLUSIONS: Patients with cutaneous/subcutaneous Ewing sarcoma may have better prognosis than those with Ewing sarcoma at other anatomical sites. Although pre-diagnostic resection without appropriate investigations is not recommended, local control may be recovered by using a combination of additional resection, chemotherapy and radiotherapy.

Nelarabine-induced myelopathy in patients undergoing allogeneic hematopoietic cell transplantation: a report of three cases.

Nelarabine is an effective treatment for T-cell acute lymphoblastic leukemia/lymphoma. Myelopathy is a rare but serious adverse event associated with this drug. Three patients who received nelarabine at the National Cancer Center Hospital from December 2014 to March 2021 developed myelopathy 20 days before, 12 days after, and 29 days after allogeneic hematopoietic cell transplantation (allo-HCT), respectively. Magnetic resonance imaging showed that two of the patients had lesions in the dorsal column or medulla oblongata, and one had no abnormalities in the head or spine. Despite treatment with intravenous immunoglobulin and methylprednisolone, all patients became unable to walk. One patient died on day 101 after allo-HCT due to progressive neurotoxicity. The other two patients showed spontaneous improvement in neurological symptoms, but one died of mucormycosis on day 476. Autopsy revealed spongiosis in the posterior funiculus in both patients who died, and also in the medulla oblongata in one patient. In the surviving patient, positron emission tomography on day 84 showed abnormal accumulation, suggesting continued inflammation. These cases demonstrated pathophysiological features of nelarabine-induced myelopathy and indicate that allo-HCT may worsen the condition. It is necessary to elucidate the underlying mechanism and establish diagnostic methods and therapies.

Surgical Treatment for Pneumothorax and Tumor-bronchial Fistula Secondary to Pulmonary Metastasis of Osteosarcoma in Pediatric and Adolescent Patients.

BACKGROUND: Pneumothorax and tumor-bronchial fistula are rare complications of pulmonary metastasis of osteosarcoma. OBSERVATIONS: We herein report the cases of 3 pediatric and adolescent patients who developed pneumothorax or tumor-bronchial fistula during treatment of pulmonary metastasis of osteosarcoma with chemotherapeutics or antiangiogenic agents. Two patients developed pneumothorax, and the other patient developed tumor-bronchial fistula. All of the patients finally underwent the surgery to treat their complications. CONCLUSIONS: Although it is not a curative surgery, surgery for pneumothorax and tumor-bronchial fistula is acceptable. The operative procedure should be considered on the basis of the predicted prognosis of the patient.

Other (Non-CNS/Testicular) Extramedullary Localizations of Childhood Relapsed Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma-A Report from the ALL-REZ Study Group.

Children with other extramedullary relapse of acute lymphoblastic leukemia are currently poorly characterized. We aim to assess the prevalence and the clinical, therapeutic and prognostic features of extramedullary localizations other than central nervous system or testis in children with relapse of acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL) treated on a relapsed ALL protocol. PATIENTS AND METHODS: Patients with relapse of ALL and LBL, treated according to the multicentric ALL-REZ BFM trials between 1983 and 2015, were analyzed for other extramedullary relapse (OEMR) of the disease regarding clinical features, treatment and outcome. Local treatment/irradiation has been recommended on an individual basis and performed only in a minority of patients. RESULTS: A total of 132 out of 2323 (5.6%) patients with ALL relapse presented with an OEMR (combined bone marrow relapse n = 78; isolated extramedullary relapse n = 54). Compared to the non-OEMR group, patients with OEMR had a higher rate of T-immunophenotype (p < 0.001), a higher rate of LBL (p < 0.001) and a significantly different distribution of time to relapse, i.e., more very early and late relapses compared to the non-OEMR group (p = 0.01). Ten-year probabilities of event-free survival (pEFS) and overall survival (pOS) in non-OEMR vs. OEMR were 0.38 ± 0.01 and 0.32 ± 0.04 (p = 0.0204) vs. 0.45 ± 0.01 and 0.37 ± 0.04 (p = 0.0112), respectively. OEMRs have been classified into five subgroups according to the main affected compartment: lymphatic organs (n = 32, 10y-pEFS 0.50 ± 0.09), mediastinum (n = 35, 10y-pEFS 0.11 ± 0.05), bone (n = 12, 0.17 ± 0.11), skin and glands (n = 21, 0.32 ± 0.11) and other localizations (n = 32, 0.41 ± 0.09). Patients with OEMR and T-lineage ALL/LBL showed a significantly worse 10y-pEFS (0.15 ± 0.04) than those with B-Precursor-ALL (0.49 ± 0.06, p < 0.001). Stratified into standard risk (SR) and high risk (HR) groups, pEFS and pOS of OEMR subgroups were in the expected range whereas the mediastinal subgroup had a significantly worse outcome. Subsequent relapses involved more frequently the bone marrow (58.4%) than isolated extramedullary compartments (41.7%). In multivariate Cox regression, OEMR confers an independent prognostic factor for inferior pEFS and pOS. CONCLUSION: OEMR is adversely related to prognosis. However, the established risk classification can be applied for all subgroups except mediastinal relapses requiring treatment intensification. Generally, isolated OEMR of T-cell-origin needs an intensified treatment including allogeneic stem cell transplantation (HSCT) as a curative approach independent from time to relapse. Local therapy such as surgery and irradiation may be of benefit in selected cases. The indication needs to be clarified in further investigations.

Impact of ALK Inhibitors in Patients With ALK-Rearranged Nonlung Solid Tumors.

PURPOSE: Anaplastic lymphoma kinase (ALK) rearrangement is a well-known driver oncogene in non-small-cell lung cancer and has also been identified in other types of tumors. However, there is limited evidence on the clinical response to ALK tyrosine kinase inhibitors (TKIs), such as alectinib and crizotinib, in rare tumors with ALK fusion. We evaluated the therapeutic effect of ALK-TKIs in rare ALK-rearranged tumors. PATIENTS AND METHODS: Between April 2012 and April 2019, clinical outcomes and characteristics of patients with ALK-rearranged nonlung solid tumors who received ALK-TKIs (alectinib and/or crizotinib) outside of clinical trials were reviewed. Expression and/or rearrangement of ALK was evaluated by immunohistochemistry, fluorescence in situ hybridization, and next-generation sequencing. The tumor response was assessed according to RECIST (version 1.1). Progression-free survival was estimated from initial ALK-TKI initiation until progression. RESULTS: We identified seven patients (inflammatory myofibroblastic tumors, n = 3; ALK-positive histiocytosis, n = 1; histiocytic sarcoma, n = 1; osteosarcoma, n = 1; and parotid adenocarcinoma, n = 1), with a median age of 17 years. Two rare ALK fusions, namely, CTNNA1-ALK and ITSN2-ALK, were identified. As initial ALK-TKI therapy, five patients received alectinib and two received crizotinib. The objective response rate for the initial ALK-TKI therapy was 85.7% (95% CI, 44 to 97), including two patients who received alectinib and achieved complete response. The median progression-free survival was 8.1 months (range, 1.7 to not estimable). There were no treatment interruptions or dose reductions because of adverse events caused by alectinib. CONCLUSION: This study highlights the potential benefit of ALK-TKIs, especially alectinib, in patients with ALK-rearranged nonlung solid tumors.