Larotrectinib in Treating Patients With Previously Untreated TRK Fusion Solid Tumors and TRK Fusion Relapsed Acute Leukemia

Solid Neoplasm Clinical Trial

Official title:

Larotrectinib (LOXO-101, NSC# 788607) for Previously Untreated TRK Fusion Pediatric Solid Tumors and TRK Fusion Relapsed Pediatric Acute Leukemias

Clinical Trial Details — Status: Active, not recruiting

Administrative data

• NCT number: NCT03834961
• Other study ID #: ADVL1823
• Secondary ID: NCI-2019-00015AD
• Status: Active, not recruiting
• Phase: Phase 2
• Start date: October 25, 2019
• Est. completion date: September 30, 2024

Study information

• Verified date: March 2024
• Source: Children's Oncology Group
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

This phase II trial studies the side effects and how well larotrectinib works in treating patients with previously untreated TRK fusion solid tumors and TRK fusion acute leukemia that has come back. Larotrectinib may stop the growth of cancer cells with TRK fusions by blocking the TRK enzymes needed for cell growth.

Description:

PRIMARY OBJECTIVE:

I. To determine the objective response rate (ORR) of children with infantile fibrosarcoma (IFS) treated with neoadjuvant larotrectinib prior to local control.

SECONDARY OBJECTIVES:

I. To determine event-free survival (EFS), overall survival (OS), and duration of response (DoR) of children with IFS treated with neoadjuvant larotrectinib prior to local control.

II. To determine the ORR, EFS, OS, and DoR of children with newly diagnosed TRK fusion solid tumors other than IFS treated with neoadjuvant larotrectinib prior to local control.

III. To describe the toxicity of larotrectinib in children with solid tumors and acute leukemia.

IV. To determine the percentage of patients with TRK fusion solid tumors with detectable circulating tumor deoxyribonucleic acid (DNA) at baseline and after 2 weeks, 4 weeks, 24 weeks of treatment, at the time of discontinuation of larotrectinib therapy, and at progression.

EXPLORATORY OBJECTIVES:

I. To determine the EFS, OS, and DoR of children with TRK fusion solid tumors other than IFS treated with adjuvant larotrectinib following upfront surgery with positive margins after neoadjuvant larotrectinib.

II. To determine the EFS, OS, and DoR of children with TRK fusion solid tumors who experience a complete response to larotrectinib and subsequently discontinue larotrectinib therapy.

III. To determine the remission induction rate for patients with recurrent/refractory TRK fusion leukemia when treated with larotrectinib.

IV. To evaluate the surgical morbidity and extent of resection of initially unresectable tumors in patients with TRK fusion solid tumors who undergo surgical resection following neoadjuvant larotrectinib.

V. To evaluate mechanisms of response and resistance to larotrectinib in children with TRK fusion cancers.

VI. To evaluate the morphologic features of TRK fusion solid tumors at time of initial biopsy to further define criteria for pathologic diagnosis of these tumors.

VII. To evaluate immunohistochemistry for pan-TRK as a screening method for TRK fusion tumors and in resection specimens following neoadjuvant treatment with larotrectinib.

VIII. To evaluate the histologic response to larotrectinib in resection specimens following neoadjuvant treatment.

IX. To evaluate circulating tumor DNA for the detection of the emergence of resistance mutations and recurrence in patients with TRK fusion solid tumors treated with larotrectinib.

X. To evaluate the ratio of cerebrospinal fluid (CSF) to concurrent plasma concentrations of larotrectinib in patients with leukemia.

XI. To evaluate the change in neurocognitive/behavioral functioning over time between baseline and 2 years post-diagnosis of patients treated on this protocol using parent-reported adaptive functioning (Adaptive Behavior Assessment System [ABAS]-III General Adaptive Composite), executive function (Behavior Rating Inventory of Executive Function Scales-Preschool Version [BRIEF-P] or BRIEF-2 Global Executive Composite Score), psychosocial functioning (Behavior Assessment System for Children [BASC]-3 Internalizing, Externalizing and Behavioral Symptoms Indices) and quality of life (Pediatric Quality of Life Inventory [PedsQL] Total score).

OUTLINE:

Patients receive larotrectinib orally (PO) or by nasogastric (NG) or gastric tube (G-tube) twice daily (BID) on days 1-28. Treatment repeats every 28 days for up to 26 cycles in the absence of disease progression or unacceptable toxicity. Patients whose tumors shrink sufficiently while taking larotrectinib may undergo surgical resection of their tumor while on study.

After completion of study treatment, patients are followed up at 3, 6, 12, 18, 24, 30, 36, and 48 months and annually thereafter for up to 5 years from the date of study entry.

Recruitment information / eligibility

• Status: Active, not recruiting
• Enrollment: 70
• Est. completion date: September 30, 2024
• Est. primary completion date: September 30, 2024
• Accepts healthy volunteers: No
• Gender: All
• Age group: N/A to 30 Years

Eligibility

Inclusion Criteria:

• Patients must be =< 30 years of age at the time of study entry

• COHORT A: Patients must have a histologic diagnosis of infantile fibrosarcoma with an NTRK1, NTRK2, or NTRK3 fusion identified in a Clinical Laboratory Improvement Act/College of American Pathologists (CLIA/CAP) certified laboratory. Fusions may be identified by fluorescence in situ hybridization (FISH) or molecular techniques (reverse transcriptase-polymerase chain reaction [RT-PCR] using primers flanking the fusion junction or next generation sequencing). For fusions identified by FISH, an ETV6 rearrangement is sufficient for eligibility in Cohort A. Identification of the upstream TRK fusion partner is not required.

• COHORT B: Patients must have a histologic diagnosis of any solid tumor other than infantile fibrosarcoma, including central nervous system (CNS) tumors but excluding high grade gliomas. An NTRK1, NTRK2, or NTRK3 fusion must be identified in a CLIA/CAP certified laboratory. Fusions may be identified by FISH or molecular techniques (RT-PCR using primers flanking the fusion junction or next generation sequencing). For fusions identified by FISH, there must be an identified rearrangement in NTRK1, NTRK2, or NTRK3 (e.g., an ETV6 rearrangement is not sufficient for eligibility) unless the patient has a diagnosis of congenital mesoblastic nephroma in which case an ETV6 rearrangement is sufficient for eligibility. Identification of the upstream TRK fusion partner is not required.

• COHORT C: Patients must have a histologic diagnosis of relapsed or refractory acute leukemia with an NTRK1, NTRK2, or NTRK3 fusion identified in a CLIA/CAP certified laboratory. Fusions may be identified by FISH or molecular techniques (RT-PCR using primers flanking the fusion junction or next generation sequencing). For fusions identified by FISH, there must be an identified rearrangement in NTRK1, NTRK2, or NTRK3 (e.g., an ETV6 rearrangement is not sufficient for eligibility). Identification of the upstream TRK fusion partner is not required.

• SOLID TUMORS (COHORTS A AND B): Patients must have measurable disease. Patients must have disease that cannot be completely resected without a predicted functional, neurologic, or significant cosmetic deficit in the opinion of the investigator.

• LEUKEMIA (COHORT C): Patients must have >= 5% blasts in the bone marrow. Extramedullary disease is permitted.

• Patients must have a Lansky or Karnofsky performance status score of >= 50, corresponding to Eastern Cooperative Oncology Group (ECOG) categories 0, 1 or 2. Use Karnofsky for patients > 16 years of age and Lansky for patients =< 16 years of age. NOTE: Neurologic deficits in patients with CNS tumors must have been stable for at least 7 days prior to study enrollment. Patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score.

• COHORTS A AND B: No prior anti-cancer therapy, including radiotherapy, other than surgical resection is permitted.

• Patients who experience recurrence after surgery alone and no other anti-cancer therapy will be eligible.

• If not eligible due to prior anticancer therapy, patients may be eligible for the larotrectinib arm of Pediatric MATCH (APEC1621A) or treatment with commercial larotrectinib off study.

• COHORT C: Patients with relapsed leukemia (Cohort C) must have fully recovered from the acute toxic effects of all prior anti-cancer therapy and must meet the following minimum duration from prior anti-cancer directed therapy prior to enrollment. If after the required timeframe, the numerical eligibility criteria are met, e.g. blood count criteria, the patient is considered to have recovered adequately.

• Cytotoxic chemotherapy or other anti-cancer agents known to be myelosuppressive. The duration of this interval must be discussed with the study chair and the study-assigned research coordinator prior to enrollment.

• A waiting period prior to enrollment is not required for patients receiving standard cytotoxic maintenance chemotherapy (i.e., corticosteroid, vincristine, thioguanine [6MP], and/or methotrexate).

• A waiting period is not required for patients receiving a single dose of intrathecal methotrexate, hydrocortisone, and/or cytarabine within 7 days prior to enrollment.

• >= 14 days must have elapsed after the completion of other cytotoxic therapy, with the exception of hydroxyurea, for patients not receiving standard maintenance therapy. Additionally, patients must have fully recovered from all acute toxic effects of prior therapy.

• Note: Cytoreduction with hydroxyurea must be discontinued >= 24 hours prior to the start of protocol therapy.

• Anti-cancer agents not known to be myelosuppressive (e.g., not associated with reduced platelet or absolute neutrophil [ANC] counts): >= 7 days after the last dose of agent. The duration of this interval must be discussed with the study chair and the study-assigned research coordinator prior to enrollment.

• Anti-cancer agents that are antibodies: >= 21 days must have elapsed from infusion of last dose of antibody, and toxicity related to prior antibody therapy must be recovered to grade =< 1. There is an exception for blinatumomab infusions, for which patients must have been off for at least 3 days and all drug related toxicity must have resolved to grade 2 or lower as outlined in the inclusion/exclusion criteria.

• Corticosteroids: If used to modify immune adverse events related to prior therapy, >= 14 days must have elapsed since last dose of corticosteroid. A waiting period prior to enrollment is not required for patients receiving corticosteroid for leukemia therapy/cytoreduction.

• Hematopoietic growth factors: >= 14 days after the last dose of a long-acting growth factor (e.g. pegfilgrastim) or 7 days for short-acting growth factor. For agents that have known adverse events occurring beyond 7 days after administration, this period must be extended beyond the time during which adverse events are known to occur. The duration of this interval must be discussed with the study chair and the study-assigned research coordinator.

• Interleukins, interferons and cytokines (other than hematopoietic growth factors): >= 21 days after the completion of interleukins, interferon or cytokines (other than hematopoietic growth factors ).

• Stem cell infusions (with or without total body irradiation [TBI]):

• Allogeneic (non-autologous) bone marrow or stem cell transplant, or any stem cell infusion including donor lymphocyte infusion (DLI) or boost infusion: >= 84 days after infusion and no evidence of graft versus host disease (GVHD).

• Autologous stem cell infusion including boost infusion: >= 42 days.

• Cellular therapy: >= 42 days after the completion of any type of cellular therapy (e.g., modified T cells, natural killer [NK] cells, dendritic cells, etc.)

• Radiation therapy (XRT)/external beam irradiation including protons: >= 14 days after local XRT; >= 150 days after TBI, craniospinal XRT or if radiation to >= 50% of the pelvis; >= 42 days if other substantial BM radiation.

• Radiopharmaceutical therapy (e.g., radiolabeled antibody): >= 42 days after systemically administered radiopharmaceutical therapy.

• Patients must not have received prior exposure to TRK inhibitors (including larotrectinib, LOXO-195, entrectinib, lorlatinib, crizotinib, or lestaurtinib).

• For patients with solid tumors without known bone marrow involvement: Peripheral absolute neutrophil count (ANC) >= 1000/mm^3 (within 7 days prior to enrollment).

• For patients with solid tumors without known bone marrow involvement: Platelet count >= 100,000/mm^3 (transfusion independent, defined as not receiving platelet transfusions for at least 7 days prior to enrollment).

• For patients with solid tumors without known bone marrow involvement: Hemoglobin >= 8.0 g/dL at baseline (within 7 days prior to enrollment) (may receive red blood cell [RBC] transfusions).

• Patients with solid tumors with known bone marrow metastatic disease will be eligible for study provided they meet the blood counts above (may receive transfusions provided they are not known to be refractory to red cell or platelet transfusions). These patients will not be evaluable for hematologic toxicity.

• For patients with leukemia: Platelet count >= 20,000/mm^3 (within 7 days prior to enrollment) (may receive platelet transfusions; must not be known to be refractory to red cell or platelet transfusion).

• For patients with leukemia: Hemoglobin >= 8.0 g/dL at baseline (within 7 days prior to enrollment) (may receive RBC transfusions; must not be known to be refractory to red cell or platelet transfusion).

• Creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 mL/min/1.73 m^2 or a serum creatinine based on age/gender as follows (within 7 days prior to enrollment):

• 1 month to < 6 months (male 0.4 mg/dL, female 0.4 mg/dL)

• 6 months to < 1 year (male 0.5 mg/dL, female 0.5 mg/dL)

• 1 to < 2 years (male 0.6 mg/dL, female 0.6 mg/dL)

• 2 to < 6 years (male 0.8 mg/dL, female 0.8 mg/dL)

• 6 to < 10 years (male 1 mg/dL, female 1 mg/dL)

• 10 to < 13 years (male 1.2 mg/dL, female 1.2 mg/dL)

• 13 to < 16 years (male 1.5 mg/dL, female 1.4 mg/dL)

• >= 16 years (male 1.7 mg/dL, female 1.4 mg/dL)

• For patients < 1 month of age, serum creatinine levels must be < 1.5 x the treating institution's creatinine upper limit of normal (ULN) for patients < 1 month of age or the creatinine clearance or radioisotope GFR must be >= 70 mL/min/1.73 m^2.

• Patients with solid tumors: Bilirubin (sum of conjugated + unconjugated) =< 1.5 x upper limit of normal (ULN) for age (within 7 days prior to enrollment). After approval of the study chair or designee, infants with a higher total bilirubin due to physiologic or breast milk jaundice are eligible if the conjugated (direct) bilirubin is =< 2 mg/dL.

• Patients with solid tumors: Serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) =< 135 U/L (within 7 days prior to enrollment). For the purpose of this study, the ULN for SGPT is 45 U/L.

• Patients with solid tumors: Serum albumin >= 2 g/dL (within 7 days prior to enrollment).

• Patients with leukemias: Conjugated (direct) bilirubin =< 1.5 x upper limit of normal (ULN) for age (within 7 days prior to enrollment).

• Patients with leukemias: SGPT (ALT) =< 225 U/L (within 7 days prior to enrollment). For the purpose of this study, the ULN for SGPT is 45 U/L.

• Patients with leukemias: Serum albumin >= 2 g/dL (within 7 days prior to enrollment).

• Patients with seizure disorder may be enrolled if on a stable antiepileptic regimen for >= 14 days and well controlled.

• Nervous system disorders (Common Terminology Criteria for Adverse Events [CTCAE] version [v] 5) except tendon reflex decreased resulting from prior therapy must be =< grade 2.

• All patients and/or their parents or legal guardians must sign a written informed consent.

• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met.

Exclusion Criteria:

• Pregnant or breast-feeding women will not be entered on this study due to risks of fetal and teratogenic adverse events as seen in animal/human studies, OR because there is yet no available information regarding human fetal or teratogenic toxicities. Pregnancy tests must be obtained in girls who are post-menarchal. Female patients of reproductive potential may not participate unless they have agreed to use a highly effective contraceptive method for the duration of study therapy and for at least one month after the final dose of larotrectinib. Males of reproductive potential with a non-pregnant female partner of child-bearing potential must use a highly effective contraception for the duration of the study and for at least one month after the final dose of larotrectinib. Because of the unknown risk of larotrectinib in nursing infants, nursing women should discontinue breastfeeding during treatment with larotrectinib and for 3 days following the final dose.

• Patients with solid tumors, including CNS tumors, requiring corticosteroids who have not been on a stable or decreasing dose of corticosteroid for at least 7 days prior to enrollment are not eligible. Patients with leukemia may receive systemic corticosteroids for cytoreduction up to 24 hours prior to the start of protocol therapy. If used to modify immune adverse events related to prior therapy, >= 14 days must have elapsed since last dose of corticosteroid.

• Patients who are currently receiving another investigational drug are not eligible.

• Patients who are currently receiving other anti-cancer agents are not eligible [except leukemia patients receiving corticosteroids or hydroxyurea, which may be continued until 24 hours prior to start of protocol therapy]. Patients with leukemia should receive a single dose of intrathecal cytarabine, hydrocortisone, and/or methotrexate within 7 days prior to Day 1 of Cycle 1 at the time of the baseline lumbar puncture.

• Patients who are receiving cyclosporine, tacrolimus or other agents to prevent graft-versus-host disease post bone marrow transplant are not eligible for this trial.

• Patients currently receiving a strong CYP3A4 inducer or inhibitor are not eligible. Strong inducers or inhibitors of CYP3A4 should be avoided from 14 days prior to enrollment to the end of the study. Note: CYP3A4 inducing anti-epileptic drugs and dexamethasone for CNS tumors or metastases, on a stable dose, are allowed.

• Patients with malabsorption syndrome or other conditions that significantly limit enteral absorption are not eligible.

• Patients who are unable to swallow capsules or liquid and do not have gastric access via a nasogastric or gastrostomy tube are not eligible.

• Patients who have an uncontrolled infection are not eligible.

• Patients who have received prior solid organ transplantation are not eligible.

• Patients who in the opinion of the investigator may not be able to comply with the safety monitoring requirements of the study are not eligible.

• Patients with high grade gliomas (HGG) are not eligible.

Related Conditions & MeSH terms

• Acute Disease
• Central Nervous System Neoplasm
• Central Nervous System Neoplasms
• Fibrosarcoma
• Infantile Fibrosarcoma
• Leukemia
• Neoplasms
• Nervous System Neoplasms
• Recurrent Acute Leukemia
• Refractory Acute Leukemia
• Solid Neoplasm

Intervention

Drug:
• Larotrectinib Sulfate
Given PO or via NG or G tube

Locations

Country	Name	City	State
Canada	IWK Health Centre	Halifax	Nova Scotia
Canada	Centre Hospitalier Universitaire Sainte-Justine	Montreal	Quebec
United States	Children's Hospital Medical Center of Akron	Akron	Ohio
United States	Lehigh Valley Hospital-Cedar Crest	Allentown	Pennsylvania
United States	C S Mott Children's Hospital	Ann Arbor	Michigan
United States	Mission Hospital	Asheville	North Carolina
United States	Children's Healthcare of Atlanta - Egleston	Atlanta	Georgia
United States	Children's Hospital Colorado	Aurora	Colorado
United States	Dell Children's Medical Center of Central Texas	Austin	Texas
United States	Sinai Hospital of Baltimore	Baltimore	Maryland
United States	Children's Hospital of Alabama	Birmingham	Alabama
United States	Saint Luke's Cancer Institute - Boise	Boise	Idaho
United States	Dana-Farber Cancer Institute	Boston	Massachusetts
United States	Montefiore Medical Center - Moses Campus	Bronx	New York
United States	Carolinas Medical Center/Levine Cancer Institute	Charlotte	North Carolina
United States	Novant Health Presbyterian Medical Center	Charlotte	North Carolina
United States	Cincinnati Children's Hospital Medical Center	Cincinnati	Ohio
United States	Cleveland Clinic Foundation	Cleveland	Ohio
United States	Nationwide Children's Hospital	Columbus	Ohio
United States	Medical City Dallas Hospital	Dallas	Texas
United States	UT Southwestern/Simmons Cancer Center-Dallas	Dallas	Texas
United States	Dayton Children's Hospital	Dayton	Ohio
United States	Rocky Mountain Hospital for Children-Presbyterian Saint Luke's Medical Center	Denver	Colorado
United States	Kaiser Permanente Downey Medical Center	Downey	California
United States	Broward Health Medical Center	Fort Lauderdale	Florida
United States	Golisano Children's Hospital of Southwest Florida	Fort Myers	Florida
United States	University of Florida Health Science Center - Gainesville	Gainesville	Florida
United States	Helen DeVos Children's Hospital at Spectrum Health	Grand Rapids	Michigan
United States	BI-LO Charities Children's Cancer Center	Greenville	South Carolina
United States	Hackensack University Medical Center	Hackensack	New Jersey
United States	Kapiolani Medical Center for Women and Children	Honolulu	Hawaii
United States	Baylor College of Medicine/Dan L Duncan Comprehensive Cancer Center	Houston	Texas
United States	Riley Hospital for Children	Indianapolis	Indiana
United States	University of Iowa/Holden Comprehensive Cancer Center	Iowa City	Iowa
United States	University of Mississippi Medical Center	Jackson	Mississippi
United States	Nemours Children's Clinic-Jacksonville	Jacksonville	Florida
United States	Bronson Methodist Hospital	Kalamazoo	Michigan
United States	Children's Mercy Hospitals and Clinics	Kansas City	Missouri
United States	Dartmouth Hitchcock Medical Center/Dartmouth Cancer Center	Lebanon	New Hampshire
United States	Arkansas Children's Hospital	Little Rock	Arkansas
United States	Children's Hospital Los Angeles	Los Angeles	California
United States	Norton Children's Hospital	Louisville	Kentucky
United States	University of Wisconsin Carbone Cancer Center	Madison	Wisconsin
United States	Marshfield Medical Center-Marshfield	Marshfield	Wisconsin
United States	Saint Jude Children's Research Hospital	Memphis	Tennessee
United States	Jackson Memorial Hospital-Holtz Children's Hospital	Miami	Florida
United States	Nicklaus Children's Hospital	Miami	Florida
United States	University of Miami Miller School of Medicine-Sylvester Cancer Center	Miami	Florida
United States	Children's Hospital of Wisconsin	Milwaukee	Wisconsin
United States	University of Minnesota/Masonic Cancer Center	Minneapolis	Minnesota
United States	Morristown Medical Center	Morristown	New Jersey
United States	Yale University	New Haven	Connecticut
United States	Ochsner Medical Center Jefferson	New Orleans	Louisiana
United States	NYP/Columbia University Medical Center/Herbert Irving Comprehensive Cancer Center	New York	New York
United States	Children's Hospital of The King's Daughters	Norfolk	Virginia
United States	Kaiser Permanente-Oakland	Oakland	California
United States	University of Oklahoma Health Sciences Center	Oklahoma City	Oklahoma
United States	Children's Hospital and Medical Center of Omaha	Omaha	Nebraska
United States	University of Nebraska Medical Center	Omaha	Nebraska
United States	Children's Hospital of Orange County	Orange	California
United States	Nemours Children's Hospital	Orlando	Florida
United States	Saint Jude Midwest Affiliate	Peoria	Illinois
United States	Children's Hospital of Philadelphia	Philadelphia	Pennsylvania
United States	Saint Christopher's Hospital for Children	Philadelphia	Pennsylvania
United States	Children's Hospital of Pittsburgh of UPMC	Pittsburgh	Pennsylvania
United States	Oregon Health and Science University	Portland	Oregon
United States	Rhode Island Hospital	Providence	Rhode Island
United States	Mayo Clinic in Rochester	Rochester	Minnesota
United States	Cardinal Glennon Children's Medical Center	Saint Louis	Missouri
United States	Mercy Hospital Saint Louis	Saint Louis	Missouri
United States	Washington University School of Medicine	Saint Louis	Missouri
United States	Primary Children's Hospital	Salt Lake City	Utah
United States	University of Texas Health Science Center at San Antonio	San Antonio	Texas
United States	UCSF Medical Center-Mission Bay	San Francisco	California
United States	Seattle Children's Hospital	Seattle	Washington
United States	Providence Sacred Heart Medical Center and Children's Hospital	Spokane	Washington
United States	Mary Bridge Children's Hospital and Health Center	Tacoma	Washington
United States	Saint Joseph's Hospital/Children's Hospital-Tampa	Tampa	Florida
United States	Children's National Medical Center	Washington	District of Columbia
United States	MedStar Georgetown University Hospital	Washington	District of Columbia
United States	Alfred I duPont Hospital for Children	Wilmington	Delaware

Sponsors (2)

Lead Sponsor	Collaborator
Children's Oncology Group	National Cancer Institute (NCI)

Countries where clinical trial is conducted

United States,  Canada, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Objective response rate (ORR) of children with infantile fibrosarcoma (IFS) treated with neoadjuvant larotrectinib prior to local control	Response rates will be calculated as the percent of evaluable patients who are responders, and confidence intervals will be constructed accounting for the two-stage design.	Up to 5 years
Secondary	Event-free survival (EFS) of children with IFS treated with neoadjuvant larotrectinib prior to local control	Will be computed one year after the last enrollment in a stratum.	Up to 5 years
Secondary	Overall survival (OS) of children with IFS treated with neoadjuvant larotrectinib prior to local control	Will be computed one year after the last enrollment in a stratum.	Up to 5 years
Secondary	Duration of response (DoR) of children with IFS treated with neoadjuvant larotrectinib prior to local control	Will be computed one year after the last enrollment in a stratum. Will be defined among patients with a confirmed best response of either PR and CR.	From first observation of either partial response (PR) or complete response (CR) until either the first observation of progressive disease (PD) (event) or last known observation of the patient (censored observation), assessed up to 5 years
Secondary	ORR of children with newly diagnosed TRK fusion solid tumors other than IFS treated with neoadjuvant larotrectinib prior to local control	Response rates will be calculated as the percent of evaluable patients who are responders, and confidence intervals will be constructed accounting for the two-stage design.	Up to 5 years
Secondary	EFS of children with newly diagnosed TRK fusion solid tumors other than IFS treated with neoadjuvant larotrectinib prior to local control	Will be computed one year after the last enrollment in a stratum.	Up to 5 years
Secondary	OS of children with newly diagnosed TRK fusion solid tumors other than IFS treated with neoadjuvant larotrectinib prior to local control	Will be computed one year after the last enrollment in a stratum.	Up to 5 years
Secondary	DoR of children with newly diagnosed TRK fusion solid tumors other than IFS treated with neoadjuvant larotrectinib prior to local control	Will be computed one year after the last enrollment in a stratum. Will be defined among patients with a confirmed best response of either PR and CR.	From first observation of either partial response (PR) or complete response (CR) until either the first observation of progressive disease (PD) (event) or last known observation of the patient (censored observation), assessed up to 5 years
Secondary	Incidence of adverse events	Per National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0. Toxicity tables will be constructed to summarize the observed incidence by type of toxicity and grade. A patient will be counted only once for a given toxicity for the worst grade of that toxicity reported for that patient. Toxicity information recorded will include the type, severity, time of onset, time of resolution, and the attribution(s) to the study regimen.	Up to 5 years
Secondary	Percentage of patients with TRK fusion solid tumors with detectable circulating tumor deoxyribonucleic acid (DNA)	The percentage of ctDNA and frequency with which patients have detectable ctDNA prior to the start of therapy and at times during therapy when subsequent serial samples are obtained will be summarized with simple summary statistics, including means, medians, ranges, and standard deviations (if numbers and distribution permit). In cases of treatment resistance, we will also perform exploratory deep sequencing of ctDNA to determine whether this method can detect the emergence of resistance mutations.	Baseline up to 5 years