Progressive metastatic infantile fibrosarcoma with multiple acquired mutations.

Infantile fibrosarcoma is the most common soft-tissue sarcoma in children under the age of 1 yr and is defined molecularly by NTRK fusion proteins. This tumor is known to be locally invasive; however, although rare, metastases can occur. The NTRK fusion acts as a driver for tumor formation, which can be targeted by first- and second-generation TRK inhibitors. Although NTRK gatekeeper mutations have been well-described as mechanisms of resistance to these agents, alternative pathway mutations are rare. Here, we report the case of a patient with infantile fibrosarcoma treated with chemotherapy and TRK inhibition that developed metastatic, progressive disease with multiple acquired mutations, including TP53, SUFU, and an NTRK F617L gatekeeper mutation. Alterations in pathways of SUFU and TP53 have been widely described in the literature in other tumors; however, not yet in infantile fibrosarcoma. Although most patients have a sustained response to TRK inhibitors, a subset will go on to develop mechanisms of resistance that have implications for clinical management, such as in our patient. We hypothesize this constellation of mutations contributed to the patient's aggressive clinical course. Taken together, we report the first case of infantile fibrosarcoma with ETV6::NTRK3 and acquired SUFU, TP53, and NTRK F617L gatekeeper mutation along with detailed clinical course and management. Our report highlights the importance of genomic profiling in recurrent infantile fibrosarcoma to reveal actionable mutations, such as gatekeeper mutations, that can improve patient outcomes.

A pharmacologically-based approach to high dose methotrexate administration to investigate nephrotoxicity and acute kidney injury biomarkers in children and adolescents with newly diagnosed osteosarcoma.

PURPOSE: High dose methotrexate (HDMTX) acute kidney injury (AKI) results in prolonged hospitalization and treatment delays. Using a pharmacologically-based approach, HDMTX was administered with standard combination therapy to patients with osteosarcoma; nephrotoxicity was assessed. METHODS: Patients were randomized by cycle to 4 h or 12 h HDMTX (12 g/m2) infusions administered with hydration, alkalization and leucovorin rescue. Urinalysis, AKI biomarkers, and estimated glomerular filtration rate using serum creatinine or cystatin C (GFRCr or GFRcysC) were obtained. Serum and urine methotrexate concentrations [MTX] were measured. RESULTS: Patients (n = 12), median (range) age 12.4 (5.7-19.2) years were enrolled; 73 MTX infusions were analyzed. Median (95% Confidence Interval) serum and urine [MTX] were 1309 (1190, 1400) µM and 16.4 (14.7, 19.4) mM at the end of 4 h infusion and 557 (493, 586) µM and 11.1 (9.9, 21.1) mM at the end of 12 h infusion. Time to serum [MTX] < 0.1 µM was 83 (80.7, 90.7) h and 87 (82.8, 92.4) h for 4 and 12 h infusions. GFRCr was highly variable, increased after cisplatin, and exceeded 150 ml/min/1.73 m2. GFRcysC was less variable and decreased at the end of therapy. AKI biomarkers were elevated indicating acute tubular dysfunction, however, did not differ between 4 and 12 h infusions. Radiographic and histological response were similar for patients receiving 4 h or 12 h infusions; the median percent tumor necrosis was > 95%. CONCLUSIONS: Reducing peak serum and urine MTX concentration by prolonging the infusion duration did not alter risk of acute kidney injury. GFRcysC was decreased at the end of therapy. Proteinuria and elevations in AKI biomarkers indicate that direct tubular damage contributes to HDMTX nephrotoxicity. CLINICAL TRIAL: NCT01848457.

Pantoprazole, an Inhibitor of the Organic Cation Transporter 2, Does Not Ameliorate Cisplatin-Related Ototoxicity or Nephrotoxicity in Children and Adolescents with Newly Diagnosed Osteosarcoma Treated with Methotrexate, Doxorubicin, and Cisplatin.

LESSONS LEARNED: Using a randomized crossover design and continuous variables such as change in hearing threshold and biomarkers of acute renal injury as short-term endpoints, it was determined that pantoprazole, an organic cation transporter 2 inhibitor, did not ameliorate cisplatin-associated nephrotoxicity or ototoxicity.Cystatin C is a robust method to estimate glomerular filtration rate in patients with cancer. Using a patient-reported outcome survey, all patients identified tinnitus and subjective hearing loss occurring "at least rarely" after cycle 1, prior to objective high-frequency hearing loss measured by audiograms.New therapies that improve outcome with less acute and long-term toxicity are needed. BACKGROUND: Organic cation transporter 2 (OCT2), which is a cisplatin uptake transporter expressed on renal tubules and cochlear hair cells but not on osteosarcoma cells, mediates cisplatin uptake. Pantoprazole inhibits OCT2 and could ameliorate cisplatin ototoxicity and nephrotoxicity. Using a randomized crossover design, we evaluated audiograms, urinary acute kidney injury (AKI) biomarkers, and glomerular filtration rate (GFR) estimated from cystatin C (GFRcysC) in patients receiving cisplatin with and without pantoprazole. MATERIALS AND METHODS: Cisplatin (60 mg/m2 × 2 days per cycle) was administered concurrently with pantoprazole (intravenous [IV], 1.6 mg/kg over 4 hours) on cycles 1 and 2 or cycles 3 and 4 in 12 patients with osteosarcoma (OS) with a median (range) age of 12.8 (5.6-19) years. Audiograms, urinary AKI biomarkers, and serum cystatin C were monitored during each cycle. RESULTS: Pantoprazole had no impact on decrements in hearing threshold at 4-8 kHz, post-treatment elevation of urinary AKI biomarkers, or GFRcysC (Fig. 1, Table 1). Histological response (percent necrosis) after two cycles was similar with or without pantoprazole. All eight patients with localized OS at diagnosis are alive and in remission; three of four patients with metastases at diagnosis have died. CONCLUSION: Pantoprazole did not ameliorate cisplatin ototoxicity or nephrotoxicity. The decrease in GFRcysC and increase in N-acetyl-ß-glucosaminidase (NAG) and creatinine demonstrate that these biomarkers can quantify cisplatin glomerular and proximal tubular toxicity. OCT2 inhibition by pantoprazole did not appear to alter antitumor response or survival.