Survival and Local Recurrence Risk in Patients with High-Risk Neuroblastoma Treated with Proton Therapy over a 10 Year Interval

PURPOSE/OBJECTIVE(S)

Patients (pts) with high-risk neuroblastoma (HR-NBL) require radiation (RT) to the primary tumor site (PS); approach is standardized within North American paradigms but remains a subject of global study. Long-term experience using proton therapy (PRT) in this population is lacking. We hypothesized that PRT would be associated with low risk of local recurrence (LR) in a large population of pts with HR-NBL spanning > 10 years.

MATERIALS/METHODS

Sequential pts with HR-NBL at a single institution received RT to PS and persistent metastatic sites (MS). Dose to PS after subtotal resection (STR) was reduced from 36 Gy to 21.6 Gy in 2019 based on results from the Children's Oncology Group ANBL0532 trial (Liu K, 2019). Analysis using Kaplan Meier method and log rank test was performed with IRB approval.

RESULTS

From 9/2010 - 12/2021, 99 pts with HR-NBL received PS RT during first-line therapy; most [78, (79%)] had adrenal primary tumors and 26 (26%) received MS RT. Median age was 48m at RT (R 11m to 17.5y) and 52 (53%) were female. All pts had multi-agent induction chemotherapy (CT) [+ dinutuximab [12 (13%)] and/ or therapeutic 131MIBG [19 (19%)] and resection of primary tumor prior to RT; 34 (34%) patients had STR with residual disease (RD) on post-op imaging, 65 (66%) had gross total resection (GTR). Dose to PS was 21.6 Gy for 78 (79%) pts and 36 Gy for 21 (21%) based on RD and treatment era; PRT was pencil beam [78 (79%)] or double scattered [22 (22%)], combined with IMRT in 2 (2%). With median FU of 4.2 yrs (R 0.5y - 12y), 80 pts (81%) are alive [66 (67%) disease-free, 14 (14%) with disease], 19 (19%) have died. Progressive disease (PD) occurred in 33 (33%), with median time to PD 24m (R 8-116m); two pts (2%) had isolated LR, 25 (25%) distant PD, and 6 (6%) concurrent LR and distant PD. Risk of LR at 10 years was 8%; absolute risk of any LR was 8% (6/78) in 21.6 Gy cohort and 9% (2/21) in 36 Gy cohort (p = NS). After induction CT, 34 (34%) pts had STR with > 1cm3 RD on axial imaging; 18/ 34 (53%) also had MIBG uptake (MIBG+) at PS. Based on treatment era, 21 pts (62%) after STR received 21.6 Gy + boost to RD (36 Gy), and 13 (38%) 21.6 alone. Of those who received 36 Gy (median FU 5.7y), 2/21 (9.5%) had LR with concurrent distant PD; of those who received 21.6 Gy (median FU 3.2y) 4/13 (31%) had LR (2 with concurrent distant PD and 2 LR only) (p = 0.03). In the 21.6 Gy GTR cohort, 2/65 (3%) had LR + distant PD. Of 8 total patients who experienced LR, 5 had MIBG + RD, 1 MIBG- RD, and 2 GTR.

CONCLUSION

We observed excellent outcomes in 99 pts treated with proton radiotherapy for HR-NBL from 2010 through 2021, with 81% of patients alive and 92% free of LR. Our data suggest that LR is rare after GTR and 21.6 Gy, and uncommon among pts with STR treated with 36 Gy. A small number of pts received 21.6 Gy after STR, however, this experience suggests that a subset of pts with RD may require RT dose > 21.6 Gy. Further work is required to further characterize individual management of PS in pts with HR-NBL with regard to extent of RD and biologic disease features.

Characteristics and outcome of patients (pts) enrolled on phase I trials: A report from the Pediatric Oncology Branch, NCI

9550

Background: Knowledge of the characteristics and outcomes of pts enrolled on pediatric phase I trials may aid in the design of future phase I trials and selection of pts. Methods: Pre-enrollment characteristics and treatment outcomes (toxicity, response, survival) were retrospectively analyzed from pts with refractory solid tumors enrolled in 16 phase I trials with similar eligibility criteria from 1992 to 2005. The relationship between patient characteristics and dose-limiting toxicity (DLT) was evaluated using multivariate analysis. Results: Of 262 pts (62% M, 38% F) eligible for analysis, 147 were on trials of myelosuppressive drugs (MS) and 115 were enrolled on trials of non-MS. 50 pts (19%) participated in =2 separate trials. Median (range) or (frequency) entry characteristics were: age 13.5 yrs (1–24); ECOG performance score 0 (30%), 1 (50%), 2 (19%); prior regimens 2 (0–9); prior stem cell transplant (20%); prior radiation (66%); concomitant medications 1 (0–12); and presence of metastatic disease (65%). 94% of pts were evaluable for the primary trial outcome, and 92% participated in pharmacokinetic (PK) studies. 17% of pts had grade 3 as their highest-grade toxicity. 22% of pts had grade 4 as their highest-grade toxicity, of which 91% were hematological. DLT rate was 18%. 5% of pts came off study due to toxicity, and treatment related death occurred in 0.3%. Age, prior radiation, medications, prior regimens, performance status, gender, transplant history, and drug dose expressed as a fraction of the maximum tolerated dose were included in the multivariate analysis. Only drug dose (OR 14.2, 95% CI 3.0–67.8) and prior radiation (OR 3.4, 95% CI 1.1–10.7) were statistically significantly associated with increased risk of developing DLT after adjusting for all other variables. The median number of cycles was 1 (range 0–31). Complete and partial response rate was 3%, however, 18% of pts had stable disease (received = 3 cycles). The median survival (Kaplan Meier analysis) from time of enrollment was 5 months. Conclusion: Standard phase I eligibility criteria selected a population of pts who tolerated the investigational agents well and >90% were evaluable for the toxicity and PK endpoints. Prior radiation was associated with a greater risk for DLT.

No significant financial relationships to disclose.

Preclinical study of the systemic toxicity and pharmacokinetics of 5-iodo-2-deoxypyrimidinone-2'-deoxyribose as a radiosensitizing prodrug in two, non-rodent animal species: implications for phase I study design

We have demonstrated previously an improved therapeutic index for oral 5-iodo-2-deoxypyrimidinone-2'-deoxyribose (IPdR) compared with oral and continuous infusion of 5-iodo-2'-deoxyuridine (IUdR) as a radiosensitizing agent using three different human tumor xenografts in athymic mice. IPdR is a prodrug that is efficiently converted to IUdR by a hepatic aldehyde oxidase, resulting in high IPdR and IUdR plasma levels in mice for > or =1 h after p.o. IPdR. Athymic mice tolerated oral IPdR at up to 1500 mg/kg/day given four times per day for 6-14 days without significant systemic toxicities. In anticipation of an investigational new drug application for the first clinical Phase I and pharmacology study of oral IPdR in humans, we studied the drug pharmacokinetics and host toxicities in two non-rodent, animal species. For the IPdR systemic toxicity and toxicology study, twenty-four male or female ferrets were randomly assigned to four IPdR dosage groups receiving 0, 15, 150, and 1500 mg/kg/day by oral gavage x 14 days prior to sacrifice on study day 15. All ferrets survived the 14-day treatment. Ferrets receiving 1500 mg/kg/day showed observable systemic toxicities with diarrhea, emesis, weight loss, and decreased motor activity beginning at days 5-8 of the 14-day schedule. Overall, both male and female ferrets receiving IPdR at 1500 mg/kg/day experienced significant weight loss (9 and 19%, respectively) compared with controls after the 14-day treatment. No weight loss or other systemic toxicities were observed in other IPdR dosage groups. Grossly, no anatomical lesions were noted at complete necropsy, although liver weights were increased in both male and female ferrets in the two higher IPdR dosage groups. Histologically, IPdR-treated animals showed dose-dependent microscopic changes in liver consisting of minimal to moderate cytoplasmic vacuolation of hepatocytes, which either occurred in the periportal area (high dosage group) or diffusely throughout the liver (lower dosage groups). Female ferrets in the highest IPdR dose group also showed decreased kidney and uterus weights at autopsy without any associated histological changes. No histological changes were found in central nervous system tissues. No significant abnormalities in blood cell counts, liver function tests, kidney function tests, or urinalysis were noted. Hepatic aldehyde oxidase activity was decreased to approximately 50 and 30% of control ferrets in the two higher IPdR dosage groups, respectively, after the 14-day treatment period. The % IUdR-DNA incorporation in ferret bone marrow at the completion of IPdR treatment was < or =0.05% in the two lower dosage groups and approximately 2% in the 1500 mg/kg/day dosage group. The % IUdR-DNA in normal liver was < or =0.05% in all IPdR dosage groups. In a pharmacokinetic study in four Rhesus monkeys, we determined the plasma concentrations of IPdR after a single i.v. bolus of 50 mg/kg over 20 min. Using a two-compartment model to fit the plasma pharmacokinetic data, we found that IPdR was cleared in these non-human primates in a biexponential manner with an initial rapid distributive phase (mean T1/2alpha = 6.5 min), followed by an elimination phase with a mean T1/2 of 63 min. The mean maximum plasma concentration of IPdR was 124+/-43 microM with a mean total body clearance of 1.75+/-0.95 l/h/kg. IPdR was below detection (<0.5 microM) in the cerebrospinal fluid. We conclude that there are dose-limiting systemic toxicities to a 14-day schedule of p.o. IPdR at 1500 mg/kg/day in ferrets that were not found previously in athymic mice. However, no significant hematological, biochemical, or histopathological changes were found. Hepatic aldehyde oxidase activity was reduced in a dose-dependent in ferret liver, suggesting partial enzyme saturation by this IPdR schedule. The plasma pharmacokinetic profile in Rhesus monkeys showing biexponential clearance is similar to our published data in athymic mice. These data are being applied

Lamivudine in children with human immunodeficiency virus infection: a phase I/II study. The National Cancer Institute Pediatric Branch-Human Immunodeficiency Virus Working Group

The safety, tolerability, pharmacokinetic profile, and preliminary activity of lamivudine (2'-deoxy-3'-thiacytidine), a novel cytidine nucleoside analogue with antiretroviral activity, in human immunodeficiency virus (HIV)-infected children beyond the neonatal period were studied. Ninety children received dosages of 1-20 mg/kg/day. Pharmacokinetic evaluation demonstrated serum and cerebrospinal fluid concentrations that increased proportionally to dose. As of January 1994, 11 children had been withdrawn from study for disease progression and 10 because of possible lamivudine-related toxicity, and 6 had died. CD4 and CD8 cell counts remained stable over 24 weeks in therapy-naive children and decrease slightly in previously treated children. Quantitative immune complex-dissociated p24 antigen and HIV RNA were decreased significantly at 12 and 24 weeks. In vitro resistance to lamivudine was documented in sequential virus isolates from some patients by 12 weeks. Lamivudine was well-tolerated and exhibited virologic activity in children, although future use in children is likely to be in combination antiretroviral regimens.

Phase I/II study of 72-hour infusional paclitaxel and doxorubicin with granulocyte colony-stimulating factor in patients with metastatic breast cancer

PURPOSE

We conducted a phase I/II trial of concurrently administered 72-hour infusional paclitaxel and doxorubicin in combination with granulocyte colony-stimulating factor (G-CSF) in patients with previously untreated metastatic breast cancer and bidimensionally measurable disease.

PATIENTS AND METHODS

We defined the maximum-tolerated dose (MTD) of concurrent paclitaxel and doxorubicin administration and then studied potential pharmacokinetic interactions between the two drugs. Forty-two patients who had not received prior chemotherapy for metastatic breast cancer received 296 total cycles of paclitaxel and doxorubicin with G-CSF.

RESULTS

The MTD was determined to be paclitaxel 180 mg/m2 and doxorubicin 60 mg/m2 each by 72-hour infusion with G-CSF. Diarrhea was the dose-limiting toxicity (DLT) of this combination, with three of three patients developing abdominal computed tomographic (CT) scan evidence of typhlitis (cecal thickening) at the dose level above the MTD. All patients developed grade 4 neutropenia (absolute neutrophil count [ANC] < 500 microL), generally less than 5 days in duration. This combination was generally safely administered at dose levels at or below the MTD. The overall response rate was 72% (28 of 39 patients; 95% confidence interval [CI], 55% to 85%), with 8% complete responses (CRs) (three of 39; 95% CI, 2% to 21%) and a median response duration of 9 months. The median overall survival time for all patients is 23 months, with a median follow-up duration of 28 months. Pharmacokinetic studies showed that administration of paclitaxel and doxorubicin together by 72-hour infusion did not affect the steady-state concentrations of either drug.

CONCLUSION

Concurrent 72-hour infusional paclitaxel and doxorubicin can be administered safely, but is associated with significant toxicity. The overall response rate of this combination in untreated metastatic breast cancer patients is similar to that achieved with other doxorubicin-based combination regimens. The modest complete response rate achieved suggests that this schedule of paclitaxel and doxorubicin administration does not produce significant additive or synergistic cytotoxicity against breast cancer.

Phase I and pharmacokinetic study of recombinant human granulocyte-macrophage colony-stimulating factor given in combination with fluorouracil plus calcium leucovorin in metastatic gastrointestinal adenocarcinoma

PURPOSE

To determine the toxicities and potential for dose escalation of intravenous (IV) bolus fluorouracil (5-FU) given with 500 mg/m2/d leucovorin (LCV) and granulocyte-macrophage colony-stimulating factor (GM-CSF).

PATIENTS AND METHODS

Thirty-seven patients received escalating doses of 5-FU/LCV on days 1 to 5 with subcutaneous GM-CSF either 5 or 10 micrograms/kg/d starting on day 6 or 3 micrograms/kg/d starting on day 1. 5-FU was escalated from 370 mg/m2/d by 15% increments between patient cohorts and within patients according to tolerance.

RESULTS

With GM-CSF starting on day 6, dose-limiting toxicity occurred during cycle no. 1 in all three patients entered at 5-FU 490 mg/m2/d. However, individual patients tolerated 5-FU doses up to 644 mg/m2/d. When all cycles were analyzed, grade 3 to 4 mucositis and grade 4 granulocytopenia complicated < or = 15% and < or = 6% of cycles with 5-FU doses < or = 560 mg/m2/d (115 cycles). With GM-CSF starting on day 1, dose-limiting granulocytopenia occurred during cycle no. 1 in five of 10 patients entered at 5-FU 490 mg/m2/d. Although the granulocyte nadirs were significantly lower at each 5-FU dose level with the concurrent GM-CSF schedule (eg, 490 mg/m2/d: median, 879/microL v3,286/microL; two-tailed P [P2] < .001), dose-limiting granulocytopenia complicated < or = 16% of cycles with 5-FU < or = 560 mg/m2/d (99 cycles); > or = grade 3 mucositis occurred in < or = 20% of cycles. Grade 3 to 4 diarrhea was unusual with either GM-CSF schedule. Most patients treated with GM-CSF > or = 5 micrograms/kg/d required dose reductions for constitutional toxicity; 3.0 to 3.8 micrograms/kg/d was better tolerated. Venous thrombosis occurred in 17% of patients (concurrent v sequential GM-CSF, 29% v 5%; P2 = .08). The median delivered 5-FU dose-intensity for GM-CSF starting either on day 6 or on day 1 was 615 and 647 mg/m2/wk (P2 = .41), respectively. Pharmacologic exposure to 5-FU increased with higher doses of 5-FU, and concurrent GM-CSF administration did not affect 5-FU clearance.

CONCLUSION

A starting dose of 425 mg/m2/d of 5-FU with LCV on days 1 to 5 could be safely combined with GM-CSF starting either on day 1 or day 6, with further 5-FU dose escalation according to individual tolerance.

A phase I study of continuous infusion 5-fluorouracil plus calcium leucovorin in combination with N-(phosphonacetyl)-L-aspartate in metastatic gastrointestinal adenocarcinoma

Preclinical studies suggest that the biochemical effects of N-(phosphonacetyl)-L-aspartate (PALA), an inhibitor of aspartate carbamoyltransferase (ACTase), may increase the metabolic activation of 5-fluorouracil (5-FU) and enhance its cytotoxicity through both RNA- and DNA-directed mechanisms. In this Phase I trial, 22 evaluable patients with adenocarcinoma of the gastrointestinal tract were entered at escalating doses of 5-FU starting at 1150 mg/m2/day given as a concurrent 72-h i.v. infusion with a fixed dose of leucovorin (LCV), 500 mg/m2/day. The dose of 5-FU was escalated within patients according to individual tolerance, and then PALA at 250 mg/m2 was added 24 h prior to the initiation of the 5-FU/LCV infusion of the subsequent cycle. Dose-limiting mucositis and myelosuppression occurred during the initial cycle in 3 of 5 patients treated with 2300 mg/m2/day 5-FU; therefore, the recommended dose of 5-FU with concurrent LCV is 2000 mg/m2/day. Twenty-seven additional patients were then treated with escalating doses of PALA ranging from 375 to 2848 mg/m2, i.v., followed 24 h later by 2000 mg/m2/day 5-FU with high-dose LCV. Dose-limiting mucositis and myelosuppression occurred during the initial cycle in 2 of 3 patients entered at 2848 mg/m2 PALA. Dose-limiting mucositis and skin rash ultimately required both PALA and 5-FU dose reductions in 4 of 6 patients treated with 1899 mg/m2 PALA. Toxicity was similar, however, in patients receiving PALA at doses ranging from 375 to 1266 mg/m2. The mean steady-state plasma concentration of 5-FU at 2000 mg/m2/day was 6.5 +/- 0.9 microM; patients with 5-FU levels > 9 microM had a significantly higher incidence of serious gastrointestinal and hematological toxicity. Compared to each patient's own baseline, a significant trend for decreasing ACTase activity with increasing PALA dose was evident using cytosol isolated from peripheral blood mononuclear cells 24 h after PALA treatment (P2 = 0.01). PALA < or = 844 mg/m2 failed to appreciably inhibit ACTase activity at 24 h in most patients; furthermore, a decrease in ACTase activity by > 50% from baseline was seen in only 29% of cycles. More consistent inhibition of ACTase activity was seen with PALA > or = 1266 mg/m2. Even with the highest PALA doses, however, ACTase activity returned to baseline by 96 h in most patients.(ABSTRACT TRUNCATED AT 400 WORDS)

A phase II study of continuous infusion 5-fluorouracil and leucovorin with weekly cisplatin in metastatic colorectal carcinoma

BACKGROUND

Prolonged infusional 5-fluorouracil (5-FU) and bolus 5-FU modulated by leucovorin are associated with higher response rates than bolus 5-FU alone. Cisplatin enhances 5-FU cytotoxicity in some preclinical models.

METHODS

The authors tested the feasibility of combining concurrent infusional leucovorin (500 mg/m2/d) with protracted infusional 5-FU (200 mg/m2/d) and weekly bolus cisplatin (20 mg/m2) in 22 patients with metastatic colorectal cancer.

RESULTS

Four partial responses (PR) were noticed among 21 evaluable patients (19%). The median time to treatment failure and median survival were 6 months and 11 months, respectively. All but two patients required 5-FU dose reduction after a median of 2 weeks because of mucositis. However, severe mucositis and diarrhea occurred in only 18% and 5% of the patients, respectively. Palmar-plantar erythrodysesthesia of mild to moderate severity occurred in 55% of patients. Megaloblastic changes were evident in the peripheral blood during therapy, and may reflect prolonged DNA-directed toxicity of 5-FU. The median tolerated dose level of 5-FU was 113 mg/m2/d (range, 64-150 mg/m2/d). Mean steady-state plasma concentrations (Cpss) of 5-FU appeared to increase linearly from 0.19 microM to 0.39 microM over the dose range 64 to 200 mg/m2/d. Patients with grade 2 gastrointestinal toxicity had significantly higher 5-FU Cpss than patients with grade 0 or 1 toxicity.

CONCLUSIONS

The early onset of toxicity with this regimen of protracted infusional 5-FU/high-dose leucovorin and weekly cisplatin required marked attenuation of the 5-FU dose intensity, and the results were no better than that expected with infusional 5-FU alone.

A phase II trial of continuous-infusion 6-mercaptopurine for childhood leukemia

A phase II pediatric trial of a continuous intravenous infusion of 6-mercaptopurine (6MP) in patients with refractory leukemia was performed. The dosing schedule, 50 mg m-2 h-1 for 48 h, was based on the results of a previous phase I trial of this approach. Among the 40 children treated for acute lymphoblastic leukemia (ALL), all of whom had received prior therapy with oral 6MP, 1 complete and 1 partial response were achieved. No response was observed in 17 patients with refractory acute nonlymphocytic leukemia (ANLL). Reversible hepatotoxicity, the primary dose-limiting toxicity, was observed in approximately 50% of cases. Mucositis was encountered infrequently and was usually not severe. 6MP given on the present continuous intravenous infusion schedule overcomes the limited and variable bioavailability of oral 6MP but shows limited activity as induction agent in children with recurrent ALL.

Effect of continuous-infusion zidovudine therapy on neuropsychologic functioning in children with symptomatic human immunodeficiency virus infection

Neuropsychologic function was assessed in 13 children with symptomatic human immunodeficiency virus disease (Centers for Disease Control Class P2), ranging in age from 14 months to 12 years. Before the initiation of treatment, eight patients were classified as having encephalopathy. Psychologic tests were administered both before and after 6 and 12 months of continuous-infusion azidothymidine (AZT; zidovudine) treatment. After 6 months of treatment a significant increase of 15.5 (+/- 3.3) IQ points was demonstrated in general cognitive functioning (p less than 0.001). Follow-up for 10 of these patients indicated that after 12 months of AZT therapy, they had maintained their gains in IQ points. Improvements in adaptive behavior after 6 months of therapy, assessed with a standardized interview, paralleled the findings on the IQ data. No significant differences in the amount of change was observed for the different subgroups. The magnitude of these improvements could not be explained by practice effects, environmental changes, or general improvement in physical state. We conclude that neuropsychologic function was significantly improved with continuous infusion AZT treatment.

Dideoxycytidine alone and in an alternating schedule with zidovudine in children with symptomatic human immunodeficiency virus infection

OBJECTIVE

To determine whether a short course of 2',3'-dideoxycytidine (ddC) could provide safe antiretroviral activity in children with symptomatic human immunodeficiency virus infection and whether it could be used with azidothymidine (AZT, zidovudine). The goal was to maintain uninterrupted antiretroviral therapy while sparing AZT-related myelosuppression and ddC-related neuropathy.

METHODS

In a pilot study, we evaluated four dosage levels of ddC--0.015, 0.02, 0.03, and 0.04 mg/kg, given orally every 6 hours--in 15 children between 6 months and 13 years of age with Centers for Disease Control P2 (i.e., symptomatic) human immunodeficiency virus infection. Thirteen patients had not had any prior antiretroviral therapy; two patients had received and benefited from AZT, but dose-limiting neutropenia had developed. At each dosage level, ddC was given for 8 consecutive weeks and then stopped. After a 30-day rest, a schedule of ddC for 1 week was followed by 3 weeks of AZT therapy (180 mg/m2 every 6 hours); this alternating schedule was repeated for as long as tolerated. Age-appropriate psychometric testing was performed before the start of ddC therapy and after 8 weeks.

RESULTS

During the 8 weeks of therapy with ddC alone, no neutropenia or anemia was observed; 6 of 9 patients had decreases in p24 antigen levels, and 8 of 15 had an increased CD4 cell count. At the 0.04 mg/kg level, a rash developed in three patients; mild mouth sores developed in 9 of 15 patients. On the alternating ddC/AZT schedule, no neuropathy was observed.

CONCLUSIONS

2',3'-Dideoxycytidine has antiretroviral activity in some children and appears to be safe for short intervals. Longer courses of ddC at lower dosage levels, and schedules integrating ddC into combination regimens, deserve to be explored.

A phase II trial of continuous-infusion 6-mercaptopurine for childhood solid tumors

A phase II pediatric trial of a continuous intravenous infusion of 6-mercaptopurine (6-MP) in patients with refractory solid tumors or lymphoma was performed. The dosing schedule of 50 mg/m2 per hour for 48 h was chosen to produce optimal cytotoxic concentrations of 6-MP. There were no complete or partial responses in the 40 patients entered in the trial. Accrual was sufficient for the conclusion to be drawn that there was greater than 95% probability that the true response rate was no greater than 22% and 26% in osteosarcoma and Ewing's sarcoma, respectively. Dose-limiting toxicity was observed in one-third of the patients and included reversible hepatotoxicity, myelosuppression, and mucositis. The excellent penetration of drug into the cerebrospinal fluid (CSF) suggests that future trials of this intravenous dosing schedule should be conducted on tumors of the CNS.

A phase I and pharmacokinetic study of trimetrexate using a 24-hour continuous-injection schedule

Trimetrexate (TMTX) is an analog of methotrexate and a potent inhibitor of the enzyme dihydrofolate reductase. In this phase I study, TMTX was given intravenously to 32 patients as a constant infusion over 24 hours every 28 days. The maximum-tolerated dose of TMTX was 200 mg/m2, with myelosuppression as the dose-limiting toxicity. Other toxicities included nausea and vomiting, stomatitis, erythema and phlebitis at the site of infusion, rash and skin hyperpigmentation, and elevated serum hepatic enzymes. Two drug-related deaths occurred secondary to leukopenia and sepsis. Twenty-six patients were evaluable for antitumor response. Twenty-one patients had progressive disease, while three patients had disease stabilization. There were two partial responses observed--one in a patient with breast cancer and a second in a patient with nasopharyngeal carcinoma. TMTX pharmacokinetics were studied in 15 patients. The drug had a mean terminal half-life of 13 hours. Steady-state was not achieved during the 24-hour infusions. Only 6% of the parent compound was excreted unchanged in the urine, and CSF levels averaged less than 2% of simultaneously measured plasma levels. A dose of 150 mg/m2 is recommended for phase II trials of TMTX using this 24-hour infusion schedule.

Phase I and pharmacokinetic evaluation of thiotepa in the cerebrospinal fluid and plasma of pediatric patients: evidence for dose-dependent plasma clearance of thiotepa

A Phase I trial of thiotepa (TT) administered as an i.v. bolus was performed in 19 children with refractory malignancies. The starting dose was 25 mg/m2 with escalations to 50, 65, and 75 mg/m2. Seven additional patients were treated with 8-h infusions at 50 or 65 mg/m2. The maximum tolerated bolus dose was 65 mg/m2. Reversible myelosuppression was the dose-limiting toxicity. The plasma and cerebrospinal fluid (CSF) pharmacokinetic parameters of TT and its major active metabolite tepa (TP) were also evaluated. When the bolus or infusion methods of TT administration were compared, there was little difference observed in any pharmacokinetic parameter for either TT or TP. The plasma disappearance of TT was rapid and biphasic with half-lives of 0.14 to 0.32 and 1.34 to 2.0 h. Dose-dependent pharmacokinetics was demonstrated by steadily declining plasma clearance with increasing TT dose. Clearance values declined from 28.6 liters/m2/h at the 25-mg/m2 dose to 11.9 liters/m2/h at the 75-mg/m2 dose. The half-life of TP was longer than that of TT and ranged between 4.3 and 5.6 h. There was evidence of the saturation of TP production. TT and TP both exhibited excellent penetration into the CSF, producing lumbar and ventricular concentrations which were nearly identical to simultaneous plasma concentrations. In one patient with a Rickham reservoir, the CSF:plasma area under the (concentration x time) curve ratios for TT and TP were 1.01 and 0.95, respectively. The above data indicate that TT can be safely administered to pediatric patients at doses higher than conventionally used. The favorable CSF penetration of TT and TP suggests that Phase II studies of TT be considered in patients with central nervous system tumors.

A pediatric phase I and pharmacokinetic study of spirohydantoin mustard

A pediatric Phase I and pharmacokinetic study of the lipophilic alkylating agent spirohydantoin mustard (SHM) was conducted in 23 patients. The dose-limiting toxicity of SHM was neurological with disorientation, delirium, or hallucinations occurring in 9 of 23 patients. These symptoms were partially reversible and preventable with physostigmine. In 17 patients who were evaluable for response to treatment (14 of whom had central nervous system malignancies), no objective tumor responses were observed. Pharmacokinetic evaluation of SHM revealed a t1/2 alpha of 1.7 +/- 0.7 min, t1/2 beta of 16 +/- 8.3 min, and total body clearance of 2134 +/- 735 ml/min/m2. Measureable peak plasma levels were less than 40% of that which produces cytotoxicity in vitro against monolayer cultures of rat 9L brain tumor. Over 90% of SHM was protein bound, greatly limiting the free drug available for central nervous system penetration. SHM cerebrospinal fluid to plasma ratios were less than 0.047. The above suggests that in spite of its lipophilicity, SHM may not reach clinically significant levels in the central nervous system at clinically tolerable doses.

Trimetrexate for the treatment of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome

Preclinical studies have demonstrated that trimetrexate is a potent inhibitor of dihydrofolate reductase from Pneumocystis carinii. On the basis of this evidence, this lipid-soluble antifolate was used as an antipneumocystis agent in 49 patients with the acquired immunodeficiency syndrome (AIDS) and pneumocystis pneumonia. Simultaneous treatment with the reduced folate leucovorin was used as a specific antidote to protect host tissues from the toxic effects of the antifolate without affecting the antipneumocystis action of trimetrexate. Patients were assigned to three groups and treated for 21 days: in Group I, trimetrexate with leucovorin was used as salvage therapy in patients in whom standard treatments (both pentamidine isethionate and trimethoprim-sulfamethoxazole) could not be tolerated or had failed (16 patients); in Group II, trimetrexate with leucovorin was used as initial therapy in patients with a history of sulfonamide inefficacy or intolerance (16 patients); and in Group III, trimetrexate with leucovorin plus sulfadiazine was used as initial therapy (17 patients). The response and survival rates were, respectively, 69 percent and 69 percent in Group I; 63 percent and 88 percent in Group II; and 71 percent and 77 percent in Group III. Trimetrexate therapy had minimal toxicity; transient neutropenia or thrombocytopenia occurred in 12 patients and mild elevation of serum aminotransferases in 4. We conclude that the combination of trimetrexate and leucovorin is safe and effective for the initial treatment of pneumocystis pneumonia in patients with AIDS and for the treatment of patients with intolerance or lack of response to standard therapies.

Phase I and clinical pharmacological study of mercaptopurine administered as a prolonged intravenous infusion

The bioavailability of oral mercaptopurine (MP) is poor, and plasma levels following p.o. dosing are highly variable. In an attempt to circumvent these problems, we conducted a Phase I trial and clinical pharmacological study of MP administered as a prolonged i.v. infusion. An infusion rate of 50 mg/sq m/h, which was designed to achieve therapeutic drug levels in plasma, was used in all patients. The infusion duration was escalated in 12-h increments. Thirty-eight patients were evaluated. The dose-limiting toxicity was mucositis. Other reversible toxicities were myelosuppression and hepatotoxicity. An infusion duration of 48 h was found to be safe, unassociated with dose-limiting toxicity. Objective responses were seen in five patients. The mean plasma steady-state MP concentration achieved was 6.9 microM with little interpatient variability seen. Allopurinol coadministration had no effect on the plasma pharmacokinetics of i.v. MP. However, allopurinol did alter the urinary metabolite pattern, decreasing thiouric acid and increasing MP and thioxanthine levels. The steady-state cerebrospinal fluid:plasma ratio for MP was 0.27, suggesting that this approach may be of value in the treatment of central nervous system cancer. MP can be safely administered as a 48-h i.v. infusion at a dose rate which reliably achieves MP levels associated with optimal antileukemic activity in vitro.

Altered central nervous system pharmacology of methotrexate in childhood leukemia: another sign of meningeal relapse

CSF and plasma antifolate concentrations during 257 intravenous (IV) infusions of high-dose methotrexate were measured in 60 children with acute lymphoblastic leukemia. In 49 children who have never had evidence for CNS leukemia, the mean steady-state CSF to plasma methotrexate ratio was 0.013 (SD = 0.01). In contrast, 11 children with overt meningeal leukemia had a 12-fold higher mean ratio of 0.157 (range, 0.013 to 0.844, p less than .01). In the group of patients studied, all of those with a CSF methotrexate concentration greater than 2 SD above the mean either had leukemic cells in the CSF or subsequently developed this condition. In two patients, overt CNS leukemia was preceded by a high CSF:plasma drug ratio at a time when there was no cytologic or clinical evidence for CNS leukemia. As previously observed with intrathecal methotrexate, we conclude that overt meningeal leukemia increases CSF drug concentrations during IV methotrexate therapy. An elevated CSF to plasma ratio may be useful to predict imminent CNS relapse or to verify completeness of response to therapy.