Phase I Trial Establishes Maximum Tolerated Dose for Pegylated Liposomal Doxorubicin Plus Ifosfamide in Advanced Soft Tissue Sarcoma
Key Insights
A phase I dose-escalation trial determined the maximum tolerated dose of pegylated liposomal doxorubicin (PLD) at 50 mg/m² when combined with ifosfamide for advanced soft tissue sarcoma treatment.
The combination demonstrated manageable toxicity with grade 3/4 hematological adverse events being most common, including leukopenia (86.96%) and neutropenia (82.61%).
Among 12 patients who continued treatment beyond dose-finding, the overall response rate reached 33.33% with a disease control rate of 83.33%.
A phase I dose-escalation trial has established the maximum tolerated dose (MTD) of pegylated liposomal doxorubicin (PLD) in combination with ifosfamide for treating advanced soft tissue sarcoma, potentially offering a safer alternative to conventional doxorubicin-based regimens. The single-center study, conducted at Huazhong University of Science and Technology, enrolled 23 patients and determined the MTD to be 50 mg/m² of PLD combined with ifosfamide at 3 g/m²/day for three days.
Study Design and Patient Population
The dose-escalation study followed a standard 3+3 design, with PLD initiated at 30 mg/m² and increased in 5 mg/m² increments up to a maximum of 70 mg/m². Patients aged 18 to 70 years with advanced soft tissue sarcoma confirmed by pathology experts were eligible, provided they had an ECOG performance status of 0 or 1 and normal bone marrow and cardiac function.
The patient cohort included 12 males (52.17%) and 11 females (47.83%) with a median age of 49 years. Most patients (95.65%) presented with stage IV disease, and fibrosarcoma was the most common histologic subtype (17.39%), followed by synovial sarcoma and leiomyosarcoma (13.04% each).
Dose-Limiting Toxicities and Safety Profile
Two patients experienced dose-limiting toxicities (DLTs) at the 55 mg/m² dose level, establishing 50 mg/m² as the MTD. One patient developed grade 4 neutropenia lasting six days, while the second experienced grade 4 neutropenia for eight days, grade 4 thrombocytopenia with recurrence post-platelet transfusion, and grade 3 alanine aminotransferase elevation.
Hematological toxicities dominated the adverse event profile, with grade 3/4 events including leukopenia (86.96%), neutropenia (82.61%), and lymphopenia (56.52%). Non-hematological toxicities were generally mild to moderate, with nausea affecting 78.26% of patients, anorexia 69.57%, and asthenia 69.57%.
"This regimen demonstrated a tolerable safety profile and promising efficacy, indicating potential benefits for patients with advanced soft tissue sarcoma," stated lead author Ting Ye, MD, of Union Hospital, Tongji Medical College, Huazhong University.
Cardiac Safety Advantages
Notably, no instances of cardiotoxicity were observed during the study period, including among the 12 patients who completed at least two treatment cycles. This represents a significant safety advantage over conventional doxorubicin, which carries well-established cardiac toxicity risks with cumulative lifetime dose limits of 450-550 mg/m².
The improved cardiac safety profile stems from PLD's liposomal encapsulation, which reduces cardiac uptake due to the enhanced permeability and retention effect. PLD primarily accumulates in the liver and spleen rather than heart tissue, distinguishing it from conventional doxorubicin.
Efficacy Results
Among the 12 patients who elected to continue treatment beyond the dose-finding phase, the overall response rate was 33.33% (95% CI, 9.92%-65.11%) and the disease control rate reached 83.33% (95% CI, 51.59%-97.91%). Four patients (33.33%) achieved partial response, six (50.00%) exhibited stable disease, and two (16.67%) experienced disease progression.
Six patients continued PLD plus ifosfamide treatment beyond four cycles, with four achieving partial response, suggesting enhanced efficacy with prolonged treatment. These results align closely with previous studies of doxorubicin plus ifosfamide combinations while potentially offering reduced toxicity.
Clinical Implications and Future Directions
The study's findings support the use of recombinant human granulocyte colony-stimulating factor (rhG-CSF) to enable higher PLD dosing. Previous phase I studies without rhG-CSF support established lower MTDs of 30-40 mg/m² for PLD plus ifosfamide combinations, highlighting the benefit of supportive care measures.
Compared to the landmark EORTC 62012 trial, which tested doxorubicin plus ifosfamide, the current study showed substantially lower rates of severe anemia (8.70% vs 35%) and thrombocytopenia (13.04% vs 33%), while febrile neutropenia occurred in only 4.35% of patients compared to 46% in the conventional regimen.
The researchers noted that their preliminary findings necessitate further research to validate efficacy and safety over multiple treatment cycles and explore the full therapeutic potential of the regimen. The study's focus on single-cycle tolerability leaves questions about cumulative toxicity and long-term treatment strategies that require additional investigation.
Treatment Considerations
Hand-foot syndrome and oral mucositis, characteristic side effects of PLD, were observed but remained mild (grade 1-2) in this study. These conditions result from doxorubicin and metal ion release in skin tissues, generating reactive oxygen species that cause keratinocyte dysfunction and inflammatory responses.
The combination of PLD at 50 mg/m² with ifosfamide represents a potentially valuable treatment option for advanced soft tissue sarcoma, offering comparable efficacy to conventional doxorubicin-based regimens with an improved safety profile, particularly regarding cardiac toxicity. The established MTD provides a foundation for future phase II studies to further evaluate this combination's therapeutic potential.