Chemotherapy of malignant gliomas: comparison of the effect of polychemo- and CCNU-therapy

Insights into the glioblastoma tumor microenvironment: current and emerging therapeutic approaches

Glioblastoma (GB) is an intrusive and recurrent primary brain tumor with low survivability. The heterogeneity of the tumor microenvironment plays a crucial role in the stemness and proliferation of GB. The tumor microenvironment induces tumor heterogeneity of cancer cells by facilitating clonal evolution and promoting multidrug resistance, leading to cancer cell progression and metastasis. It also plays an important role in angiogenesis to nourish the hypoxic tumor environment. There is a strong interaction of neoplastic cells with their surrounding microenvironment that comprise several immune and non-immune cellular components. The tumor microenvironment is a complex network of immune components like microglia, macrophages, T cells, B cells, natural killer (NK) cells, dendritic cells and myeloid-derived suppressor cells, and non-immune components such as extracellular matrix, endothelial cells, astrocytes and neurons. The prognosis of GB is thus challenging, making it a difficult target for therapeutic interventions. The current therapeutic approaches target these regulators of tumor micro-environment through both generalized and personalized approaches. The review provides a summary of important milestones in GB research, factors regulating tumor microenvironment and promoting angiogenesis and potential therapeutic agents widely used for the treatment of GB patients.

Combined modality therapy of operated astrocytomas grade III and IV. Confirmation of the value of postoperative irradiation and lack of potentiation of bleomycin on survival time: a prospective multicenter trial of the Scandinavian Glioblastoma Study Group

In a controlled, prospective, randomized investigation, started in 1974, 118 patients with supratentorial astrocytoma Grade III--IV were divided into three groups. Groups 1 and 2 received 45 Gy postoperatively to the whole supratentorial brain. Bleomycin in 15-mg doses and a total dose of 180 mg or placebo was given intravenously three times a week, one hour prior to radiotherapy, during weeks 1, 2, 4 and 5. Group 3 received conventional care but no radiotherapy or chemotherapy. Median survival rates of patients were 10.8 months in Groups 1 and 2, and 5.2 months in Groups 3, a statistically significant difference. With regard to performance, the patients in Group 3 deteriorated faster than patients in Groups 1 and 2. Bleomycin had no positive or negative influence on survival.

Glioblastoma multiforme

Glioblastoma multiforme is the most common primary brain tumor of adults, as well as the most malignant. Its etiology is unknown, but the tumor is thought to arise through dedifferentiation of adult astrocytes. It occurs most frequently between the ages of 40 and 60, in men more often than in women (1.5:1). Important early symptoms include subtle personality change, headache, weakness, and intellectual impairment; specific complaints and physical findings depend on the location of the lesion. The initial diagnostic test should be a CT-scan; it will detect more than 90% of malignant astrocytomas. Surgery remains the cornerstone of treatment; patients receiving radical debulking have a median survival of 8 months compared to the 3 month survival of unoperated cases. Modern neurosurgical technique, neuroanesthesia, mannitol, and corticosteroids have reduced the surgical mortality to 3%. Most patients also receive 4500 rads of whole-brain irradiation and 1800 rads to the operative site; radiotherapy increases the median survival of operated patients by 2 to 3 months. An additional small increment in survival time and some improvement in quality of survival can be achieved by nitrosourea chemotherapy; the latter is usually given as 100 mg/m2/day x 3 days of BCNU every eight to ten weeks. Experimental treatments under study include the use of radiosensitizers, the role of immunotherapy and the application of microwave-induced hyperthermia. Two-year survival remains 10% to 20%, and there are virtually no five-year survivors. An optimal combined modality treatment plan, one in which each cellular compartment of this truly multiforme tumor is effectively addressed, remains to be designated.

Combination chemotherapy (COMP protocol) and radiotherapy of anaplastic supratentorial gliomas

Postoperative survival time and recurrence-free intervals in 116 consecutive patients with supratentorial grade III and IV gliomas (glioblastomas, gliosarcomas, anaplastic astrocytomas, and ependymomas) were compared in unselected groups receiving different forms of treatment. Postoperative high-voltage radiotherapy (31 patients, dosage 4,000--6,000 rads) and combined chemotherapy consisting of CCNU, vincristine, amethopterine, and procarbazine in 15-day circles (COMP protocol) (12 patients) showed the same median survival time of 10.6 months and comparable recurrence-free intervals of 6.8 and 7.0 months, respectively. These results were significantly different from a control group (39 patients) receiving best postoperative supportive (conventional) care (median survival 5.4 months, free interval 3.7 months). Combination of postoperative radiotherapy with simultaneous polychemotherapy (COMP protocol), evaluated in 18 patients, did not significantly change the recurrence-free interval (median 7.0 months), but increased the median survival time to 12.9 months, which was significantly superior to the two other treatment groups. The toxic side effects of COMP therapy were moderate and essentially haematological. In general, simultaneous radiation and chemical treatment was well tolerated after major tumour resection. These preliminary results of postoperative combination of radiation and polychemotherapy for anaplastic supratentorial gliomas appear encouraging, but further trials for optimization of combined therapeutic strategies are warranted.