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MRI

with contrast of a glioblastoma WHO grade IV in a 15-year-old boy

MRI

with contrast of a glioblastoma WHO grade IV in a 15-year-old boy

Glioblastoma multiforme (GBM) is the most common and aggressive type of primary

, accounting for 52% of all primary brain tumor cases and 20% of all intracranial tumors. Despite being the most prevalent form of primary brain tumor, GBMs occur in only 2–3 cases per 100,000 people in Europe and North America.

Treatment can involve

of the tumor, combined with the best available treatment, the survival rate for GBM remains very low. However, many advances in microsurgery techniques, radiotherapy and chemotherapy are slowly increasing the survival time of patients diagnosed with glioblastoma.

Glioblastoma multiform can be divided into three subgroups dependent on Karnofsky Performance Score (KPS), the age of the patient, and treatment:^[1]

RPA class	Definition	Historical Median Survival Time	Historical 1-Year Survival	Historical 3-Year Survival	Historical 5-Year Survival
III	Age <50, KPS >= 90	17.1 months	70%	20%	14%
IV	Age < 50, KPS < 90	11.2 months	46%	7%	4%
	Age > 50, KPS >= 70, surgical removal with good neurologic function
V + VI	Age >= 50, KPS >= 70, surgical removal with poor neurologic function	7.5 months	28%	1%	0%
	Age >= 50, KPS >= 70, no surgical removal
	Age >= 50, KPS < 70

Causes

GBM is more common in males, although the reason for this is not clear

.

Pathogenesis

Glioblastomas multiforme are characterized by the presence of small areas of

astrocytomas

, post-mortem autopsies have revealed that most glioblastomas multiforme are not caused by previous lesions in the brain.

Unlike

.

The tumor may take on a variety of appearances, depending on the amount of hemorrhage,

lateral ventricle

is usually deformed, and both lateral and third ventricles may be displaced.

Symptoms

Although common symptoms of the disease include seizure, nausea and vomiting, headache, and hemiparesis, the single most prevalent symptom is a progressive memory, personality, or neurological deficit due to temporal and frontal lobe involvement. The kind of symptoms produced depends highly on the location of the tumor, more so than on its pathological properties. The tumor can start producing symptoms quickly, but occasionally is asymptomatic until it reaches an enormous size. See Symptoms section in:

Diagnosis

In early stages, when viewed with

, which can, at the same time, remove as much tumor as possible. Although the entire tumor can never be removed, in theory due to its multicentricity and diffuse character, partial resection ("debulking") can still prolong survival slightly.

Treatment

It is very difficult to treat glioblastoma due to several complicating factors:[10]

• The tumor cells are very resistant to chemotherapy and other conventional therapies
• The brain is susceptible to damage due to therapy
• The brain has a very limited capacity to repair itself
• Many drugs cannot cross the
  blood brain barrier
  to act on the tumor

Treatment of primary brain tumors and brain metastases consists of both symptomatic and palliative therapies.

Symptomatic therapy

Supportive treatment focuses on relieving symptoms and improving the patient’s neurologic function. The primary supportive agents are anticonvulsants and corticosteroids.

• Historically, around ninety percent of patients with glioblastoma underwent anticonvulsant treatment, although is has been estimated that only approximately 40% of patients required this treatment. Recently, it has not been recommended that neurosurgeons administer anticonvulsants prophylactically, and should wait until a seizure occurs before prescribing this medication^[11]. Those receiving phenytoin concurrent with radiation may have serious skin reactions such as erythema multiforme and Stevens–Johnson syndrome.

• Corticosteroids, usually dexamethasone given 4 to 10 mg every 4 to 6 h, can reduce peritumoral edema (through rearrangement of the blood-brain barrier), diminishing mass effect and lowering intracranial pressure, with a decrease in headache or drowsiness.

Palliative therapy

Palliative treatment usually is conducted to improve quality of life and to achieve a longer survival time. It includes surgery, radiation therapy, and chemotherapy. A maximally feasible resection with maximal tumor-free margins ("debulking") is usually performed along with external beam radiation and chemotherapy.

Surgery

Surgery is the first stage of treatment of glioblastoma. An average GBM tumor contains 10¹¹ cells, which is on average reduced to 10⁹ cells after surgery. It is used to take a section for diagnosis, to remove some of the symptoms of a large mass pressing against the brain, to remove disease before secondary resistance to radiotherapy and chemotherapy, and to prolong survival.

The greater the extent of tumor removal, the longer the survival time. Removal of 98% or more of the tumor has been associated with a significantly longer median survival time than if less than 98% of the tumor is removed^[12]. The chances of near-complete initial removal of the tumor can be greatly increased if the surgery is guided by a fluorescent dye known as 5-aminolevulinic acid^[13].

Radiotherapy

On average,

.

Chemotherapy

The standard of care for glioblastoma includes chemotherapy during and after radiotherapy. On average, chemotherapy after surgery and radiotherapy can initially reduce the tumor size to 10⁶ cells. The use of temozolomide both during radiotherapy and for six months post radiotherapy results in a significant increase in median survival with minimal additional toxicity^[16]. This treatment regime is now standard for most cases of glioblastoma where the patient is not enrolled in a clinical trial^[17][18].

Clinical trials

There are hundreds of

underway to assess the ability of new drugs and strategies to treat glioblastoma and extend the duration of survival. Below are some studies that have published promising results that have extended the survival of patients with GBM.

Pre-clinical studies

• A possible therapy technique is to use viruses to attack the cancer. A modified herpes simplex virus has been engineered to invade tumor cells, and shows some efficacy in mice^[19].
• cell line, and rats injected with a human lung cancer cell and given dichloroacetate in their drinking water had smaller tumors than the rats that did not drink dichloroacetate^[20]
  .

Phase I

• Glioblastoma patients treated with motexafin gadolinium had a median survival time that was greater than a comparison group receiving standard care^[21].
• In recent studies, the antimalarial drug chloroquine has been shown to increase mid-term survival when given in combination with conventional therapy, although this difference did not reach statistical significance due to small sample size^[22][23][24].
• The use of injecting magnetic nanoparticles into the tumors of patients with recurrent GBM has been shown to be safe and feasible and resulted in promising survival rates.^[25]. Promising survival rates have been observed in animal models^[26], however, as yet there are not any results from efficacy studies in humans.

Phase II

• Increased intracavity treatment with the radiopharmaceutical Chlorotoxin-linked-¹³¹iodine (131-I-TM-601) has been associated with increased survival of GBM patients^[27].
• Intracavity treatment with Iodine¹³¹ mouse 81C6 monoclonal antibody improves survival of patients recently diagnosed with glioblastoma^[28].
• Microinfusion with the
  antisense oligonucleotide AP 12009 into the tumor site resulted in a median survival time that exceeded published baselines with conventional chemotherapy^[29]
  .
• Patients receiving the radiosensitizer RSR-13 (efaproxiral) have demonstrated a slight increase in median survival, although supplemental oxygen was required during treatment due to hypoxia[30].
• Patients with recurrent glioblastoma who received a combination of bevacizumab and irinotecan showed an improvement in progression-free survival compared to historical survival data^[31].

Phase III

• Implantation of
  BiCNU-impregnated wafers - trade name Gliadel - at the time of primary resection, improved median survival and prolonged the time until tumor recurrence, compared with placebo wafers^[10]
  .
• Treatment of patients with newly-diagnosed glioblastoma multiforme with photodynamic therapy as an adjuvent treatment has been associated with better prognosis and improved KPS^[32][33].

Recurrences

Long-term disease-free survival is unlikely, and the tumor will often reappear, usually within 2 cm of the original site, and 10% may develop new lesions at distant sites. More extensive surgery and intense local treatment after recurrence has been associated with improved survival.^[34].

Prognosis

The median survival time from the time of diagnosis without any treatment is 3 months. Increasing age (> 60 years of age) carries a worse prognostic risk. Death is usually due to cerebral edema or increased intracranial pressure. One in twenty of glioblastoma patients survive for more than three years, and approximately one in 5,000 glioblastoma patients survive for decades^[35]. Ben Williams has now survived glioblastoma for more than twelve years^[36].

Survival of more than three years has been associated with younger age at diagnosis, a good initial KPS, and MGMT methylation ^[35]. A DNA test can be conducted on glioblastomas to determine whether or not the promoter of the MGMT gene is methylated. Patients with a methylated MGMT promoter have been associated with significantly greater long-term survival than patients with an unmethylated MGMT promoter^[37]. This DNA characteristic is intrinsic to the patient and currently cannot be altered externally.

Long-term survival has also been associated with those patients who receive surgery, radiotherapy, and temozolomide chemotherapy^[35]. However, much remains unknown about why some patients survive longer with glioblastoma.

References

Additional reading

• Cancer Management: Brain Tumors
• Treatment Options for Glioblastoma and other Glios

External links

• National Cancer Institute Clinical Trials
• North America Brain Tumor Coalition
• German Brain Tumor Association
• Glioblastoma multiforme - A new Viro-therapy developed at the Hebrew University - An IsraCast article
• Emedicine.com article on glioblastoma multiforme
• Young Adults Surviving Glioblastoma support group
• Glioblastoma Images MedPix Medical Image Database

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