New Tools and Techniques for Improved Surgical Outcomes for Patients with Brain Tumors

By Michael Vogelbaum, MD, PhD
Program Leader and Chief of Neurosurgery, Neuro-Oncology

The goals of brain tumor surgery are to obtain tissue for diagnosis/classification and remove as much of the bulk tumor as possible. For benign tumors, a complete surgical resection may be curative. But for newly diagnosed malignant tumors, surgery alone is never curative, no matter the extent of tumor removal, although the extent of resection provides additional time to some patients. Surgery for recurrent malignant tumors is intended to preserve or restore neurological functioning, obtain tumor tissues under specialized conditions for translational research, and/or engage in therapeutic development in the OR. One of the key principles of brain tumor surgery is to maximize the extent of resection of tumor tissue while minimizing the potential impact of surgery on neurological functioning.

Surgery for Brain Tumors

There are various neurosurgical approaches used to remove brain tumors.

• Stereotactic biopsy
• Craniotomy/tumor resection
• Laser Interstitial Thermal Therapy
• Endonasal Endoscopic Approaches
• Intraventricular Endoscopic Approaches

Surgery tools used include:

• Surgical navigation systems
• Intraoperative Imaging Modalities, including ultrasound/CT/MRI
• Fluorophores (e.g. 5-ALA)
• Intraoperative Pathology Evaluation

To preserve neurological functioning, some of the techniques are:

• Pre-operative functional imaging
• fMRI
• Navigated TMS
• White matter mapping (DTI, rsMRI)
• Intraoperative mapping and monitoring with use of:
  • Surgical navigation
  • Cranial nerve monitoring
  • Awake craniotomy (speech, motor monitoring)
  • Electrocorticography/cortical stimulation (speech, motor mapping)
  • White matter stimulation

Surgery for skull base tumors

Challenges associated with resection of skull base tumors include complex bony and soft tissue anatomy, cranial nerves, vascular structures, internal carotid and vertebral arteries, dural sinuses and jugular veins which reconstruction is needed to avoid CSF leak/meningitis.

There are multiple specialized approaches that have been developed to address skull base tumors, and in general, these are best performed by neurosurgeons who have specialized training in skull base approaches. One of the more recent advances relates to the use of minimally invasive approaches to address tumors of the anterior skull base, in which a neurosurgeon and a Head & Neck surgeon work together to access the skull base via an endonasal endoscopic approach.

Endonasal endoscopy approach (EEA) is a type of surgery in which tumors located in the anterior skull base are removed through the nose. Endonasal endoscopies are primarily used to remove tumors from the base of the skull and the top of the spine. Because the instruments used for this type of surgery are small and flexible, they can allow a surgeon to access hard-to-reach areas that would otherwise require a more invasive operation. As a result, EEA surgery provides a lower complication rate, shorter recovery time, and no scarring.

Surgery for brain metastasis

The goals of treatment for brain metastases are local control, preservation of neurological function, and preservation of neuro-cognitive function. Treatment modalities include:

• Surgical resection
• Radiotherapy
• Whole Brain Radiotherapy
• Fractionated Stereotactic Radiosurgery (fSRS/fSRT)*
• Stereotactic Radiosurgery (SRS)*
• Brachytherapy*
• Systemic therapy
• Targeted therapies
• Immunotherapies

* These approaches involve the expertise of both a neurosurgeon and a radiation oncologist.

Surgical considerations for primary brain tumors include an infiltrative component that “co-exists” with normal brain cells that extend well beyond tumor mass, metastatic brain tumors, limited local invasion and/or access to tumor mass require transit through “normal” brain.

Surgery is necessary when there’s a brain mass without known or suspected primary cancer, brain metastasis that produces neurological symptoms directly or due to associated edema, or a large brain metastasis that is unlikely to be effectively controlled via SRS/fSRS (> 3 cm in diameter and some might argue > 2 cm).

Primary medical therapy for brain metastases

For some primary cancers (e.g., melanoma, breast, lung), targeted or immunotherapies can produce radiographic responses in the CNS. However, the questions remain about the reliability and durability of responses. At  Moffitt Cancer Center, patients with brain metastases should be managed by a highly coordinated, multidisciplinary team of neurosurgeons, radiation oncologists, neuro-oncologist in collaboration with the primary medical oncology team. This truly personalized care of surgery, SRS/fSRS, WBRT (or HA-WBRT), and medical therapy should be given individually or in combination depending upon a multitude of patient and disease factors.

Surgery for gliomas

In general, surgery for gliomas and glioblastoma remains nearly as dismal today as they were more than two decades ago. The standard therapeutic modalities are surgery and surgery radiotherapy, cytotoxic chemotherapy, and maybe alternating electrical fields. The most significant advances have been in biology and sub-classification, not therapy.

The surgical approaches for glioma surgery are stereotactic biopsy and resection. The advantages of the stereotactic biopsy include small procedures, faster recovery than resection, and provides a diagnosis. The limitations are, however, include sampling error, no intrinsic therapeutic value, hemorrhage, intraparenchymal lesions only, and may increase the duration of steroid dependency.

Some of the surgical resection include diagnosis, reduction of mass effect/elevated intracranial pressure, survival benefit, or delivery of adjunctive therapies. Its draw backs are higher risk of neurological morbidity, more discomfort than biopsy, and longer hospital stay.

The choice of specific surgical options depends upon:

• Size and location of lesion
• Associated edema or herniation
• Whether focal or multi-focal
• Suspected pathology
• Patient functioning at presentation
• Overall health (age, comorbidities)

The goal of surgical resection for high grade gliomas is maximal resection of the enhancing mass (but not surrounding infiltrative tumor) is a standard. For low grade gliomas, resection of all infiltrating tumor (if safe) is standard. Recent evidence suggests that resection of infiltrating tumor for some high-grade gliomas provides survival benefit.

• Image Guidance

        It can be argued that surgical navigation is the most important advance that have occurred in glioma surgery over the past 30 years. As is the case with anything “new” in medicine, there was a lot of early resistance.

        One of the advantages of image guidance is that we can perform limited footprint craniotomies, as we can plan the safest trajectory for deep lesions and tailor extent of resection to respect anatomical boundaries. Some limitations could include brain shift and loss of registration, mitigated by positioning, and use of intraoperative MRI and/or ultrasound.

• Intraoperative MRI. Some considerations for this type of surgery include:
  • Field Strength
  • Low Field – 0.12 to 0.5 T
  • Conventional – 1.5 T
  • High Field – 3.0 T or higher
  • Image quality and Field of View
  • Relates to field strength and magnet/coil design
  • Impact on Surgical Flow – Design of OR Suite
  • Requirement for MRI-compatible instrumentation
  • Anesthesia considerations
  • Compatibility with Surgical Navigation systems

Intraoperative fluorophores are an alternative to intraoperative MRI. It is a "lower technology" imaging approach that can be used to document the presence of residual tumor. 5-aminolevulinic acid (5-ALA) is a fluorophore that provides the greatest tumor specificity. Its use, however, is limited to high grade (enhancing) gliomas.

At Moffitt, we consider it a great privilege to partner with referring physicians. When you refer your patient to Moffitt, you will be entrusting his or her care to a diverse team of specialists who will collaboratively design an individualized treatment plan to meet his or her unique needs. Because we perform a high volume of surgeries, our neurosurgeons have acquired extensive skills and experience in utilizing awake craniotomies with functional mapping and monitoring, 5-ALA guided tumor resection, and other complex techniques. In addition to the very latest therapies, we also offer our patients a full range of compassionate supportive care services to help them navigate their cancer journey more comfortably and effectively.

If you'd like to refer a patient to Moffitt Cancer Center, complete our online form or contact a physician liaison for assistance. As part of our efforts to shorten referral times as much as possible, online referrals are typically responded to within 24 - 48 hours.