Key points

Patient population

Over a 20-year period, 473 patients (32 of whom were children or adolescents) with skull-base malignancies were operated on by the author in the setting of a tertiary-care comprehensive cancer center. A multidisciplinary team experienced in the assessment and treatment of skull-base malignancy evaluated all patients preoperatively. The anterior skull base was most commonly affected in the adult population, whereas the middle skull base was the most commonly affected site in children. Fig. 1 depicts the skull-base region affected and whether the patient was a child or an adult. In adults the most commonly encountered abnormalities were squamous cell carcinoma, adenoid cystic carcinoma, chondrosarcoma, olfactory neuroblastoma, and adenocarcinoma. Sarcomas constituted 38% of the malignancies in adults but 75% of the malignancies in children. The most common abnormalities by site are listed in Box 1 . Fig. 1 shows the breakdown between sarcoma and nonsarcoma pathology at each skull-base site. The middle skull base is relatively the most likely site for a sarcoma.

Skull-base region affected, relative age of patient, and nature of malignancy (sarcoma vs nonsarcoma). ASB, anterior skull base; MSB, middle skull base; PSB, posterior skull base.

( Courtesy of Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center; with permission.)

Patient population

Over a 20-year period, 473 patients (32 of whom were children or adolescents) with skull-base malignancies were operated on by the author in the setting of a tertiary-care comprehensive cancer center. A multidisciplinary team experienced in the assessment and treatment of skull-base malignancy evaluated all patients preoperatively. The anterior skull base was most commonly affected in the adult population, whereas the middle skull base was the most commonly affected site in children. Fig. 1 depicts the skull-base region affected and whether the patient was a child or an adult. In adults the most commonly encountered abnormalities were squamous cell carcinoma, adenoid cystic carcinoma, chondrosarcoma, olfactory neuroblastoma, and adenocarcinoma. Sarcomas constituted 38% of the malignancies in adults but 75% of the malignancies in children. The most common abnormalities by site are listed in Box 1 . Fig. 1 shows the breakdown between sarcoma and nonsarcoma pathology at each skull-base site. The middle skull base is relatively the most likely site for a sarcoma.

Skull-base region affected, relative age of patient, and nature of malignancy (sarcoma vs nonsarcoma). ASB, anterior skull base; MSB, middle skull base; PSB, posterior skull base.

( Courtesy of Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center; with permission.)

Management paradigms

The foundation of all management decisions rests on a representative biopsy of the tumor, properly identified and diagnosed by experts in surgical pathology with experience in head and neck malignancy, neural tumors, and sarcoma pathology. Inaccurate diagnoses can lead to both undertreatment and overtreatment, with their attendant toxicity and morbidity. Cohen and colleagues discuss an example of the problems encountered with misdiagnosis with respect to sinonasal olfactory neuroblastoma. In a series of 12 consecutive patients referred with the biopsy-proven diagnosis of olfactory neuroblastoma only 2 patients, on review by an expert pathologist, did in fact harbor this tumor. Revised diagnoses included pituitary adenoma (3 patients), neuroendocrine carcinoma (3), sinonasal undifferentiated carcinoma (2), and melanoma (2). These revised diagnoses led to significant alterations in the initially proposed treatment plan in 8 of 10 patients, including the recommendation of observation alone in the 3 patients with pituitary adenomas, 1 of whom had been rendered blind by radiation necrosis of his optic nerves (the tumor had been aggressively treated as an olfactory neuroblastoma).

With the correct pathologic diagnosis in hand, each patient should be evaluated by members of a multidisciplinary group including medical and radiation oncology, dental oncology, head and neck surgery, neurosurgery, and plastic surgery. Additional consultations with speech pathology, audiology, otology, and ophthalmology may be necessary. In this setting the combined expertise of each individual is brought to bear on the patient’s problem and leads to the construction of the optimal management plan for each patient. The skull-base neurosurgeon’s main contribution is the determination, along with the rest of the surgical team, as to whether the tumor can be completely encompassed by a surgical resection that carries acceptable morbidity. With experience the neurosurgeon can also identify which tumor pathologic/biological factors make resection (with its attendant morbidity) worthwhile, or those instances whereby a complete tumor resection may not be necessary (usually to maintain function). Along with the determination of tumor resectability, the availability and nature of adjuvant therapies and the medical and psychic candidacy of the patient for surgery/treatment is taken into consideration.

The simplest management paradigm, surgical excision alone, may be applicable to certain low-grade malignancies such as low-grade chondrosarcomas, low-grade papillary adenocarcinomas, and desmoid tumors. Complete resection can result in cure or long-term remission, although late recurrence can be an issue.

The management paradigm most applicable to the majority of patients with skull-base malignancy is that of surgical extirpation followed by external beam radiation therapy. This approach is generally the recommended treatment for lower-stage squamous cell carcinomas, olfactory neuroblastoma, adenocarcinoma, adenoid cystic carcinoma, and most metastases, and may be used in some patients with low-grade sarcomas. Induction chemotherapy may also be used in the context of an organ-sparing (usually orbital-sparing) approach. Data supporting this approach are limited although early studies show promise, with one group of investigators reporting a response rate in excess of 90%. Similarly, investigators from the University of Chicago reported complete histologic response in 5 of 16 patients and a 10-year locoregional and distant control rate exceeding 90%. At the author’s institution this is an especially common pathway for patients with squamous cell carcinoma and sinonasal undifferentiated carcinoma. Induction chemotherapy with cisplatin, a taxane, and 5-fluorouracil with or without gemcitabine has been shown to be an effective combination for patients with squamous cell carcinoma. In a recent study from M.D. Anderson, patients with advanced sinonasal squamous cell carcinoma were treated with induction chemotherapy with a platinum-based and taxane based regimen. Just over two-thirds of the patients achieved at least a partial response, while 24% had progressive disease and 9% had stable disease. The 2-year survival for patients with at least a partial response or stable disease after induction chemotherapy was 77%, in contrast to only 36% for patients with progressive disease. Similarly, the author’s practice, and that of others, has increasingly been to use induction chemotherapy with cisplatin-based programs (usually in combination with etoposide) for sinonasal undifferentiated carcinoma with or without surgical resection, dependent on the response to chemotherapy ( Fig. 2 ). For certain abnormalities surgical resection may not be a necessary part of the management paradigm. For patients with moderate to poorly differentiated neuroendocrine carcinoma, induction chemotherapy with cisplatin or carboplatin with etoposide frequently results in a complete or substantial response, which may be consolidated with definitive radiotherapy. Long-term survival has been reported with this strategy, but a standard chemoradiation schedule has not been defined. Other abnormalities that fall into this treatment paradigm include lymphoma, Ewing sarcoma, and most pediatric rhabdomyosarcomas and malignant peripheral nerve sheath tumors.

This 23-year-old man presented with acute obtundation and headache. Computed tomography imaging revealed a large frontal tumor with intracerebral hematoma. Initial sagittal postcontrast T1-weighted magnetic resonance imaging (MRI) ( A ) revealed a large sinonasal tumor with intracerebral extension. The patient was taken to the operating room emergently, and underwent resection of all intracranial tumor and evacuation of hematoma. ( B ) Postoperative sagittal postcontrast T1-weighted MRI. Pathology was consistent with sinonasal undifferentiated carcinoma. He was subsequently treated with 4 cycles of cisplatin and etoposide with partial response evident on the post-chemotherapy sagittal postcontrast T1-weighted MRI ( C ). He then underwent formal anterior craniofacial resection. The postoperative sagittal postcontrast T1-wieghted MRI ( D ) confirmed complete tumor removal. Extensive pathologic analysis could not identify any viable tumor. He was treated postoperatively with intensity-modulated radiation therapy to a dose of 60 Gy in 30 fractions. He is free of disease 3 years later.

( Courtesy of Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center; with permission.)

A relatively recent addition to management paradigms has been the planned use of postoperative single-fraction stereotactic radiation boost to areas of either proven or potential microscopic tumor residual. This approach has been most commonly applied in patients with squamous cell carcinoma and adenoid cystic carcinoma in the presence of, or potential presence of, perineural tumor extension ( Fig. 3 ). It is too early to judge the usefulness of this modality in disease control and survival, although several patients remain without recurrence more than 3 years after treatment. The author’s current management paradigms and applicable malignancies are listed in Box 2 .

Axial postcontrast T1-weighted MRI with superimposed radiosurgical treatment plan. This female patient with invasive squamous cell carcinoma of the skin of the right eyebrow had been extensively treated with multiple surgeries and external beam radiation. At recurrence she underwent wide local excision of the tumor with orbitectomy. Residual disease in the cavernous sinus was treated with radiosurgery to a dose of 15 Gy at the 50% isodose line.

( Courtesy of Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center; with permission.)

Box 2

• 
  

  Surgical resection

  
  
  
  
  • 
    

    Low-grade chondrosarcoma

    
    
  • 
    

    Basal cell carcinoma

    
    
  • 
    

    Desmoid fibromatosis

    
    
  • 
    

    Some other low-grade sarcomas and low-grade adenocarcinomas

  
  
  
  
• 
  

  Surgical resection and postoperative radiation therapy

  
  
  
  
  • 
    

    Olfactory neuroblastoma

    
    
  • 
    

    Adenocarcinoma

    
    
  • 
    

    Adenoid cystic carcinoma

    
    
  • 
    

    Squamous cell carcinoma

    
    
  • 
    

    Most metastases

    
    
  • 
    

    Some low-grade sarcomas

  
  
  
  
• 
  

  Pre- and postoperative chemotherapy, surgical resection, and postoperative radiation therapy

  
  
  
  
  • 
    

    Squamous cell carcinoma

    
    
  • 
    

    High-grade sarcomas

    
    
  • 
    

    SNUC and other neuroendocrine carcinomas

    
    
  • 
    

    Melanoma

  
  
  
  
• 
  

  Chemotherapy and radiation therapy

  
  
  
  
  • 
    

    Lymphoma

    
    
  • 
    

    Ewing sarcoma

    
    
  • 
    

    Most rhabdomyosarcomas and MPNST

    
    
  • 
    

    Some patients with SNUC and other neuroendocrine carcinomas

  
  
  
  
• 
  

  Chemotherapy, radiation therapy, surgical resection, and stereotactic radiosurgery

  
  
  
  
  • 
    

    Squamous cell carcinoma especially with perineural extension

    
    
  • 
    

    Adenoid cystic carcinoma

    
    
  • 
    

    Some high-grade sarcomas, SNUC

  
  

Abbreviations: MPNST, malignant peripheral nerve sheath tumor; SNUC, sinonasal undifferentiated carcinoma.

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