CyberKnife for Head and Neck Tumors

Stereotactic radiosurgery became a viable treatment option for patients with a variety of cancers and benign conditions involving the brain with the introduction of the Gamma Knife and linear accelerator based radiosurgery systems approximately 20 years ago.  Since that time tens of thousands of patients have been treated safely and without invasive surgery for tumors and problems that used to require invasive surgery.

With the introduction of the Cyberknife, a new, improved generation of radiosurgery has arrived.  Patients no longer have to have a headframe attached by pins to their head, as new software allows patients to be treated more accurately but without any hardware attached to them.  Any lesion which could be treated with the Gamma Knife or any other radiosurgery system can now be treated painlessly and with submillimeter accuracy by the Cyberknife.

Head & Neck Conditions Treated With CyberKnife:

 

Nasopharynx cancer (NPC)

Nasopharynx cancer (NPC) is a relatively rare tumor. Radiation therapy is considered the cornerstone and mainstay of treatment. Some evidence from controlled studies suggests incorporating chemotherapy with the radiation therapy may help improve control rates in selected situations.

Specific Radiation Therapy Approaches for NPC

Intensity Modulated Radiation Therapy (IMRT) Alone:
IMRT has essentially replaced traditional radiation therapy for treatment of NPC. IMRT allows for better dose conformality, vital for treating the nasopharynx as it is situated in an area close to many critical structures, including the brain stem, spinal cord, brain. IMRT also better spares the parotid gland which is involved in saliva production, which affords patients better quality of life due to less dry mouth as a chronic side effect of radiation therapy.

IMRT with radiosurgery boost, including CyberKnife:
Some studies have shown that stereotactic radiosurgery (SRS) is an effective boost method for delivering additional radiation therapy dose to the nasopharynx tumor after initial therapy with IMRT. A ‘boost’ is treating a focal area with radiation to go to a higher dose. Focal radiation therapy with treatment machines like CyberKnife helps further spare surrounding normal tissue. It should be noted however that highly focal treatment with CyberKnife alone is generally not an option for NPC since it is crucial to commence therapy with broader field radiation to treat potential lymph node involvement in the neck in addition to covering the nasopharynx region.

Case Studies:


Treatment for Recurrent Nasopharynx Cancer (NPC)

Occasionally after radiotherapy for NPC, local recurrence of disease may occur in the nasopharynx, with no evidence of disease elsewhere in the body, called metastases.

There is evidence that re-treatment may lead to long term control, especially if the recurrence occurs greater than two years from completion of initial treatment.

Cyberknife is particularly appealing for treating recurrent disease due to dose conformality the treatment offers, so critical in the setting of re-irradiation. Re-treatment is considered high risk due to risk of tissue damage, and sparing of surrounding normal tissue in the setting of attempted salvage treatment is of utmost importance.

 

Miscellaneous Tumors of the Skull Base

The skull base is a region of the body just below the skull, the upper most area of the neck. The area is anatomically very complex, as a myriad of nerves, blood vessels and other soft tissues traverse through a relatively small area.

Tumors involving this region are relatively rare, and when they arise, it presents a formidable challenge. Surgery is often difficult due to presence of critical nearby structures which may lead to functional difficulties for a patient after surgery. Therefore, surgery has to be as limited as possible, while ensuring most of the disease is removed.

Stereotactic radiosurgery, such as CyberKnife, is playing an increasing role in treating cancers of the skull base after surgery to clear up any microscopic disease after the operation. The treatment may also be used as stand alone treatment for unresectable tumors, or tumors known to respond well to radiation.

Tumors of this area include:  glomus tumors, schwannomas, sarcomas or metastases to this area from another site.

 

Recurrent Head & Neck Cancers

Occasionally, tumors may recur in a site previously irradiated. In selected situations, it may be possible to treat the area with stereotactic radiation using CyberKnife. The technology is appealing since it allows treatment to a small defined area with minimal dose to surrounding normal tissues. This is vitally important in the setting of retreatment, since the tissue dose has to minimized, having had previous radiation.

Areas of treatment include lymph nodes of the neck, tumors of the oral cavity and pharynx and larynx.

Site specific stereotactic radiosurgery/radiotherapy retreatment literature

There is considerable evidence that radiosurgical salvage of post-radiotherapy skull base and nasopharynx relapses provides durable local control in a high percentage of patients, with an apparently lower complication rate than is seen with conventional reirradiation techniques (31-36). The preponderance of published radiosurgery experience for recurrent head and neck lesions has been gained with Gamma Knife radiosurgery.

The frameless CyberKnife® design, multiple treatment capability, and virtually unlimited dose-coverage capability compared with Gamma Knife indicates a much larger spectrum of applicability to recurrent head and neck lesions with CyberKnife®.

Case Studies:

 

References

  1. Cmelak AJ, Cox RS, Adler JR et al.  Radiotherapy for skull base malignancies and nasopharyngeal cancer. International Journal of Radiation Oncology Biology Physics 1997 15:37 (5) pp 994-1003
  2. Tate, DJ, Adler JR, Chang SD et al. Stereotactic radiosurgical boost following radiotherapy in primary nasopharyngeal carcinoma – impact on local control. International Journal of Radiation Oncology Biology Physics 1999 Nov 1 45(4) 915-21
  3. Pai PC, Chuang CC, Wei KC et al.  Stereotactic radiosurgery for locally recurrent nasopharynx cancer. Head Neck 2002 Aug 24 (8) 748-53

 

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