Cancer nasopharynx and the role of Cyberknife
Cancer nasopharynx is a type of head and neck cancer that affects the squamous cells that line the nasopharynx. The nasopharynx is the back of the throat that includes two openings on either side that lead to the ears. It is believed that an Asian or Chinese ethnic background has an increased risk for developing this type of cancer. Other known risk factors include an exposure to the Epstein-Barra virus (EBV) and drinking large quantities of alcohol. Because the cancer can affect the various parts of the nasopharynx, the signs and symptoms include bleeding from nose or throat, difficulty in breathing from nose, speaking, pain in ears, hearing (ringing, reduced hearing) and swellings on one or both sides of neck(lymph nodes). Patients may also complain of lump/soreness in the back of the throat and an increased frequency of headaches. A detailed history and clinical examination can lead to a diagnosis; however, in many cases other investigations are often necessary. Imaging studies can include CT, MRI, and PET scans. In addition, a hearing test may also be required as well as a blood check for the EBV. Finally, a biopsy from the tumour site is provides valuable information to know the type and stage the cancer.
Radiotherapy is the main stay of treatment and the only curative treatment for cancer of nasopahrynx. Light chemotherapy along with radiation over 7 weeks is the curative treatment for localized cancer of nasopharynx.This needs to be followed by 2-4 cycles of chemotherapy to prevent a metastases later on.Side-effects such as mucositis (inflammation and ulceration of the lining the mouth and throat) can occur,however they recover within 4-6 weeks post treatment. Surgery of cancer nasopharynx is an option for residual neck nodes after the radiation and chemotherapy.that is considered in patients. Since nasopharynx is surrounded by critical areas like eyes,nerves that supply the eyes,pituitary,brain,salivary glands and swallowing structures,it needs extreme care in planning and delivery of treatment. Intensity modulated radiation or volumetric modulated arc therapy gives the best chance of tumour killing dose to be deposited in the tumour.Image guidance(IGRT) is required everyday to correct any change in position in the treatment room.
Cyberknife is a special robotic radiosurgery system that helps boost the radiation for tumours that are 3 cms or less after the conventional fractionated treatment.Tomotherapy is another device that helps deliver the best form of intensity modulated radiation with daily IGRT. Some centers have reported good control of the local tumors for up to 80% for at least two years. This has been observed to be of benefit in small tumors and recurrent tumors where adjoining vital anatomical structures, such as the carotid arteries, are to be protected from unwanted effects of the radiation. In addition, Cyberknife is a completely painless procedure.
Before Cyberknife became available High Dose Rate(HDR)brachytherapy was used for boosting the residual disease in the nasopharynx and still is available for small tumour that are less than one centimeter in size with 100% control rates for selected cases.