Recently, a patient with nasopharyngeal cancer was examined in a local hospital for 2 months for blood in the aspirated sputum and tinnitus. After the diagnosis of nasopharyngeal cancer was confirmed by nasopharyngeal biopsy, gamma-knife treatment was applied. 6 months later, another swelling appeared in the nasopharynx, and the diagnosis of nasopharyngeal cancer recurrence was confirmed by nasopharyngeal biopsy. However, less than 4 months after the treatment, the nasopharyngeal cancer recurred again. The patient was referred to another hospital and received conventional radiation therapy with an irradiation dose of 30 Gy. 3 months later, the patient again developed snotty blood, headache and right nasal congestion, so he was referred to Sun Yat-sen University Cancer Hospital. The examination revealed a nasopharyngeal anterior wall mass with forward invasion of the right nasal cavity and bone destruction at the skull base, which was diagnosed as uncontrolled nasopharyngeal cancer after treatment.
The recurrent recurrence of nasopharyngeal cancer after γ-knife treatment is mainly related to the improper selection of indications for γ-knife treatment of tumors.
The γ-knife was invented by Swedish scientists in 1968 for the treatment of cerebrovascular diseases such as cerebrovascular malformation, and the indications were only extended to the treatment of tumors later. During the treatment, the patient wears a treatment cap like a motorcycle helmet with 201 holes inside. γ-rays are shot to the tumor center from different directions through these holes, so that the irradiation dose to the tumor center is high, while the irradiation dose to the normal tissues around the tumor is low, which plays the role of removing the tumor like surgery, so it is called γ-knife. However, not all tumors are suitable for γ-knife treatment. γ-knife treatment has restrictions on the volume and shape of tumors, which should be spherical in shape and less than 3 cm in diameter. Otherwise, some of the tumors may not be irradiated or the irradiation dose is very low and become a source of recurrence.
Most of nasopharyngeal carcinomas are undifferentiated carcinomas with high malignancy, which often invade the parapharyngeal space, skull base bone, oropharynx, nasal cavity and metastasize to the lymph nodes in the neck, and some of them also invade the intracranial brain tissue, orbit or paranasal sinus, forming a tumor with extremely irregular shape.
For recurrence of nasopharyngeal cancer after γ-knife treatment, the choice of treatment method is more difficult. Because nasopharyngeal cancer has a chance to be cured only by using radiotherapy, most doctors still consider radiotherapy first. However, in order to prevent serious sequelae, doctors are afraid to give higher irradiation doses because the biological effect of γ-knife irradiation is different from that of conventional radiation therapy. 30Gy of γ-knife irradiation is significantly greater than 30Gy of conventional radiation therapy, and it is not yet possible to accurately calculate or estimate the reciprocal relationship between these two irradiation doses. If doctors dare not give radical dose, or give radical dose but the tumor cells are resistant to radiation, it is difficult to get effective control of nasopharyngeal cancer, and the above patient is a typical example. Therefore, primary treatment of nasopharyngeal cancer is not suitable for gamma-knife treatment.