The Effectiveness Comparison Between Single Gamma Knife Radiotherapy And Several Times Gamma Knife Radiotherapy In The Skull Base Chordoma And Its Prognostic Analysis

[Research background] chordoma, originated from the spinal cord of embryonic residual, is a rare low-grade malignant tumor. Among them, 39% lesions located in the base of skul. Surgical resection has been a significant therapeutic option for this lesion, however,chordoma in the skull base is adjacent to the complex neurovascular structures, surgery is hardly to complete resect the lesion. The recurrence is still at a high level after operation alone. To date, large numbers of studies have shown that the postoperative adjuvant radiotherapy can improve local control rates, even in the complete resection ones. For skull base chordoma, stereotactic radiosurgery(SRS)is a kind of ideal treatment as the outstanding radiation biological effect to conventional radiotherapy. In recent years, With development of stereotactic radiotherapy technology, more and more skull base chordoma has been deal with gamma knife. Under precise stereotactic technology, large arranged dose gamma rays beam will be emitted to the preliminary selected target spot. Due to the radiation dose gradient is great in the targeted area, the total dose in the target area is lethal dose, at the meantime, surrounding tissues of target area is immune to radiation damage. It has been reported that combined postoperative stereotactic gamma knife treatment will improve control rates and survival rates compare to operation alone, in addition, gamma knife has satisfactory therapeutic effects to postoperative residual chordoma and recurrence chordoma. However, the treatment effect of gamma knife is associated with the volume, surrounding significant structure, patients, tolerance of the chordoma,so that, we use tumor split or fractionated irradiation technology in stereotactic gamma knife radiotherapy. There has no domestic and international report focus on the clinical effect difference between the single irradiation and fractionated irradiation in the skull base chordoma. In our study, We analyze the short-term and long-term control of gamma knife in the postoperative skull base chordoma, investigate the clinical effect difference between the single irradiation and fractionated irradiation in the skull base chordoma, in order to provide data and evidence in gamma knife treat skull base chordoma.[Materials and Methods] the skull base chordoma patients treated with gamma knife in the 363 hospital gamma knife center from January 2009 to December 2013, has been collected. Inclusion criteria:①patients with chordoma have been treated with gamma knife radiotherapy after surgical operation and postoperative pathology diagnosis is available ②patients treat with gamma knife without chemotherapy before ③patients treat with gamma knife without other radiotherapy before ④lesion located in skull base ⑤no radiation therapy relevant contraindications. Exclusion criteria ①patients with other malignant tumor the follow②-up data is incomplete.Statistical analysis was performed with Statistical software SPSS17.0, the whole patients is divided into two groups- single treatment group and fractionated treatment group according to the patients treated with gamma knife single or several times. Comparing the difference of the two group in control rate and incidence of adverse reactions by chi-square test and(or) Fisher’s exact test and Kaplan Meier method is used to survival analysis. Cox proportional hazards regression model is used to analyze the patients associated survival factors, such as gender, age, postoperative residual tumor size, pathological pattern, margin dose,radiation methods(single and several times)et al. P-values of <0.05 were considered statistically significant.[results] 37 patients with skull base chordoma has been collected in this study, among them, there are 20 male patients(54.05%), 17 patients with women(45.95%). Age range from 27 to 71 years old, average age is 48.73 years old, follow-up time ranges from 12 to 60 months and the median follow-up time is 23 months. Single treatment group has 20 cases, 13 male patients and 7 female patients, the average edge dose in this group is 13.80 Gy(10-15Gy). Fractionated treatment group has 17 cases, 8 patients were male, 9 patients were female, the cumulative average edge dose in this group is 9.71Gy(8-11Gy),treatment plan was divided into 2-3 times, time interval for 7 days. The different control rate between the single treatment group and fractionated treatment group is no statistically significant( X2 =0.187,P=0.746>0.05), The incidence of adverse reactions between the Single treatment group and Fractionated treatment group is no statistically significant.( X2 =1.884,P=0.246>0.05). The tumor control rate will be better with higher edge dose(X2 =8.663,P=0.003<0.05). In the Cox regression model analysis, gender, age and pathological types is not associated with prognosis, while, postoperative residual tumor size,margin dose, radiation methods(single and several times) is associated with prognosis(P= 0.039, 0.036, 0.048, respectively, p<0.05)[conclusion] The local control rate of skull base chordoma has no significant difference between a single gamma knife radiotherapy and fractionated gamma knife radiotherapy, but fractionated gamma knife radiotherapy will improve the long-term prognosis and survival rate.