The Relationship Between Primary Tumor Volume And Treatment Outcome In Nasopharyngeal Carcinoma With Radiotherapy

Purpose: To study the range of primary tumor volume among T stage lesions by using pretreatment computed tomography images(CT) in nasopharyngeal carcinoma patients treated with radiotherapy, and to investigate the correlation of primary tumor volume with treatment outcome.Methods and materials: From December 1995 to March 1998, one hundred and seventy eight patients with newly diagnosed nasopharyngeal carcinoma were treated with late-course accelerated hyperfractionated radiotherapy alone, among them,154 patients whose pretreatment computed tomography images(CT)were intact in our hospital. All patients were histologically proven as poorly differentiated squamous cell carcinoma. The total dose of nasopharynx was 78Gy/60Fx/6w. The primary tumor volume was obtained by outlining the tumor contour on CT, followed by the summation of area technique of STAR 1000. The median follow –up time was 63.6 months. Kaplan Meier method was used to calculate survival rates and local control rates of patients. Results: A large variation in tumor volume was observed in any T lesions. The mean primary tumor volume and rang were as follows (cm3):T1 18.9(0.55~59.33), T2 25.8(2.22~80.64),T3 39.3(13.9~87.97) and T4 59.7(26.18~115.0).There were apparently overlaps of primary tumor volume among different T stages. The 5-year local control rate was 86.3%. According to tumor volume, all patients were divided into four groups :≤20cm3,21～40cm3,41～60cm3 and >60cm3,and the 5-year local control rates were as follows: 91.9%,91.0%,75.3% and 52.2% respectively. Irrespective of different T lesions, the difference of local control rates in patients with primary tumor volume ≤40cm3 was not statistical. The 5-year overall survival and disease-free survival rates were 69.2% and 56.5% in all patients. The disease-free survival and distant metastases-free survival rates of four groups based on tumor volume were 67.6%,60.7%,35.8% and 22.0%;and 77.8%,63.8%,36.4% and 19.3%, respectively. Univariant analysis showed that patients with large tumor volume(>60cm3) had a poor 5-year local control , disease-free survival and distant relapse free survival rates. Primary tumor volume was found to be an independent prognostic factor of local control in multivariant analysis, but the significance did not reach statistically in predicting disease-free survival rate or distant relapse free survival rate. The main reason of failure and death was distant metastasis.Conclusion: This study demonstrates a large variation of primary tumor volume in any T stage of nasopharyngeal carcinoma, and there are apparently overlaps among different T lesions. Patients with bulky tumors have poor local control and survival rates. Primary tumor volume represents an important prognostic factor for treatment outcome. Aggressive treatments should be given to patients whose tumor volume is more than 60cm3.