Reduction of Normal Tissue Complication Probability by Limiting Dose of Parotid Gland in Prophylactic Cranial Irradiation for Small Cell Lung Cancer
GONG Yan-ping;QIAN Jian-jun;The Second Affiliated Hospital of Soochow University;
[Objective] To reduce the normal tissue complication probability(NTCP) in prophylactic cranial irradiation(PCI) for small cell lung cancer(SCLC),and to provide evidence for sparing of parotid in whole brain radiation therapy. [Methods] Twenty-four SCLC patients receiving PCI were recruited. Parotids were delineated and three plans named as 2D,2D_M and IMRT were designed according to different degree of dose limiting on parotid,subsequently the parotid dose volume and NTCP were evaluated. [Results] The mean total parotids volume was(36.04±4.41)cc,that of left and right parotid was(17.89±3.86)cc and(18.15±4.41)cc,respectively. The mean value of biological equivalent dose(BED) of parotids in plans 2D,2D_M and IMRT was(1684±416)cGy,(1210 ±366)cGy and(839 ±128)cGy,respectively. For 2D plans in which the parotids were not spared,the dose of parotids was excess in 10 patients(T41.67%T),including the dose of right and left parotid was 2000cGy in 7(29.17%) and 2500cGy in 2(8.33%); for 2D_M only 1 patients(4.16%) whose dose of unilateral parotid was 2000cGy; while there was no dose excess in IMRT.The average NTCP of the three plans were(5.08 ±2.56)%,(3.12±1.42)% and(1.91±0.40)%(P0.05).[Conclusion] Normal tissue complication probability of parotid can be effectively reduced by limiting its dose in prophylactic cranial irradiation for patients with small cell lung cancer.