title: Effect of dosimetric factors on occurrence and volume of temporal lobe necrosis following intensity modulated radiation therapy for nasopharyngeal carcinoma: a case-control study.
abstract: OBJECTIVE
  To determine dosimetric risk factors for the occurrence of temporal lobe necrosis (TLN) among nasopharyngeal carcinoma (NPC) patients treated with intensity modulated radiation therapy (IMRT) and to investigate the impact of dose-volume histogram (DVH) parameters on the volume of TLN lesions (V-N).
  
  
  METHODS
  Forty-three NPC patients who had developed TLN following IMRT and 43 control subjects free of TLN were retrospectively assessed. DVH parameters included maximum dose (Dmax), minimum dose (Dmin), mean dose (Dmean), absolute volumes receiving specific dose (Vds) from 20 to 76 Gy (V20-V76), and doses covering certain volumes (Dvs) from 0.25 to 6.0 cm(3) (D0.25-D6.0). V-Ns were quantified with axial magnetic resonance images.
  
  
  RESULTS
  DVH parameters were ubiquitously higher in temporal lobes with necrosis than in healthy temporal lobes. Increased Vds and Dvs were significantly associated with higher risk of TLN occurrence (P<.05). In particular, Vds at a dose of ≥70 Gy were found with the highest odds ratios. A common increasing trend was detected between V-N and DVH parameters through trend tests (P for trend of <.05). Linear regression analysis showed that V45 had the strongest predictive power for V-N (adjusted R(2) = 0.305, P<.0001). V45 of <15.1 cm(3) was relatively safe as the dose constraint for preventing large TLN lesions with V-N of >5 cm(3).
  
  
  CONCLUSIONS
  Dosimetric parameters are significantly associated with TLN occurrence and the extent of temporal lobe injury. To better manage TLN, it would be important to avoid both focal high dose and moderate dose delivered to a large area in TLs.
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Xin
authors: X
authors: Zhou
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Xiaomin
authors: X
authors: Ou
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Tingting
authors: T
authors: Xu
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Xiaosheng
authors: X
authors: Wang
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Chunying
authors: C
authors: Shen
authors: Department of Diagnostic Radiology, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Jianhui
authors: J
authors: Ding
authors: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China. Electronic address: hucsu62@yahoo.com.
authors: Chaosu
authors: C
authors: Hu
mesh_terms: D002277:Carcinoma; D016022:Case-Control Studies; D017024:Chemotherapy, Adjuvant / Q000379:methods; D006801:Humans; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D009336:Necrosis / Q000473:pathology; D020360:Neoadjuvant Therapy / Q000379:methods; D058958:Organs at Risk / Q000473:pathology / Q000528:radiation effects; D011832:Radiation Injuries / Q000473:pathology*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D013702:Temporal Lobe / Q000473:pathology* / Q000528:radiation effects