title: Clinical and dosimetric predictors of acute hematologic toxicity in rectal cancer patients undergoing chemoradiotherapy.
abstract: OBJECTIVE
  To identify clinical and dosimetric factors associated with hematologic toxicity (HT) during chemoradiotherapy for rectal cancer.
  
  
  METHODS
  We analyzed 120 rectal cancer patients treated with neoadjuvant pelvic radiotherapy (PRT) with concurrent 5-fluorouracil-based chemotherapy. The coxal (ilium, ischium, and pubis) bone marrow (BM), sacral BM, and femoral BM were contoured and dose-volume parameters were extracted. Associations between cell count trend and clinical predictors were tested using repeated-measures analysis of variance (ANOVA) test. Associations between clinical variables, Vx (percentage volume receiving x Gy), and cell count ratio at nadir were tested using linear regression models.
  
  
  RESULTS
  Nadirs for white blood cell count (WBC), absolute neutrophil count (ANC), and platelets (PLT) occurred in the second week of PRT and the fifth week for hemoglobin and absolute lymphocyte count (ALC). Using cell count ratio, patients treated with 3DCRT had a lower WBC ratio trend during PRT compared to patients treated with IMRT (p=0.04), and patients ⩾59 years of age had a lower hemoglobin ratio trend during PRT (p=0.02). Using absolute cell count, patients treated with 3DCRT had lower ANC cell count trend (p=0.03), and women had lower hemoglobin cell count trend compared to men (p=0.03). On univariate analysis, use of 3DCRT was associated with a lower WBC ratio at nadir (p=0.02). On multiple regression analysis using dosimetric variables, coxal BM V45 (p=0.03) and sacral BM V45 (p=0.03) were associated with a lower WBC and ANC ratio at nadir, respectively.
  
  
  CONCLUSIONS
  HT trends during PRT revealed distinct patterns: WBC, ANC, and PLT cell counts reach nadirs early and recover, while hemoglobin and ALC decline steadily. Patients who were treated with 3DCRT and older patients experienced lower cell count ratio trend during PRT. Dosimetric constraints using coxal BM V45 and sacral BM V45 can be considered.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
authors.forename: T Jonathan
authors.initials: TJ
authors.lastname: Yang
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
authors.forename: Jung Hun
authors.initials: JH
authors.lastname: Oh
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
authors.forename: Aditya
authors.initials: A
authors.lastname: Apte
authors.affiliation: Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
authors.forename: Christina H
authors.initials: CH
authors.lastname: Son
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Deasy
authors.affiliation: Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA. Electronic address: goodmank@mskcc.org.
authors.forename: Karyn A
authors.initials: KA
authors.lastname: Goodman
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001853:Bone Marrow / Q000528:radiation effects; D000069287:Capecitabine; D059248:Chemoradiotherapy / Q000009:adverse effects* / Q000379:methods; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D005260:Female; D005269:Femur / Q000528:radiation effects; D005472:Fluorouracil / Q000008:administration & dosage / Q000031:analogs & derivatives; D006402:Hematologic Diseases / Q000209:etiology*; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D010384:Pelvic Bones / Q000528:radiation effects; D010976:Platelet Count; D011874:Radiometry; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects; D012004:Rectal Neoplasms / Q000628:therapy*; D012044:Regression Analysis; D012189:Retrospective Studies; D012447:Sacrum / Q000528:radiation effects
chemical_list: D003841:Deoxycytidine; D000069287:Capecitabine; D005472:Fluorouracil
keywords: Acute radiation toxicity; Clinical predictors; Dose constraint; Rectal cancer