title: Different rectal toxicity tolerance with and without simultaneous conventionally-fractionated pelvic lymph node treatment in patients receiving hypofractionated prostate radiotherapy.
abstract: OBJECTIVE
  To investigate added morbidity associated with the addition of pelvic elective nodal irradiation (ENI) to hypofractionated radiotherapy to the prostate.
  
  
  METHODS
  Two-hundred twelve patients, treated with hypofractionated radiotherapy to the prostate between 2004 and 2011, met the inclusion criteria for the analysis. All patients received 70 Gy to the prostate delivered over 28 fractions and 103 (49%) received ENI consisting of 50.4 Gy to the pelvic lymphatics delivered simultaneously in 1.8 Gy fractions. The mean dose-volume histograms were compared between the two subgroups defined by use of ENI, and various dose-volume parameters were analyzed for effect on late lower gastrointestinal (GI) and genitourinary (GU) toxicity.
  
  
  RESULTS
  Acute grade 2 lower GI toxicity occurred in 38 (37%) patients receiving ENI versus 19 (17%) in those who did not (p = 0.001). The Kaplan-Meier estimate of grade ≥ 2 lower GI toxicity at 3 years was 15.3% for patients receiving ENI versus 5.3% for those who did not (p = 0.026). Each rectal isodose volume was increased for patients receiving ENI up to 50 Gy (p ≤ 0.021 for each 5 Gy increment). Across all patients, the absolute V70 of the rectum was the only predictor of late GI toxicity. When subgroups, defined by the use of ENI, were analyzed separately, rectal V70 was only predictive of late GI toxicity for patients who received ENI. For patients receiving ENI, V70 > 3 cc was associated with an increased risk of late GI events.
  
  
  CONCLUSIONS
  Elective nodal irradiation increases the rates of acute and late GI toxicity when delivered simultaneously with hypofractioanted prostate radiotherapy. The use of ENI appears to sensitize the rectum to hot spots, therefore we recommend added caution to minimize the volume of rectum receiving 100% of the prescription dose in these patients.
authors.affiliation: University of Alabama at Birmingham Department of Radiation Oncology, 1700 6th Avenue, South Birmingham, AL 35249, USA. ammcdonald@uabmc.edu.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: McDonald
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Baker
authors.forename: Richard A
authors.initials: RA
authors.lastname: Popple
authors.forename: Kiran
authors.initials: K
authors.lastname: Shekar
authors.forename: Eddy S
authors.initials: ES
authors.lastname: Yang
authors.forename: Rojymon
authors.initials: R
authors.lastname: Jacob
authors.forename: Rex
authors.initials: R
authors.lastname: Cardan
authors.forename: Robert Y
authors.initials: RY
authors.lastname: Kim
authors.forename: John B
authors.initials: JB
authors.lastname: Fiveash
mesh_terms: D000368:Aged; D003198:Computer Simulation; D019583:Dose Fractionation, Radiation; D005500:Follow-Up Studies; D041981:Gastrointestinal Tract / Q000473:pathology* / Q000528:radiation effects; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology* / Q000528:radiation effects; D008297:Male; D009367:Neoplasm Staging; D010388:Pelvis / Q000473:pathology* / Q000528:radiation effects; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology / Q000473:pathology; D011836:Radiation Tolerance; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012007:Rectum / Q000473:pathology / Q000528:radiation effects; D014566:Urogenital System / Q000473:pathology* / Q000528:radiation effects