title: De-escalation of the cumulative central radiation dose according to the tumor response can reduce rectal toxicity without compromising the treatment outcome in patients with uterine cervical cancer.
abstract: OBJECTIVE
  To assess the treatment outcome and toxicity of a low cumulative central dose using a midline block (MLB) during external beam radiotherapy (EBRT).
  
  
  METHODS
  Between January 1988 and December 2010, 1559 patients with FIGO stage IB-IIB uterine cervical cancer that underwent EBRT and high-dose-rate intracavitary brachytherapy (HDR-ICBT) were retrospectively analyzed. During EBRT, MLB was performed (n=1195, MLB group) when a sufficient response was achieved to insert the tandem through the cervical canal and place ovoids in the vaginal cavity. MLB was not applied for patients with a slow tumor response (n=364, non-MLB group). The doses were estimated according to the International Commission on Radiation Units and Measurements (ICRU) points. The biologically equivalent dose in 2-Gy fractions (EQD2) was calculated to estimate the cumulative dose from EBRT and ICBT.
  
  
  RESULTS
  EQD2pointA, EQD2rectum, and EQD2bladder were all significantly lower in the MLB group (all P<0.05). The 10-year grade≥2 late rectal toxicity rate was significantly lower in the MLB group (P=0.012), while there was no significant difference in late genitourinary and small bowel toxicity. ICRU rectal and bladder doses showed significant predictability on late rectal and bladder toxicities. After propensity score matching, all patient and tumor characteristics were well matched and the survival and recurrence rates between the two groups were similar (all P>0.05), despite the lower EQD2pointA in the MLB group (P<0.001).
  
  
  CONCLUSIONS
  Applying MLB according to tumor response during EBRT lowered the cumulative central dose and reduced late rectal toxicity without compromising treatment outcome.
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Women's Cancer Clinic, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Gwi Eon
authors.initials: GE
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Woong Sub
authors.initials: WS
authors.lastname: Koom
authors.affiliation: Women's Cancer Clinic, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Sang Wun
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Women's Cancer Clinic, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Eun Ji
authors.initials: EJ
authors.lastname: Nam
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Chang-Ok
authors.initials: CO
authors.lastname: Suh
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea; Women's Cancer Clinic, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea; Yonsei Song-Dang Institute for Cancer Research, Yonsei University College of Medicine, Seoul, Republic of Korea. Electronic address: ybkim3@yuhs.ac.
authors.forename: Yong Bae
authors.initials: YB
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods; D002277:Carcinoma / Q000532:radiotherapy* / Q000556:secondary; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011878:Radiotherapy / Q000009:adverse effects* / Q000379:methods*; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects*; D012189:Retrospective Studies; D015996:Survival Rate; D013997:Time Factors; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D055815:Young Adult
keywords: Midline block; Radiotherapy; Toxicity; Uterine cervical cancer