Kyung Hwan Kim1, Sunghoon Kim2, Gwi Eon Kim1, Woong Sub Koom1, Sang Wun Kim2, Eun Ji Nam2, Chang-Ok Suh1, Yong Bae Kim3. 1. Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea. 2. Women's Cancer Clinic, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea. 3. 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.
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.
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.