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Int J Radiat Oncol Biol Phys. 2014 Apr 1;88(5):1074-84. doi: 10.1016/j.ijrobp.2014.01.015.

Risk of late toxicity in men receiving dose-escalated hypofractionated intensity modulated prostate radiation therapy: results from a randomized trial.

Author information

1
Departments of Radiation Oncology and Radiation Physics, The University of Texas, MD Anderson Cancer Center, Houston, Texas. Electronic address: khoffman1@mdanderson.org.
2
Departments of Radiation Oncology and Radiation Physics, The University of Texas, MD Anderson Cancer Center, Houston, Texas.

Abstract

OBJECTIVE:

To report late toxicity outcomes from a randomized trial comparing conventional and hypofractionated prostate radiation therapy and to identify dosimetric and clinical parameters associated with late toxicity after hypofractionated treatment.

METHODS AND MATERIALS:

Men with localized prostate cancer were enrolled in a trial that randomized men to either conventionally fractionated intensity modulated radiation therapy (CIMRT, 75.6 Gy in 1.8-Gy fractions) or to dose-escalated hypofractionated IMRT (HIMRT, 72 Gy in 2.4-Gy fractions). Late (≥90 days after completion of radiation therapy) genitourinary (GU) and gastrointestinal (GI) toxicity were prospectively evaluated and scored according to modified Radiation Therapy Oncology Group criteria.

RESULTS:

101 men received CIMRT and 102 men received HIMRT. The median age was 68, and the median follow-up time was 6.0 years. Twenty-eight percent had low-risk, 71% had intermediate-risk, and 1% had high-risk disease. There was no difference in late GU toxicity in men treated with CIMRT and HIMRT. The actuarial 5-year grade ≥2 GU toxicity was 16.5% after CIMRT and 15.8% after HIMRT (P=.97). There was a nonsignificant numeric increase in late GI toxicity in men treated with HIMRT compared with men treated with CIMRT. The actuarial 5-year grade ≥2 GI toxicity was 5.1% after CIMRT and 10.0% after HIMRT (P=.11). In men receiving HIMRT, the proportion of rectum receiving 36.9 Gy, 46.2 Gy, 64.6 Gy, and 73.9 Gy was associated with the development of late GI toxicity (P<.05). The 5-year actuarial grade ≥2 GI toxicity was 27.3% in men with R64.6Gy ≥ 20% but only 6.0% in men with R64.6Gy < 20% (P=.016).

CONCLUSIONS:

Dose-escalated IMRT using a moderate hypofractionation regimen (72 Gy in 2.4-Gy fractions) can be delivered safely with limited grade 2 or 3 late toxicity. Minimizing the proportion of rectum that receives moderate and high dose decreases the risk of late rectal toxicity after this hypofractionation regimen.

PMID:
24661661
DOI:
10.1016/j.ijrobp.2014.01.015
[Indexed for MEDLINE]

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