Mathematical Model for Evaluating Incidence of Acute Rectal Toxicity During Conventional or Hypofractionated Radiotherapy Courses for Prostate Cancer

Lidia Strigari, Giorgio Arcangeli, Stefano Arcangeli, Marcello Benassi

Research output: Contribution to journalArticle

Abstract

Purpose: To describe the radiation-induced acute rectal toxicity (ART) using a modified Lyman-Kutcher-Burman normal tissue complication probability model and parameters set, taking into account the overall treatment time. Methods and Materials: A total of 160 patients underwent three-dimensional conformal radiotherapy to the prostate and seminal vesicles and were randomized to receive 80 Gy in 40 fractions within 8 weeks (Group A) or 62 Gy in 20 fractions within 5 weeks, 4 d/wk (Group B). An additional 52 patients (Group C) underwent intensity-modulated radiotherapy with a hypofractionation schedule consisting of 56 Gy, delivered in 16 fractions (4/wk) of 3.5 Gy. Patients were followed for ART weekly during treatment. The overall treatment time, rectal dose-volume histograms, and ART status, defined as Radiation Therapy Oncology Group Grade 2 or greater gastrointestinal toxicity, were used to determine the modified Lyman-Kutcher-Burman model parameters. The m and n values were obtained from the cohort, and the tolerance doses for 50% complication probability for uniform irradiation [TD50(1)k] were obtained for each fractionation schedule indicated with k. Results: Of 212 patients treated with localized prostate radiotherapy, 65 developed Grade for ≥1 week during treatment. The m and n value was 0.17 and 0.08, respectively. The TD50(1)k parameter was 79, 62.5, and 53 Gy, respectively for Group A, B, and C. Conclusion: The optimized modified Lyman-Kutcher-Burman normal tissue complication probability model allowed us to describe the ART data from conventional and hypofractionated regimens, using the dose-volume histograms and overall treatment time. This model could prove useful in designing hypofractionation schedules to reduce the incidence of ART.

Original languageEnglish
Pages (from-to)1454-1460
Number of pages7
JournalInternational Journal of Radiation Oncology Biology Physics
Volume73
Issue number5
DOIs
Publication statusPublished - Apr 1 2009

Keywords

  • Hypofractionation
  • Normal tissue complication probability
  • Prostate cancer
  • Radiation-induced rectal acute toxicity

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Cancer Research

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