High external parametrial dose can increase the probability of radiation proctitis in patients with uterine cervix cancer

Objective. The aim of this study was to evaluate the relationship between e xternal parametrial dose and radiation proctitis after external irradiation and high-dose-rate intracavitary (HDR-IC) brachytherapy among patients wit h cervical cancer. Methods. From May 1993 through December 1996, 191 patients with stage TB-IV A cervical cancer were managed by curative-intent radiotherapy. External ir radiation to the whole pelvis (44-45 Gy/22-25 fractions) was delivered to a ll patients initially. One hundred twenty-seven patients received additiona l bilateral parametrial and sidewall boost (5.4-14.4 Gy/ 3-8 fractions) wit h 4-cm midline shielding. HDR-IC brachytherapy, 19.2-24 Gy/ 5 fractions to Point A, was given after external irradiation. Patients receiving an extern al dose of 44-45, 50-54, and >54 Gy mere categorized as no parametrial boos t (NPMB), low parametrial boost (LPMB), and high parametrial boost (HPMB) g roup, respectively. The actuarial proctitis rate was compared among the thr ee groups. Results. Three-year overall and Grade 2-4 proctitis rates were 30 and 15%, respectively. Overall proctitis rates were 12, 34, and 51% in the NPMB, LPM B, and HPMB groups (P < 0.0001), respectively. Grade 2-4 proctitis rates we re 5, 17, and 27% in the NPMB, LPMB, and HPMB groups (P = 0.0022), respecti vely. In multivariate analysis of overall and Grade 2-4 radiation proctitis , external parametrial dose was the only independent prognostic factor (P = 0.0002 and 0.0030, respectively). Conclusion. Regardless of central shielding after 43-45 Gy whole pelvis irr adiation, more patients with high external parametrial dose developed radia tion proctitis. Incomplete midline shielding of the upper rectum may be the cause. Diminishing the external beam doses further may decrease rectal com plications, (C) 2000 Academic Press.