Purpose: To assess the factors that predict late GI and GU morbidity in radiation treatment of the prostate.
Methods and materials: Seven hundred twelve consecutive prostate cancer patients treated at this institution between 1986 and 1994 (inclusive) with conformal or conventional techniques were included in the analysis. Patients had at least 3 months follow-up and received at least 65 Gy. Late GI Grade 3 morbidity was rectal bleeding (requiring three or more procedures) or proctitis. Late Grade 3 GU morbidity was cystitis or stricture. Multivariate analysis (MVA) was used to assess factors related to the complication-free survival. The factors assessed were age, occurrence of side effects > or = Grade 2 during treatment, irradiated volume parameters (use of pelvic fields, treatment of seminal vesicles to full dose or 57 Gy, and use of additional rectal shielding), dose, comorbidities, and other treatments (hormonal manipulation, TURP).
Results: Acute GI and GU side effects (Grade 2 or higher) were noted in 246 and 201 patients, respectively; 67 of these patients exhibited both. GI side effects were not correlated with GU side effects acutely. Late and acute morbidities were correlated (both GI and GU). Fifteen of the 712 patients expressed Grade 3 or 4 GI injuries 3 to 32 months after the end of treatment, with a mean of 14.3 months. One hundred fifteen patients expressed Grade 2 or higher GI morbidity (mean: 13.7 months). The 43 Grade 2 or higher GU morbidities occurred significantly later (mean: 22.7 months). Central axis dose was the only independent variable significantly related to the incidence of late GI morbidity on MVA. No treatment volume parameters were significant for Grade 3. The following parameters were significantly related (by MVA) to Grade 2 GI morbidity: central axis dose, use of the increased rectal shielding, androgen deprivation therapy starting before RT. Acute and late GI morbidities were highly correlated. History of diabetes, treatment of pelvic nodes, and age less than 60 years were significantly related to acute GI side effects. The parameters significantly related to late Grade 2 or higher GU morbidity were central axis dose, androgen deprivation therapy (Zoladex or Lupron) prior to radiation therapy (RT), history of obstructive symptoms, and acute GU side effects. There were too few late Grade 3 GU morbidities to perform multivariate analysis. Acute GU side effects were highly correlated with late GU injury. The following were correlated with acute GU side effects: history of diabetes (+), treatment with conformal fields (-), TURP before RT (-), presentation with urinary obstructive symptoms.
Conclusion: Both late GI and GU morbidity demonstrate a dose dependence, but only the volume dependence observed is a reduction in late Grade 2-4 GI morbidity by increasing the rectal shielding in the lateral fields for the final 10 Gy. Moreover, both late GI and GU morbidity was increased in patients treated with hormone manipulation prior to RT. GI and GU injuries were correlated with their corresponding acute side effects. GI and GU complications must not be combined for analysis to determine the factors related to their occurrence.