To report
the incidence and predictors of treatment-related toxicity
at 10 years after three-dimensional conformal radiotherapy
(3D-CRT) and intensity-modulated radiotherapy (IMRT) for
localized prostate cancer. Between 1988 and 2000, 1571
patients with stages T1–T3 prostate cancer were treated with
3D-CRT/IMRT with doses ranging from 66 to 81 Gy. The median
follow-up was 10 years. Posttreatment toxicities were all
graded according to the National Cancer Institute's Common
Terminology Criteria for Adverse Events.
Results
The
actuarial likelihood at 10 years for the development of
Grade ≥2 GI toxicities was 9%.
The use of IMRT
significantly reduced the risk of gastrointestinal (GI)
toxicities compared with patients treated with conventional
3D-CRT (13% to 5%). Among patients who experienced
acute symptoms the 10-year incidence of late toxicity was
42%, compared with 9% for those who did not experience acute
symptoms (p < 0.0001).
The
10-year incidence of late Grade ≥2 genitourinary (GU)
toxicity was 15%. Patients treated with 81 Gy (IMRT) had
a 20% incidence of GU symptoms at 10 years, compared with a
12% for patient treated to lower doses (p = 0.01). Among
patients who had developed acute symptoms during treatment,
the incidence of late toxicity at 10 years was 35%, compared
with 12% (p < 0.001). The incidence of Grade 3 GI and GU
toxicities was 1% and 3%, respectively.
Conclusions
Serious
late toxicity was unusual despite the delivery of high
radiation dose levels in these patients. Higher doses were
associated with increased GI and GU Grade 2 toxicities, but
the risk of
proctitis was significantly reduced with IMRT. Acute
symptoms were a precursor of late toxicities in these
patients.