Biochemical failure after carbon ion radiotherapy for prostate cancer.
Biochemical failure after radiotherapy for prostate cancer occurs infrequently, but some cases progress to a poor outcome. The aim of this study was to examine prognosis after biochemical failure. A total of 728 patients were treated with carbon ion radiotherapy, and biochemical failure occurred in 90 (12.4%). Their outcomes were examined according to risk factors, histological findings, and androgen deprivation therapy (ADT). Biochemical failure rates were 12%, 6%, and 15% in low-, intermediate- and high-risk patients. Most patients responded favorably to salvage therapy. Some high-risk patients (25%) progressed to poor outcome; half experienced failure after ADT, while the rest during ADT, indicating that ADT had a slight influence. Patients who died from their disease had approximately two years of biochemical failure-free time and three years of survival after failure. Their tumor showed the presence and the increased proportion of histologically high-grade growth patterns. Histological growth patterns and short biochemical failure-free time are prognostic factors for poor outcome regardless of ADT.