MIAMI BEACH--Early-stage prostate cancer patients treated with three-dimensional conformal radiotherapy (3D-CRT) at the University of Michigan Medical Center had excellent survival rates with few complications, Howard Sandler, MD, reported at the American Society for Therapeutic Radiology and Oncology (ASTRO) meeting.
The use of 3D-CRT allows radiation oncologists to better focus the radiation treatments to all angles of the prostate and thus give higher radiation doses to the tumor while preserving normal tissues, Dr. Sandler said. The technique creates dose distributions based on anatomic data derived from computed tomography (see image on page 1).
Dr. Sandler, associate professor and director of clinical programs at the Ann Arbor center, said that the study involved 707 patients with localized prostate cancer treated with 3D-CRT. The median total radiation dose was 69 Gy. Excluded from the study were patients who were node positive, who had undergone post-prostatectomy radiotherapy, or who had received preradiation androgen ablation.
For analysis, patients were divided into two subgroups: favorable (those with preradiation PSA levels of 20 or below and early-stage tumors) and unfavorable (later-stage disease and higher PSA levels). The favorable group included a surgical subset (109 patients) restricted to patients with PSA less than 10 and age below 70. Patients have been followed for up to 8 years (median, 36 months).
The favorable subgroup patients had an 87% disease-free survival rate at 5 years. In the unfavorable group, only 22% were disease free at 5 years, emphasizing the importance of early detection, Dr. Sandler said. Five-year survival for the surgical group was 83%.
"In addition to the excellent survival rates for favorable patients, the complication rates for all patients in our study were very low--3% or less," Dr. Sandler said. The risk of grade 4 complications was only 0.5%.
Preradiation PSA level proved to be the most critical predictor of treatment success, he said. At 5 years, those with preradiation PSA levels below 4 had an 87% disease-free survival rate; those with PSA levels between 4 and 10 had a 72% survival rate; PSA 10 to 20, a 37% survival rate, and PSA greater than 20, a 26% survival rate.