Conformal RT Shows Good Survival Rates In Michigan Study of Localized Prostate Cancer

MIAMI BEACH--Early-stage prostate cancer patients treated withthree-dimensional conformal radiotherapy (3D-CRT) at the Universityof Michigan Medical Center had excellent survival rates with fewcomplications, Howard Sandler, MD, reported at the American Societyfor Therapeutic Radiology and Oncology (ASTRO) meeting.

The use of 3D-CRT allows radiation oncologists to better focusthe radiation treatments to all angles of the prostate and thusgive higher radiation doses to the tumor while preserving normaltissues, Dr. Sandler said. The technique creates dose distributionsbased on anatomic data derived from computed tomography (see imageon page 1).

Dr. Sandler, associate professor and director of clinical programsat the Ann Arbor center, said that the study involved 707 patientswith localized prostate cancer treated with 3D-CRT. The mediantotal radiation dose was 69 Gy. Excluded from the study were patientswho 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-stagetumors) 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 survivalrate at 5 years. In the unfavorable group, only 22% were diseasefree at 5 years, emphasizing the importance of early detection,Dr. Sandler said. Five-year survival for the surgical group was83%.

"In addition to the excellent survival rates for favorablepatients, the complication rates for all patients in our studywere very low--3% or less," Dr. Sandler said. The risk ofgrade 4 complications was only 0.5%.

Preradiation PSA level proved to be the most critical predictorof treatment success, he said. At 5 years, those with preradiationPSA levels below 4 had an 87% disease-free survival rate; thosewith PSA levels between 4 and 10 had a 72% survival rate; PSA10 to 20, a 37% survival rate, and PSA greater than 20, a 26%survival rate.

In an interview with Oncology News International, Dr. Sandlerdescribed the work as a "benchmark study, showing where westand with this treatment at the University of Michigan."

NCI Study Underway

He noted that the National Cancer Institute is funding a phaseI/II dose-escalation study of 3D-CRT in prostate cancer patients.Currently underway at nine institutions, including the Universityof Michigan, and headquartered at Washington University in St.Louis, the study has enrolled about 125 patients to date.

Dr. Sandler added that since treatment with 3D-CRT appears tobe superior to conventional radiotherapy, phase III trials willprobably involve randomization between different doses of radiationdelivered via 3D conformal techniques rather than between 3D-CRTand conventional techniques.

Dr. Sandler's colleagues in the study were P. William McLaughlin,MD, and Kathleen Kish of the University of Michigan and ProvidenceHospital.