Adjuvant Radiation Shows Promise for High-Risk Radical Prostatectomy Patients

Stephanie Doyle

May 20, 2008

May 20, 2008 (Orlando, Florida) — Adjuvant therapy increases the likelihood of cure in patients undergoing radical prostatectomy and should be offered to all high-risk postprostatectomy patients, according to the findings presented here at the American Urological Association 2008 Annual Meeting.

Adjuvant radiation significantly reduces the risk for biochemical recurrence in men with advanced (pT3) disease, according to the latest data from Southwest Oncology Group trial 8794, a significant, long-term study.

"This is an answer we've been waiting for for a very long time," presenter Gregory P. Swanson, MD, associate professor of radiation oncology, urology and radiology at the University of Texas Health Science Center at San Antonio, told Medscape Urology.

The randomized study hypothesized that adjuvant radiotherapy improves disease-free survival in patients with surgical stage C (T3N0M0) carcinoma of the prostate. The primary end point was metastasis-free survival.

"We asked ourselves, for high-risk patients after surgery, can we do something more?" Dr. Swanson said. "The benefit of radiation after surgery is not a new concept for oncologists — it's a new concept for urologists. But the long-term benefit was unknown. The only way to answer this was a randomized study."

Eligible patients had clinical stage A or B (T1 or T2) cancer confined to the prostate, or clinical stage C (T3N0M0) cancer outside the prostate, with at least 1 of the following factors: seminal vesicle involvement, cancer inked surgical margin, or extension beyond prostatic capsule. Patients were randomized within 16 weeks of surgery.

Of the 431 patients enrolled, 425 were eligible. Half the eligible patients (n = 214) were given radiation and half (n = 211) received no treatment. The untreated group consisted of 67% white and 20% African American men, and had a median age of 65.8 years. The group receiving treatment had a median age of 64.1 years and was 72% white and 19% African American.

The primary end point was positive. Radiation significantly reduced recurrence by all parameters and increased metastatic disease-free and overall survival. At 15 years out, metastasis-free survival was 49% in the treated group and 40% in the untreated group (P = 0.021).

"But that's not all," Dr. Swanson said. "With the survival curve, the P value was .031 and, at 15 years, 50% of radiation of patients had survived," compared with 39% of the untreated group.

At 10 years, the percentage of those who did not have a relapse in PSA levels was 52% in the treated group and 26% in the untreated group. "Radiation really pushed that back," Dr. Swanson said.

Any downsides — the long-term effects of radiation — are minor, such as urinary and rectal irritation, which seem to improve over time, and a possible increase in urinary leakage or scarring, Dr. Swanson said.

Brantley Thrasher, MD, chairman of the department of urology at the University of Kansas, in Lawrence, who was not involved with the study, cautioned physicians who learn about the successes of adjuvant radiation not to overtreat patients.

"People are asking about how pragmatic it is to treat everyone,'' Dr. Thrasher said. "Why not wait on a very low-level PSA bump? That is always going to be an argument on [trial] 8794."

With 30% to 40% of patients, the cancer won't recur — without any treatment, said Dr. Thrasher, who recommended waiting for that slight "bump" in PSA before treatment. "These are compelling data, don't get me wrong, but I am not treating everyone," he said.

But Ian M. Thompson, MD, lead investigator and chair of the department of urology at the University of Texas Health Science Center at San Antonio, called the study findings a "homerun."

"To improve survival by almost 2 years is extreme," Dr. Thompson told Medscape Urology. "This is really a remarkably big deal."

Funding was provided by a grant from the National Cancer Institute. The researchers have disclosed no relevant financial relationships.

American Urological Association (AUA) 2008 Annual Meeting. Presented May 20, 2008.


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