High Doses of Stereotactic Body Radiotherapy for Patients With Organ-Confined Prostate Cancer Shows High Relapse-Free Survival

Patients Now Have an Alternative to Lengthy and Expensive Treatments and Surgery

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| Source: American Society for Radiation Oncology

BOSTON, Oct. 30, 2012 (GLOBE NEWSWIRE) -- Patients with organ-confined prostate cancer have new treatment options using high doses of focused stereotactic body radiotherapy (SBRT) instead of traditional lengthy treatment courses or surgery, according to research presented today at the American Society for Radiation Oncology's (ASTRO's) 54th Annual Meeting.

The first long-term study of prostate stereotactic body radiotherapy with a large number of patients evaluated the biochemical relapse-free survival (bRFS) rates over a five-year period for patients with organ-confined prostate cancer. The findings show that prostate cancer is very sensitive to a higher, targeted dose of radiation rather than more frequent lower doses over time, which means that patients now have a viable option of choosing a one-week course of therapy as opposed to an eight- or nine-week course of treatment. The study evaluated low-, intermediate- and high-risk patients, who showed actuarial disease-free survival rates of 95 percent, 90 percent and 80 percent, respectively, after five years.

The study included 1,101 patients from eight institutions who were treated with focused stereotactic body radiotherapy between 2003 and 2011. All patients received CyberKnife stereotactic body radiotherapy, and the median dose was 36.25 Gy (35-40 Gy range) delivered either with four or five fractions; this is equivalent to a range of 90-112 Gy in conventional fractionation, assuming an alpha/beta ratio of 1.5 Gy. Patients were segmented into low-, intermediate- and high-risk categories, comprised of 59 percent, 30 percent and 11 percent, respectively, in each group. For low- and intermediate-risk cases, these results compare favorably with other modalities at five years. High-risk cases also appear to do very well although the results for this subset of patients are preliminary due to the small number of patients with five-year follow-up. The median follow-up for all cases was 36 months (range one to 66). Biochemical relapse, defined as a rise greater than 2 ng/ml above nadir, was determined in a total of 49 patients, nine of whom had a resolution of the rise and showed no clinical signs of a relapse. Additionally, androgen deprivation therapy was given to 146 patients and appeared to make no difference in the outcome of biochemical relapse.

"Therapy options for patients with organ-confined prostate cancer can be time consuming and costly with traditional radiotherapy methods," said Alan Katz, MD, JD, lead author of the study and a radiation oncologist at Flushing Radiation Oncology in Flushing, N.Y. "We found that higher doses of stereotactic radiotherapy with fewer fractions yielded great results in terms of tumor control. Our results show that additional standard radiation treatment added to SBRT is probably unnecessary, even with high-risk patients."

Organizations who participated in the study include Flushing Radiation Oncology in Flushing, N.Y.; Cyberknife Center of Tampa Bay in Tampa, Fla.; Beth Israel Deaconess Medical Center in Boston; Cyberknife Centers of San Diego; San Bortolo Hospital in Vicenza, Italy; Swedish Medical Center in Seattle; Georgetown University Hospital in Washington; and UCLA Medical Center in Los Angeles.

The abstract, "Five-year Biochemical Control Rates for Stereotactic Body Radiotherapy for Organ Confined Prostate Cancer: A Multi-institutional Pooled Analysis," will be presented during ASTRO's 54th Annual Meeting at 1:30 p.m. Eastern time on Wednesday, October 31, 2012. To speak with Dr. Katz, call Michelle Kirkwood on October 28 – 31, 2012, in the ASTRO Press Office at the Boston Convention and Exhibition Center at 617-954-3461 or 617-954-3462, or email michellek@astro.org.

ASTRO's 54th Annual Meeting, held in Boston, October 28 – 31, 2012, is the premier scientific meeting in radiation oncology and brings together more than 11,000 attendees including oncologists from all disciplines, medical physicists, dosimetrists, radiation therapists, radiation oncology nurses and nurse practitioners, biologists, physician assistants, practice administrators, industry representatives and other health care professionals from around the world. The theme of the 2012 Annual Meeting is "Advancing Patient Care through Innovation" and examines how innovation in technology and patient care delivery can lead to improved patient outcomes. The four-day scientific meeting includes six plenary papers and 410 oral presentations in 63 oral scientific sessions, and 1,724 posters and 130 digital posters in 18 tracks/topic areas.

ABOUT ASTRO

ASTRO is the largest radiation oncology society in the world, with more than 10,000 members who specialize in treating patients with radiation therapies. As the leading organization in radiation oncology, biology and physics, the Society is dedicated to improving patient care through education, clinical practice, advancement of science and advocacy. For more information on radiation therapy, visit www.rtanswers.org. To learn more about ASTRO, visit www.astro.org.
 
2012 American Society for Radiation Oncology (ASTRO) 54th Annual Meeting
News Briefing, Tuesday, October 30, 3:15 p.m. – 4:00 p.m. Eastern time

Scientific Session: Wednesday, October 31, 2012, 1:30 – 3:00 p.m. Eastern time, Boston Convention & Exhibition Center

365 Five-year Biochemical Control Rates for Stereotactic Body Radiotherapy for Organ Confined Prostate Cancer: A Multi-institutional Pooled Analysis

A. Katz1, D. Freeman2, J. Aronovitz3, D. Fuller4, G. Bolzicco5, R. Meier6, S. Collins7, J. Wang8, M. Steinberg8, C. King8, 1Flushing Radiation Oncology, Flushing, NY, 2Cyberknife Center of Tampa Bay, Tampa, FL, 3Beth Israel Deaconess Medical Center, Boston, MA, 4Cyberknife Centers of San Diego, San Diego, CA, 5San Bortolo Hospital, Vicenza, Italy, 6Swedish Medical Center, Seattle, WA, 7Georgetown University Hospital, Washington, DC, 8UCLA Medical Center, Los Angeles, CA

Purpose/Objective(s): To report the 5-year biochemical relapse-free survival (bRFS) rates from a pooled multi-institutional dataset of a large number of localized prostate cancer patients treated with stereotactic body radiotherapy (SBRT).

Materials/Methods: The outcome data from 1101 patients with localized adenocarcinoma of the prostate were pooled from 8 institutions. Patients were treated between 2003 and 2011. The distribution by stage was 92% T1-2a and 8% T2b-3. The distribution by Gleason score (GS) was 72% Gleason 6, 20% Gleason 7 and 8% Gleason 8-10. The distribution by risk(NCCN) was 59% low, 30% intermediate and 11% high-risk. Median baseline PSA was 5.4 ng/ml; 88% of PSAs were less than 10 ng/ml, 10% were 10-20 ng/ml and 2% were more than 20 ng/ml. All patients had CyberKnife SBRT as the radiotherapeutic modality. The median dose was 36.25 Gy (35-40 Gy range) delivered either with 4 or 5 fractions; this is equivalent to a range of 90-112 Gy in conventional fractionation, assuming an alpha/beta ratio of 1.5 Gy. In most cases, the PTV was the GTV expanded by 5mm, 3mm posteriorly; 2 mm of this was to account for errors in target definition and delivery. Androgen deprivation therapy was given to 146 (14%) patients. Biochemical relapse, defined as a rise more than 2 ng/ml above nadir, was determined in a total of 49 patients. Of the 49, 9 had resolution of the rise (i.e. the less than 2 ng/ml rise was a large bounce). However, outcome analyses were performed on all 49 cases; no cases were excluded.

Results: The median follow-up for all 1101 cases was 36 months (range 1 to 66). For all patients, the biochemical relapse-free actuarial survival (bRFS) rate at 5 years was 93%. The 5-year actuarial bRFS rates for Gleason score less than 6, Gleason score 7 and Gleason score more than 8 were 95%, 83% and 78%, respectively (p=0.001). The 5-year actuarial bRFS rates for iPSA less than 4, iPSA 4-10, iPSA 10-20, and iPSA greater than 20 were 96%, 94%, 82% and 73%, respectively (p=0.001). The 5-year actuarial bRFS rates for low-, intermediate- and high-risk patients were 95%, 90%, and 80%, respectively (p less than 0.001). No difference in bRFS was observed with the use of androgen deprivation (p=0.76). A PSA bounce of more than 0.20 ng/ml was observed in 16% of the patients at a median of 36 months (range 6-60). The median bounce magnitude was 0.505 ng/ml (range 0.2-5.29). For the 335 cases with a minimum of 4 years of follow-up (median 53 months), the 5-year bRFS rates for low- and intermediate-risk cases were 97% and 89%, respectively.

Conclusion: With a large cohort of patients treated with stereotactic body radiotherapy, with a reasonably long followup period, excellent efficacy was demonstrated at 5 years. For high risk cases, the results are preliminary, given the small number of cases treated. However, for low and intermediate risk cases, these results compare favorably with other modalities. These results support a low alpha beta ratio for prostate cancer.

Author Disclosure Block: 
A. Katz: F. Honoraria; Accuray. D. Freeman: F. Honoraria; Accuray. J. Aronovitz: None. D. Fuller: None. G. Bolzicco: None. R. Meier: None. S. Collins: G. Consultant; Accuray. J. Wang: None. M. Steinberg: None. C. King: None.

Michelle Kirkwood, 703-286-1600,