Cyberknife results

[Guest guest]

Update of Cyberkife results for 304 patients at one facility.

Free full pdf of paper available at: http://www.biomedcentral.com/content/pdf/1471-2490-10-1.pdf

The Best to You and Yours!

Jon in Nevada

Stereotactic body radiotherapy for organ-confined prostate cancer - Abstract BMC Urol. 2010 Feb 1;10(1):1. Katz AJ, Santoro M, R, Diblasio F, Witten M

Improved understanding of prostate cancer radiobiology combined with advances in delivery of radiation to the moving prostate offer the potential to reduce treatment-related morbidity and maintain quality of life (QOL) following prostate cancer treatment.

We present preliminary results following stereotactic body radiotherapy (SBRT) treatment for organ-confined prostate cancer.

SBRT was performed on 304 patients with clinically localized prostate cancer: 50 received 5 fractions of 7 Gy (total dose 35 Gy) and 254 received 5 fractions of 7.25 Gy (total dose 36.25 Gy). Acute and late toxicity was assessed using the Radiation Therapy Oncology Group scale. The Expanded Prostate Cancer Index Composite questionnaire was used to assess QOL. Prostate-specific antigen response was monitored.

At a median 30-month (26 - 37 month, range) follow-up there were no biochemical failures for the 35-Gy dose level. Acute Grade II urinary and rectal toxicities occurred in 4% of patients with no higher Grade acute toxicities. One Grade II late urinary toxicity occurred with no other Grade II or higher late toxicities. At a median 17-month (8 - 27 month, range) follow-up the 36.25 Gy dose level had 2 low- and 2 high-risk patients fail biochemically (biopsy showed 2 low- and 1 high-risk patients were disease-free in the gland). Acute Grade II urinary and rectal toxicities occurred in 4.7% (12/253) and 3.6% (9/253) of patients, respectively. For those patients with a minimum of 12 months follow-up, 5.8% (12/206) had late Grade II urinary toxicity and 2.9% (6/206) had late Grade II rectal toxicities. One late Grade III urinary toxicity occurred; no Grade IV toxicities occurred. For both dose levels at 17 months, bowel and urinary QOL returned to baseline values; sexual QOL decreased by 10%.

The low toxicity and maintained QOL are highly encouraging. Additional follow-up is needed to determine long-term biochemical control and maintenance of low toxicity and QOL.

PubMed Abstract PMID:20122161

--------------------------------------------------------------------------Beyond the Abstract - Stereotactic body radiotherapy for organ-confined prostate cancer, by Alan J. Katz, MD, JD Katz AJOur paper reports on the largest series of patients treated with CyberKnife® for prostate cancer at one institution.

In the year since we compiled the data, we have continued to be encouraged by the efficacy and toxicity profile. We still have not seen a local failure in the low or intermediate risk patients, with our early group treated with 35gy having a median followup of 42 months. For two reasons, we have decreased our dose back from 36.25 Gy to 35 Gy. First, 35 Gy has been very effective, with a 36 month median PSA of 0.15, which is highly predictive of excellent long-term control according to the literature. Secondly, our 36.25 group did experience a small increase in the rate of Grade2-3 urethral toxicity.This is predictable based on the radiobiology. If the alpha-beta ratio for prostate cancer is 1.5 (that is, prostate cancer cells are highly sensitive to dose per fraction), then 35Gy in 5 fractions is the equivalent of 92 Gy in 1.8Gy fractions. This dose is on the flat part of the dose response curve, and therefore dose escalation is not necessary to maximize control. The alpha beta ratio for late complications is probably around 3, and therefore the 35Gy dose is in the 70-75 Gy range for late complications. Therefore, I believe we are on the steep part of the dose response curve for complications and the 3% increase in the dose to 36.25 predictably increased toxicity in the urethra by bringing us to almost 80 GY dose equivalent. Adjusting the dose down should and does reduce late toxicity.

We did not see a concomitant increase in rectal toxicity, probably because we spared the rectal tissues with the conformality achieved with CyberKnife® technology, and we used the radioprotector Amifostine intrarectally prior to each fraction. Our potency preservation remains at 80%.

I am especially encouraged by our excellent results with intermediate and high risk disease with CyberKnife® alone. I will be publishing a series of patients who received a CyberKnife® boost after 45Gy to the pelvis for this category. There appears to be no benefit to adding the external beam in terms of efficacy and there is slightly greater rectal toxicity. If CyberKnife® alone is optimal treatment, this will afford a wide range of prostate cancer patients the chance to reduce their treatments from 45 to 5. This would be a huge benefit to older patients, especially those that have to travel long distances for radiation therapy. In addition, there is a great cost benefit to society. Medicare reimbursement for a five day CyberKnife® treament is less than IMRT and a small fraction of the cost of Proton beam therapy.

I believe that my series and the other two series, from Naples and Stanford, provides substantial early evidence that this dose fractionation scheme is highly effective and safe when delivered with CyberKnife® technology. Since my PSA nadirs are so low, I am very optimistic that our data will hold up with more follow up over time. It should be time for those who claim this treatment to be experimental to soften their position. To date, no form of radiotherapy has been compared to another with a prospective randomized trial. Therefore, I do not believe this to be necessary before offering patients the option of CyberKnife®. However,I would welcome such a trial against IMRT,protons or brachytherapy.