An earlier thread started on 1/12/2011 informed us of impressive results from a study with five year average (median) follow-up ("CyberKnife - 5 year results). Tall Allen wrote that Dr. King, the lead author had told him that 80% of the men in the study had had no ED, an unusually high level of success. However, that success was not documented specifically either in the abstract of the study or in the complete paper, which used more general terms regarding "rectal" and "genetourinary" toxicity.
Now we have some written documentation from two other doctors, Katz and Santoro, who reported their results in Poster Abstract #88 for prostate cancer at the Genitourinary Cancer Symposium, currently in session, sponsored by ASCO (American Society of Clinical Oncology).
With a median 48 months of follow-up (range of follow-up 46 to 53 months) on 42 low-risk and 8 intermediate-risk patients, the projected 48 month rate for grade 2 (moderate) genetourinary side effects were 95.5%
, and the rate for freedom from rectal toxicity was 97.8%!
There were no side effects higher than grade 3. Moreover, "Of the 36 patients that were potent prior to treatment 29 (80.5%) maintained potency."
That is especially impressive as the average age at time of treatment in the whole study was 69.5 years; four years later, 80.5% were still potent, with an average age probably in the 70s. Katz and Santoro also documented excellent success in controlling cancer at the four year point: with 3 of the 50 patients dying due to other causes, only 1 of the remaining 47 patients experienced a recurrence.
Freeman and King, authors of the earlier paper with five year results, also presented a poster abstract, #94, which recapped their paper. (A complete free copy of the entire paper is available via a link provided with the abstract on www.pubmed.gov.)
A third abstract, "CyberKnife for prostate cancer: Is cost-effective?", #87, by A. Parthan, N. Pruttivarasin, ... C. Weinstein, looked at the cost of CK, IMRT, surgery and proton therapy, also considering cost per quality year of life. The concluded that "Initial CK costs are higher than surgery, but CK patients have better quality of life. CK patients have lower lifetime costs and higher QALYs [Quality Adjusted Life Years] than IMRT and PT patients." I'm always skeptical of such models until I've seen the details, and I lack professional skill in evaluating them, but I'll accept this as at least one indicator that CK SBRT is a low-cost leader.
I'm thinking that well-done brachytherapy and IMRT have recorded such outstanding results over long periods, in excess of ten years, that they will have staying power despite the likely strong emergence of SBRT.
However, proton therapy, with its far higher cost, so far inferior success in avoiding recurrence compared with CyberKnife SBRT, brachy, IMRT, and brachy/IMRT combo, and lack of superiority in avoiding side effects, is likely to come under heavy unfavorable scrutiny by patients and the health care system.
Maybe that will finally persuade the proton physicians/researchers to publish updated results, which are long overdue.
It will be nice to eventually have ten year SBRT data for reassurance, but the success rates for radiation at five years are typically quite stable for following years. The five year data from Freeman and King on cancer control success plus general side effect results, and the Katz and Santoro results give us a solid basis for confidence.