Katz and Kang
have posted their 9-year SBRT outcomes on 515 patients. This represents the
longest tracking of SBRT outcomes -- just one year short of the IMRT tracking
reported by Alicikus et al. on a starting cohort of 170 patients treated at Memorial Sloan
Kettering Cancer Center.
The patients were treated between 2006-2010 using the CyberKnife
platform.
- · 324 were low risk, 139 intermediate risk, and 52 were high risk according to NCCN definitions.
- · 70 patients received adjuvant ADT for up to one year.
- · 158, all with Gleason score<4+3, received 35 Gy in 5 fractions.
- · 357 received 36.25 Gy in 5 fractions
- · Median age was 69
- · Median PSA was 6.5 ng/ml
After a median followup of 84 months:
- · Oncological Control:
o 9-yr
freedom from biochemical failure was:
§
95% for low-risk men
§
89% for intermediate risk men
§
66% for high-risk men
o Median
PSA nadir was .1 ng/ml
o No
difference in biochemical control for the lower vs. the higher radiation dose.
o 99.6%
prostate cancer survival
o 86%
overall survival
- · Toxicity:
o Late
rectal toxicity:
§
Grade 2: 4%
o Late
urinary toxicity:,
§
Grade 2: 9.5%
§
Grade 3: 1.9%
§
Grade 2 or 3: 6.9% for the lower radiation dose
vs. 13.2% for the higher dose.
o Patient-reported
bowel and urinary quality-of-life (EPIC questionnaire) declined at one month
then returned to baseline by 2 years. Sexual quality-of-life declined by 29% at
last followup.
These are clearly excellent results for any kind of radical
therapy. The authors conclude:
“These long-term results appear superior to standard IMRT with
lower cost and are strikingly similar to HDR therapy.”
While it’s
tempting to conclude that neither the higher dose of radiation, with its
greater toxicity, nor the addition of ADT conferred any incremental benefit,
that can only be proved with a randomized clinical trial. Until so proven, it
must be understood as only a good hypothesis to be discussed by patients with
their radiation oncologists. It is also worth noting that these reflect the outcomes
of one very expert practitioner. There is an SBRT registry currently collecting
data across many treatment centers.
The reported
outcomes are nearly identical to those reported at 7 years (see this link and this link and this link), indicating very stable control and no additional late term
toxicity with longer followup. In light of that, its low cost, convenience, and
the fact that the standard of care, IMRT, has only one more year of follow-up on
a much smaller sample size, it’s difficult to understand why some insurance
companies still balk at covering SBRT for low and intermediate risk patients.
Medicare does cover it.
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