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Radiother Oncol. 2016 Jan;118(1):112-7. doi: 10.1016/j.radonc.2015.12.020. Epub 2016 Jan 12.

Dose-escalation of five-fraction SABR in prostate cancer: Toxicity comparison of two prospective trials.

Author information

1
Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Canada; Department of Radiation Oncology, University of Toronto, Canada.
2
Department of Radiation Oncology, CancerCare Manitoba, Canada.
3
Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Canada; Department of Medical Physics, Odette Cancer Centre, Canada.
4
MacroStat, Inc, Toronto, Canada.
5
Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Canada.
6
Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Canada; Department of Radiation Oncology, University of Toronto, Canada; Institute of Health Policy, Measurement and Evaluation, University of Toronto, Canada. Electronic address: andrew.loblaw@sunnybrook.ca.

Abstract

PURPOSE:

To compare biochemical outcome and toxicities of two prospective 5-fraction stereotactic ablative radiotherapy (SABR) studies in prostate cancer.

MATERIALS AND METHODS:

84 patients in pHART3 received 35 Gy, 30 patients in pHART6 received 40 Gy in 5-fractions to the prostate alone, once weekly. 4mm and 5mm PTV margins were used, respectively. Biochemical outcome, acute, late and cumulative genitourinary (GU)/gastrointestinal (GI) toxicities were compared.

RESULTS:

Median follow-up was 74 and 36 months, respectively. Median prostate specific antigen nadir was 0.4 ng/ml and 0.3 ng/ml. 2-, 4- and 6-year biochemical relapse-free survival (bRFS-2+nadir) was 100%, 98.7% and 95.9% in pHART3; 100%, 100% and not reached in pHART6 (p=0.91). There was one acute grade 3 GU (retention) and late grade 4 GI (fistula) toxicity in pHART3, none in pHART6. One patient in each study had persisting grade 2+ toxicity at the last follow-up. pHART6 patients had a greater grade 2+ cumulative GU (5% versus 24.2%) and GI (7.6% versus 26.2%) toxicities.

CONCLUSIONS:

Patients receiving dose-escalated SABR had slightly lower PSA nadir and similar bRFS, longer follow-up is needed to better estimate biochemical outcomes. There was a greater risk of grade 2 toxicity in pHART6 but not grade 3+ toxicities. Persisting toxicity at the last follow-up is similar.

KEYWORDS:

Image-guided radiotherapy; Prostate cancer; Stereotactic ablative radiotherapy; Toxicity

PMID:
26796591
DOI:
10.1016/j.radonc.2015.12.020
[Indexed for MEDLINE]

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