CyberKnife Stereotactic Radiotherapy as Monotherapy for Low- to Intermediate-Stage Prostate Cancer: Early Experience, Feasibility, and Tolerance
ABSTRACT The CyberKnife (CK), a linear accelerator mounted on a robotic device, enables excellent dose conformation to the target and minimizes dose to surrounding normal tissue. It is a very suitable device for performing hypofractionated stereotactic body radiotherapy as monotherapy for low- to intermediate-risk prostate cancer patients. We report our early experience using this technique.
Between June 2008 and June 2009, 10 patients underwent CK monotherapy as treatment for their prostate cancer (stage <or=T2b, Gleason score (GS) <or=7, initial PSA <or=15 microg/L). The prescribed dose was 38 Gy in four daily fractions of 9.5 Gy. The International Prostate Symptom Score and Radiation Therapy Oncology Group symptom scale were prospectively administered before and at 0.5, 1, 2, 3, 6, and 12 months.
Median age of the patients was 71 years (range, 66-76). Three patients had stage T2a and 7a T1c disease, one patient had GS of 7, and all others had GS of 6. Median follow-up was 5.1 months. Median initial PSA was 8.3 ng/mL (range, 1.3-13.6 ng/mL). Median planning target volume delineated on computed tomography after matching with the magnetic resonance imaging scan was 107 cc (range, 42-158 cc). The median V100 of the prostate was 95.8% (range, 94.8-97.2). The D95 of the prostate was 38.3 Gy (range, 38.1-38.8 Gy). The constraints for the bladder, rectum, and urethra were well met. The International Prostate Symptom Scores after 3 months were stable compared with the pretreatment scores. Urinary and bowel Radiation Therapy Oncology Group symptoms were mild and within the expected levels.
This regimen of stereotactic CK monotherapy for low- to intermediate-risk prostate cancer with excellent dose coverage of the prostate was well tolerated. Data collection is ongoing for further assessment of toxicity and PSA response.
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ABSTRACT: Stereotactic body radiation therapy (SBRT) combines the latest advancements in image guidance, planning, and treatment delivery to direct tumoricidal doses to the target. This is accomplished with acceptable sparing of normal tissues which was not practical or feasible with traditional techniques. Over the last decade, SBRT is evolving and in some areas has been established as the contemporary standard of care. This is especially the case in inoperable non-small cell lung cancers, where it has emerged as highly effective with successful results that have been reproduced around the world. Several other applications of SBRT require continued studies and careful design of additional prospective studies. The technique demands the latest developments in patient immobilization, dosimetry planning, and delivery of the intended dose to the target using near real-time imaging and precise assessment of expected tumor motion during the treatment. In addition, dosimetric parameters must spare a significant portion of functional subunits in the adjacent normal tissues. A careful consideration in selection of eligible patients cannot be stressed enough. Increased efficacy combined with convenient fractionation schedule remains highly attractive for patients. Long-term results with favorable outcomes with similar or reduced treatment-related morbidity will further accelerate the acceptance of SBRT.Technical Basis of Radiation Therapy, 01/2011: pages 363-400;
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ABSTRACT: Hypofractionated, stereotactic body radiotherapy (SBRT) is an emerging treatment approach for prostate cancer. We present the outcomes for low-risk prostate cancer patients with a median follow-up of 5 years after SBRT. Between Dec. 2003 and Dec. 2005, a pooled cohort of 41 consecutive patients from Stanford, CA and Naples, FL received SBRT with CyberKnife for clinically localized, low-risk prostate cancer. Prescribed dose was 35-36.25 Gy in five fractions. No patient received hormone therapy. Kaplan-Meier biochemical progression-free survival (defined using the Phoenix method) and RTOG toxicity outcomes were assessed. At a median follow-up of 5 years, the biochemical progression-free survival was 93% (95% CI = 84.7% to 100%). Acute side effects resolved within 1-3 months of treatment completion. There were no grade 4 toxicities. No late grade 3 rectal toxicity occurred, and only one late grade 3 genitourinary toxicity occurred following repeated urologic instrumentation. Five-year results of SBRT for localized prostate cancer demonstrate the efficacy and safety of shorter courses of high dose per fraction radiation delivered with SBRT technique. Ongoing clinical trials are underway to further explore this treatment approach.Radiation Oncology 01/2011; 6(1, article 3):3. DOI:10.1186/1748-717X-6-3 · 2.36 Impact Factor
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ABSTRACT: The aim of this study was to systematically analyse the effect of catheter displacements both on target coverage and normal tissue irradiation in fractionated high dose rate (HDR) prostate brachytherapy, using a simulation study, and to define tolerances for catheter displacement ensuring that both target coverage and normal tissue doses remain clinically acceptable. Besides the effect of total implant displacement, also displacements of catheters belonging to selected template rows only were evaluated in terms of target coverage and normal tissue dose, in order to analyse the change in dose distribution as a function of catheter dwell weight and catheter location. Five representative implant geometries, with 17 catheters each, were selected. The clinical treatment plan was compared to treatment plans in which an entire implant displacement in caudal direction over 3, 5, 7 and 10 mm was simulated. Besides, treatment plans were simulated considering a displacement of either the central, most ventral or most dorsal catheter rows only, over 5 mm caudally. Due to displacement of the entire implant the target coverage drops below the tolerance of 93% for all displacements studied. The effect of displacement of the entire implant on organs at risk strongly depended on the patient anatomy; e.g., for 80% of the implant geometries the V(80) of the rectum exceeded its tolerance for all displacements. The effect of displacement of catheters belonging to selected template rows depended strongly on the relative weight of each catheter row when considering the target coverage and on its location when considering the dose in the organs at risk. This study supports the need for a check of the catheter locations before each fraction and correction of deviations of the catheter position exceeding 3mm.Radiotherapy and Oncology 02/2011; 98(2):192-7. DOI:10.1016/j.radonc.2010.12.009 · 4.86 Impact Factor