M.R. Witten

Stereotactic Body Radiotherapy as Boost for Organ-confined Prostate Cancer

Stereotactic body radiotherapy (SBRT) boost following external beam radiation therapy (EBRT) for advanced localized prostate cancer may reduce toxicity while escalating the dose. We present preliminary biochemical control and urinary, rectal and sexual toxicities for 73 patients treated with SBRT as a boost to EBRT. Forty-one intermediate- and 32 high-risk localized prostate cancer patients received 45 Gy EBRT with SBRT boost. Twenty-eight patients (38.3%) received a total SBRT boost dose of 18 Gy (3 fractions of 6 Gy), 28 patients (38.3%) received 19.5 Gy (3 fractions of 6.5 Gy), and 17 patients (23.2%) received 21 Gy (3 fractions of 7 Gy). Toxicity was assessed using the Radiation Therapy Oncology Group urinary and rectal toxicity scale. Biochemical failure was assessed using the Phoenix definition. The median follow-up was 33 months (range, 22 − 43 months). Less than 7% Grade II and no higher grade acute toxicities occurred. To date, one Grade III and no Grade IV late toxicities occurred. For the 97% of patients with 24 months minimum follow-up, 71.8% achieved a PSA nadir threshold of 0.5 ng/mL. Three intermediate-risk and seven high-risk biochemical failures occurred; one high-risk patient died of his cancer. Three-year actuarial biochemical control rates were 89.5% and 77.7% for intermediate- and high-risk patients, respectively. SBRT boost for prostate cancer treatment is safe and feasible with minimal acute toxicity. At 33 months late toxicity and biochemical control are promising. Long-term durability of these findings remains to be established.

CyberKnife boost for patients with cervical cancer unable to undergo brachytherapy

Standard radiation therapy for patients undergoing primary chemosensitized radiation for carcinomas of the cervix usually consists of external beam radiation followed by an intracavitary brachytherapy boost. On occasion, the brachytherapy boost cannot be performed due to unfavorable anatomy or because of coexisting medical conditions. We examined the safety and efficacy of using CyberKnife stereotactic body radiotherapy (SBRT) as a boost to the cervix after external beam radiation in those patients unable to have brachytherapy to give a more effective dose to the cervix than with conventional external beam radiation alone. Six consecutive patients with anatomic or medical conditions precluding a tandem and ovoid boost were treated with combined external beam radiation and CyberKnife boost to the cervix. Five patients received 45 Gy to the pelvis with serial intensity-modulated radiation therapy boost to the uterus and cervix to a dose of 61.2 Gy. These five patients received an SBRT boost to the cervix to a dose of 20 Gy in five fractions of 4 Gy each. One patient was treated to the pelvis to a dose of 45 Gy with an external beam boost to the uterus and cervix to a dose of 50.4 Gy. This patient received an SBRT boost to the cervix to a dose of 19.5 Gy in three fractions of 6.5 Gy. Five percent volumes of the bladder and rectum were kept to ≤75 Gy in all patients (i.e., V75 Gy ≤ 5%). All of the patients remain locally controlled with no evidence of disease following treatment. Grade 1 diarrhea occurred in 4/6 patients during the conventional external beam radiation. There has been no grade 3 or 4 rectal or bladder toxicity. There were no toxicities observed following SBRT boost. At a median follow-up of 14 months, CyberKnife radiosurgical boost is well tolerated and efficacious in providing a boost to patients with cervix cancer who are unable to undergo brachytherapy boost. Further follow-up is required to see if these results remain durable.

Cyberknife radiosurgery in treating trigeminal neuralgia

Purpose To assess the short term efficacy of Cyberknife stereotactic radiosurgical treatment of trigeminal neuralgia (TN). Methods 17 consecutive patients with medically or surgically refractory unilateral TN were treated with Cyberknife radiosurgery. Using superimposed CT cisternogram and MR images, the target segment of the trigeminal nerve was consistently defined as a 6 mm length of nerve approximately 2–3 mm distal to the dorsal root entry zone of the brainstem. A radiosurgical rhizotomy was performed with the Cyberknife utilizing a single collimator to deliver an average maximum dose of 73.06 Gy (range 72.91–73.73) to the target. Results Follow-up data were available for 16 of the 17 patients post-treatment (range 1–27 months, average 11.8 months). Overall, 14 of 16 (88%) patients responded favorably with either partial or complete relief of symptomatology. 11 of these patients were successfully free of all pain at some point in their post-treatment course, with seven patients pain free to the last follow-up visit (average 5.0 months, range 1–13 months). Symptoms recurred in four patients, taking place at 3, 7.75, 9 and 18 months after Cyberknife therapy. Only two patients reported side effects. One patient developed a bothersome feathery dysesthesia while the second patient reported a non-bothersome mild jaw hypoesthesia. There were no substantial complications related to stereotactic radiosurgery. Conclusion Cyberknife radiosurgery is a viable treatment alternative in patients with TN with competitive efficacy demonstrated in our group of patients while minimizing adverse effects.

Prostate-Specific Antigen Bounce Following Stereotactic Body Radiation Therapy for Prostate Cancer

Introduction: Prostate-specific antigen (PSA) bounce after brachytherapy has been well-documented. This phenomenon has also been identified in patients undergoing stereotactic body radiation therapy (SBRT). While the parameters that predict PSA bounce have been extensively studied in prostate brachytherapy patients, this study is the first to analyze the clinical and pathologic predictors of PSA bounce in prostate SBRT patients. Materials and Methods: Our institution has maintained a prospective database of patients undergoing SBRT for prostate cancer since 2006. Our study population includes patients between May 2006 and November 2011 who have at least 18 months of follow-up. All patients were treated using the CyberKnife treatment system. The prescription dose was 35–36.25 Gy in five fractions. Results: One hundred twenty patients were included in our study. Median PSA follow-up was 24 months (range 18–78 months). Thirty-four (28%) patients had a PSA bounce. The median time to PSA bounce was 9 months, and the median bounce size was 0.50 ng/mL. On univariate analysis, only younger age (p = 0.011) was shown to be associated with an increased incidence of PSA bounce. Other patient factors, including race, prostate size, prior treatment by hormones, and family history of prostate cancer, did not predict PSA bounces. None of the tumor characteristics studied, including Gleason score, pre-treatment PSA, T-stage, or risk classification by NCCN guidelines, were associated with increased incidence of PSA bounces. Younger age was the only statistically significant predictor of PSA bounce on multivariate analysis (OR = 0.937, p = 0.009). Conclusion: PSA bounce, which has been reported after prostate brachytherapy, is also seen in a significant percentage of patients after CyberKnife SBRT. Close observation rather than biopsy can be considered for these patients. Younger age was the only factor that predicted PSA bounce.

A Retrospective Review of CyberKnife Stereotactic Body Radiotherapy for Adrenal Tumors (Primary and Metastatic): Winthrop University Hospital Experience

The adrenal gland is a common site of cancer metastasis. Surgery remains a mainstay of treatment for solitary adrenal metastasis. For patients who cannot undergo surgery, radiation is an alternative option. Stereotactic body radiotherapy (SBRT) is an ablative treatment option allowing larger doses to be delivered over a shorter period of time. In this study, we report on our experience with the use of SBRT to treat adrenal metastases using CyberKnife technology. We retrospectively reviewed the Winthrop University radiation oncology data base to identify 14 patients for whom SBRT was administered to treat malignant adrenal disease. Of the factors examined, the biological equivalent dose (BED) of radiation delivered was found to be the most important predictor of local adrenal tumor control. We conclude that CyberKnife-based SBRT is a safe, non-invasive modality that has broadened the therapeutic options for the treatment of isolated adrenal metastases.

Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer: A Small Academic Hospital Experience

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has been shown to have increased local control and overall survival relative to conventional external beam radiation therapy in patients with medically inoperable stage I non-small cell lung cancer (NSCLC). Excellent rates of local control have been demonstrated both in clinical trials and in single-center studies at large academic institutions. However, there is limited data on the experiences of small academic hospitals with SBRT for stage I NSCLC. The purpose of this study is to report the local control and overall survival rates in patients treated with SBRT for stage I NSCLC at Winthrop-University Hospital (WUH), a small academic hospital. Materials/Methods: This is a retrospective review of 78 stage I central and peripheral NSCLC tumors treated between December 2006 and July 2012 with SBRT at WUH. Treatment was given utilizing fiducials and a respiratory tracking system. If the fiducials were not trackable, a spine tracking system was used for tumor localization. CT-based planning was performed using the ray trace algorithm. Treatment was delivered over consecutive days to a median dose of 4800 cGy delivered in four fractions. The Kaplan–Meier method was used to calculate local control and overall survival. Results: The median age was 78.5 years. Fifty-four percent of the patient population was female. Sixty seven percent of the tumors were stage IA, and 33% of the tumors were stage IB. Fifty-three percent of the tumors were adenocarcinomas and 29% were squamous cell carcinomas, with the remainder being of unknown histology or NSCLC, not otherwise specified The 2-year local control rate was 87%, and the 2-year overall survival was 68%. Conclusion: Our findings support that local control and overall survival at a small academic hospital are comparable to that of larger academic institutions’ published experiences with SBRT for stage I NSCLC.

A memetic algorithm for dosimetric optimization in CyberKnife robotic radiosurgical treatment planning

A memetic algorithm is proposed for optimizing beam weights for robotic radiosurgical treatments delivered via the CyberKnife (Accuray, Inc., Sunnyvale, CA) system. The fitness function includes terms representing the tumor as well as terms representing organs-at-risk, and is of a quadratic form. Optimization involves inverse treatment planning, during which a set of beam weights is sought such that the user-specified radiation dose distribution is produced by the optimized ensemble of beam weights; the dose to the tumor is maximized, while the doses to the critical structures are minimized. In the present study, four distinct CT data sets for patients with carcinoma of the prostate were used to generate eight treatment plans, so that for each data set, a hypofractionated treatment plan (5 fractions) was created, as well as a treatment plan for a standard protracted dose fractionation schedule (38 fractions). In all cases, the memetic algorithm produced a treatment plan satisfying all clinical criteria in optimization times of 22–46 minutes.

An evolutionary algorithm for optimization of affine transformation parameters for dose matrix warping in patient-specific quality assurance of radiotherapy dose distributions

Patient-specific quality assurance for sophisticated treatment delivery modalities in radiation oncology, such as intensity-modulated radiation therapy (IMRT), necessitates the measurement of the delivered dose distribution, and the subsequent comparison of the measured dose distribution with that calculated by the treatment planning software. The degree to which the calculated dose distribution is reproduced upon delivery is an indication that the treatment received by the patient is acceptable. A new method for the comparison between the planned and delivered dose distributions is introduced; it assesses the agreement between planar two-dimensional dose distributions. The method uses an evolutionary algorithm to optimize the parameters of the affine transformation, consisting of translation, rotation, and dilation (or erosion), that will warp the measured dose distribution to the planned dose distribution. The deviation of the composite transformation matrix from the identity matrix is an indication of an average geometrical error in the delivered dose distribution, and represents a systematic error in dose delivery. The residual errors in radiation dose at specific points are local errors in dose delivery. The method was applied to IMRT fields consisting of horizontal intensity bands. Analysis shows the method to be a promising tool for patient-specific quality assurance.

MP05-18 PROSTATE FIDUCIAL MARKER PLACEMENT IN PATIENTS WHILE ON ANTICOAGULATION: FEASIBILITY PRIOR TO PROSTATE SBRT

Objectives: Fiducial marker placement is required in patients undergoing robotic-based Stereotactic Body Radiotherapy (SBRT) for prostate cancer in order to track the six degrees of prostate motion that occur intrafractionally, during treatment. Many patients take anticoagulant medication due to other comorbidities. Anticoagulation therapy can cause patients to bleed during procedures and, in general practice, are often temporarily discontinued prior to invasive medical procedures to reduce that risk. However, some patients may not be able to temporarily discontinue anticoagulation therapy due to an increased risk of a thromboembolic event from their comorbid medical conditions. We looked at a series of our patients who were unable to discontinue anticoagulation therapy prior to fiducial marker placement and report on their outcomes to assess whether they experienced bleeding complications from the procedure. Methods: From August, 2015 to January, 2016, 16 consecutive patients on chronic anticoagulation therapy and who were not cleared to stop these medications underwent fiducial marker placement into the prostate for treatment and planning purposes. The most common indications for uninterrupted anticoagulation therapy in this cohort included: recent stent placement (6=number); myocardial infarction (6=number); pulmonary embolus (2=number); and atrial fibrillation (2=number.) Anticoagulation therapy included Aspirin (7=number); Plavix (5=number); Coumadin (3=number); Lovenox (2=number); Eliquis (1=number); Brillinta (1=number); Pradaxa (1=number); and Effient (1=number). 6 patients were on more than one of these agents at the time of fiducial marker placement. All patients had Emla cream placed on the perineum and lidocaine gel placed into the rectum prior to the procedure for numbing purposes. A transrectal ultrasound was placed for visualization of the prostate and normal anatomy as well as to provide real time image guidance of marker placement during the procedure. 2 needles with 2 fiducial markers and a spacer in each were placed transperineally into the prostate under ultrasound guidance using a brachytherapy grid. The needles were then removed after the fiducial markers were placed and gentle pressure was applied to the perineum by the nursing staff. All patients were monitored for bleeding afterwards by a registered nurse. Results: All 16 consecutive patients who were on anticoagulation and underwent fiducial marker placement were discharged home the same day of the procedure. No patient experienced significant bleeding. Conclusions: Transperineal fiducial marker placement in patients who are unable to Open Access Abstract

Previous Cryotherapy and Older Age Predict for Faster Biochemical Response After Definitive SBRT for Prostate Cancer.

Conclusions: Table 1: Univariate Analysis, PSA Decline •Stereotactic Body Radiation Therapy (SBRT) remains an emerging treatment option for men with prostate adenocarcinoma with low or intermediate risk disease. •Despite a growing volume of investigation, there is a paucity of data that characterizes predictors of post-treatment PSA kinetics in the initial six-month window. •Cryosurgery is an evolving minimally invasive therapy for the treatment of focal prostate cancer. •The effect of previous cryosurgery on PSA kinetics following salvage SBRT has not been previously explored. •This study reports the effect of age and previous cryosurgery on initial PSA kinetics for patients that have undergone definitive SBRT for low or intermediate risk prostate cancer.