Performance assessment of a new optimization system for robotic SBRT MLC-based plans.

PURPOSE: To assess the performance of a new optimization system, VOLO, for CyberKnife MLC-based SBRT plans in comparison with the existing Sequential optimizer. METHODS: MLC-plans were created for 25 SBRT cases (liver, prostate, pancreas and spine) using both VOLO and Sequential. Monitor units (MU), delivery time (DT), PTV coverage, conformity (nCI), dose gradient (R50%) and OAR doses were used for comparison and combined to obtain a mathematical score (MS) of plan quality for each solution. MS strength was validated by changing parameter weights and by a blinded clinical plan evaluation. The optimization times (OT) and the average segment areas (SA) were also compared. RESULTS: VOLO solutions offered significantly lower mean DT (-19%) and MU (-13%). OT were below 15 min for VOLO, whereas for Sequential, values spanned from 8 to 160 min. SAs were significantly larger for VOLO: on average 10 cm2 versus 7 cm2. VOLO optimized plans achieved a higher MS than Sequential for all tested parameter combinations. PTV coverage and OAR sparing were comparable for both groups of solutions. Although slight differences in R50% and nCI were found, the parameters most affecting MS were MU and DT. VOLO solutions were selected in 80% of cases by both physicians with 88% inter-observer agreement. CONCLUSIONS: The good performance of the VOLO optimization system, together with the large reduction in OT, make it a useful tool to improve the efficiency of CK SBRT planning and delivery. The proposed methodology for comparing different planning solutions can be applied in other contexts.

CyberKnife MLC-based treatment planning for abdominal and pelvic SBRT: Analysis of multiple dosimetric parameters, overall scoring index and clinical scoring.

PURPOSE: This study evaluated the plan quality of CyberKnife MLC-based treatment planning in comparison to the Iris collimator for abdominal and pelvic SBRT. Multiple dosimetric parameters were considered together with a global scoring index validated by clinical scoring. METHODS AND MATERIALS: Iris and MLC plans were created for 28 liver, 15 pancreas and 13 prostate cases including a wide range of PTV sizes (24-643 cm3). Plans were compared in terms of coverage, conformity (nCI), dose gradient (R50%), homogeneity (HI), OAR doses, PTV gEUD, MU, treatment time both estimated by TPS (tTPS) and measured. A global plan quality score index was calculated for IRIS and MLC solutions and validated by a clinical score given independently by two observers. RESULTS: Compared to Iris, MLC achieved equivalent coverage and conformity without compromising OAR sparing and improving R50% (p < 0.001). MLC gEUD was slightly lower than Iris (p < 0.05) for abdominal cases. MLC reduced significantly MU (-15%) and tTPS (-22%). Time reduction was partially lost when measured. The global score index was significantly higher for MLC solutions which were selected in 73% and 64% of cases respectively by the first and second observer. CONCLUSION: Iris and MLC comparison was not straightforward when based on multiple dosimetric parameters. The use of a mathematical overall score index integrated with a clinical scoring was essential to confirm MLC plans advantages over Iris solutions.

Salvage stereotactic re-irradiation with CyberKnife for locally recurrent head and neck cancer: a single center experience.

AIMS AND BACKGROUND: We report the toxicity and preliminary clinical outcome in patients affected by locally recurrent head and neck cancer treated with stereotactic re-irradiation. METHODS: Between February 2012 and August 2013, 17 patients were treated with CyberKnife as stereotactic re-irradiation for locally recurrent head and neck cancer. All patients had previously received a full dose radiation treatment with radical intent, with a median total dose of 66 Gy (range, 50-70) delivered with standard fractionation. The median interval between the primary radiotherapy and re-irradiation was 24 months (range, 10-168). RESULTS: All patients completed the prescribed treatment, which was delivered in 5 fractions. The median tumor dose administered was 30 Gy (range, 25-35) prescribed to the 80% isodose line. Treatment sites were as follows: neck lymph nodes in 5 patients, paranasal sinuses in 5, oropharynx in 2, nasopharynx, and larynx, oral cavity, nasal fossa and parotid gland each in 1 patient. The median target volume treated was 58.7 cm3 (range, 8.5-211.3). Sixteen patients (94%) were evaluated for response. At a median follow-up of 7.5 months (range, 2-17), 4 patients achieved complete response (25%), 5 had partial response (31%) and 7 showed stable disease (44%). No patient showed in-field progression after re-irradiation. Grade 3 acute toxicity was noted in one patient only; no late side effect was observed during the follow-up. CONCLUSIONS: Stereotactic re-irradiation with CyberKnife is an appealing non-surgical salvage treatment for selected patients with local-regionally recurrent head and neck cancer.

Cyberknife stereotactic radiosurgery for the re-irradiation of brain lesions: a single-centre experience.

PURPOSE: The aim of our study was to retrospectively evaluate the feasibility and clinical benefit of cyberknife stereotactic radiosurgery (CSRS) in patients treated at Florence University for recurrent, pre-irradiated brain lesions. MATERIALS AND METHODS: Thirteen patients were retreated with cyberknife. Mean age was 47.1 years (range 33-77 years). Karnofsky performance status ranged from 60 to 100 (median 80). Eleven (84.6%) out of 13 patients had metastatic lesions: four (36.4%) had primary lung, three (27.2%) had primary breast cancer and four (36.4%) other types of solid malignancies. Two (15.4%) out of 13 patients had recurrent of glioblastoma. RESULTS: In terms of compliance with CSRS, the majority of patients did not develop any acute side effects. However, two (15.4%) out of 13 patients developed acute grade 2 toxicity requiring an increase of steroid medication. At the time of the last follow-up, response rates were as follows: complete response in one case (16.6%), partial response in three (50%) and stable disease in two (33.4%). CONCLUSIONS: Re-irradiation with CSRS is a feasible and effective option for pre-irradiated, recurrent brain lesions to obtain clinical benefit without excessive acute toxicity.

Clinical outcome of stereotactic body radiotherapy for abdominal lymph node metastases.

Aims and background. To report the clinical outcome of linac-based or robotic, image-guided stereotactic body radiotherapy in patients affected by abdominal lymph node metastases from different primary cancers. Methods and methods. Twenty-six patients with 32 abdominal lymph node metastases were consecutively treated at the University of Florence between April 2011 and May 2012. The mean follow-up was 4.6 months (SD, 3.9; range, 0.3-13). The dose prescription ranged between 24 Gy and 36 Gy delivered in 1-5 fractions. Results. In terms of local control, complete response to stereotactic body radiotherapy was obtained in 18 cases (66.7%), partial response in 7 (25.9%), and stable disease in 2 (7.4%). At the Cox univariate regression analysis, an increased risk of partial response or absence of local response to radiotherapy was found for subjects of the female sex (P = 0.036), age less than 50 years (P = 0.022), primary tumor of the genital tract (P = 0.007), and previous chemotherapy (P = 0.057). An excellent local control rate (90.9%) was obtained in patients affected by abdominal lymph node metastases of prostatic origin. Conclusions. Stereotactic body radiotherapy for abdominal lymph node metastases is a safe and effective treatment in terms of high rates of local control, especially in a subset of patients affected by prostate cancer.

Stereotactic body radiotherapy for cardiac and paracardiac metastases: University of Florence experience.

PURPOSE: This study sought to evaluate acute toxicity and local control in patients who underwent extracranial stereotactic body radiation therapy (SBRT) for paracardiac and cardiac metastatic lesions, defined as such when located at a maximum distance of 1 cm from the heart or inside its parenchyma. MATERIALS AND METHODS: Between January 2009 and May 2011, 16 patients with paracardiac and cardiac lesions were treated with SBRT. For dose specification, in 15 of 16 patients, the prescription dosage was 36 Gy in three fractions (70% isodose). In one patient, the target lesion was inside the heart, and the prescription dosage was 30 Gy in three fractions (70% isodose). RESULTS: Regarding response to stereotactic radiotherapy, we recorded one (6%) complete response (CR), six (37%) partial responses (PR), five (32%) stable disease (SD) and four (25%) local failures. Median interval to local failure was 5.2 (range, 3-12) months. The cause of death was distant progression of disease in all four patients. Compliance to treatment was excellent; no patient developed cardiological symptoms or electrocardiographic abnormalities, even months after SBRT. CONCLUSIONS: Results of our retrospective study indicate that SBRT represents a safe and effective treatment option for patients with cardiac and paracardiac metastases.

Stereotactic radiotherapy for adrenal gland metastases: university of Florence experience.

PURPOSE: To evaluate a retrospective single-institution outcome after hypofractionated stereotactic body radiotherapy (SBRT) for adrenal metastases. METHODS AND MATERIALS: Between February 2002 and December 2009, we treated 48 patients with SBRT for adrenal metastases. The median age of the patient population was 62.7 years (range, 43-77 years). In the majority of patients, the prescription dose was 36 Gy in 3 fractions (70% isodose, 17.14 Gy per fraction at the isocenter). Eight patients were treated with single-fraction stereotactic radiosurgery and forty patients with multi-fraction stereotactic radiotherapy. RESULTS: Overall, the series of patients was followed up for a median of 16.2 months (range, 3-63 months). At the time of analysis, 20 patients were alive and 28 patients were dead. The 1- and 2-year actuarial overall survival rates were 39.7% and 14.5%, respectively. We recorded 48 distant failures and 2 local failures, with a median interval to local failure of 4.9 months. The actuarial 1-year disease control rate was 9%; the actuarial 1- and 2-year local control rate was 90%. CONCLUSION: Our retrospective study indicated that SBRT for the treatment of adrenal metastases represents a safe and effective option with a control rate of 90% at 2 years.

Efficacy of eradicative radiotherapy for limited nodal metastases detected with choline PET scan in prostate cancer patients.

AIMS AND BACKGROUND: In patients with recurrent prostate cancer, discriminating local or systemic recurrence is critical to decide second-line treatment. We investigated the capability of stereotactic body radiotherapy to treat limited nodal recurrences, detected using choline PET scan. METHODS AND STUDY DESIGN: Seventy-one patients with biochemical failure were studied after prostate cancer treatment: prostatectomy (28), radiotherapy (15) or both (28). Following computed tomography and choline PET imaging, stereotactic body radiotherapy was delivered on pathological lymphatic areas by 6 MV Linac, using dynamic micromultileaf collimation and intensity-modulated arc therapy optimization. Sixty days post-treatment, choline PET/CT imaging was carried out. RESULTS: Median follow-up was 29 months (range, 14.4-48). Choline PET detected recurrences in 39 of 71 patients. Median PSA velocity was 0.40 ng/ml/year in PET-negative patients and 2.88 ng/ml/year in PET-positive subjects (P < 0.05). Twenty-five patients with limited nodal recurrences, out of the 71 submitted to choline PET, received eradicative radiotherapy. Persistent regression was recorded in 13; early spread to bone was found in 2 cases; lymph node recurrences in 8, all in sites outside the irradiated areas; 2 patients were lost to follow-up. At the 3-year follow-up, overall survival, disease-free survival and local control rates were 92%, 17% and 90%, respectively. In patients with a complete regression, PSA fell from 5.65 to 1.40 ng/ml (median). PSA nadir value (median 1.06 ng/ml) was maintained for 5.6 months (median). CONCLUSIONS: Stereotactic body radiotherapy was effective in disease eradication of limited nodal recurrences from prostate cancer, saving patients from, or at least postponing, systemic treatments.

On-line image guidance for frameless stereotactic radiotherapy of lung malignancies by cone beam CT: comparison between target localization and alignment on bony anatomy.

INTRODUCTION: Free-breathing stereotactic radiotherapy for lung malignancies requires reliable prediction of respiratory motion and accurate target localization. A protocol was adopted for reproducibility and reduction of respiratory motion and for target localization by CBCT image guidance. Tumor respiratory displacements and tumor positioning errors relative to bony anatomy alignment are analyzed. MATERIALS AND METHOD: Image guided SRT was performed for 99 lung malignancies. Two groups of patients were considered: group A did not perform any breathing control; group B controlled visually their respiratory cycle and volumes on an Active Breathing Coordinator (ABC) monitor during the acquisition of simulation CT and CBCT, and treatment delivery. GTV on end inhale and exhale CT data sets were fused in an ITV and the extent of tumor motion evaluated between these 2 phases. A pre-treatment CBCT was acquired and aligned to the reference CT using bony anatomy; for tumor positioning the ITV contour on the reference CT was matched to the visible tumor on CBCT. Interobserver variability of tumor positioning was evaluated. ITV and CBCT tumor dimensions were compared. RESULTS: 3D tumor breathing displacement (mean+/-SD) was significantly higher for group A (14.7+/-9.9 mm) than for group B (4.7+/-3.1 mm). The detected differences between tumor and bony structure alignment below 3 mm were 68% for group B and 45% for group A, reaching statistical significance. Interobserver variability was 1.7+/-1.1 mm (mean+/-SD). Dimensions of tumor image on CBCT were consistent with ITV dimensions for group B (max difference 14%). CONCLUSIONS: The adopted protocol seems effective in reducing respiratory internal movements and margin. Tumor positioning errors relative to bony anatomy are also reduced. However bony anatomy as a surrogate of the target may still lead to some relevant positioning errors. Target visualization on CBCT is essential for an accurate localization in lung SRT.

Cone beam CT image guidance for intracranial stereotactic treatments: comparison with a frame guided set-up.

PURPOSE: An analysis is performed of the setup errors measured by a kV cone beam computed tomography (CBCT) for intracranial stereotactic radiotherapy (SRT) patients immobilized by a thermoplastic mask and a bite-block and positioned using stereotactic coordinates. We evaluated the overall positioning precision and accuracy of the immobilizing and localizing systems. The potential of image-guided radiotherapy to replace stereotactic methods is discussed. METHODS AND MATERIALS: Fifty-seven patients received brain SRT. After a frame-guided setup, before each fraction (131 fractions), a CBCT was acquired and the detected displacements corrected online. Translational and rotational errors were analyzed calculating overall mean and standard deviation. A separate analysis was performed for bite-block (in conjunction with mask) and for simple thermoplastic mask. Interobserver variability for CBCT three-dimensional registration was assessed. The residual error after correction and intrafractional motion were calculated. RESULTS: The mean module of the three-dimensional displacement vector was 3.0 +/- 1.4 mm. Setup errors for bite block and mask were smaller (2.9 +/- 1.3 mm) than those for thermoplastic mask alone (3.2 +/- 1.5 mm), but statistical significance was not reached (p = 0.15). Interobserver variability was negligible. The maximum margin calculated for residual errors and intra fraction motion was small but not negligible (1.57 mm). CONCLUSIONS: Considering the detected setup errors, daily image guidance is essential for the efficacy of SRT treatments when mask immobilization is used, and even when a bite-block is used in conjunction. The frame setup is still used as a starting point for the opportunity of rotational corrections. Residual margins after on-line corrections must be evaluated.

Relevance of biologically equivalent dose values in outcome evaluation of stereotactic radiotherapy for lung nodules.

PURPOSE: Different biologically equivalent dose (BED) values associated with stereotactic radiotherapy (SRT) of patients with primary and metastatic pulmonary nodules were studied. The BED values were calculated for tumoral tissue and low alpha/beta ratio, assuming that better local response could be obtained by using stereotactic high-BED treatment. METHODS AND MATERIALS: Fifty-eight patients with T1-T3 N0 non-small-cell lung cancer and 46 patients with metastatic lung nodules were treated with SRT. The BED was calculated for alpha/beta ratios of 3 and 10. Overall survival (OS) was assessed according to Kaplan-Meier and appraised as a function of three BED levels: low (30-50 Gy), medium (50-70 Gy), and high (70-98 Gy; alpha/beta = 10). RESULTS: The OS rates for all 104 patients at 12, 24, and 36 months were 73%, 48.3%, and 35.8%, respectively. Local response greater than 50% for low, medium, and high BED values was observed in 54%, 47%, and 73%, respectively. In the high-BED treated group, OS rates at 12, 24, and 36 months (80.9%, 70%, and 53.6%, respectively) were significantly improved compared with low- (69%, 46.1%, and 30.7%, respectively) and medium-BED (67%, 28%, and 21%, respectively) treated patients. Results are also discussed in terms of BED calculated on alpha/beta 3 Gy characteristic of the microcapillary bed. No acute toxicity higher than Grade 1 was observed. CONCLUSIONS: Radioablation of pulmonary neoplastic nodules may be achieved with SRT delivered by using a high-dose fraction with high BED value.