Breakdown of middle lamella pectin by (●) OH during rapid abscission in Azolla.

Azolla, a small water fern, abscises its roots and branches within 30 min upon treatment with various stresses. This study was conducted to test whether, in the rapid abscission that occurs in Azolla, breakdown of wall components of abscission zone cells by (●) OH is involved. Experimentally generated (●) OH caused the rapid separation of abscission zone cells from detached roots and the rapid shedding of roots from whole plants. Electron microscopic observations revealed that (●) OH rapidly and selectively dissolved a well-developed middle lamella between abscission zone cells and resultantly caused rapid cell separation and shedding. Treatment of abscission zones of Impatiens leaf petiole with (●) OH also accelerated the separation of abscission zone cells. However, compared with that of Azolla roots, accelerative effects in Impatiens were weak. A large amount of (●) OH was cytochemically detected in abscission zone cells both of Azolla roots and of Impatiens leaf petioles. These results suggest that (●) OH is involved in the cell separation process not only in the rapid abscission in Azolla but also in the abscission of Impatiens. However, for rapid abscission to occur, a well-developed middle lamella, a unique structure, which is sensitive to the attack of (●) OH, might be needed.

Statin use not associated with improved outcomes in patients treated with brachytherapy for prostate cancer.

PURPOSE: To investigate the association between statin use and prostate cancer outcomes in intermediate- and high-risk patients treated with brachytherapy for prostate cancer. METHODS AND MATERIALS: Between 1998 and 2010, 754 men with National Comprehensive Cancer Network intermediate- (n = 627) and high-risk (n = 127) prostate cancer were treated with prostate brachytherapy at our institution. Patients received either low-dose-rate or high-dose-rate brachytherapy as monotherapy or in combination with supplemental external beam radiotherapy. Two hundred eighty-five patients (37.8%) also received androgen-deprivation therapy. Two hundred seventy-three men (36.2%) were identified as taking statin medication before initiating radiation therapy. Prostate-specific antigen relapse-free survival (PSA-RFS), distant metastasis-free survival (DMFS), and overall survival were compared using log-rank tests. Associations of patient and treatment characteristics with outcomes were analyzed with univariate and multivariate regression. The median followup was 48 months. RESULTS: The 8-year PSA-RFS for intermediate-risk, high-risk, and all patients was 92.2%, 64.1%, and 87.7%, respectively. The 8-year DMFS was 97.1%, 82.9%, and 94.9%, respectively. The 8-year overall survival for the entire cohort was 86.6%. There were no significant differences between statin users and nonusers when stratified by risk group, nor when analyzed as a full cohort. On multivariate analysis, Gleason score 4 + 3 = 7 and >7 were significantly associated with worse PSA-RFS (p ≤ 0.003 and <0.001, respectively). Gleason score > 7 (p = 0.008) and the use of neoadjuvant androgen-deprivation therapy (p = 0.03) was associated with worse DMFS. Statin use did not significantly impact PSA-RFS or DMFS. CONCLUSIONS: Pretreatment statin use is not associated with improved outcomes in intermediate- and high-risk patients undergoing prostate brachytherapy-based regimens for prostate cancer.

Dose to the bladder neck is the most important predictor for acute and late toxicity after low-dose-rate prostate brachytherapy: implications for establishing new dose constraints for treatment planning.

PURPOSE: To identify an anatomic structure predictive for acute (AUT) and late (LUT) urinary toxicity in patients with prostate cancer treated with low-dose-rate brachytherapy (LDR) with or without external beam radiation therapy (EBRT). METHODS AND MATERIALS: From July 2002 to January 2013, 927 patients with prostate cancer (median age, 66 years) underwent LDR brachytherapy with Iodine 125 (n=753) or Palladium 103 (n=174) as definitive treatment (n=478) and as a boost (n=449) followed by supplemental EBRT (median dose, 50.4 Gy). Structures contoured on the computed tomographic (CT) scan on day 0 after implantation included prostate, urethra, bladder, and the bladder neck, defined as 5 mm around the urethra between the catheter balloon and the prostatic urethra. AUT and LUT were assessed with the Common Terminology Criteria for Adverse Events, version4. Clinical and dosimetric factors associated with AUT and LUT were analyzed with Cox regression and receiver operating characteristic analysis to calculate area under the receiver operator curve (ROC) (AUC). RESULTS: Grade ≥2 AUT and grade ≥2 LUT occurred in 520 patients (56%) and 154 patients (20%), respectively. No grade 4 toxicities were observed. Bladder neck D2cc retained a significant association with AUT (hazard ratio [HR], 1.03; 95% confidence interval [CI], 1.03-1.04; P<.0001) and LUT (HR, 1.01; 95% CI, 1.00-1.03; P=.014) on multivariable analysis. In a comparison of bladder neck with the standard dosimetric variables by use of ROC analysis (prostate V100 >90%, D90 >100%, V150 >60%, urethra D20 >130%), bladder neck D2cc >50% was shown to have the strongest prognostic power for AUT (AUC, 0.697; P<.0001) and LUT (AUC, 0.620; P<.001). CONCLUSIONS: Bladder neck D2cc >50% was the strongest predictor for grade ≥2 AUT and LUT in patients treated with LDR brachytherapy. These data support inclusion of bladder neck constraints into brachytherapy planning to decrease urinary toxicity.

Favourable long-term outcomes with brachytherapy-based regimens in men ≤60 years with clinically localized prostate cancer.

OBJECTIVE: To report long-term outcomes of men ≤60 years treated with brachytherapy (BT) for low- and intermediate-risk prostate cancer. PATIENTS AND METHODS: Of 1655 patients treated with BT for clinically localized prostate cancer between January 1998 and May 2008 at Memorial Sloan-Kettering Cancer Center, 236 patients with National Comprehensive Cancer Network low- (n = 178) or intermediate-risk (n = 58) prostate cancer were ≤60 years old with a 3-year minimum follow-up, and represent the subjects of this report. Brachytherapy was given either as monotherapy (n = 169) or with external beam radiation therapy (EBRT; n = 67). Forty-four patients (19%) received neoadjuvant cytoreductive hormone therapy. The 'nadir+2' definition was used for prostate-specific antigen (PSA) recurrence. Common Terminology Criteria for Acute Events (CTCAE) v 3.0 was used to grade genitourinary (GU) and gastrointestinal (GI) toxicity. Potency was defined as the ability to obtain an erection suitable for intercourse or an International Index of Erectile Function score ≥ 22. The Kaplan-Meier method and Cox regression were used for statistical analysis. The median follow-up was 83 months. RESULTS: The 8-year PSA relapse-free survival (RFS), cancer-specific and overall survival rates for the entire cohort were 96, 99 and 96%, respectively. For patients with low-risk disease, the 8-year PSA RFS rate was 97% and for intermediate-risk patients it was 94% (P = 0.34). There was no difference in PSA RFS between BT alone and combined therapy (P = 0.17). Late grade ≥ 2 GU and GI toxicity was 14 and 3%, respectively. Of 150 patients potent before treatment, 76 (51%) were potent at last follow-up, with 50/76 (66%) using no medication. There was no significant difference in post-treatment potency between BT alone and BT with EBRT (P = 0.74). CONCLUSIONS: Brachytherapy provides patients aged ≤ 60 years with low- and intermediate-risk prostate cancer with excellent outcomes and has a low risk of significant long-term GU or GI morbidity. Erectile function is preserved in >50% of patients and the majority do not require erectile dysfunction medication.

A new risk classification system for therapeutic decision making with intermediate-risk prostate cancer patients undergoing dose-escalated external-beam radiation therapy.

BACKGROUND: The management of intermediate-risk prostate cancer (PCa) is controversial, in part due to the heterogeneous nature of patients falling within this classification. OBJECTIVE: We propose a new risk stratification system for intermediate-risk PCa to aid in prognosis and therapeutic decision making. DESIGN, SETTING, AND PARTICIPANTS: Between 1992 and 2007, 1024 patients with National Comprehensive Cancer Network intermediate-risk PCa and complete biopsy information were treated with definitive external-beam radiation therapy (EBRT) utilizing doses ≥ 81 Gy. Unfavorable intermediate-risk (UIR) PCa was defined as any intermediate-risk patient with a primary Gleason pattern of 4, percentage of positive biopsy cores (PPBC) ≥ 50%, or multiple intermediate-risk factors (IRFs; cT2b-c, prostate-specific antigen [PSA] 10-20, or Gleason score 7). INTERVENTION: All patients received EBRT with ≥ 81 Gy with or without neoadjuvant and concurrent androgen-deprivation therapy (ADT). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Univariate and multivariate analyses were performed using a Cox proportional hazards model for PSA recurrence-free survival (PSA-RFS) and distant metastasis (DM). PCa-specific mortality (PCSM) was analyzed using a competing-risk method. RESULTS AND LIMITATIONS: Median follow-up was 71 mo. Primary Gleason pattern 4 (hazard ratio [HR]: 3.26; p<0.0001), PPBC ≥ 50% (HR: 2.72; p=0.0007), and multiple IRFs (HR: 2.20; p=0.008) all were significant predictors of increased DM in multivariate analyses. Primary Gleason pattern 4 (HR: 5.23; p<0.0001) and PPBC ≥ 50% (HR: 4.08; p=0.002) but not multiple IRFs (HR: 1.74; p=0.21) independently predicted for increased PCSM. Patients with UIR disease had inferior PSA-RFS (HR: 2.37; p<0.0001), DM (HR: 4.34; p=0.0003), and PCSM (HR: 7.39; p=0.007) compared with those with favorable intermediate-risk disease, despite being more likely to receive neoadjuvant ADT. Short follow-up and retrospective study design are the primary limitations. CONCLUSIONS: Intermediate-risk PCa is a heterogeneous collection of diseases that can be separated into favorable and unfavorable subsets. These groups likely will benefit from divergent therapeutic paradigms.

Separation of abscission zone cells in detached Azolla roots depends on apoplastic pH.

In studies on the mechanism of cell separation during abscission, little attention has been paid to the apoplastic environment. We found that the apoplastic pH surrounding abscission zone cells in detached roots of the water fern Azolla plays a major role in cell separation. Abscission zone cells of detached Azolla roots were separated rapidly in a buffer at neutral pH and slowly in a buffer at pH below 4.0. However, cell separation rarely occurred at pH 5.0-5.5. Light and electron microscopy revealed that cell separation was caused by a degradation of the middle lamella between abscission zone cells at both pH values, neutral and below 4.0. Low temperature and papain treatment inhibited cell separation. Enzyme(s) in the cell wall of the abscission zone cells might be involved in the degradation of the pectin of the middle lamella and the resultant, pH-dependent cell separation. By contrast, in Phaseolus leaf petioles, unlike Azolla roots, cell separation was slow and increased only at acidic pH. The rapid cell separation, as observed in Azolla roots at neutral pH, did not occur. Indirect immunofluorescence microscopy, using anti-pectin monoclonal antibodies, revealed that the cell wall pectins of the abscission zone cells of Azolla roots and Phaseolus leaf petioles looked similar and changed similarly during cell separation. Thus, the pH-related differences in cell separation mechanisms of Azolla and Phaseolus might not be due to differences in cell wall pectin, but to differences in cell wall-located enzymatic activities responsible for the degradation of pectic substances. A possible enzyme system is discussed.

Short-term androgen-deprivation therapy improves prostate cancer-specific mortality in intermediate-risk prostate cancer patients undergoing dose-escalated external beam radiation therapy.

PURPOSE: We investigated the benefit of short-term androgen-deprivation therapy (ADT) in patients with intermediate-risk prostate cancer (PC) receiving dose-escalated external beam radiation therapy. METHODS AND MATERIALS: The present retrospective study comprised 710 intermediate-risk PC patients receiving external beam radiation therapy with doses of ≥81 Gy at a single institution from 1992 to 2005, including 357 patients receiving neoadjuvant and concurrent ADT. Prostate-specific antigen recurrence-free survival (PSA-RFS) and distant metastasis (DM) were compared using the Kaplan-Meier method and Cox proportional hazards models. PC-specific mortality (PCSM) was assessed using competing-risks analysis. RESULTS: The median follow-up was 7.9 years. Despite being more likely to have higher PSA levels, Gleason score 4 + 3 = 7, multiple National Comprehensive Cancer Network intermediate-risk factors, and older age (P≤.001 for all comparisons), patients receiving ADT had improved PSA-RFS (hazard ratio [HR], 0.598; 95% confidence interval [CI], 0.435-0.841; P=.003), DM (HR, 0.424; 95% CI, 0.219-0.819; P=.011), and PCSM (HR, 0.380; 95% CI, 0.157-0.921; P=.032) on univariate analysis. Using multivariate analysis, ADT was an even stronger predictor of improved PSA-RFS (adjusted HR [AHR], 0.516; 95% CI, 0.360-0.739; P<.001), DM (AHR, 0.347; 95% CI, 0.176-0.685; P=.002), and PCSM (AHR, 0.297; 95% CI, 0.128-0.685; P=.004). Gleason score 4 + 3 = 7 and ≥50% positive biopsy cores were other independent predictors of PCSM. CONCLUSIONS: Short-term ADT improves PSA-RFS, DM, and PCSM in patients with intermediate-risk PC undergoing dose-escalated external beam radiation therapy.

Intraoperative 32P high-dose rate brachytherapy of the dura for recurrent primary and metastatic intracranial and spinal tumors.

BACKGROUND: Treatment of spinal and intracranial tumors with dural involvement is complicated by radiation tolerance of sensitive structures, especially in the setting of previous treatment. OBJECTIVE: To evaluate whether intraoperative brachytherapy with short-range sources allows therapeutic dose delivery without damaging sensitive structures. METHODS: The median doses of previous treatment were 3000 cGy (range, 1800-7200 cGy) for 8 patients with primary/recurrent and 17 patients with metastatic spinal tumors and 5040 cGy (range, 1300-6040 cGy) for 5 patients with locally recurrent and 2 patients with metastatic intracranial tumors. Patients underwent gross total or maximal resection of the tumor and were then treated with an intraoperative brachytherapy plaque consisting of a flexible silicone film incorporating P. A dose of 1000 cGy was delivered to a depth of 1 mm; the percent depth dose was less than 1% at 4 mm from the prescription depth. Median postoperative radiation doses of 2700 cGy (range, 1800-3000 cGy) were delivered to 15 spinal tumor patients and 3000 cGy (range, 1800-3000 cGy) to 3 intracranial tumor patients. The median follow-up was 4.4 months (range, 2.6-23.3 months) for spinal tumor patients and 5.3 months (range, 0.7-16.2) for intracranial tumor patients. RESULTS: At 6-month follow-up, for all spinal tumor patients, local progression-free survival and overall survival rates were both 83.3% (95% confidence interval [CI]: 62.3%-94.3%); for all intracranial tumor patients, the local progression-free survival rate was 62.5% (95% CI: 23.8%-90.9%) and the overall survival rate was 66.7% (95% CI: 26.7%-92.9%). There were no intraoperative or postoperative complications secondary to radiotherapy. CONCLUSION: Use of the P brachytherapy plaque is technically simple and not associated with increased risk of complications, even after multiple radiation courses. Local control rates were more than 80% in patients with proven radiation-resistant spinal disease.

Predicting biochemical tumor control after brachytherapy for clinically localized prostate cancer: The Memorial Sloan-Kettering Cancer Center experience.

PURPOSE: To identify predictors of biochemical tumor control and present an updated prognostic nomogram for patients with clinically localized prostate cancer treated with brachytherapy. METHODS AND MATERIALS: One thousand four hundred sixty-six patients with clinically localized prostate cancer were treated with brachytherapy alone or along with supplemental conformal radiotherapy. Nine hundred one patients (61%) were treated with Iodine-125 ((125)I) monotherapy to a prescribed dose of 144Gy, and 41 (4.5%) were treated with Palladium-103 ((103)Pd) monotherapy to a prescribed dose of 125Gy. In patients with higher risk features (n=715), a combined modality approach was used, which comprised (125)I or (103)Pd seed implantation or Iridium-192 high-dose rate brachytherapy followed 1-2 months later by supplemental intensity-modulated image-guided radiotherapy to the prostate. RESULTS: The 5-year prostate-specific antigen relapse-free survival (PSA-RFS) outcomes for favorable-, intermediate-, and high-risk patients were 98%, 95%, and 80%, respectively (p<0.001). Multivariate Cox regression analysis identified Gleason score (p<0.001) and pretreatment PSA (p=0.04) as predictors for PSA tumor control. In this cohort of patients, the use of neoadjuvant and concurrent androgen deprivation therapy did not influence biochemical tumor control outcomes. In the subset of patients treated with (125)I monotherapy, D(90)>140Gy compared with lower doses was associated with improved PSA-RFS. A nomogram predicting PSA-RFS was developed based on these predictors and had a concordance index of 0.70. CONCLUSIONS: Results with brachytherapy for all treatment groups were excellent. D(90) higher than 140Gy was associated with improved biochemical tumor control compared with lower doses. Androgen deprivation therapy use did not impact on tumor control outcomes in these patients.

Ten-year outcomes of high-dose, intensity-modulated radiotherapy for localized prostate cancer.

BACKGROUND: The authors investigated long-term tumor control and toxicity outcomes after high-dose, intensity-modulated radiation therapy (IMRT) in patients who had clinically localized prostate cancer. METHODS: Between April 1996 and January 1998, 170 patients received 81 gray (Gy) using a 5-field IMRT technique. Patients were classified according to the National Comprehensive Cancer Network-defined risk groups. Toxicity data were scored according to the Common Terminology Criteria for Adverse Events Version 3.0. Freedom from biochemical relapse, distant metastases, and cause-specific survival outcomes were calculated. The median follow-up was 99 months. RESULTS: The 10-year actuarial prostate-specific antigen relapse-free survival rates were 81% for the low-risk group, 78% for the intermediate-risk group, and 62% for the high-risk group; the 10-year distant metastases-free rates were 100%, 94%, and 90%, respectively; and the 10-year cause-specific mortality rates were 0%, 3%, and 14%, respectively. The 10-year likelihood of developing grade 2 and 3 late genitourinary toxicity was 11% and 5%, respectively; and the 10-year likelihood of developing grade 2 and 3 late gastrointestinal toxicity was 2% and 1%, respectively. No grade 4 toxicities were observed. CONCLUSIONS: To the authors' knowledge, this report represents the longest followed cohort of patients who received high-dose radiation levels of 81 Gy using IMRT for localized prostate cancer. The findings indicated that high-dose IMRT is well tolerated and is associated with excellent long-term tumor-control outcomes in patients with localized prostate cancer.

Improved biochemical outcomes with statin use in patients with high-risk localized prostate cancer treated with radiotherapy.

PURPOSE: To investigate the association between 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and biochemical and survival outcomes after high-dose radiotherapy (RT) for prostate cancer. METHODS AND MATERIALS: A total of 1711 men with clinical stage T1-T3 prostate cancer were treated with conformal RT to a median dose of 81 Gy during 1995-2007. Preradiotherapy medication data were available for 1681 patients. Three hundred eighty-two patients (23%) were taking a statin medication at diagnosis and throughout RT. Nine hundred forty-seven patients received a short-course of neoadjuvant and concurrent androgen-deprivation therapy (ADT) with RT. The median follow-up was 5.9 years. RESULTS: The 5- and 8-year PSA relapse-free survival (PRFS) rates for statin patients were 89% and 80%, compared with 83% and 74% for those not taking statins (p=0.002). In a multivariate analysis, statin use (hazard ratio [HR] 0.69, p=0.03), National Comprehensive Cancer Network (NCCN) low-risk group, and ADT use were associated with improved PRFS. Only high-risk patients in the statin group demonstrated improvement in PRFS (HR 0.52, p=0.02). Across all groups, statin use was not associated with improved distant metastasis-free survival (DMFS) (p=0.51). On multivariate analysis, lower NCCN risk group (p=0.01) and ADT use (p=0.005) predicted improved DMFS. CONCLUSIONS: Statin use during high-dose RT for clinically localized prostate cancer was associated with a significant improvement in PRFS in high-risk patients. These data suggest that statins have anticancer activity and possibly provide radiosensitization when used in conjunction with RT in the treatment of prostate cancer.

Comparison of PSA relapse-free survival in patients treated with ultra-high-dose IMRT versus combination HDR brachytherapy and IMRT.

PURPOSE: We report on a retrospective comparison of biochemical outcomes using an ultra-high dose of conventionally fractionated intensity-modulated radiation therapy (IMRT) vs. a lower dose of IMRT combined with high-dose-rate (HDR) brachytherapy to increase the biologically effective dose of IMRT. METHODS: Patients received IMRT of 86.4Gy (n=470) or HDR brachytherapy (21Gy in three fractions) followed by IMRT of 50.4Gy (n=160). Prostate-specific antigen (PSA) relapse was defined as PSA nadir+2. Median followup was 53 months for IMRT alone and 47 months for HDR. RESULTS: The 5-year actuarial PSA relapse-free survival (PRFS) for HDR plus IMRT vs. ultra-high-dose IMRT were 100% vs. 98%, 98% vs. 84%, and 93% vs. 71%, for National Comprehensive Cancer Network low- (p=0.71), intermediate- (p<0.001), and high-risk (p=0.23) groups, respectively. Treatment (p=0.0006), T stage (p<0.0001), Gleason score (p<0.0001), pretreatment PSA (p=0.0037), risk group (p<0.0001), and lack of androgen-deprivation therapy (p=0.0005) were significantly associated with improved PRFS on univariate analysis. HDR plus IMRT vs. ultra-high-dose IMRT (p=0.0012, hazard ratio [HR]=0.184); age (p=0.0222, HR=0.965); and risk group (p<0.0001, HR=2.683) were associated with improved PRFS on multivariate analysis. CONCLUSION: Dose escalation of IMRT by adding HDR brachytherapy provided improved PRFS in the treatment of prostate cancer compared with ultra-high-dose IMRT, independent of risk group on multivariate analysis, with the most significant benefit for intermediate-risk patients.

Combined brachytherapy with external beam radiotherapy for localized prostate cancer: reduced morbidity with an intraoperative brachytherapy planning technique and supplemental intensity-modulated radiation therapy.

PURPOSE: To report the acute and late treatment-related toxicities of combined permanent interstitial (125)I implantation delivered via real-time intraoperative planning and supplemental intensity-modulated radiotherapy (IMRT) for patients with clinically localized prostate cancer. METHODS AND MATERIALS: One hundred twenty-seven patients were treated with a combined modality (CM) regimen consisting of (125)I implantation (110Gy) using a transrectal ultrasound-guided approach followed 2 months later by 50.4Gy of IMRT directed to the prostate and seminal vesicles. Late toxicity was scored according to the NCI Common Terminology Criteria for Adverse Events toxicity scale. The acute and late toxicities were compared to a contemporaneously treated cohort of 216 patients treated with (125)I alone to a prescribed dose of 144Gy. RESULTS: The incidence of Grade 2 acute rectal and urinary side effects was 1% and 10%, respectively, and 2 patients developed Grade 3 acute urinary toxicities. The 4-year incidence of late Grade 2 gastrointestinal toxicity was 9%, and no Grade 3 or 4 complications have been observed. The 4-year incidence of late Grade 2 gastrourinary toxicities was 15% and 1 patient developed a Grade 3 urethral stricture, which was corrected with urethral dilatation. The percentage of patients who experienced resolution of late rectal and urinary symptoms was 92% and 65%, respectively. Multivariate analysis revealed that in addition to higher baseline International Prostate Symptom Score, those patients treated with implant alone compared to CM were more likely to experience Grade 2 acute urinary symptoms. Increased Grade 2 late rectal toxicities were noted for CM patients (9% vs. 1%; p=0.001) as well as a significant increase for late Grade 2 urinary toxicities (15% vs. 9%; p=0.004). CONCLUSIONS: Adherence to dose constraints with combination real-time brachytherapy using real-time intraoperative planning and IMRT is associated with a low incidence of acute and late toxicities. Acute urinary side effects were significantly less common for CM patients compared to those treated with implantation alone. Late Grade 2 rectal and urinary toxicities were more common for patients treated with CM compared to implant alone.

Accurate setup of paraspinal patients using a noninvasive patient immobilization cradle and portal imaging.

Because of the proximity of the spinal cord, effective radiotherapy of paraspinal tumors to high doses requires highly conformal dose distributions, accurate patient setup, setup verification, and patient immobilization. An immobilization cradle has been designed to facilitate the rapid setup and radiation treatment of patients with paraspinal disease. For all treatments, patients were set up to within 2.5 mm of the design using an amorphous silicon portal imager. Setup reproducibility of the target using the cradle and associated clinical procedures was assessed by measuring the setup error prior to any correction. From 350 anterior/posterior images, and 303 lateral images, the standard deviations, as determined by the imaging procedure, were 1.3 m, 1.6 m, and 2.1 in the ant/post, right/left, and superior/inferior directions. Immobilization was assessed by measuring patient shifts between localization images taken before and after treatment. From 67 ant/post image pairs and 49 lateral image pairs, the standard deviations were found to be less than 1 mm in all directions. Careful patient positioning and immobilization has enabled us to develop a successful clinical program of high dose, conformal radiotherapy of paraspinal disease using a conventional Linac equipped with dynamic multileaf collimation and an amorphous silicon portal imager.