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We aimed to compare prototype treatment plans for a new biology-guided radiotherapy (BgRT) machine in its intensity-modulated radiation therapy (IMRT) mode with those using existing IMRT delivery techniques in treatment of nasopharyngeal carcinoma (NPC). We retrospectively selected ten previous NPC patients treated in 33 fractions according to the NRG-HN001 treatment protocol. Three treatment plans were generated for each patient: a helical tomotherapy (HT) plan with a 2.5-cm jaw, a volumetric modulated arc therapy (VMAT) plan using 2 to 4 6-MV arc fields, and a prototype IMRT plan for a new BgRT system which uses a 6-MV photon beam on a ring gantry that rotates at 60 rotations per minute with a couch that moves in small incremental steps. Treatment plans were compared using dosimetric parameters to planning target volumes (PTVs) and organs at risk (OARs) as specified by the NRG-HN001 protocol. Plans for the three modalities had comparable dose coverage, mean dose, and dose heterogeneity to the primary PTV, while the prototype IMRT plans had greater dose heterogeneity to the non-primary PTVs, with the average homogeneity index ranging from 1.28 to 1.50 in the prototype plans. Six of all the 7 OAR mean dose parameters were lower with statistical significance in the prototype plans compared to the HT and VMAT plans with the other mean dose parameter being comparable, and all the 18 OAR maximum dose parameters were comparable or lower with statistical significance in the prototype plans. The average left and right parotid mean doses in the prototype plans were 10.5 Gy and 10.4 Gy lower than those in the HT plans, respectively, and were 5.1 Gy and 5.2 Gy lower than those in the VMAT plans, respectively. Compared to that with the HT and VMAT plans, the treatment time was longer with statistical significance with the prototype IMRT plans. Based on dosimetric comparison of ten NPC cases, the prototype IMRT plans achieved comparable or better critical organ sparing compared to the HT and VMAT plans for definitive NPC radiotherapy. However, there was higher dose heterogeneity to non-primary targets and longer estimated treatment time with the prototype plans. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: To evaluate residual patient setup errors and daily dose variations of different less-than-daily image guidance (IG) strategies in the delivery of external beam radiotherapy for esophageal cancer. Material and methods: Daily image-guided setup data for 25 consecutive esophageal cancer patients treated with helical tomotherapy were evaluated. Seven less-than-daily IG strategies with different imaging frequencies were simulated. For each IG strategy, the daily residual setup errors were calculated. Using TomoTherapy Planned Adaptive software, daily dose variations to the clinical target volume, heart, and lungs were evaluated in five representative patients. Results: With 0% (60%) IG frequency, the margins required for adequate coverage of the clinical target volume were 13mm (10mm), 14mm (11mm), and 5mm (5mm) in the left–right, superior–inferior, and anterior–posterior directions, respectively. Even with 60% IG frequency, 10% of the fractions had more than 10% decrease in the dose level covering 95% of the target, and 14% and 13% of the fractions had more than 10% increase in total lung volume receiving at least 0.8Gy per fraction, and heart volume receiving at least 1.2Gy per fraction, respectively. Conclusion: Substantial residual setup errors would occur for treatment fractions without IG even if the most frequent less-than-daily IG strategy was to be used, which could lead to significant daily dose variations for the target volume and adjacent normal tissues. Daily image guidance is recommended throughout the course of treatment in conformal radiotherapy for esophageal cancer. [Copyright &y& Elsevier]

Purpose: For intensity-modulated radiotherapy of nasopharyngeal cancer, accurate dose delivery is crucial to the success of treatment. This study aimed to evaluate the significance of daily image-guided patient setup corrections and to quantify the parotid gland volume and dose variations for nasopharyngeal cancer patients using helical tomotherapy megavoltage computed tomography (CT). Methods and Materials: Five nasopharyngeal cancer patients who underwent helical tomotherapy were selected retrospectively. Each patient had received 70 Gy in 35 fractions. Daily megavoltage CT scans were registered with the planning CT images to correct the patient setup errors. Contours of the spinal cord and parotid glands were drawn on the megavoltage CT images at fixed treatment intervals. The actual doses delivered to the critical structures were calculated using the helical tomotherapy Planned Adaptive application. Results: The maximal dose to the spinal cord showed a significant increase and greater variation without daily setup corrections. The significant decrease in the parotid gland volume led to a greater median dose in the later phase of treatment. The average parotid gland volume had decreased from 20.5 to 13.2 cm3 by the end of treatment. On average, the median dose to the parotid glands was 83 cGy and 145 cGy for the first and the last treatment fractions, respectively. Conclusions: Daily image-guided setup corrections can eliminate significant dose variations to critical structures. Constant monitoring of patient anatomic changes and selective replanning should be used during radiotherapy to avoid critical structure complications. [Copyright &y& Elsevier]

Purpose: To use pretreatment megavoltage computed tomography (MVCT) scans to evaluate setup variations in anterior-posterior (AP), lateral, and superior-inferior (SI) directions and rotational variations, including pitch, roll, and yaw, for esophageal cancer patients treated with helical tomotherapy. Methods and Materials: Ten patients with locally advanced esophageal cancer treated by combined chemoradiation using helical tomotherapy were selected. After patients were positioned using their skin tattoos/marks, MVCT scans were performed before every treatment and automatically registered to planning kilovoltage CT scans according to bony landmarks. Image registration data were used to adjust patient setups before treatment. A total of 250 MVCT scans were analyzed. Correlations between setup variations and body habitus, including height, weight, relative weight change, body surface area, and patient age, were evaluated. Results: The standard deviations for systematic setup corrections in AP, lateral, and SI directions and pitch, roll, and yaw rotations were 1.5, 3.7, and 4.8 mm and 0.5 degrees, 1.2 degrees, and 0.8 degrees, respectively. The appropriate averages of random setup variations in AP, lateral, and SI directions and pitch, roll, and yaw rotations were 2.9, 5.2, and 4.4 mm, and 1.0 degrees, 1.2 degrees, and 1.1 degrees, respectively. Setup variations were stable throughout the entire course of radiotherapy in all three translational and three rotational displacements, with little change in magnitude. No significant correlations were found between setup variations and body habitus variables. Conclusions: Daily MVCT scans before each treatment can effectively detect setup errors and thereby reduce planning target volume (PTV) margins. This will reduce radiation dose to critical organs and may translate into lower treatment-related toxicities. [ABSTRACT FROM AUTHOR]

Abstract: This study evaluated the efficacy of using helical tomotherapy for conformal avoidance treatment of anal adenocarcinoma. We retrospectively generated step-and-shoot intensity-modulated radiotherapy (sIMRT) plans and helical tomotherapy plans for two anal cancer patients, one male and one female, who were treated by the sIMRT technique. Dose parameters for the planning target volume (PTV) and the organs-at-risk (OARs) were compared between the sIMRT and the helical tomotherapy plans. The helical tomotherapy plans showed better dose homogeneity in the PTV, better dose conformity around the PTV, and, therefore, better sparing of nearby OARs compared with the sIMRT plans. In-vivo skin dose measurements were performed during conformal avoidance helical tomotherapy treatment of an anal cancer patient to verify adequate delivery of skin dose and sparing of OARs. [Copyright &y& Elsevier]

Abstract: We compare different radiotherapy techniques—helical tomotherapy (tomotherapy), step-and-shoot IMRT (IMRT), and 3-dimensional conformal radiotherapy (3DCRT)—for patients with mid-distal esophageal carcinoma on the basis of dosimetric analysis. Six patients with locally advanced mid-distal esophageal carcinoma were treated with neoadjuvant chemoradiation followed by surgery. Radiotherapy included 50 Gy to gross planning target volume (PTV) and 45 Gy to elective PTV in 25 fractions. Tomotherapy, IMRT, and 3DCRT plans were generated. Dose-volume histograms (DVHs), homogeneity index (HI), volumes of lung receiving more than 10, 15, or 20 Gy (V10, V15, V20), and volumes of heart receiving more than 30 or 45 Gy (V30, V45) were determined. Statistical analysis was performed by paired t-tests. By isodose distributions and DVHs, tomotherapy plans showed sharper dose gradients, more conformal coverage, and better HI for both gross and elective PTVs compared with IMRT or 3DCRT plans. Mean V20 of lung was significantly reduced in tomotherapy plans. However, tomotherapy and IMRT plans resulted in larger V10 of lung compared to 3DCRT plans. The heart was significantly spared in tomotherapy and IMRT plans compared to 3DCRT plans in terms of V30 and V45. We conclude that tomotherapy plans are superior in terms of target conformity, dose homogeneity, and V20 of lung. [Copyright &y& Elsevier]

Abstract: Purpose: To compare step-and-shoot intensity-modulated radiation therapy (SAS-IMRT) and helical tomotherapy (Tomo) dosimetry plans for patients who have received adjuvant radiation therapy for retroperitoneal sarcomas (RSTS). Methods and Materials: A retrospective review was performed for seven patients who received either SAS-IMRT or Tomo as adjuvant radiation therapy for RSTS. In each case, a treatment plan of the other modality was generated so that SAS-IMRT and Tomo could be compared. Results: The average percentage of clinical target volume (CTV) that received less than the prescription dose was 1.4% for Tomo compared to 3.8% for SAS-IMRT. Both SAS-IMRT and Tomo plans provided comparable and significant reductions in volume of small bowel receiving greater than 45Gy compared to simple opposing standard radiation fields. For the ipsilateral kidney, Tomo significantly reduced the volume of kidney that received at least 15Gy (average 22% for Tomo vs. 56% for SAS-IMRT). Conclusion: Both SAS-IMRT and Tomo can encompass the large CTV often required for patients with RSTS, although Tomo provides superior dose uniformity. Both SAS-IMRT and Tomo can minimize the volume of small bowel receiving greater than 45Gy. Tomo was superior to SAS-IMRT in minimizing the volume of ipsilateral kidney irradiated to greater than 15Gy when the CTV is adjacent to a kidney. Dose escalation and target margin expansion may thus become realistic possibilities. [Copyright &y& Elsevier]

Purpose: Toxicities after organ sparing myeloablative total marrow irradiation (TMI) conditioning regimens have not been well characterized. The purpose of this study is to report pulmonary, renal, thyroid, and cataract toxicities from a prospective trial monitoring patients up to 8 years after TMI.Methods and Materials: A total of 142 patients with primarily multiple myeloma or acute leukemia undergoing hematopoietic cell transplantation were evaluated. Follow-up included pulmonary function tests, serum creatinine, glomerular filtration rate, thyroid panel, and ophthalmologic examinations performed at 100 days, 6 months, and annually. Median TMI dose was 14 Gy (10-19 Gy) delivered at 1.5 to 2.0 Gy twice per day at a dose-rate of 200 cGy/min.Results: Median age was 52 years (range 9-70). Median follow-up (range) for all patients was 2 years (0-8) and for patients alive at the time of last follow-up (n = 50), 5.5 years (0-8). Mean organ doses in Gy were lung 7.0, kidneys 7.1, thyroid 6.7, and lens 2.8. The crude incidence of radiation pneumonitis (RP) was 1 of 142 (0.7%). The cumulative incidence of infection and RP (I/RP) was 22.7% at 2 years post-TMI. Mean lung dose ≤8 Gy predicted for significantly lower rates of I/RP (2-year cumulative incidence 20.8% vs 31.8%, P = .012). No radiation-induced renal toxicity was noted. Hypothyroidism occurred in 6.0% and cataract formation in 7.0% of patients.Conclusions: TMI delivered with intensity modulated radiation therapy results in lower organ doses and was associated with fewer toxicities compared with historical cohorts treated with conventional total body irradiation. Keeping the mean lung dose to 8 Gy or less was associated with lower pulmonary complications. Further evaluation in clinical trials of intensity modulated radiation therapy to deliver TMI, total marrow and lymphoid irradiation, and organ sparing conformal total body irradiation is warranted. [ABSTRACT FROM AUTHOR]

Purpose: To use pretreatment megavoltage-computed tomography (MVCT) scans to evaluate positioning variations in pitch, roll, and yaw for patients treated with helical tomotherapy. Methods and Materials: Twenty prostate and 15 head-and-neck cancer patients were selected. Pretreatment MVCT scans were performed before every treatment fraction and automatically registered to planning kilovoltage CT (KVCT) scans by bony landmarks. Image registration data were used to adjust patient setups before treatment. Corrections for pitch, roll, and yaw were recorded after bone registration, and data from fractions 1–5 and 16–20 were used to analyze mean rotational corrections. Results: For prostate patients, the means and standard deviations (in degrees) for pitch, roll, and yaw corrections were −0.60 ± 1.42, 0.66 ± 1.22, and −0.33 ± 0.83. In head-and-neck patients, the means and standard deviations (in degrees) were −0.24 ± 1.19, −0.12 ± 1.53, and 0.25 ± 1.42 for pitch, roll, and yaw, respectively. No significant difference in rotational variations was observed between Weeks 1 and 4 of treatment. Head-and-neck patients had significantly smaller pitch variation, but significantly larger yaw variation, than prostate patients. No difference was found in roll corrections between the two groups. Overall, 96.6% of the rotational corrections were less than 4°. Conclusions: The initial rotational setup errors for prostate and head-and-neck patients were all small in magnitude, statistically significant, but did not vary considerably during the course of radiotherapy. The data are relevant to couch hardware design for correcting rotational setup variations. There should be no theoretical difference between these data and data collected using cone beam KVCT on conventional linacs. [Copyright &y& Elsevier]