A. Colonias

Intraoperative 125I brachytherapy for high-risk stage I non-small cell lung carcinoma

PURPOSE Preliminary assessment of feasibility, efficacy, acute and chronic side effects associated with permanent intraoperative placement of 125I vicryl mesh brachytherapy in a select group of high-risk Stage I NSCLC who have undergone video-assisted thoracoscopic resection (VATR). METHODS AND MATERIALS From January 8, 1997 to March 16, 1998, 23 patients with Stage I NSCLC at high risk for conventional surgery due to cardiopulmonary compromise underwent combined VATR and intraoperative placement of 125I seeds embedded in vicryl mesh. Seeds embedded in vicryl suture were attached with surgical clips to a sheet of vicryl mesh, and thoracoscopically inserted over the target area (tumor bed and staple line) with nonabsorbable suture or surgical clips. A total dose of 100-120 Gy prescribed to the periphery of the target area (defined as the staple line and tumor bed with a 1-cm margin) was delivered. RESULTS The mean target area covered was 48 cm2 (range 40-72) and mean total activity was 22 mCi (range 17.2-28.2). The median length of postoperative stay was 7 days. The median follow-up was 11 months (range 2-20). Postoperative CT scans of the chest revealed no dislodgement of the seeds and no local recurrence in any patient. Three patients developed distant metastasis (1 died 6 months postoperatively; the other 2 are currently alive with disease). One patient developed an ipsilateral recurrence in the right lower lobe after having had a right upper lobe resection. There were 3 postoperative deaths due to medical comorbid conditions or surgical complications (1 in the immediate postoperative period). Pulmonary function testing performed 3 months after implantation revealed no significant difference between preoperative and postoperative values: mean preoperative FVC was 2.3 L (range 1.31-3.0) and postoperative FVC was 2.2 L (range 1.1-3.9), p = 0.42; mean preoperative FEV1 was 1.2 L (range 0.71-2.2), and postoperative FEV1 was 1.5 L (range 0.8-2.9), p = 0.28. CONCLUSION Review of early data suggests that intraoperative 125I vicryl mesh brachytherapy in high-risk Stage I NSCLC is potentially effective and well tolerated, with no significant decline in measurable pulmonary function studies and no increase in postoperative complications. Longer follow-up is needed to determine ultimate local control and survival.

Urinary morbidity with a modified peripheral loading technique of transperineal 125i prostate implantation

PURPOSE Analysis of urinary morbidity within the first 12 months following a modified peripheral loading technique for permanent transperineal transrectal ultrasound (TRUS) guided (125)I prostate implantation and comparison of urinary morbidity with various clinical and implant parameters. MATERIALS AND METHODS Between October 1, 1996, and March 11, 1998, 87 patients with favorable, early stage prostate cancer were treated with permanent transperineal TRUS guided (125)I prostate implantation. A peripheral loading technique was utilized for source placement with 75-80% source distribution in the periphery and 20-25% source distribution centrally. A mean total activity of 38 mCi of (125)I was implanted (range, 19-66 mCi). The mean source activity was 0.43 mCi/source (range, 0.26-0.61 mCi/source) and the mean number of sources implanted was 88 (range, 56-134). The minimum prescribed dose to the prostate was 145 Gy. The median D(90), V(100), and V(150) were 152 Gy (range, 104-211 Gy), 92% (range, 71-99%), and 61% (range, 11-89%), respectively. The median follow-up time was 19 months (range, 12-29 months). Urinary morbidity was scored at 3 weeks and then at 3-month intervals for the first 2 years using a modified Radiation Therapy Oncology Group (RTOG) grading system (scale 0-5). RESULTS Most patients developed at least minor urinary symptoms with frequency or nocturia being the most common. Overall, 79% (69/87) of patients experienced urinary morbidity with 21% (18/87) reporting no symptoms. The incidence of overall Grade 1 urinary morbidity was 37% (32/87); Grade 2 morbidity was 37% (32/87); and Grade 3 morbidity was 6% (5/87). There was no Grade 4 or 5 morbidity. The incidence of Grade 0 frequency/nocturia was 36% (31/87); Grade 1 was 33% (29/87); Grade 2 was 30% (26/87); and Grade 3 was 1% (1/87). Grade 0 dysuria was seen in 56% (49/87) of patients; 32% (28/87) had Grade 1; 10% (9/87) Grade 2; and 1% (1/87) Grade 3 dysuria. Most urinary symptoms started a few weeks after implantation and began to subside by 6 months. At 12 months, 22% (19/87) of patients had persistent urinary symptoms (78% Grade 0, 15% Grade 1, 3% Grade 2, and 3% Grade 3). The mean urethral point dose was 174 Gy (range, 99-315 Gy). The mean number of sources implanted correlated significantly with the likelihood of developing acute urinary morbidity (p = 0.03). The total activity implanted also correlated with the morbidity outcome dysuria (p = 0.01) with a threshold seen at 37 mCi. Urethral point dose, source activity, intraoperative TRUS prostate volume, D(90), V(100), V(150), patient age, pretreatment PSA, Gleason score, and T stage did not correlate with morbidity. CONCLUSIONS Permanent transperineal TRUS guided (125)I prostate implantation using a modified peripheral loading technique is associated with mild urinary morbidity that resolves in 78% of patients by 12 months. Grade 3 urinary morbidity was encountered in only 6% (5/87) of patients. Urinary morbidity may be related to the total number of sources implanted and/or the total activity implanted. Overall urinary morbidity was not correlated with urethral point dose, source activity, intraoperative TRUS prostate volume, D(90), V(100), V(150), patient age, pretreatment PSA, Gleason score, and T stage. The low incidence of urinary morbidity may be a consequence of our modified peripheral loading technique and/or the selection of patients with good-to-excellent preimplant urological parameters. Longer follow-up is necessary to assess biochemical control rates and long-term morbidity.

Tolerance of the aorta using intraoperative iodine-125 interstitial brachytherapy in cancer of the lung

PURPOSE A retrospective review to assess the efficacy and morbidity of surgical resection and (125)I interstitial lung brachytherapy placed in approximation to the aorta. METHODS AND MATERIALS The records and postoperative films of 278 patients who had undergone intrathoracic (125)I brachytherapy at our institution were reviewed. All patients had undergone a gross total resection of a non-small-cell lung cancer using segmental resection, wedge resection, or sublobar resection. Frozen section margins of resection were required to be negative before the intraoperative delivery of the implant. Of those reviewed, 29 patients were implanted with (125)I impregnated Vicryl mesh that contacted greater than 50% with the aorta. Implants consisted of (125)I seeds sewn into a nomographically guided geometric array. Only implants where 50% or greater of the implant volume directly approximated the aorta were selected for inclusion into this study. The mean aortic volume receiving the entire prescribed dose was 17.2cc (mean surface area=34.4cm(2)) and the mean prescribed dose was 114Gy (range, 85-120) over the permanent life of the implant calculated by isodose curve distribution at a depth of 0.5cm from the plane of the implant. Five patients have received postoperative mediastinal dose supplementation with external beam irradiation to further address occult mediastinal nodal disease not revealed during the intraoperative frozen section analysis. RESULTS All patients tolerated the surgery and brachytherapy well with no perioperative mortality. With a median followup of 45.3 months (range, 1-117), 1 of the 29 patients suffered a fatal hemorrhage from suspected great vessel rupture. A review of this case demonstrated that the interstitial therapy had been supplemented with 4500cGy of external irradiation, which overlapped a small portion of the implant volume overlying the aorta. No other patients suffered even minor events referable to the implant and have continued to do well without symptomatic evidence of chronic sequelae as of the publication of this article or the time of their death. Local control has been achieved in all patients still living and had been achieved in all patients who died from subsequent progression of metastatic disease or other cause. CONCLUSIONS Interstitial (125)I intrathoracic brachytherapy is a safe and effective method when used with sublobar resection in high-risk stage I non-small-cell lung cancer patients and may be used even in situations that require placement of the sources in close approximation to the aorta. The tolerance of the aorta seems to be greater than previously thought, and may well exceed 12,000cGy over the permanent life of the interstitial implant. Interstitial (125)I brachytherapy can safely be used to deliver significant radiation dose in direct contact with the aorta but supplemental, overlapping external beam irradiation should be avoided.

Multidisciplinary treatment of synchronous primary rectal and prostate cancers

Background A 58-year-old Caucasian man with a history of irritable bowel syndrome and occasional rectal bleeding presented with a 4-week history of progressive, bright red blood per rectum. A digital rectal examination revealed a 3 cm distal, midrectal mass. Laboratory tests showed an elevated serum prostate-specific antigen of 32 ng/ml but other physical and medical examinations were unremarkable.Investigations Digital rectal examination, colonoscopy, rectal mass biopsy, endorectal ultrasound, transrectal ultrasound-guided prostate biopsy, CT scan and MRI.Diagnosis Clinical stage III (T3N1M0), moderately differentiated adenocarcinoma of the rectum and clinical stage II (T1cN0M0) adenocarcinoma of the prostate.Management Intensity-modulated radiation therapy, chemoradiation, chemotherapy, hormone therapy and surgery.

SU‐FF‐T‐178: Dosimetric and Technical Aspects of Intraoperative I‐125 Brachytherapy for Stage I Non‐Small Cell Lung Cancer

Purpose: Initial outcome data from our institution have shown that sublobar resection in combination with I‐125 brachtherapy is associated with recurrence rates of 2.0%, compared to 18.6% with sublobar resection alone. The objective of this work is to present the technical and dosimetric aspects required to execute this procedure from the radiationoncology perspective, as well as to analyze the dose distributions of patients treated with this technique. Method and Materials: I‐125 seeds in vicryl suture were embedded into vicryl mesh and surgically inserted providing a 2.0 cm margin on each side of the resection staple line. A nomogram was developed to determine the suture spacing in the vicryl mesh, as a function of seed activity in order to deliver 120 Gy at a distance of 0.5 cm above and below the seed array. Postoperative dosimetry consists of CT‐based planning and dose volume analysis. Results:Dose distributions, DVH data, mean dose and NTCP values for lung were analyzed in a group of patients. The mean doses ranged from 3.72 Gy to 9.10 Gy. NTCP values were below 1%. DVH data shows that a small volume of ipsilateral lung was irradiated for all patients. A comparison of brachytherapy with external beam therapy was investigated for one patient. Brachtherapy was judged to be superior to external beam therapy. Results showed that most of the ipsilateral lung volume received a lower dose when treated with an implant to 120 Gy compared to external beam therapy treated to 60 Gy. Conclusions:Lungbrachytherapy with I‐125 at the time of sublobar resection is a precise and conformal option of dosedelivery for stage I NSCLC patients with compromised physiologic reserve. Patient related toxicity has not been linked to this procedure. This simple technique provides significant lung sparing when compared to standard external beam therapy.

Megavoltage conebeam CT cine as final verification of treatment plan in lung stereotactic body radiotherapy

To analyse the clinical impact of megavoltage conebeam computed tomography (MV‐CBCT) cine on internal target volume (ITV) coverage in lung stereotactic body radiotherapy (SBRT).

SU‐E‐T‐329: Measurement of I‐125 Brachytherapy Dose in Lung

Purpose: Sublobar resection and intraoperative placement of I‐125 seeds along the staple line is an accepted treatment for patients with high risk stage I non‐small cell lungcancer. The dosimetry standard for such an implant is to follow the TG43U1 protocol, which assigns water as the universal medium for dose calculation. This may not be appropriate for lungtissue. The purpose of this study is to characterize the dose distribution in lung relative to water using radiochromic film. Methods: Seven Amersham 6711 I‐125 seeds were sandwiched between slabs of Solid Water® on one side and lung‐equivalent material on the other side. A sheet of Gafchromic EBT2 film was inserted parallel to the sources axes at the depth of measurement in the water and the lung simultaneously. Separate measurements were performed for three depths of 0.5, 1.0 and 1.5 cm. The seeds were far enough apart from each other so as not to influence the measurement from the neighboring seeds. The exposures lasted 2 hours, 5.5 hours and 15 hours for 0.5 cm, 1.0 cm and 1.5 cm, respectively. The total dose in water for these exposure times was 52 cGy, 35 cGy and 39 cGy, respectively. The ratios of lung over Solid Water® doses were averaged over the 7 seeds. Results: The lung to Solid Water® dose ratio was 1.071±0.062, 1.205±0.090 and 1.259±0.053 for the depths of 0.5, 1.0 and 1.5 cm, respectively. Conclusions: The dose in lung is quite similar to the dose in water at the depth of 0.5 cm, which is the prescription depth for a typical lung low dose rate brachytherapy implant. However, the attenuation in lung is smaller than in water, leading to an underestimation of lungdose at 1.5 cm by approximately 25% when TG43 parameters are used.

TU‐C‐204B‐10: Beam's‐Eye‐View MV Fluoroscopy during SBRT for Tumor Tracking and Treatment Verification

Purpose The radiotherapy treatment beam captured in megavoltage fluoroscopy (MVF) mode contains a record of tumor motion during treatment. This studys objectives were to use MVF to: 1) verify whether a tumor remains fully within the treatment beam; and 2) assess the reduction of tumor motion during the beam‐on period by respiratory gating. Method and Materials Electronic portal imaging was used to capture beams‐eye ‐view fluoroscopic movies of target movement within the treatment beam during SBRT.Dose rate was 300 MU/min; no imagingdose beyond the treatment dose was required. Images were captured at 7–13 frames/sec. Three lungcancer and 2 livercancer patients were studied over 5 fractions each; 2 were respiratory gated. For livertumors, implanted gold fiducial markers and surgical clips provided surrogates of tumor motion. Custom image analysis and tracking software was written using MeVisLab/VTK/ITK. Deformable registration between image frames was used to warp tumor contours and compute the tumor center of mass and tumor borders relative to the ITV/PTV as a function of time. Results MVF tumor tracking yielded tumor range‐of‐motion measurements of 4–10 mm in the lungcancer patients, and liver fiducial tracking yielded motion measurements of 14mm and 11mm in the livercancer patients. Large tumor motions due to infrequent large inspirations were reduced by respiratory gating with 75% inspiration threshold. Ungated motion was measured from pre‐treatment cone‐beam projection data. Gating reduced the tumor range of motion from 14mm to 9mm for the lung patient and from 17mm to 14mm for liver patient. Conclusions Motion measured via MV fluoroscopy during SBRT can be used to verify whether planned margins are adequate and evaluate the effectiveness of respiratory gating. Future work towards real ‐time processing could provide control signals for gating or dynamic multi ‐leaf collimators. Research sponsored by Siemens Corporation.

Image storage in radiation oncology: What did we learn from diagnostic radiology?

The Digital Imaging and Communications in Medicine (DICOM) standard was developed by the National Electrical Manufacturers Association (NEMA) and the American College of Radiology (ACR) for medical image archiving and retrieval. An extension to this implemented a standard named DICOM-RT for use in Radiation Oncology. There are currently seven radiotherapy-specific DICOM objects which include: RT Structure Set, RT Plan, RT Dose, RT Image, RT Beams Treatment Record, RT Brachy Treatment Record, and RT Treatment Summary Record. The type of data associated with DICOM-RT includes (1) Radiation treatment planning datasets (CT, MRI, PET) with radiation treatment plans showing beam arrangements, isodose distributions, and dose volume histograms of targets/normal tissues and (2) Image-guided radiation modalities such as Siemens MVision mega-voltage cone beam CT (MV-CBCT). With the advent of such advancing technologies, there has been an exponential increase in image data collected for each patient, and the need for reliable and accessible image storage has become critical. A potential solution is a Radiation Oncology specific picture archiving and communication systems (PACS) that would allow data storage from multiple vendor devices and support the storage and retrieval needs not only of a single site but of a large, multi-facility network of radiation oncology clinics. This PACS system must be reliable, expandable, and cost-effective to operate while protecting sensitive patient image information in a Health Insurance Portability and Accountability Act (HIPAA) compliant environment. This paper emphasizes the expanding DICOM-RT storage requirements across our network of 8 radiation oncology clinics and the initiatives we undertook to address the increased volume of data by using the ImageGrid (CANDELiS Inc, Irvine CA) server and the IGViewer license (CANDELiS Inc, Irvine CA) to create a DICOM-RT compatible PACS system.

WE‐E‐224C‐02: Investigation of Simple IMRT Delivery to Stage I Lung Cancer Patients with Significant Respiratory Motion Using Respiratory Gated CT Scans

Purpose: To investigate the use of IMRT for the treatment of stage I lungcancer associated with significant respiratory motion using 4DCT data. Method and Materials: A 4DCT scan ‐ covering a full respiratory cycle in 10 phases ‐ of a patient with a 1.8 cm diameter lungcancer was used to design several static step‐and‐shoot IMRT plans. Three plans were designed: two using snapshots of the tumor (mid‐inhale, full‐exhale), one using the superposition of all phases. Because of the significant tumor motion (maximum excursion of 2.5 cm) the effect of different margins around the CTV were studied. To reduce interplay between the MLC movement and respiratory motion in an ungated delivery, the number of intensity‐levels was minimized while maintaining coverage to the PTV and minimizing dose to OARs. Results: In this case‐study five‐field IMRT plans were generated using 18 MV photons delivering a total dose of 66 Gy in 33 fractions to the PTV. Plans based on snapshot scans of the lung only resulted in full coverage, if large margins (3 cm) were incorporated. All plans based on superimposed scans achieved full coverage, while allowing tight margins and minimizing the dosage to OARs. A small number of intensity‐levels (3–5 per beam) were sufficient for PTV coverage, thereby reducing the risk of unwanted interplay effects between MLC movement and respiratory motion. Conclusion: Using snapshot free‐breathing CT scans for treatment planning can lead to geometrical misses and underdosage of the target volume unless large PTV margins are applied at the expense of increased dose to OARs. Taking the superimposed CT scans of all respiratory phases for treatment planning ensures the full coverage of the tumor volume, without increasing dose to OARs. For this case‐study only a small number of segments were needed, allowing the application of IMRT despite significant tumor motion.