High Dose Rate Treatment Research Articles

SU‐E‐T‐887: Cyberknife Treatment for Early Stage Oral Tongue Cancer — Feasibility Study

Purpose: Oral tongue carcinoma is a highly curable cancer treated by radiation therapy and especially by interstitial brachytherapy. However, multiple hairpins, needles or hollow catheters are needed to be inserted into the tumor bed for both low‐dose‐rate (LDR) and high‐dose‐rate (HDR) interstitial radiotherapy. The whole insertion procedure is quite invasive and painful to the patient each time it is administered. Therefore, the main aim of this study is to investigate the potential use of Cyberknife in the treatment of oral tongue cancer, which would dramatically reduce unpleasant experiences associated with HDR/LDR treatments. Methods: Using CT images of the patient treated with the HDR interstitial implant, a structure (GTV) was created out of the applicator. A special device will be used to immobilize the tongue during treatment. In CyberKnife treatment planning, the Xsight Spine tracking method was used for patient localization. A 2 mm margin in all directions was added to account for potential localization uncertainties. Subsequent planning is based on prescribing 2000 cGy in 5 fractions to the PTV. Results: The isodose line of 66% (20 Gy in 5 fractions) covers the outer boundary of the PTV in the CyberKnife plan. The conformity index is 1.26 with 98.76% of the target volume covered by the prescription line. The maximum dose inside PTV is 30.3 Gy while the HDR treatment delivers more than 40 Gy to more than 20% of the PTV. Only 3.4 cc of the right mandible receives more than 10 Gy. The maximum dose to left mandible is only 4.4 Gy. The total treatment time is about 18 min/fraction. Conclusions: It is shown that Cyberknife treatment can be a viable alternative to interstitial HDR treatments, which may greatly improve the patient care with tongue cancer.

TH-A-BRA-01: Review of the Radiobiological Principles of Radiotherapy

Mechanisms by which radiation kills cells and ways cell damage can be repaired will be reviewed. The effect of radiobiological parameters which we can control for radiotherapy will be discussed including dose/fraction, number of fractions, time between fractions, overall treatment time, and the LET of the radiation. Reasons why we fractionate the way we do will be discussed, along with how sparing of normal tissues using conformal techniques might affect optimal fractionation. The importance of time between fractions will be presented, especially if cancer cells which exhibit hyper‐radiosensitivity are present. The linear‐quadratic model for cell survival for high and low dose rate treatments and the effect of repopulation will be presented and discussed. The effect of LET will be presented as far as the RBE is concerned for both high and low doses. Learning Objectives: 1. To understand the importance for radiation therapy of dose/fraction, number of fractions, time between fractions, dose rate, overall treatment time, and the LET of the radiation. 2. To understand how geometrical sparing of normal tissues might affect optimal fractionation. 3. To understand the linear‐quadratic model for radiotherapy.

SU-E-T-758: Cyberknife Treatment of Endometrial Cervical Cancer

Purpose: Conventional high dose rate treatment of cervical cancer involves placement of tandem and ring applicators inside the patient. Prior to this, a surgeon sutures the Smit sleeve to the cervix. Before each treatment (5 fractions), the ring and tandem applicator is inserted into the patient with subsequent imaging using CT scanner or fluoroscopy. The whole insertion procedure is quite invasive and painful to the patient each time it is administered. Therefore, the main aim of this study is to investigate the potential use of Cyberknife in the treatment of cervical cancer, which would dramatically reduce unpleasant experiences associated with HDR treatments Methods: Using the CTimages of the patient that underwent HDR treatment to the cervix, a structure was created out of the applicator. PTV was generated out of this structure by expanding the tandem by 10 mm and the ring by 8 mm in all directions. Thus formed PTV can be created out of different tandem and ring sizes and angles to generate different templates that would be fused to patient CT data based on the position of cervical os. Subsequent planning is based on prescribing 600 cGy to the PTV Results: The isodose line of 72% (30 Gy in 5 fractions) covers the outer boundary of the PTV. Only 0.48% of the bladder volume receives the highest dose of 22.5 Gy, well below the required 80% of the prescription. 0.6% of the rectum volume receives the highest dose of 15.83 Gy, well below the required 60% of the prescription. The B and P points receive 17.3% and 6.5% of the prescription correspondingly. The total treatment time is 25 min Conclusions: It is shown that Cyberknife treatment can be a viable alternative to endometrial HDR treatments, which may greatly improve the patient care with cervical cancer.

Interstitial High-Dose-Rate Brachytherapy Under Local Anesthesia for Early Stage Prostate Cancer: A Report of 546 Cases

Purpose: Transrectal ultrasound (TRUS)-guided interstitial implant for prostate cancer using low-dose-rate (LDR) and high-dose-rate (HDR) techniques has been reported with results comparing very favorably to external beam radiation therapy. TRUS interstitial implant of the prostate has been traditionally performed under general or spinal anesthetic in an operating room. We report our results with a technique performed under local anesthesia in a department procedure room.Materials and Methods: Patients with T1 and T2 localized prostate cancer were judged to be candidates for TRUS guided interstitial implant. Conscious sedation consisted of intravenous Morphine (12–22 mg) and Versed (6–14 mg), or intravenous Demerol (25–250 mg) and Versed (3–12 mg), and Ativan (0–2 mg). Local anesthetic was given with a mixture of 1% Lidocaine, 0.25% Marcaine, 1:100,000 Epinephrine, and 4% Sodium Bicarbonate neutralizing solution (120 cc). Local anesthesia was given to a 5 x 5 cm perineal area to a depth of 10 cm under TRUS guidance. The implants were placed under mobile multi-plane prostate template (Radiation Therapy Products Prostate Template) guidance using from 3 to 4 planes, and 12 to 22 needles. Needle spacing was 1.0 cm. The implant procedure included sigmoidoscopy and cystoscopy.Results: Between 2002 and 2010, 546 TRUS-guided prostate implants were performed under local anesthesia. Median implant time was 45 minutes (range: 30 to 150 minutes). HDR treatment was given using the Nucletron afterloading system. The implant volume received 2,250 cGy in 3 fractions prescribed to the 100% isodose line, given over 24 hours. Urethral dose points (12–16) were followed, and limited to ≤105% of the prescription dose. The procedure was well tolerated, with all patients having completed the procedure. Four patients developed respiratory suppression, and required reversal with Narcan. All recovered uneventfully. Otherwise, there have been no acute complications to date.Conclusions: TRUS interstitial implant of the prostate under local anesthesia is feasible. Implant time, complications, cost, and scheduling convenience, compare favorably to general or spinal anesthetic technique. Purpose: Transrectal ultrasound (TRUS)-guided interstitial implant for prostate cancer using low-dose-rate (LDR) and high-dose-rate (HDR) techniques has been reported with results comparing very favorably to external beam radiation therapy. TRUS interstitial implant of the prostate has been traditionally performed under general or spinal anesthetic in an operating room. We report our results with a technique performed under local anesthesia in a department procedure room. Materials and Methods: Patients with T1 and T2 localized prostate cancer were judged to be candidates for TRUS guided interstitial implant. Conscious sedation consisted of intravenous Morphine (12–22 mg) and Versed (6–14 mg), or intravenous Demerol (25–250 mg) and Versed (3–12 mg), and Ativan (0–2 mg). Local anesthetic was given with a mixture of 1% Lidocaine, 0.25% Marcaine, 1:100,000 Epinephrine, and 4% Sodium Bicarbonate neutralizing solution (120 cc). Local anesthesia was given to a 5 x 5 cm perineal area to a depth of 10 cm under TRUS guidance. The implants were placed under mobile multi-plane prostate template (Radiation Therapy Products Prostate Template) guidance using from 3 to 4 planes, and 12 to 22 needles. Needle spacing was 1.0 cm. The implant procedure included sigmoidoscopy and cystoscopy. Results: Between 2002 and 2010, 546 TRUS-guided prostate implants were performed under local anesthesia. Median implant time was 45 minutes (range: 30 to 150 minutes). HDR treatment was given using the Nucletron afterloading system. The implant volume received 2,250 cGy in 3 fractions prescribed to the 100% isodose line, given over 24 hours. Urethral dose points (12–16) were followed, and limited to ≤105% of the prescription dose. The procedure was well tolerated, with all patients having completed the procedure. Four patients developed respiratory suppression, and required reversal with Narcan. All recovered uneventfully. Otherwise, there have been no acute complications to date. Conclusions: TRUS interstitial implant of the prostate under local anesthesia is feasible. Implant time, complications, cost, and scheduling convenience, compare favorably to general or spinal anesthetic technique.

A Multi-institutional Study of Implementation, Tolerance and Early Clinial Results With Non-invasive Image-Guided Breast Brachytherapy for Tumor Bed Boost

interstitial implant and High-dose-rate (HDR) radiation afterloading compares very favorably to EBRT in selected patients. We report median 6 year followup in 273 cases. Materials andMethods: Patients with Tis, T1, and T2 tumors measuring# 4 cm, negative surgical margins, and#3 axillary lymph nodes were judged to be candidates for interstitial implant. Implants were performed under stereotactic mammographic guidance with conscious sedation and local anesthesia. The implants were placed using a custom designed template with 3 to 8 planes, and 8 to 74 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation treatment planning was performed using CT scanning and the Plato System. Treatment volumes ranged from 25 cm to 458 cm. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 cGy in 10 fractions prescribed to the planning target volume, given BID over 5 days. Results: Between 2000 and 2010, 273 patients underwent interstitial HDR implant. The procedure was well tolerated. No patient required hospital admission. With a median followup 72 months (range 6e132 months), local recurrence occurred in 4.0% (11/273). Cosmetic results were good to excellent in 89.0% (243/273) of the patients. There were no infections. Wound healing complications developed in 2.9% (8/273). Three of these patients had received anthracycline based Chemotherapy. The other five had large (O200 cm) implant volumes. In patients with catheter spacing of 1.5 cm and V-150% O30%, 9.5% (8/84) developed wound complications vs. 0% (0/189) in patients with catheter spacing of 1.0 cm and V-150% !30% (p 5 0.0001). Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis. Conclusions: With median 72-month followup, breast conservation radiation therapy utilizing interstitial multi-catheter HDR implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatment with anthracyclinebased chemotherapy, large (O200 cm) implant volumes, and V-150% O30%, appear to be relative contraindications to interstitial HDR implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications. Compared to MammoSite technique, the interstitial multi-catheter method offers greater flexibility of radiation delivery. Advantages, include no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture, balloon movement, air gaps, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon.

Comparison of high–dose rate prostate brachytherapy dose distributions with iridium-192, ytterbium-169, and thulium-170 sources

Purpose Recent studies have identified that among different available radionuclides, the dose characteristics and shielding properties of ytterbium-169 ( 169Yb) and thulium-170 ( 170Tm) may suit high–dose rate (HDR) brachytherapy needs. The purpose of this work was to compare clinically optimized dose distributions using proposed 169Yb and 170Tm HDR sources with the clinical dose distribution from a standard microSelectron V2 HDR iridium-192 ( 192Ir) brachytherapy source (Nucletron B.V., Veenendaal, The Netherlands). Methods and materials CT-based treatment plans of 10 patients having prostate volumes ranging from 17 to 92 cm 3 were studied retrospectively. Clinical treatment of these patients involved 16 catheters and a microSelectron V2 HDR 192Ir source. All dose plans were generated with inverse planning simulated annealing optimization algorithm. Dose objectives used for the 192Ir radionuclide source were used for the other two radionuclides. The dose objective parameters were adjusted to obtain the same clinical target (prostate) volume coverage as the original 192Ir radionuclide plan. A complete set of dosimetric indices was used to compare the plans from different radionuclides. A pairwise statistical analysis was also performed. Results and conclusions All the dose distributions optimized with specific 192Ir, 169Yb, and 170Tm sources satisfied the standard clinical criteria for HDR prostate implants, such as those for the Radiation Therapy Oncology Group clinical trial 0321, for combined HDR and external beam treatment for prostate adenocarcinoma. For equivalent clinical target volume dose coverage, the specific 169Yb and 170Tm sources resulted in a statistically significant dose reduction to organs at risk compared with microSelectron V2 HDR 192Ir source. This study indicates that a 170Tm or 169Yb radionuclide source may be an alternative to the 192Ir radionuclide sources in HDR brachytherapy.

Use of megavoltage computed tomography with image registration for high–dose rate treatment planning of an oral tongue cancer using a custom oral mold applicator with embedded lead shielding

Purpose A patient with a lateral oral tongue cancer was treated with high–dose rate brachytherapy using an oral applicator with embedded lead shielding making conventional simulation, using either kilovoltage computed tomography or radiographs, impossible because of scatter artifact. Methods and materials Treatment simulation was accomplished using megavoltage computed tomography (MVCT) simulation on a helical tomotherapy unit. Because of difficulty in visualization of the catheters on the patient MVCT images, Velocity AI image registration software (Velocity Medical Solutions, Atlanta, GA) was used to register an MVCT of the applicator itself with the patient MVCT simulation. The treatment plan was manually optimized to prescribe 4 Gy/fraction to the gross tumor volume. Results The patient tolerated the treatment well, with no evidence of disease 6 months after treatment. Thermoluminescent dosimeter measurements showed that the shielding reduced the dose by up to 90%, depending on the location of the thermoluminescent dosimeter. While the patient was treated using dose distributions calculated in a homogeneous medium (Task Group-43), an approximation of the true dose distributions was retrospectively calculated using Acuros (Varian Medical Systems Inc., Palo Alto, CA), which accounts for heterogeneities in the patient. Discussion Use of the MVCT with image registration allowed treatment planning in the presence of lead shielding. Dose–volume histograms showed that recalculation of the dose using heterogeneity correction did not affect the dose to the gross tumor volume, but that the dose to normal structures (maxilla and mandible) was reduced by the lead shielding. Conclusion The use of MVCT and image registration allows for optimized planning in the presence of shielding, which would not be possible with conventional kilovoltage computed tomography.

Interstitial High Dose Rate (HDR) Brachytherapy under Local Anesthesia for Early Stage Prostate Cancer: A Report of 524 Cases

Interstitial High Dose Rate (HDR) Brachytherapy under Local Anesthesia for Early Stage Prostate Cancer: A Report of 524 Cases

Interstitial High Dose Rate (HDR) Brachytherapy for Ductal Carcinoma In Situ of the Breast: Median 6 Year Results of 63 Cases using Multi-catheter Technique

External Beam Radiation Therapy (EBRT) has been the standard of care for breast conservation radiation therapy, in both Invasive Ductal Carcinoma (IDC) and Ductal Carcinoma In Situ (DCIS). Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorably to EBRT in selected cases of IDC. There is little data regarding HDR in DCIS. We report our HDR results in 63 patients with DCIS. Patients with Tis, T1, and T2 tumors measuring ≤ 4 cm, negative surgical margins, and ≤ 3 axillary lymph nodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographic guidance with conscious sedation and local anesthesia. The implants were placed with a custom designed template using from 3 to 8 planes, and 8 to 74 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation Treatment planning was performed using CT Scanning and the Plato System. Treatment volumes ranged from 25 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 c Gy in 10 fractions prescribed to the Planning Target Volume, given BID over 5 days. Between 2000 and 2010, 268 patients underwent Interstitial HDR Implant. The procedure was well tolerated. No patient required hospital admission. With a median follow-up 72 months (range, 6-128 months), local recurrence (LR) occurred in 3.7% (10/268). LR occurred in 3.5% (7/205) of patient with IDC vs. 4.8% (3/63) in DCIS (p = 0.70). Cosmetic results were good to excellent in 89.5% (240/268) of the patients. There were no infections. Wound healing complications developed in 3.0% (8/268). Three of these patients had received anthracycline based Chemotherapy. The other five had large (> 200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of > 30%. Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis. With median 72 month follow-up, Breast Conservation radiation therapy utilizing Interstitial Multi-Catheter HDR Implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. There was no difference in LR between patients with IDC and DCIS. Treatment with anthracycline based Chemotherapy, large (> 200 cm3) implant volumes, and V-150% > 30%, appear to be relative contraindications to Interstitial HDR Implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications.

SU-GG-T-73: High Dose Rate (HDR) Brachytherapy Using Foley and Catheter Technique for Treatment of Urethral Cancer

Purpose: To present an innovative treatment technique using Foley Catheter and high dose rate (HDR) brachytherapy for localized urethral cancer. Introduction: Urethral cancer that is localized between bladder neck and penile area presents a significant challenge for external beam irradiation treatment. Irregular surface plus large depth variations often lead to severe skinreactions in scrotal and penile area. This limits the total dose a patient can receive. To overcome this limitation, we developed a technique using High Dose Rate (HDR) brachytherapy delivered through a Foley Catheter. Methods and Materials: A 61 year old gentleman with cancer of penile urethra was treated with external beam using 10 MV photons to the dose of 39.6 Gy. Patient had considerable acute skinreactions in the scrotal and penile area, resulting treatment break. An alternative technique using HDR system was developed. The biggest challenge for HDR treatment was holding the catheter in place, reproducibility, and high mucosal dose. The patient was catheterized with largest Foley catheter and through this Foley; a 6 French endobronchial catheter was inserted. The inflated Foley helped us to secure and reproduce the HDR catheter for multiple fractions. Patient was CT‐Simmed using Foley and Catheter with X‐ray localizer for HDR planning. Based on Linear Quadratic model, HDR fractionation of 4.5 Gy/F times 5F, was planned to take total dose equivalent to 74 Gy with 2Gy/F. Results: Patient received five fractions of HDR treatment delivered bi‐weekly. The catheter placement was confirmed using CTimaging before each HDR treatment. At the end of each fraction, the HDR catheter was removed. Patient tolerated all treatments very well. The early results for this technique appear very promising. Conclusions: This alternative delivery technique allowed adequate dose to the cancer, while sparing morbidity to the soft tissues of his penus, scrotum and rectum.

SU-GG-T-66: Dosimetric Comparison between Contura MLB and MammoSite ML

Purpose: To quantify the dosimetric differences between Contura and Mammosite Multi‐lumen (ML) plans for Accelerated Partial Breast Irradiation (APBI) Method and Materials: Twenty High Dose Rate (HDR) treatment plans using the new Mammosite ML balloon applicator were retrospectively generated for patients previously treated with HDR‐APBI using Contura Multi Lumen Balloon applicator. ML lumens were placed by coincidence with the central lumen and oriented with an offset lumen closest to skin. Plans were optimized using the same constraints and had the same D95 target coverage. Dosimetric parameters from Contura and Mammosite plans were extracted and compared. These parameters included: max dose to skin, max dose to ribs, target coverage, conformity and dose homogeneity indices. Results: For large skin/rib to balloon distances, treatment plans with these two APBI techniques can achieve comparable coverage and dose homogeneity. V100, V150 and V200 were in the range of 0.2 to 3 cm3, 0.2 to 3.6cm3 and respectively 0.3 to 1.2cm3 typically lower for Contura. The ML conformity index was an average of 0.83 (min 0.71) versus 0.84 (min 0.74) for Contura. In constrained cases (small skin and rib distances), the maximum dose to skin was higher for ML, on average by 10% with a maximum of up to 20%. The differences for the maximum dose to closest ribs in these cases were smaller than 5%. Conclusion: For balloons placed at larger distances from skin and/or chest wall, the two balloon applicators achieve comparable target coverage, conformity and dose homogeneity. However, for smaller breast sizes, when the balloon becomes close to both skin and chest wall, Contura can achieve a better skin sparing than MammoSite, likely due to its lumen geometry. Conflict of Interest: DA, DT are consultants for SenoRx. Inc.

SU-GG-T-65: Dosimetric Verification of HDR Treatment Planning System Dose Calculations by Farmer Chamber Measurements in Water

Purpose: To evaluate the applicability of Farmer ion chambers for absolute dosimetry of high dose rate (HDR) brachytherapy sources in water and the potential to use this methodology for brachytherapy treatment planning system (TPS) dose calculation validation. Method and Materials: Water tank absolute dosimtric measurements of 192Ir doses were performed with a Farmer ionization chamber. Autoradiography was used for determination of absolute source position and subsequent alignment of the source with the chamber. A small solid water phantom was used for brachy catheter support. The phantom was immersed in a water tank equipped with a chamber holding mechanism capable of 1D motion. The chamber and the electrometer used for absolute dose measurements had ADCL traceable calibration factors for external beam reference dosimetry (calibrated in water with 60Co beam). Doses were measured from 2 cm to 11 cm away from a single dwell position. Measurements were compared to doses calculated by Oncentra HDR TPS as well as simple hand calculations, utilizing point source geometry, inverse square dose falloff and published data for radial dose falloff due to attenuation. Results: The measured and the TPS doses agreed within 3% up to 8 cm from the source, within 4% from 8 cm to 10 cm, and within 6% at 11 cm. The hand calculations, performed as a simple consistency check, agreed with the TPS within 1% across the entire tested range. Conclusions: The presented results indicate that Farmer chambers are suitable for absolute dosimetry of 192Ir sources over the useful HDR therapeutic range (2 cm to 10 cm). Absolute measurements in water performed with Farmer chambers can be easily employed for commercial TPS dosimetric commissioning as well as for routine dosimetric checks of the HDR delivery systems.

TU-D-BRB-01: PET/CT Guided Dose Redistribution for HDR Interstitial Brachytherapy of Cervical Cancer

Purpose: Advances in functional imaging may allow identification and targeting of tumor sub-volumes based on their biological characteristics, allowing selective boosting of dose to radio-resistant sub-volumes during treatment planning. The purpose of this study was to redistribute high dose regions toward the PET-hot regions as identified on PET/CT images during High-Dose-Rate (HDR) brachytherapy for cervical cancer while maintaining a clinically acceptable DVH. Material and Methods: FDG-PET and CT images were acquired and registered. The tumor volume was contoured and segmented into sub-volumes based on their Standardized Uptake Values (SUV) in PET images. The sub-volumes with higher SUV were considered metabolically active and therefore required higher radiation dose. The integral tumor was prescribed a uniform dose from external beams followed by a boost dose delivered by HDR interstitial brachytherapy. The HDR treatment plan was optimized using a home-brew software implementation of an Adaptive Simulated Annealing (ASA) algorithm. The tumor dose was then redistributed by increasing and decreasing the prescription dose to sub-volumes with higher and lower SUV respectively such that the integral tumor prescription dose was kept constant. A routine cervical cancer case with both uniform and PET-guided plans is presented. Both plans were optimized based on a generalized Equivalent Uniform Dose (gEUD) cost function and renormalized to V100=95% of prescribed dose to the integral PTV. Their isodose distributions and DVHs were compared. Results: The PET-guided plan had larger hot spots in and near the PET sub-volume while the DVH of PTV was kept the same as that of the uniformly prescribed plan. Doses to critical organs were also reduced in the PET-guided plan. Conclusions: The approach described used PET/CT imaging guiding dose redistribution within PTV so that the hot spots encompass metabolically active tumor sub-volumes. An IRB approved treatment protocol is underway to study the clinical efficiency of this approach.

Interstitial High-Dose-Rate Brachytherapy for Early Stage Breast Cancer: Median 6-Year Followup of 251 Cases Using Multi-Catheter Technique

Purpose: External beam radiation therapy (EBRT) has been the standard of care for breast conservation radiation therapy. Recent data indicate that interstitial implant and high-dose-rate (HDR) radiation afterloading compares very favorably to EBRT in selected patients.Materials and Methods: Patients with Tis, T1, and T2 tumors measuring ≤4 cm, negative surgical margins, and ≤3 axillary lymph nodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographic guidance with conscious sedation and local anesthesia. The implants were placed using the Anderson-Nair Template using from 3 to 8 planes, and 8 to 62 needles. Catheters were subsequently threaded through the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation treatment planning was performed using CT scanning and the Plato™ system. Treatment volumes ranged from 25 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 cGy in 10 fractions prescribed to the planning target volume, given BID over 5 days.Results: Between 2000 and 2009, 251 patients underwent interstitial HDR implant. The procedure was well tolerated. No patient required hospital admission. With a median followup 72 months (range 6-120 months), local recurrence occurred in 4.0% (10/251). Cosmetic results were good to excellent in 89.2% (224/251) of the patients. There were no infections. Wound healing complications developed in 3.2% (8/251). Three of these patients had received anthracycline based Chemotherapy. The other five had large (>200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of >30%. Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis.Conclusions: With median 72 month followup, breast conservation radiation therapy utilizing interstitial multi-catheter HDR implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatment with anthracycline-based chemotherapy, large (>200 cm3) implant volumes, and V-150% > 30%, appear to be relative contraindications to interstitial HDR implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications. Compared to MammoSite® technique, the interstitial multi-catheter method offers greater flexibility of radiation delivery. Advantages, include no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture, balloon movement, air gaps, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon. Purpose: External beam radiation therapy (EBRT) has been the standard of care for breast conservation radiation therapy. Recent data indicate that interstitial implant and high-dose-rate (HDR) radiation afterloading compares very favorably to EBRT in selected patients. Materials and Methods: Patients with Tis, T1, and T2 tumors measuring ≤4 cm, negative surgical margins, and ≤3 axillary lymph nodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographic guidance with conscious sedation and local anesthesia. The implants were placed using the Anderson-Nair Template using from 3 to 8 planes, and 8 to 62 needles. Catheters were subsequently threaded through the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation treatment planning was performed using CT scanning and the Plato™ system. Treatment volumes ranged from 25 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 cGy in 10 fractions prescribed to the planning target volume, given BID over 5 days. Results: Between 2000 and 2009, 251 patients underwent interstitial HDR implant. The procedure was well tolerated. No patient required hospital admission. With a median followup 72 months (range 6-120 months), local recurrence occurred in 4.0% (10/251). Cosmetic results were good to excellent in 89.2% (224/251) of the patients. There were no infections. Wound healing complications developed in 3.2% (8/251). Three of these patients had received anthracycline based Chemotherapy. The other five had large (>200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of >30%. Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis. Conclusions: With median 72 month followup, breast conservation radiation therapy utilizing interstitial multi-catheter HDR implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatment with anthracycline-based chemotherapy, large (>200 cm3) implant volumes, and V-150% > 30%, appear to be relative contraindications to interstitial HDR implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications. Compared to MammoSite® technique, the interstitial multi-catheter method offers greater flexibility of radiation delivery. Advantages, include no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture, balloon movement, air gaps, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon.

Interstitial High-Dose-Rate Brachytherapy for Ductal Carcinoma In Situ of the Breast: Median 6-Year Results of 59 Cases Using Multi-Catheter Technique

Purpose: External beam radiation therapy (EBRT) has been the standard of care for breast conservation radiation therapy, in both invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS). Recent data indicate that interstitial implant and high-dose-rate (HDR) radiation afterloading compares very favorably to EBRT in selected cases of IDC. There are little data regarding HDR in DCIS. We report our HDR results in 59 patients with DCIS. Materials and Methods: Patients with Tis, T1, and T2 tumors measuring ≤4 cm, negative surgical margins, and ≤3 axillary lymph nodes were judged to be candidates for interstitial implant. Implants were performed under stereotactic mammographic guidance with conscious sedation and local anesthesia. The implants were placed using the Anderson-Nair template using from 3 to 8 planes, and 8 to 62 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation treatment planning was performed using CT scanning and the Plato™ system (Nucletron B.V., Veenendaal, The Netherlands). Treatment volumes ranged from 25 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 cGy in 10 fractions prescribed to the planning target volume, given BID over 5 days. Results: Between 2000 and 2009, 251 patients underwent interstitial HDR implant. The procedure was well tolerated. No patient required hospital admission. With a median followup 72 months (range 6-120 months), local recurrence occurred in 4.0% (10/251). LR occurred in 3.6% (7/192) of patient with IDC vs. 5.1% (3/59) in DCIS (p = 0.70). Cosmetic results were good to excellent in 89.2% (224/251) of the patients. There were no infections. Wound healing complications developed in 3.2% (8/251). Three of these patients had received anthracycline based Chemotherapy. The other five had large (>200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of >30%. Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis. Conclusions: With median 72-month followup, breast conservation radiation therapy utilizing interstitial multi-catheter HDR implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. There was no difference in LR between patients with IDC and DCIS. Treatment with anthracycline-based chemotherapy, large (>200 cm3) implant volumes, and V-150% >30%, appear to be relative contraindications to interstitial HDR implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications. Compared to MammoSite® technique, the interstitial multi-catheter method offers greater flexibility of radiation delivery. Advantages include, no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture, balloon movement, air gaps, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon.

Quality Control Of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control

Purpose: Statistical process control (SPC) is a quality control method used to ensure that a process is on-target and operating with minimal variation. The focus of this study is to determine if SPC is a viable technique for evaluating the proper operation of a high-dose-rate (HDR) brachytherapy treatment delivery system. Materials and Methods: Thomson-Nielsen MOSFET Dosimetry System (MOSFET model 502RD) was used as the dosimeter. MOSFET dosimeters (MD) were calibrated against a Farmer-type ionization chamber at a distance of 1.6 cm from 192Ir in water. A surrogate prostate patient was developed utilizing Vyse Ordance™ gelatin. Needle placement was performed according to our prostate HDR clinical protocol. A total of 10 MD were placed from prostate base to apex. Three detector trains of three MD each, spaced 2.5 cm apart, were inserted into two detector holders at the prostate periphery as well as in the urethra. The remaining MD was placed at the apex on the periphery. CT guidance was used to accurately position the first detector in each train at the base. The plan consisted of 12 needles with 129 dwell positions spaced 0.5 cm apart, delivering a prescribed peripheral dose of 200 cGy. Marks were placed on the needles at the template, and the distance from the template to the needle hub was recorded to allow accurate repositioning of each needle. Sixteen accurate treatment trials were delivered as planned. Subsequently a number of treatments were delivered with errors introduced. The errors were: wrong patient (i.e., a clinical plan for a different patient with 12 needles), wrong source calibration (3 & 7 day source decay inaccuracy), wrong sequence (i.e. two needles connected to incorrect location in turret), single needle displaced inferiorly 5mm, and entire implant displaced 2mm and 4mm inferiorly. Each MD constituted an evaluation subgroup size of one (bias correction factors d2 & d3 determined for n = 2 for consistency with established SPC methodology). The range was therefore determined by the difference between sequential treatment delivery measurements. Two process behavior charts (PBC), an average and range chart, were developed for each MD. Results: There were 4 false positives resulting from 160 measurements from 16 accurately delivered treatments. Generally speaking, data points resulting from accurately delivered treatments were well within PBC limits. The PBC indicate that measurements made at the base and apex were much more sensitive to treatment delivery errors. Each of the errors introduced was correctly identified by either the average or range PBC for measurements made at the base (2 out of 3 locations) and apex (all 4 locations). The PBC for measurements made at mid-gland (3 locations) were less sensitive to errors in treatment delivery. The only errors detected at these locations were “wrong patient” and “wrong source calibration.” Conclusions: SPC is a viable methodology to assess the quality of HDR treatment delivery. Further development is necessary to determine the most effective positioning of the MD for detecting potential treatment delivery errors.

Optimisation-based thermal treatment planning for catheter-based ultrasound hyperthermia

A patient-specific optimisation-based hyperthermia treatment planning program for catheter-based ultrasound technology was developed for a priori evaluation of proposed applicator implant strategies and determination of initial applied power settings. The interstitial and endocavity heating applicators, designed for delivering 3-D controllable hyperthermia within High Dose Rate (HDR) brachytherapy implants, consist of linear and sectored arrays of ultrasound transducers with variable power control in both length and angle. A 3D biothermal model, which incorporates relevant anatomical structures and implant geometries based upon HDR treatment planning, has been developed to simulate the temperature distributions induced by these ultrasound applicators within the catheter implants. A temperature-based constrained optimisation algorithm was devised and integrated within the finite-element thermal solver to determine the optimal applied power levels. A temperature-expressed objective function and constraints were employed to limit maximum temperature (Tmax), maximise target coverage (Ttarget), and minimise thermal exposure to normal tissue and surrounding organs. The optimisation-based treatment planning was applied on representative examples of clinical HDR implants for endocavity treatment of cervix (n = 3) and interstitial treatment of prostate (n = 3). Applicator positioning and orientation, Tmax, and Ttarget, were varied, and temperature volume and thermal dose volume histograms calculated for each plan. The optimisation approach provided optimal applied power levels (4–24 independent transducer sections) leading to conforming or tailored temperature distributions for all cases, as indicated with improved temperature index T90 in the target volume and negligible temperature and thermal dose (t43,max < 1 min) exposure in surrounding non-targeted tissues, such as bladder and rectum. The precision of the optimised power estimates was shown to be within <5% for a range of starting levels and were similarly convergent. The execution times of this optimisation (<16 min) and forward thermal treatment planning (<22 min) is sufficiently fast to be integrated into the clinical setting. This optimisation-based treatment planning platform for catheter-based ultrasound applicators is a useful tool to provide feedback for applicator selection (sector angle, number of transducer sections along length), positioning (angle or orientation), optimal initial power settings, and has potential to significantly improve the delivery of hyperthermia in conjunction with HDR brachytherapy.

Interstitial High Dose Rate (HDR) Brachytherapy under Local Anesthesia for Early Stage Prostate Cancer: A Report of 467 Cases

Transrectal Ultrasound (TRUS) guided interstitial implant for prostate cancer using Low Dose Rate (LDR) and High Dose Rate (HDR) techniques has been reported with results comparing very favorably to external beam radiation therapy. TRUS interstitial implant of the prostate has been traditionally performed under general or spinal anesthetic in an operating room. We report our results with a technique performed under local anesthesia in a Department procedure room. Patients with T1 and T2 localized prostate cancer were judged to be candidates for TRUS guided interstitial implant. Conscious sedation consisted of intravenous Morphine (12-22 mg) and Versed (6-14 mg), or intravenous Demerol (50-175 mg) and Versed (3-12 mg). Local anesthetic was given with a mixture of 1% Lidocaine, 0.25% Marcaine, 1:100,000 Epinephrine, and 4% Sodium Bicarbonate neutralizing solution (20-120 cc). Local anesthesia was given to a 5 x 5 cm perineal area to a depth of 10 cm under TRUS guidance. The implants were placed under mobile multi-plane prostate template (Radiation Therapy Products Prostate Template) guidance using from 3 to 4 planes, and 12 to 22 needles. Needle spacing was 1.0 cm. The implant procedure included sigmoidoscopy and cystoscopy. Between 2002 and 2009, 467 TRUS guided prostate implants were performed under local anesthesia. Median implant time was 45 minutes (range : 30 to 150 minutes). HDR treatment was given using the Nucletron afterloading system. The implant volume received 2,250 cGy in 3 fractions prescribed to the 100% Isodose line, given over 24 hours. Urethral dose points (12-16) were followed, and limited to ≤ 105% of the prescription dose. The procedure was well tolerated, with all patients having completed the procedure. Three patients developed respiratory suppression, and required reversal with Narcan. All recovered uneventfully. Otherwise, there have been no acute complications to date. TRUS interstitial implant of the prostate under local anesthesia is feasible. Implant time, complications, cost, and scheduling convenience, compare favorably to general or spinal anesthetic technique.

Salvage High Dose Rate Brachytherapy after Primary External Beam Irradiation in Localized Prostate Cancer: A Case Report

No standard treatment exists for locally relapsed prostate cancer after primary external beam radiotherapy with no evidence of distant metastases. Radical prostatectomy, brachytherapy, cryotherapy and high-intensity focused ultrasound are currently used as local salvage treatments. Data on the safety and effectiveness of high dose rate (HDR) brachytherapy in this scenario are limited. We report on a patient who has no evidence of disease and no late urinary or gastrointestinal toxicity 33 months after receiving HDR treatment for recurrent prostate cancer.

SU‐FF‐T‐42: A Novel Approach to Scar Boost in Mesothelioma Treatment

Purpose: To evaluate the potential advantages of high dose rate(HDR) brachytherapy for boosting mesothelioma incisions extending beyond the hemithoracic target volume. HDR treatment was compared with abutted, enface electron fields. Methods and Materials: One case describes catheter placement, dosimetric advantages, setup uncertainties, and treatment delivery. The right lateral decubitus position, in alpha cradle, was selected to permit consideration of HDR versus electrons. Comparative analyses of treatment plans were performed, and HDR setup and dosimetry were preferred. The HDR treatment utilized 3 catheters atop 5mm of bolus. The HDR setup required physician to confirm catheter placement. Tape, 5mm bolus, and wet towels secured the catheters and provided shielding. The prescription was 3.0Gy to 1.2cm from catheter including bolus (7mm depth in tissue). Dwell positions every 5mm were used to cover the entire length of the scars (22cm and 34cm). The corresponding electron plan required 5 thin strip cutouts and a physician present to approve field setup and feathering of the junctions. A phantom was used to simulate treatment of lesion with electrons and entire process was timed. Results: The total setup and treatment time for 6 HDR treatments was approximately 270minutes (time varies with activity, prescription dose, and volume) compared with 450minutes for 15 electron fractions (2Gy/fraction). Planning time for either modality is comparable. Electron treatments involve additional time for cutting blocks, measuring cutout factors, and physician approved junction changes. One additional concern is dose homogeneity caused by feathering electrons versus brachytherapy which provides a reliable dose distribution. Conclusions: HDR brachytherapy provided an optimal solution over the complicated and time‐consuming electron treatment and should be considered as a viable option for mesothelioma patients with a considerable scar length beyond hemithoracic target volume. Clinical data to support the use of brachytherapy over electrons for coverage of incisional scars is still needed.