Trastuzumab with trimodality treatment for esophageal adenocarcinoma with HER2 overexpression: NRG Oncology/RTOG 1010

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Background: Trastuzumab is a monoclonal antibody against human epidermal growth factor receptor 2 (HER2). The primary objective of RTOG 1010 was to determine if trastuzumab increases disease-free survival (DFS) when combined with trimodality treatment for patients with HER2 overexpressing esophageal adenocarcinoma. Methods: This open label, randomized phase III trial included patients with newly diagnosed stage T1N1-2, T2-3N0-2 adenocarcinoma of the esophagus involving the mid, distal, or esophagogastric junction and up to 5cm of the stomach. All patients received chemotherapy (C) of paclitaxel, 50mg/m2 and carboplatin AUC = 2, weekly for 6 weeks, with radiation (XRT: 3D-CRT or IMRT, 50.4 Gy in 28 fractions) followed by surgery. Patients were randomized 1:1 to receive weekly trastuzumab 4mg/kg week 1 then 2mg/kg/weekly x 5 during CXRT then 6 mg/kg for 1 dose prior to surgery and 6mg/kg every 3 weeks for 13 treatments after surgery. HER2 status was determined by IHC and gene amplification by FISH. With a 2-sided alpha of 0.05, 162 DFS events provide 90% power to detect a signal for an increase in median DFS from 15 to 25 months. DFS and overall survival (OS) were estimated by the Kaplan-Meier method. and arms were compared using the log rank test. The Cox proportional hazards model was used to analyze treatment effect. Results: 571 patients were entered for assessment of HER2 expression, 203 HER2+ patients randomized. The median follow-up for alive patients is 5.0 years. The estimated 2, 3, and 4-year DFS (95% CI) for the CXRT +trastuzumab arm were 41.8% (31.8%, 51.7%), 34.3% (24.7%, 43.9%), and 33.1% (23.6%, 42.7%), respectively, and for the CXRT arm were 40.0% (30.0%, 49.9%), 33.4% (23.8%, 43.0%), and 30.1% (20.7%, 39.4%), respectively; log-rank p = 0.85. The median DFS time is 19.6 months (13.5-26.2) for the CXRT +trastuzumab arm compared to 14.2 months (10.5-23.0) for the CXRT arm. The hazard ratio (95% CI) comparing the DFS of CXRT+trastuzumab arm to the CXRT arm was 0.97 (0.69, 1.36). The median OS time was 38.5 months (26.2-70.4) for the CXRT+trastuzumab arm compared to 38.9 months (29.0-64.5) for the CXRT arm, hazard ratio (95% CI): 1.01 (0.69, 1.47). There was no statistically significant increase in treatment-related toxicities with the addition of trastuzumab including no increase in cardiac events. Conclusions: The addition of trastuzumab to trimodality treatment did not improve DFS for patients with HER2 overexpressing esophageal adenocarcinoma. Supported by NCI grants U10CA180868, UG1CA189867, U10CA180822 and Genentech. Clinical trial information: NCT01196390 .

Complete neoadjuvant treatment for rectal cancer: A single institution experience

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Background: Full dose adjuvant chemotherapy following preoperative chemoradiation and surgery is poorly tolerated in stage II and III rectal cancer. We reviewed our institution’s experience with complete neoadjuvant treatment for rectal cancer since publication of the BrUOG R-224 trial results. Methods: After obtaining IRB approval, Data on patients with stage II and III rectal cancer who underwent complete neoadjuvant therapy were collected.. Patients who were planned to receive 8 cycles of modified FOLFOX6, chemoradiation with capecitabine 825 mg/m2 twice daily and 50.4 Gy intensity-modulated radiation therapy, then surgery were included. Results: Thirty-five patients were treated with complete neoadjuvant therapy between January 2014 and December 2017. Median age was 58 years (27 to 75 y); 1 patient (3%) was clinical stage II and 34 (97%) stage III. Twenty-seven patients (77%) received all 8 cycles of mFOLFOX6, of whom 24 completed subsequent chemoradiation. Therefore 69% of patients completed therapy according to the BrUOG R-224 protocol. Pathologic complete response (ypT0N0) was observed in 9 patients (26%). Treatment related toxicities resulted in dose reductions or treatment interruption in 57% and 29% of patients receiving chemotherapy and chemoradiation respectively. Conclusions: Complete neoadjuvant therapy for clinical stage II to III rectal cancer is well-tolerated in routine practice and offers an alternative to preoperative chemoradiation, surgery, then adjuvant full dose chemotherapy.

New Cardiac Abnormalities After Radiotherapy in Breast Cancer Patients Treated With Trastuzumab

PURPOSE

To evaluate cardiac imaging abnormalities after modern radiotherapy and trastuzumab in breast cancer patients.

PATIENTS AND METHODS

All patients treated with trastuzumab and radiotherapy for breast cancer between 2006 and 2014 with available cardiac imaging (echocardiogram or multigated acquisition scan) were retrospectively analyzed. Cardiac abnormalities included myocardial abnormalities (atrial or ventricular dilation, hypertrophy, hypokinesis, and impaired relaxation), decreased ejection fraction > 10%, and valvular abnormalities (thickening or stenosis of the valve leaflets). Breast laterality (left vs. right) and heart radiation dose volume parameters were analyzed for association with cardiac imaging abnormalities.

RESULTS

A total of 110 patients with 57 left- and 53 right-sided breast cancers were evaluated. Overall, 37 patients (33.6%) developed a new cardiac abnormality. Left-sided radiotherapy was associated with an increase in new cardiac abnormalities (relative risk [RR] = 2.51; 95% confidence interval [CI], 1.34-4.67; P = .002). Both myocardial and valvular abnormalities were associated with left-sided radiotherapy (myocardial: RR = 2.21; 95% CI, 1.06-4.60; P = .029; valvular: RR = 3.30; 95% CI, 0.98-10.9; P = .044). There was no significant difference in decreased ejection fraction between left- and right-sided radiotherapy (9.6% vs. 2.1%; P = .207). A mean heart dose > 2 Gy as well as volume of the heart receiving 20 Gy (V20), V30, and V40 correlated with cardiac abnormalities (mean heart dose > 2 Gy: RR = 2.00; P = .040).

CONCLUSION

New cardiac abnormalities, including myocardial and valvular dysfunction, are common after trastuzumab and radiotherapy. The incidence of new abnormalities correlates with tumor laterality and cardiac radiation dose exposure. Long-term follow-up is needed to understand the clinical significance of these early imaging abnormalities.

Pain management in patients undergoing treatment for head and neck cancer with opiate use disorder on medication-assisted treatment

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Background: Buprenorphine, a partial agonist at the mu opiate receptor, is an effective pain medication and use has increased for patients with cancer pain, especially those with concurrent opiate use disorder (OUD). Substance use disorder is common in head and neck cancer patients since alcohol and tobacco are predisposing factors. Definitive chemoradiation (chemoRT) for head and neck cancer is a difficult treatment with a high burden of symptoms, including mucositis pain, dysphagia and odynophagia. Patients undergoing concurrent chemoRT routinely require systemic opiates to manage pain and tolerate treatment. This is a review of our institution’s experience using buprenorphine and methadone for pain management in patients with OUD during chemoRT for head and neck cancer. Methods: We reviewed all cases seen in the Lifespan Cancer Institute head and neck cancer multidisciplinary clinic between July 2018 and June 2019. Approximately 40% of patients had a history of opiate use disorder and one-fifth of those were on medication-assisted treatment with buprenorphine or methadone. The charts of patients with OUD were reviewed with respect to history of buprenorphine or methadone use, pain scores during chemoRT, effectiveness of pain medications during chemoRT, and change of pain medication during treatment. Results: 5 patients on buprenorphine and 4 patients on methadone underwent treatment with chemoRT for head and neck cancer. Despite effectiveness for pain with other cancer patients, we did not find that buprenorphine was an effective opiate for patients undergoing chemoRT for head and neck cancer. All patients on buprenorphine had to be rotated off to another opiate (generally methadone) to achieve adequate pain relief. Median time to pain medication change was 3 weeks (range: prior to starting to week 5/7). The patients on methadone generally were able to tolerate treatment with minor adjustments to their methadone. Conclusions: The ceiling effect of buprenorphine that makes it effective for OUD is a barrier to managing the severe pain from chemoRT for head and neck cancer, while methadone is effective for both pain control and maintenance of sobriety during a taxing treatment.

Adjuvant FOLFOX + nab-paclitaxel (FOLFOX-A)for pancreatic cancer, BrUOG 278: A Brown University oncology research group phase II study

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Background: Adjuvant FOLFIRINOX increases survival in pancreatic cancer but is associated with significant toxicity. The Brown University Oncology Research Group (BrUOG) developed the FOLFOX-A regimen in a phase I study in advanced pancreatic cancer (Am J Clin Oncol, 2016). Phase II studies (BrUOG 292 and BrUOG 318) have shown substantial activity in patients with metastatic and locally advanced disease. Highly active regimens have the potential to improve survival in the adjuvant setting. The primary objective of BrUOG 295 was to determine the feasibility of administering 10 cycles of FOLFOX-A. Secondary objectives were toxicity and disease free survival. Methods: Patients received oxaliplatin, 85mg/m2 day 1, nab-paclitaxel, 150mg/m2 and leucovorin 400mg/m2 day 1 and fluorouracil 2400mg/m2 by continuous IV infusion over 46 hours. Myeloid growth factor support was optional. Cycles were repeated every 14 days for up to 10. Oxaliplatin was dose reduced to 68mg/m2 for grade 2 neurotoxicity. CTCAE version 4 toxicity scales were utilized. Results: The study reached its initial accrual goal of 25 patients. The median age was 60 (43-69). Twenty-one patients were node +. Twelve of the first 20 patients have received 10 cycles of FOLFOX-A and 17 of the first 20 patients received > 8 cycles. The most common grade >3 toxicities were neutropenia grade 3 (N = 3), grade 4 (N = 3) and fatigue grade 3 (n = 13). One patient had grade 3 neuropathy. Conclusions: Adjuvant FOLFOX-A is well tolerated with low incidences of grade 3 neuropathy and gastrointestinal toxicity. Toxicity, feasibility and disease free survival will be updated at the May 2019 BrUOG DSMB meeting. Clinical trial information: NCT02022033.

Abstract P2-12-12: Identifying optimal candidates for three-dimensional bioabsorbable marker placement during breast cancer treatment: Incidence and predictors of postoperative complications

OBJECTIVES: Radiation therapy (RT) is often an integral component of postoperative breast cancer management. Three dimensional (3D) bioabsorbable markers have been designed to assist CT-based tumor bed targeting during the RT process. There have been limited reports detailing complications following placement of such devices. This retrospective analysis attempts to identify demographic and treatment characteristics associated with complications after 3D bioabsorbable marker placement in a cohort of breast cancer patients treated at an academic medical center. METHODS: Records of 160 patients receiving a 3D bioabsorbable marker during initial breast surgery for DCIS or breast cancer were reviewed. Ten devices were removed at subsequent re-excision or mastectomy; therefore, 150 patients were ultimately evaluable. Demographic, tumor and operative/treatment characteristics were collected. Variables including body mass index (BMI), diabetes mellitus (DM), smoking, chemotherapy or RT use and excision volume (EV) were analyzed using multivariable logistic regression analysis (MVA). Endpoints included reoperation for wound complications (re-op), receipt of postoperative antibiotics (abx) and clinically palpable 3D bioabsorbable marker. RESULTS: Median follow-up was 8.2 months. Six (6/150, 4%) patients required re-op for wound complications and 5 required 3D bioabsorbable marker removal due to complications. Twenty (20/150, 13.3%) patients received abx for clinically detected postoperative wound infections. At last follow-up, 61 (61/150, 40.6%) patients noted persistent perceived fullness of the device at the lumpectomy site, and the 3D bioabsorbable marker remained palpable by the physician in 95 (95/150, 63.3%) patients. On MVA, DM and larger EV were associated with greater rates of re-op (p=0.020 and 0.012, respectively, Table 1). Mean EV was 279 cc among the re-op cohort and 85.5 cc among the no re-op cohort. DM, receipt of chemotherapy and larger EV were associated with postoperative abx prescription (p=0.005, 0.009 and 0.005, respectively, Table 2). Mean EV was 169.6 cc among those who received abx and 81.5 cc among those who did not. Larger EV was the only statistically significant predictor of a clinically palpable bioabsorbable marker during follow-up (p=0.044).

Table 1. Multivariable Analysis: Reoperation for Wound ComplicationsVariablep-valueBMI0.986Diabetes0.020Smoking0.999Excision Volume0.012Chemotherapy0.079Radiation0.113

Evolving prevalence and incidence trends of SCC of the anal canal: A SEER study

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Background: The incidence of squamous cell carcinoma of the anal canal (SCCA) has been rising in the last three decades. With changing patient demographics and behaviors, the trends in prevalence and incidence of the disease have changed in recent years. Methods: The Surveillance, Epidemiology, and End Results (SEER) data set from 2000 to 2014 was analyzed for trends in prevalence and incidence of SCCA and for associated demographic and tumor characteristics including stage (localized vs. regional vs. distant disease), age (20-34, 35-49, 50-64, > 65 years), and race/ethnicity (White, Black, American Indian/American Natives (AI/AN), American Pacific Islanders (API)). Results: 16,540 patients with SCCA were identified in the SEER database within the study period. The prevalence rate of SCCA was 0.01% (of 2000 standard U.S population), and the age-adjusted incidence rate of SCCA was 1.3/100,000. Prevalence and incidence was highest in patients age 50-64 and in the black population. Trend analysis of incidence demonstrated that while incidence rate continued to increase from 2000 to 2014, the average annual percentage change (APC) of incidence decreased from 4.80 before 2009 to 1.44 after. Patient population was divided into two groups: 2000-2008, with incidence of 1.6/100,000 and 2009-2014, with incidence of 2.1/100,000 (RR = 1.29, 95%CI = 1.25-1.33, p < 0.001). Incidence in the 2009-2014 group increased compared to the 2000-2008 group among all staged SCCA, patients 50 years of age and older (RR = 1.41, p < 0.001 and RR = 1.37, p < 0.001 for age groups 50-64 and > 65, respectively), and black (RR = 1.33, p < 0.001) and white (RR = 1.32, p < 0.001) race/ethnicity groups. APC in the 2009-2014 group decreased in all staged SCCA, increased in patients age 20-34, and decreased in all racial groups except AI/AN. Conclusions: There is a higher incidence and prevalence of SCCA in patients 50 years or older and in those of black ethnicity. Incidence of SCCA has increased in the US from 2000-2014, but the average APC in incidence has been decreasing except for in young patients and in those of AI/AN ethnicity. Awareness of disease prevalence and the pattern of change in incidence rate is important in the effort of disease prevention.

ADXS11-001 Lm-LLO Immunotherapy, Mitomycin, 5-fluorouracil (5-FU) and Intensity-modulated radiation therapy (IMRT) for Anal Cancer

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Background: Human papillomavirus (HPV) DNA is present in the majority of anal cancer. ADXS11-001 Lm-LLO immunotherapy is a live attenuated Listeria monocytogenes ( Lm) bioengineered to secrete a HPV-16-E7 fusion protein targeting HPV transformed cells. The Lmvector is phagocytosed by antigen presenting cells where it cross presents, stimulating MHC class 1 and 2 pathways resulting in specific T-cell immunity. The objective of this study was to determine the safety of ADXS11-001 with mitomycin, 5-FU and IMRT (chemoradiation therapy, CRT) and obtain preliminary data on progression free survival (PFS) in locally advanced anal cancer. Methods: Eligibility included patients (pts) with anal squamous cell cancer and stages T1N2-N3; T2( < 4 cm)N1-N3; T2(≥4cm)N0-N3, T3N0-3, T4N0-3; without evidence of metastases. Pts received standard 54 Gy IMRT with 2 cycles of mitomycin and 5-FU. ADXS11-001, 1x109colony forming units IV, was given x 1 dose before CRT then x 3 additional monthly doses after CRT. Results: The study enrolled the first pt in April 2013. Ten patients were treated (median age 62.5, range 37-71) including 5 with pelvic adenopathy. Two patients had grade 3 toxicities related to the vaccine including chills/rigors (n = 2), back pain (n = 1), hyponatremia (n = 1). All toxicities were within 24 hours of the vaccine and resolved successfully with standard care. There was no exacerbation of CRT toxicities or myelosuppression. One patient had a grade 5 cardiopulmonary event shortly after beginning 5-FU treatment which was judged to be unlikely related to ADXS11-001and possibly related to CRT. Eight patients treated on the study had a complete response at six-month sigmoidoscopy. One additional patient who did not undergo six-month sigmoidoscopy had complete response on sigmoidoscopy performed at approximately one year. Eight of 9 patients (89%) are disease-free at a median follow-up of 34 months. Conclusions: ADXS11-001 can be safely administered with CRT for anal cancer. Promising PFS was observed in patients with locally advanced disease. Clinical trial information: NCT01671488.

Stereotactic Body Radiation Therapy Boost After Concurrent Chemoradiation for Locally Advanced Non-Small Cell Lung Cancer: A Phase 1 Dose Escalation Study

PURPOSE

Stereotactic body radiation therapy (SBRT) boost to primary and nodal disease after chemoradiation has potential to improve outcomes for advanced non-small cell lung cancer (NSCLC). A dose escalation study was initiated to evaluate the maximum tolerated dose (MTD).

METHODS AND MATERIALS

Eligible patients received chemoradiation to a dose of 50.4 Gy in 28 fractions and had primary and nodal volumes appropriate for SBRT boost (<120 cc and <60 cc, respectively). SBRT was delivered in 2 fractions after chemoradiation. Dose was escalated from 16 to 28 Gy in 2 Gy/fraction increments, resulting in 4 dose cohorts. MTD was defined when ≥2 of 6 patients per cohort experienced any treatment-related grade 3 to 5 toxicity within 4 weeks of treatment or the maximum dose was reached. Late toxicity, disease control, and survival were also evaluated.

RESULTS

Twelve patients (3 per dose level) underwent treatment. All treatment plans met predetermined dose-volume constraints. The mean age was 64 years. Most patients had stage III disease (92%) and were medically inoperable (92%). The maximum dose level was reached with no grade 3 to 5 acute toxicities. At a median follow-up time of 16 months, 1-year local-regional control (LRC) was 78%. LRC was 50% at <24 Gy and 100% at ≥24 Gy (P=.02). Overall survival at 1 year was 67%. Late toxicity (grade 3-5) was seen in only 1 patient who experienced fatal bronchopulmonary hemorrhage (grade 5). There were no predetermined dose constraints for the proximal bronchial-vascular tree (PBV) in this study. This patient's 4-cc PBV dose was substantially higher than that received by other patients in all 4 cohorts and was associated with the toxicity observed: 20.3 Gy (P<.05) and 73.5 Gy (P=.07) for SBRT boost and total treatment, respectively.

CONCLUSIONS

SBRT boost to both primary and nodal disease after chemoradiation is feasible and well tolerated. Local control rates are encouraging, especially at doses ≥24 Gy in 2 fractions. Toxicity at the PBV is a concern but potentially can be avoided with strict dose-volume constraints.

Patterns of care of locoregional radiation therapy in patients with stage IV rectal cancer: A SEER analysis

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Background: Per the 2012 NCCN guidelines, pelvic radiation therapy (RT) is one of the preferred treatment regimens for patients with metastatic rectal cancer (MRC). This study aims to analyze patterns of care and outcomes data for the use of neoadjuvant/adjuvant pelvic RT in patients with MRC using the SEER database. Methods: Patients with stage IV rectal or rectosigmoid cancer were identified in the SEER database (1973-2009). Patients were stratified according to their primary site of disease (rectum vs. rectosigmoid), T-, and N-stage. Treatment regimens (+/- surgical resection, +/-RT, or a combination of both) were recorded. Fischer's exact test was used to compare RT rates based on stratified factors. 2-yr survival rates were compared among treatment groups. Results: A total of 6,873 patients with stage IV rectal CA and 3,417 patients with rectosigmoid CA were identified. In total, 20.5% of rectal CA patients received surgery alone while 38.7% received RT alone or RT + surgery. Within the rectosigmoid group, 51.4% of patients received surgery alone and 15.1% of patients received either RT alone or RT + surgery. The use of RT differed significantly between those with Tis-2 and T3-4 disease (p < 0.001) and between those with N0 vs. N1-2 disease (p < 0.001). 2-yr and 5-yr survival differed significantly between treatment groups with the highest survival rates among those receiving surgery and RT. Detailed data is provided in the table below. Conclusions: The primary treatments for patients with MRC include surgery +/- RT. RT is used more commonly in patient with primary rectal (as opposed to rectosigmoid) tumors, N0, or Tis-T2 disease. Treatment with combination surgery and RT is associated with prolonged survival. [Table: see text]

The effect of dose-volume parameters and interfraction interval on cosmetic outcome and toxicity after 3-dimensional conformal accelerated partial breast irradiation

PURPOSE

To evaluate dose-volume parameters and the interfraction interval (IFI) as they relate to cosmetic outcome and normal tissue effects of 3-dimensional conformal radiation therapy (3D-CRT) for accelerated partial breast irradiation (APBI).

METHODS AND MATERIALS

Eighty patients were treated by the use of 3D-CRT to deliver APBI at our institutions from 2003-2010 in strict accordance with the specified dose-volume constraints outlined in the National Surgical Adjuvant Breast and Bowel Project B39/Radiation Therapy Oncology Group 0413 (NSABP-B39/RTOG 0413) protocol. The prescribed dose was 38.5 Gy in 10 fractions delivered twice daily. Patients underwent follow-up with assessment for recurrence, late toxicity, and overall cosmetic outcome. Tests for association between toxicity endpoints and dosimetric parameters were performed with the chi-square test. Univariate logistic regression was used to evaluate the association of interfraction interval (IFI) with these outcomes.

RESULTS

At a median follow-up time of 32 months, grade 2-4 and grade 3-4 subcutaneous fibrosis occurred in 31% and 7.5% of patients, respectively. Subcutaneous fibrosis improved in 5 patients (6%) with extended follow-up. Fat necrosis developed in 11% of women, and cosmetic outcome was fair/poor in 19%. The relative volume of breast tissue receiving 5%, 20%, 50%, 80%, and 100% (V5-V100) of the prescribed dose was associated with risk of subcutaneous fibrosis, and the volume receiving 50%, 80%, and 100% (V50-V100) was associated with fair/poor cosmesis. The mean IFI was 6.9 hours, and the minimum IFI was 6.2 hours. The mean and minimum IFI values were not significantly associated with late toxicity.

CONCLUSIONS

The incidence of moderate to severe late toxicity, particularly subcutaneous fibrosis and fat necrosis and resulting fair/poor cosmesis, remains high with continued follow-up. These toxicity endpoints are associated with several dose-volume parameters. Minimum and mean IFI values were not associated with late toxicity.

Axillary lymph node dose with tangential whole breast radiation in the prone versus supine position: a dosimetric study

Background

Prone breast positioning reduces skin reaction and heart and lung dose, but may also reduce radiation dose to axillary lymph nodes (ALNs).

Methods

Women with early stage breast cancer treated with whole breast irradiation (WBI) in the prone position were identified. Patients treated in the supine position were matched for treating physician, laterality, and fractionation. Ipsilateral breast, tumor bed, and Level I, II, and III ALNs were contoured according to the RTOG breast atlas. Clips marking surgically removed sentinel lymph nodes (SLN)s were contoured. Treatment plans developed for each patient were retrospectively analyzed. V90_% and V95_% was calculated for each axillary level. When present, dose to axillary surgical clips was calculated.

Results

Treatment plans for 46 women (23 prone and 23 supine) were reviewed. The mean V90_% and V95_% of ALN Level I was significantly lower for patients treated in the prone position (21% and 14%, respectively) than in the supine position (50% and 37%, respectively) (p < 0.0001 and p < 0.0001, respectively). Generally, Level II & III ALNs received little dose in either position. Sentinel node biopsy clips were all contained within axillary Level I. The mean V95_% of SLN clips was 47% for patients treated in the supine position and 0% for patients treated in the prone position (p < 0.0001). Mean V90_% to SLN clips was 96% for women treated in the supine position but only 13% for women treated in the prone position.

Conclusions

Standard tangential breast irradiation in the prone position results in substantially reduced dose to the Level I axilla as compared with treatment in the supine position. For women in whom axillary coverage is indicated such as those with positive sentinel lymph node biopsy who do not undergo completion axillary dissection, treatment in the prone position may be inappropriate.

A novel ytterbium-169 brachytherapy source and delivery system for use in conjunction with minimally invasive wedge resection of early-stage lung cancer

PURPOSE

To describe a novel source-delivery system for intraoperative brachytherapy in patients with early-stage lung cancer that is readily adaptable to a video-assisted thoracoscopic surgery approach and can be precisely delivered to achieve optimal dose distribution.

METHODS AND MATERIALS

Radioactive ytterbium-169 ((169)Yb) was sealed within a titanium tube 0.28 mm in diameter and then capped and resealed by titanium wires laser welded to the tube to serve as the legs of a tissue-fastening system. Dose simulations were performed using Monte Carlo computer code (Los Alamos National Laboratory, Los Alamos, NM) to mimic the geometric and elemental compositions of the source, fastening apparatus, and surroundings.

RESULTS

Five test source capsules were subjected to a tensile load to failure. Failure in each capsule occurred in the wire of the fastener leg; there were no weld failures. Monte Carlo simulations and subsequent dose measurement showed the perturbation by the source legs in the deployed (bent over) position to be small (4-5%) for (169)Yb and much less than that for iodine-125 (32%).

CONCLUSION

We have developed a (169)Yb brachytherapy source-delivery system that can be used in conjunction with commercially available surgical stapling instruments, facilitates the precise placement of brachytherapy sources relative to the surgical margin, assures the seeds remain fixed in their precise position for the duration of the treatment, overcomes the technical difficulties of manipulating the seeds through the narrow surgical incision associated with video-assisted thoracoscopic surgery, and reduces the radiation dose to the clinicians.