Radiation Exposure and Safety Precautions Following 131Cs Brachytherapy in Patients with Brain Tumors

Cesium-131 (Cs) brachytherapy is a safe and convenient treatment option for patients with resected brain tumors. This study prospectively analyzes radiation exposure in the patient population who were treated with a maximally safe neurosurgical resection and Cs brachytherapy. Following implantation, radiation dose rate measurements were taken at the surface, 35 cm, and 100 cm distances. Using the half-life of Cs (9.69 d), the dose rates were extrapolated at these distances over a period of time (t = 30 d). Data from dosimetry badges and rings worn by surgeons and radiation oncologists were collected and analyzed. Postoperatively, median dose rate was 0.2475 mSv h, 0.01 mSv h, and 0.001 mSv h and at 30 d post-implant, 0.0298 mSv h, 0.0012 mSv h, and 0.0001 mSv h at the surface, 35 cm, and 100 cm, respectively. All but one badge and ring measured a dose equivalent corresponding to ~0 mSv h, while 1 badge measured 0.02/0.02/0.02 mSv h. There was a significant correlation between the number of seeds implanted and dose rate at the surface (p = 0.0169). When stratified by the number of seeds: 4-15 seeds (n = 14) and 20-50 seeds (n = 4) had median dose rates of 0.1475 mSv h and 0.5565 mSv h, respectively (p = 0.0015). Using National Council on Radiation Protection guidelines, this study shows that dose equivalent from permanent Cs brachytherapy for the treatment of brain tumors is limited, and it maintains safe levels of exposure to family and medical personnel. Such information is critical knowledge for the neurosurgeons, radiation oncologists, nurses, hospital staff, and family as this method is gaining nationwide popularity.

Biological imaging in clinical oncology: radiation therapy based on functional imaging

Radiation therapy is one of the most effective tools for cancer treatment. In recent years, intensity-modulated radiation therapy has become increasingly popular in that target dose-escalation can be done while sparing adjacent normal tissues. For this reason, the development of measures to pave the way for accurate target delineation is of great interest. With the integration of functional information obtained by biological imaging with radiotherapy, strategies using advanced biological imaging to visualize metabolic pathways and to improve therapeutic index and predict treatment response are discussed in this article.

Higher locoregional recurrence rate for triple-negative breast cancer following neoadjuvant chemotherapy, surgery and radiotherapy

Background

Breast cancer subtype, determined by expression of estrogen/progesterone receptor (ER/PR) and human epidermal growth factor receptor (HER)-2, is predictive for prognosis. The importance of subtype to locoregional recurrence (LRR) following neoadjuvant chemotherapy (NAC) is unknown, particularly after adjuvant radiotherapy (RT).

Methods

We retrospectively identified 160-breast cancer patients registered at Columbia University Medical Center from 1999 to 2012 treated with NAC, surgery and adjuvant RT.

Results

Patients were grouped by receptor status: hormone receptor positive (HR+) [(ER or PR+)/HER2−; n = 75], HER2+ (n = 46), or triple-negative (TNBC) [ER (−) PR (−) HER2 (−); n = 36]. The median follow-up was 28 months. 92.0% received an anthracycline-taxane based NAC and 80.4% of HER2+ patients received trastuzumab. All underwent surgical resection followed by RT. 15.6% had a pathologic complete response (pCR): 26% of HER2+, 5% of HR+, and 25% of TN. The actuarial rate of DM was 13.8% for the entire cohort, with equivalent rates by subtypes in non-pCR patients. The overall rate of LRR was 8%. However, the LRR rate was significantly higher for TNBC patients (22.2%) than HER2+ (5.6%) (p = 0.025) or HR+ (3.0%) (p = 0.037) in non-pCR group. In the pCR group, two patients had recurrence; one LRR and one a DM, both had TNBC. All LRR occurred in or near the radiation field.

Conclusions

TNBC patients with < pCR to NAC have a significantly higher LRR rate as compared to other subtypes even with surgery and adjuvant RT. Our data support a need to further intensify local therapy in TNBC patients.

Comparison of primary radiation versus robotic surgery plus adjuvant radiation in high-risk prostate cancer: a single center experience

OBJECTIVE

The objective of this study was to compare robotic-prostatectomy plus adjuvant radiation therapy (RPRAT) versus primary RT for high-risk prostate cancer (HRPCa).

MATERIALS AND METHODS

A retrospective chart review was performed for the HRPCa patients treated in our institution between 2000 and 2010. One hundred and twenty-three patients with high-risk disease were identified. The Chi-square test and Fisher's exact test were used to compare local control and distant failure rates between the two treatment modalities. For prostate-specific antigen comparisons between groups, Wilcoxon rank-sum test was used.

RESULTS

The median follow-up was 49 months (range: 3-138 months). Local control, biochemical recurrence rate, distant metastasis, toxicity, and disease-free survival were similar in the two groups.

CONCLUSIONS

Primary RT is an excellent treatment option in patients with HRPCa, is equally effective and less expensive treatment compared with RPRAT. A prospective randomized study is required to guide treatment for patients with HRPCa.

Outcomes of gamma knife radiosurgery, bi-modality & tri-modality treatment regimens for patients with one or multiple brain metastases: the Columbia University Medical Center experience

Optimal treatment of brain metastases (BMs) is debatable. However, surgery or gamma knife radiosurgery (GKRS) improves survival when combined with whole brain radiotherapy (WBRT) versus WBRT alone. We retrospectively reviewed an institutional database of patients treated with GKRS for BMs from 1998 to 2013 to explore effects of single or multi-modality therapies on survival. There were 528 patients with median age 62 years. Histologies included 257 lung, 102 breast, 62 melanoma, 40 renal cell, 29 gastrointestinal, and 38 other primary cancers. Treatments included: 206 GKRS alone, 111 GKRS plus WBRT, 109 GKRS plus neurosurgical resection (NSG), and 102 all three modalities. Median overall survival (mOS) was 16.6 months. mOS among patients with one versus multiple metastasis was 17.2 versus 16.0 months respectively (p = 0.825). For patients with one BM, mOS following GKRS alone, GKRS plus WBRT, GKRS plus NSG, and all three modalities was 9.0, 19.1, 25.5, and 25.0 months, respectively, and for patients with multiple BMs, mOS was 8.6, 20.4, 20.7, 24.5 months for the respective groups. Among all patients, multivariate analysis confirmed that tri-modality group had the longest survival (HR 0.467; 95 % CI 0.350-0.623; p < 0.001) compared to GKRS alone; however, this was not significantly different than bi-modality approaches. Uncontrolled primary extra-CNS disease, age and KPS were also independent predictors of survival. Patients treated with GKRS plus NSG, GKRS plus WBRT, or all three modalities had improved OS versus GKRS alone. In our analysis, resection and GKRS allowed avoidance of WBRT without shortening survival.

Calibration of a detector array through beam profile reconstruction with error-locking

An iterative method is proposed to calibrate radiation sensitivities of an arbitrary two-dimensional (2D) array of detectors. The array is irradiated with a wide open- field beam at the central position, as well as at laterally and longitudinal shifted positions; the 2D beam profile of the wide field is reconstructed iteratively from the ratios of shifted images to the central image. The propagation errors due to output variation and inaccurate array positioning are estimated and removed from the reconstructed beam profile by an error-locking scheme with narrow open-field irradiations. The beam profile is interpolated when necessary and then compared to raw detector responses to determine sensitivities. Two additional methods were implemented for comparison: 1) the commercial iterative calibration method for MapCHECK2 with translation and rotation operations; 2) a labor-intensive noniterative method without the issue of error propagation. A MapCHECK2 2D detector array was used to validate the proposed method with the 6 MV photon beam from a Varian iX linear accelerator. All calibration methods were repeated three times. A total of 5, 9, and 29 irradiations were required to implement the commercial method, the proposed method and the noniterative method respec- tively. Moreover, a 5 mm positioning error was intentionally introduced into the calibration procedures of the commercial and the proposed method to test their robustness. Under the normal operation condition of the linear accelerator and with careful alignment of the MapCHECK2, the deviations of the calibrated sensitivities of the proposed method and commercial method with respect to the noniterative method were 0.30% ± 0.29% and 0.92% ± 0.63% respectively; when the 5 mm positioning error was presented, these two methods resulted in deviations of 0.40% ± 0.36% and 3.58% ± 1.94%, respectively. A patient study suggested that, due to this 5 mm positioning error, the mean DTA (dose to agreement) passing rate by the commercial method was 2.7% lower than that by the noniterative method, whereas the proposed method led to a comparable passing rate. It is evident from this study that the proposed iterative method leads to within 1% mean calibration results to established methods. It requires much fewer number of measurements than noniterative method and is more robust against the positioning error than the commercial iterative method. The method also eliminates the need of rotation operations and, therefore, is applicable to inline detector arrays without rotation function, such as electronic portal imager device (EPID). 

Comparing outcomes in poorly-differentiated versus anaplastic thyroid cancers treated with radiation: a surveillance, epidemiology, and end results analysis

PURPOSE

Poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC) are considered the most aggressive cancers of the head and neck. The aim of the study was to evaluate and compare survival outcomes in PDTC and ATC in a large population-based cohort.

MATERIALS AND METHODS

Patients with PDTC and ATC diagnosed from 1973 to 2008 were obtained from Surveillance, Epidemiology, and End RESULTS database. Kaplan-Meier survival analysis and log-rank analyses were performed to evaluate (1) The effect of histology on cause-specific survival (CSS) and (2) the influence of factors such as treatment, treatment sequence, race, sex, and age on CSS. Multivariate analysis was performed to assess the independent effect of these factors on CSS.

RESULTS

A total of 1352 patients with PDTC and ATC were identified. PDTC constituted 52.4% of patients versus 47.6% for ATC. Median CSS was similar in the two histology groups (P = 0.14). Both PDTC and ATC patients receiving radioisotopes showed a significantly better CSS compared to external beam radiation (P < 0.0001). PDTC and ATC Patients receiving radiation prior to surgery demonstrated a significantly lower CSS compared to patients receiving radiation postoperatively (P < 0.0001). Female gender and black/nonwhite race tended to improve CSS in PDTC and ATC patients (P = 0.29 and P = 0.03, for gender and race, respectively). However, multivariate analysis revealed only type of radiation treatment and age to be independently associated with CSS.

CONCLUSION

This is the first large population-based study evaluating PDTC and ATC outcomes in patients who received radiation treatment. Radioisotope use and timing of radiotherapy (postoperative vs. preoperative) were associated with improved CSS in both histologies.

Phase I/II study of resection and intraoperative cesium-131 radioisotope brachytherapy in patients with newly diagnosed brain metastases

OBJECT

Resected brain metastases have a high rate of local recurrence without adjuvant therapy. Adjuvant whole-brain radiotherapy (WBRT) remains the standard of care with a local control rate > 90%. However, WBRT is delivered over 10-15 days, which can delay other therapy and is associated with acute and long-term toxicities. Permanent cesium-131 ((131)Cs) implants can be used at the time of metastatic resection, thereby avoiding the need for any additional therapy. The authors evaluated the safety, feasibility, and efficacy of a novel therapeutic approach with permanent (131)Cs brachytherapy at the resection for brain metastases.

METHODS

After institutional review board approval was obtained, 24 patients with a newly diagnosed metastasis to the brain were accrued to a prospective protocol between 2010 and 2012. There were 10 frontal, 7 parietal, 4 cerebellar, 2 occipital, and 1 temporal metastases. Histology included lung cancer (16), breast cancer (2), kidney cancer (2), melanoma (2), colon cancer (1), and cervical cancer (1). Stranded (131)Cs seeds were placed as permanent volume implants. The prescription dose was 80 Gy at a 5-mm depth from the resection cavity surface. Distant metastases were treated with stereotactic radiosurgery (SRS) or WBRT, depending on the number of lesions. The primary end point was local (resection cavity) freedom from progression (FFP). Secondary end points included regional FFP, distant FFP, median survival, overall survival (OS), and toxicity.

RESULTS

The median follow-up was 19.3 months (range 12.89-29.57 months). The median age was 65 years (range 45-84 years). The median size of resected tumor was 2.7 cm (range 1.5-5.5 cm), and the median volume of resected tumor was 10.31 cm(3) (range 1.77-87.11 cm(3)). The median number of seeds used was 12 (range 4-35), with a median activity of 3.82 mCi per seed (range 3.31-4.83 mCi) and total activity of 46.91 mCi (range 15.31-130.70 mCi). Local FFP was 100%. There was 1 adjacent leptomeningeal recurrence, resulting in a 1-year regional FFP of 93.8% (95% CI 63.2%-99.1%). One-year distant FFP was 48.4% (95% CI 26.3%-67.4%). Median OS was 9.9 months (95% CI 4.8 months, upper limit not estimated) and 1-year OS was 50.0% (95% CI 29.1%-67.8%). Complications included CSF leak (1), seizure (1), and infection (1). There was no radiation necrosis.

CONCLUSIONS

The use of postresection permanent (131)Cs brachytherapy implants resulted in no local recurrences and no radiation necrosis. This treatment was safe, well tolerated, and convenient for patients, resulting in a short radiation treatment course, high response rate, and minimal toxicity. These findings merit further study with a multicenter trial.

Surveillance, epidemiology, and end results-based analysis of the impact of preoperative or postoperative radiotherapy on survival outcomes for T3N0 rectal cancer

PURPOSE

Preoperative chemoradiation has been established as standard of care for T3/T4 node-positive rectal cancer. Recent work, however, has called into question the overall benefit of radiation for tumors with lower risk characteristics, particularly T3N0 rectal cancers. We retrospectively analyzed T3N0 rectal cancer patients and examined how outcomes differed according to the sequence of treatment received.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) database was used to analyze T3N0 rectal cancer cases diagnosed between 1998 and 2008. Treatment consisted of surgery alone (No RT), preoperative radiation followed by surgery (Neo-Adjuvant RT), or surgery followed by postoperative radiation (Adjuvant RT). Demographic and tumor characteristics of the three groups were compared using t-tests for the comparison of means. Survival information from the SEER database was utilized to estimate cause-specific survival (CSS) and to generate Kaplan-Meier survival curves. Multivariate analysis (MVA) of features associated with outcomes was conducted using Cox proportional hazards regression models with Adjuvant RT, Neo-Adjuvant RT, No RT, histological grade, tumor size, year of diagnosis, and demographic characteristics as covariates.

RESULTS

10-Year CSS estimates were 66.1% (95% CI 62.3-69.6%; P=0.02), 73.5% (95% CI 68.9-77.5%; P=0.02), and 76.1% (95% CI 72.4-79.4%; P=0.02), for No RT, Neo-Adjuvant RT, and Adjuvant RT, respectively. On MVA, Adjuvant RT (HR=0.688; 95% CI, 0.578-0.819; P<0.001) was associated with significantly decreased risk for cancer death. By contrast, Neo-Adjuvant RT was not significantly associated with improved cancer survival (HR=0.863; 95% CI, 0.715-1.043; P=0.127).

CONCLUSION

Adjuvant RT was associated with significantly higher CSS when compared with surgery alone, while the benefit of Neo-Adjuvant RT was not significant. This indicates that surgery followed by Adjuvant RT may still be an important treatment plan for T3N0 rectal cancer with potentially significant survival advantages over other treatment sequences.

Administration of concurrent vaginal brachytherapy during chemotherapy for treatment of endometrial cancer

PURPOSE

To evaluate the tolerability and toxicity of administering vaginal brachytherapy (VB) concurrently during chemotherapy compared with the sequential approach for patients with endometrial cancer.

METHODS AND MATERIALS

A retrospective analysis of 372 surgically staged patients with endometrial cancer American Joint Committee on Cancer 2009 stages I to IV treated with adjuvant postoperative radiation therapy (RT) at our institution from 2001 to 2012 was conducted. All patients received VB+external beam RT (EBRT)+6 cycles of adjuvant carboplatin- and paclitaxel-based chemotherapy. The VB mean dose was 15.08 Gy (range, 15-20 Gy), with 3 to 4 weekly applications, and the EBRT mean dose was 45 Gy delivered with 3-dimensional or intensity modulated RT techniques. Hematologic, gastrointestinal (GI), and genitourinary (GU) toxicities were assessed by Common Toxicity Criteria (CTC) and compared between sequential and concurrent chemotherapy and VB schedules.

RESULTS

Among patients who received RT and adjuvant chemotherapy, 180 of 372 patients (48%) received RT sandwiched between cycles 3 and 4 of chemotherapy. A separate group of 192 patients (52%) were treated with VB during the first 3 cycles of chemotherapy, with a weekly application on nonchemotherapy days, and received the EBRT portion in a sandwiched fashion. Patients treated with VB during chemotherapy had a decreased overall treatment time by 4 weeks (P<.001; 95% confidence interval: 3.99-4.02) and sustained no difference in CTC-graded acute hematologic, GI, or GU toxicities in comparison with the patients treated with VB and chemotherapy in a sequential manner (P>.05). CTC grade 3 or 4 hematologic, GI, and GU toxicities were zero.

CONCLUSIONS

VB during chemotherapy is well tolerated, decreases overall treatment time, and does not render more toxicity than the sequential regimen.

Prostate-specific membrane antigen expression in tumor-associated vasculature of breast cancers

Prostate-specific membrane antigen (PSMA) has been found to be expressed in the tumor-associated neovasculature of multiple solid tumor types including breast cancers. However, thus far, the number of cases studied from some tumor types has been limited. In this study, we set out to assess PSMA expression in the tumor-associated vasculature associated with invasive breast carcinomas in a sizable cohort of patients. One hundred and six patients with AJCC stage 0-IV breast cancer were identified. Ninety-two of these patients had primary breast cancer [invasive breast carcinoma with or without co-existing ductal carcinoma in situ (DCIS) (74) or DCIS alone (18)]. In addition, 14 patients with breast cancer metastases to the brain were identified. Immunohistochemical staining for PSMA and CD31 was performed on parallel representative tumor sections in each case. Tumor-associated vascular endothelial cell PSMA immunoreactivity was semi-quantitatively assessed based on two parameters: overall percent of endothelial positivity and staining intensity. PSMA expression for tumor-associated vascular endothelial cells was scored 0 if there was no detectable PSMA expression, 1 if PSMA staining was detectable in 5-50%, and 2 if PSMA expression was positive in >50% of microvessels. CD 31 staining was concurrently reviewed to confirm the presence of vasculature in each case. Tumor-associated vasculature was PSMA-positive in 68/92 (74%) of primary breast cancers and in 14/14 (100%) of breast cancers metastatic to brain. PSMA was not detected in normal breast tissue or carcinoma cells. All but 2 cases (98%) showed absence of PSMA expression in normal breast tissue-associated vasculature. The 10-year overall survival was 88.7% (95% CI = 80.0%, 93.8%) in patients without brain metastases. When overall survival (OS) was stratified based on PSMA score group, patients with PSMA scores of 0, 1, and 2 had 10-year OS of 95.8%, 96.0%, and 79.7%, respectively (p = 0.12). When PSMA scores of 0 and 1 were compared with 2, there was a statistically significant difference in OS (96.0% vs 79.7%, respectively, p = 0.05). Patients with a PSMA score of 2 had a significantly higher median tumor size compared with patients in the lower PSMA score groups (p = 0.04). Patients with higher nuclear grade were more likely to have a PSMA score of 2 compared with patients with lower nuclear grade (p < 0.0001). Patients with a PSMA score of 2 had a significantly higher median Ki-67 proliferation index compared with patients in the lower PSMA score groups (p < 0.0001). Patients with estrogen receptor (ER)-negative tumors were more likely to have a PSMA score of 2 compared with patients with ER-positive tumors (p < 0.0001). Patients with progesterone receptor (PR)-negative tumors were more likely to have a PSMA score of 2 compared with patients with PR-positive tumors (p = 0.03). No significant association was observed between PSMA score group status and lymph node involvement (p = 0.95). Too little variability was present in Human epidermal growth factor receptor-2 (Her2/neu) amplified tumors to correlate with PSMA score group status. To date, this is the first detailed assessment of PSMA expression in the tumor-associated vasculature of primary and metastatic breast carcinomas. Further studies are needed to evaluate whether PSMA has diagnostic and/or potential therapeutic value.

Stereotactic body radiation therapy (SBRT) for early stage lung cancer delivers clinically significant radiation to the draining lymph nodes

BACKGROUND

To evaluate clinically significant radiotherapy (RT) dose to draining lymph nodes (LN) in patients treated with SBRT.

FINDINGS

Early stage non-small cell lung cancer patients treated with SBRT were selected for analysis. Patients received SBRT if they were not considered eligible for surgical resection. RT plans for 29 patients (32 lesions) were analyzed. For each patient, ipsilateral and contralateral levels 2, 3, 4, 5, 6, 7 and ipsilateral hilar LN stations were contoured. Dose volume histograms and dosimetric coverage of each lymph node region were obtained for each patient. There were 14 males and 15 females. Median age was 75 (range 60-89). Clinically significant RT was received at the corresponding draining lymph node station depending on the primary tumor location. Friedman's non-parametric test revealed a statistically significant difference in RT dose to LN stations depending on the location of the tumor (p<0.0001).

CONCLUSION

SBRT for early stage lung cancer results in significant RT dose to the draining LN. This RT dose may be sufficient to eliminate subclinical microscopic disease despite being a highly conformal treatment. Prospective studies are needed to evaluate if SBRT is comparable to lobectomy plus mediastinal lymph node dissection as a treatment option.

Automatic shape-based level set segmentation for needle tracking in 3-D TRUS-guided prostate brachytherapy

Prostate brachytherapy is an effective treatment for early prostate cancer. The success depends critically on the correct needle implant positions. We have devised an automatic shape-based level set segmentation tool for needle tracking in 3-D transrectal ultrasound (TRUS) images, which uses the shape information and level set technique to localize the needle position and estimate the endpoint of needle in real-time. The 3-D TRUS images used in the evaluation of our tools were obtained using a 2-D TRUS transducer from Ultrasonix (Richmond, BC, Canada) and a computer-controlled stepper motor system from Thorlabs (Newton, NJ, USA). The accuracy and feedback mechanism had been validated using prostate phantoms and compared with 3-D positions of these needles derived from experts' readings. The experts' segmentation of needles from 3-D computed tomography images was the ground truth in this study. The difference between automatic and expert segmentations are within 0.1 mm for 17 of 19 implanted needles. The mean errors of automatic segmentations by comparing with the ground truth are within 0.25 mm. Our automated method allows real-time TRUS-based needle placement difference within one pixel compared with manual expert segmentation.

Predicting the risk of secondary lung malignancies associated with whole-breast radiation therapy

PURPOSE

The risk of secondary lung malignancy (SLM) is a significant concern for women treated with whole-breast radiation therapy after breast-conserving surgery for early-stage breast cancer. In this study, a biologically based secondary malignancy model was used to quantify the risk of secondary lung malignancies (SLMs) associated with several common methods of delivering whole-breast radiation therapy (RT).

METHODS AND MATERIALS

Both supine and prone computed tomography simulations of 15 women with early breast cancer were used to generate standard fractionated and hypofractionated whole-breast RT treatment plans for each patient. Dose-volume histograms (DVHs) of the ipsilateral breast and lung were calculated for each patient on each plan. A model of spontaneous and radiation-induced carcinogenesis was used to determine the relative risks of SLMs for the different treatment techniques.

RESULTS

A higher risk of SLMs was predicted for supine breast irradiation when compared with prone breast irradiation for both the standard fractionation and hypofractionation schedules (relative risk [RR] = 2.59, 95% confidence interval (CI) = 2.30-2.88, and RR = 2.68, 95% CI = 2.39-2.98, respectively). No difference in risk of SLMs was noted between standard fractionation and hypofractionation schedules in either the supine position (RR = 1.05, 95% CI = 0.97-1.14) or the prone position (RR = 1.01, 95% CI = 0.88-1.15).

CONCLUSIONS

Compared with supine whole-breast irradiation, prone breast irradiation is associated with a significantly lower predicted risk of secondary lung malignancy. In this modeling study, fractionation schedule did not have an impact on the risk of SLMs in women treated with whole-breast RT for early breast cancer.

Panoramic cone beam computed tomography

PURPOSE

Cone-beam computed tomography (CBCT) is the main imaging tool for image-guided radiotherapy but its functionality is limited by a small imaging volume and restricted image position (imaged at the central instead of the treatment position for peripheral lesions to avoid collisions). In this paper, the authors present the concept of "panoramic CBCT," which can image patients at the treatment position with an imaging volume as large as practically needed.

METHODS

In this novel panoramic CBCT technique, the target is scanned sequentially from multiple view angles. For each view angle, a half scan (180° + θ(cone) where θ(cone) is the cone angle) is performed with the imaging panel positioned in any location along the beam path. The panoramic projection images of all views for the same gantry angle are then stitched together with the direct image stitching method (i.e., according to the reported imaging position) and full-fan, half-scan CBCT reconstruction is performed using the stitched projection images. To validate this imaging technique, the authors simulated cone-beam projection images of the Mathematical Cardiac Torso (MCAT) thorax phantom for three panoramic views. Gaps, repeated/missing columns, and different exposure levels were introduced between adjacent views to simulate imperfect image stitching due to uncertainties in imaging position or output fluctuation. A modified simultaneous algebraic reconstruction technique (modified SART) was developed to reconstruct CBCT images directly from the stitched projection images. As a gold standard, full-fan, full-scan (360° gantry rotation) CBCT reconstructions were also performed using projection images of one imaging panel large enough to encompass the target. Contrast-to-noise ratio (CNR) and geometric distortion were evaluated to quantify the quality of reconstructed images. Monte Carlo simulations were performed to evaluate the effect of scattering on the image quality and imaging dose for both standard and panoramic CBCT.

RESULTS

Truncated images with artifacts were observed for the CBCT reconstruction using projection images of the central view only. When the image stitching was perfect, complete reconstruction was obtained for the panoramic CBCT using the modified SART with the image quality similar to the gold standard (full-scan, full-fan CBCT using one large imaging panel). Imperfect image stitching, on the other hand, lead to (streak, line, or ring) reconstruction artifacts, reduced CNR, and/or distorted geometry. Results from Monte Carlo simulations showed that, for identical imaging quality, the imaging dose was lower for the panoramic CBCT than that acquired with one large imaging panel. For the same imaging dose, the CNR of the three-view panoramic CBCT was 50% higher than that of the regular CBCT using one big panel.

CONCLUSIONS

The authors have developed a panoramic CBCT technique and demonstrated with simulation data that it can image tumors of any location for patients of any size at the treatment position with comparable or less imaging dose and time. However, the image quality of this CBCT technique is sensitive to the reconstruction artifacts caused by imperfect image stitching. Better algorithms are therefore needed to improve the accuracy of image stitching for panoramic CBCT.

Secondary rectal malignancy risk reduction with IMRT and rectal balloon placement during radiation therapy

e15162

Background: The risk of secondary rectal malignancies (SRMs) is a significant concern following radiation therapy for prostate cancer patients. Modern prostate radiotherapy techniques include the use of intensity modulated radiation therapy (IMRT) and rectal balloons to decrease treatment related toxicity. These technologies may also lower the likelihood of radiation-induced SRMs. In this study, a novel biologically-based carcinogenesis model was used to quantify and to compare the predicted risks of SRMs in men treated with or without a rectal balloon in place using either standard 3-D conformal radiotherapy (3D-CRT) or IMRT radiotherapy. Methods: Treatment plans were developed for ten clinically localized prostate cancer patients using CT scans obtained both with and without a rectal balloon in place. Target and normal structures were contoured, and dose-volume histograms (DVHs) for these organs were determined with a planned 3D-CRT dose of 75.6 Gy or with a planned IMRT dose of 81 Gy. A biologically-based mathematical model of spontaneous and radiation-induced carcinogenesis was used to determine the excess absolute risk of SRMs for each plan. These risks were then compared to one another and to the baseline population. Results: Treatment with IMRT and a rectal balloon in place resulted in a significantly lower mean rectal wall dose in all patients compared with treatment with 3D-CRT without a rectal balloon. The average mean rectal wall dose with IMRT and a rectal balloon in place was 31.0 Gy versus 40.1 Gy with 3D-CRT without the rectal balloon (p < 0.001). A significantly higher risk of SRMs was predicted for patients treated with 3-D CRT without rectal balloons when compared with patients treated with IMRT with balloons in place (p < 0.001, relative risk 1.30; 95% confidence interval 1.16-1.44). Conclusions: For prostate cancer patients treated with definitive radiotherapy, the use of IMRT and rectal balloons during radiation, when compared to treatment with 3-D conformal radiotherapy, is associated with a significant reduction in the predicted risk of secondary rectal malignancies.

Case-control study of prophylactic cranial irradiation in nonmetastatic non-small cell lung cancer

7050

Background: Prophylactic cranial irradiation (PCI) reduces the incidence of brain metastases in NSCLC patients after primary therapy, but its impact on survival is uncertain. We report on the largest study of survival in patients treated with and without PCI for non-small cell lung cancer (NSCLC). Methods: We reviewed 17 Surveillance, Epidemiology and End Results (SEER) registries for a retrospective study on patients who had PCI as part of their primary treatment for NSCLC from 1988 - 97. Cases were limited to those with non-metastatic (Stage I-III) NSCLC. To balance the cohorts, we matched each PCI patient with four non-PCI patients on stage, histology, race and sex. Associations between treatment type, clinical factors, and demographics were assessed using the Chi-squared test. Survival time was calculated as the number of months from diagnosis to the date of death. Survival was censored as of the last month when patients were known to be alive. Overall (OS) and cancer cause-specific survival (CSS) were investigated using the Kaplan-Meier, competing risks, Cox proportional hazards, and log-rank tests. Results: We found 472 PCI matched to 1,888 non-PCI patients. Characteristics were balanced across groups: race (p = 1.00), sex (p = 0.95), histology (p = 1.00), stage (p = 1.00), and surgery (p = 0.81). PCI group was younger, median age 64 vs 68 (p < 0.01). PCI vs no PCI median OS was 8 vs 10 months (p < 0.01). OS was 14% vs 28% at 2 years and 5% vs 12% at 5 years, PCI vs no PCI respectively (p < 0.01). Stage III OS was also different; 10% vs 21% at 2 years, PCI vs no PCI respectively (p < 0.01). Median CSS was the same at 9 months in both groups. Median follow-up was 14 years. Conclusions: PCI was not associated with improved OS or CSS in these NSCLC patients, and PCI may have a detrimental effect on OS. In limited-stage small cell lung cancer, a retrospective SEER analysis during the 1988 – 97 period showed a survival benefit in treated patients with PCI, which has been confirmed with prospective studies. To date, 4 prospective trials examining PCI for NSCLC have shown a reduced incidence of brain metastases, but the effect on survival is unclear. Further investigation is needed to determine whether PCI for NSCLC increases the risk of other causes of death.

Association of IL17-expressing γδ t cells with acute radiation-induced pneumonitis

e21097

Background: Radiation pneumonitis is a substantial cause of morbidity and mortality with thoracic radiation for lung cancer. Little is known about the crucial mechanisms of the inflammatory response. We seek to determine if a key mediator of organ-specific inflammatory disorders and innate immune response, IL-17+ γδ T cells, is associated with radiation pneumonitis. Methods: C3HBe/FeJ mice (7 mice/group) were sham-irradiated as controls or exposed to a single dose of 15 Gy thoracic X-ray to develop pneumonitis. We have previously shown that TGFβ has an immunosuppressive activity in radiation pneumonitis. To potentiate the radiation pneumonitis, one group of mice was administered anti-TGFβ therapy with inhibitory TGFβ mAb (1D11, i.p.10 mg/kg/wk). Bronchoalveolar lavage fluid was assessed for cytology and inflammatory cytokine level. Lung tissues were examined for cell infiltration and histopathological changes. Cell surface marker and intracellular cytokine staining were performed on lymphocytes from the digested lungs by flow cytometry. Results: At 10 weeks post-irradiation, the lungs of the irradiated mice showed substantially more alveolar wall edema and increased infiltration of inflammatory cells compared with sham controls. Pneumonitis-involved lungs contained more IL-17+ γδ T cells (0.85% ± 0.00%) compared with sham controls (0.33% ± 0.02%), p<0.001. Furthermore increased IL-17+ γδ T cells were associated with potentiated radiation pneumonitis with anti-TGFβ therapy. There was a significant increased alveolar inflammation in irradiated mice injected with anti-TGFβ mAb. Anti-TGFβ irradiated lungs also contained significantly more IL-17+ γδ T cells (1.17% ± 0.13%) compared with irradiated controls (0.72% ± 0.13%), p<0.001. There was no increase of other TGFβ-dependent T cell subtypes such as IFNγ+ αβ T cells (Th1), IL-17+ αβ T cells (Th17), CD25+ Foxp3+ Tregs, nor activated macrophages in the potentiated pneumonitis lungs. Conclusions: Our findings implicate a novel role for IL17-expressing γδ T cells in radiation pneumonitis. This study reveals this innate immune response pathway as a potential target for therapeutic intervention in radiation lung injury

Predicting the risk of secondary malignancies associated with stereotactic body radiation therapy

e17562

Background: Treatment of early-stage non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) is associated with high rates of local control and long-term overall survival. With increasing frequency, SBRT is a treatment option for operable tumors which raises the question of the risk of long-term toxicities such as radiation-induced secondary malignancies. There has been no previous risk assessment or epidemiological studies of secondary malignancies with high-dose hypofractionated SBRT. In this study, we seek to quantify the predicted rates of secondary lung malignancies in patients treated with SBRT for stage I-II NSCLC. Methods: Treatment plans for 14 stage I-II NSCLC patients treated with definitive-intent SBRT at Columbia University Medical Center were retrospectively assessed. Median patient age was 73 years (range 54 - 86) with median tumor size of 2.8 cm (range 1.2 - 5.0). SBRT doses ranged from 40-60 Gy in 3-5 fractions. Dose-volume histograms for target PTV and normal lung were generated from planning CT scans. A biologically-based mathematical model of spontaneous and radiation-induced carcinogenesis was used to determine the excess absolute risk and the median lifetime estimated relative risk of secondary lung malignancies for each plan. These risks were then compared using 2-sided t-tests. Results: For all patients, the median lifetime estimated absolute risk of secondary lung malignancy was 1.06% (95% CI 0.62%-1.98%), and the median lifetime estimated relative risk of secondary lung malignancy was 1.61 (95% CI 1.47-1.75) after SBRT. For patients aged less than 65 years, median estimated absolute risk of secondary malignancies was higher (2.8%) than for patients age 65 and older (0.37%), p < 0.001. PTV volume less than 50 cc vs greater than 50 cc, T1 vs T2 tumors, and gender were not significantly associated with differences in estimated absolute risk or estimated relative risk of secondary malignancies. Conclusions: As SBRT is potentially indicated in younger medically operable patients, the long-term late toxicities need to be determined. This study suggests that the risk of second lung malignancies from high-dose SBRT even in younger patients would be minimal.

Small-molecule synthetic compound norcantharidin reverses multi-drug resistance by regulating Sonic hedgehog signaling in human breast cancer cells

Multi-drug resistance (MDR), an unfavorable factor compromising treatment efficacy of anticancer drugs, involves upregulated ATP binding cassette (ABC) transporters and activated Sonic hedgehog (Shh) signaling. By preparing human breast cancer MCF-7 cells resistant to doxorubicin (DOX), we examined the effect and mechanism of norcantharidin (NCTD), a small-molecule synthetic compound, on reversing multidrug resistance. The DOX-prepared MCF-7R cells also possessed resistance to vinorelbine, characteristic of MDR. At suboptimal concentration, NCTD significantly inhibited the viability of DOX-sensitive (MCF-7S) and DOX-resistant (MCF-7R) cells and reversed the resistance to DOX and vinorelbine. NCTD increased the intracellular accumulation of DOX in MCF-7R cells and suppressed the upregulated the mdr-1 mRNA, P-gp and BCRP protein expression, but not the MRP-1. The role of P-gp was strengthened by partial reversal of the DOX and vinorelbine resistance by cyclosporine A. NCTD treatment suppressed the upregulation of Shh expression and nuclear translocation of Gli-1, a hallmark of Shh signaling activation in the resistant clone. Furthermore, the Shh ligand upregulated the expression of P-gp and attenuated the growth inhibitory effect of NCTD. The knockdown of mdr-1 mRNA had not altered the expression of Shh and Smoothened in both MCF-7S and MCF-7R cells. This indicates that the role of Shh signaling in MDR might be upstream to mdr-1/P-gp, and similar effect was shown in breast cancer MDA-MB-231 and BT-474 cells. This study demonstrated that NCTD may overcome multidrug resistance through inhibiting Shh signaling and expression of its downstream mdr-1/P-gp expression in human breast cancer cells.