SU-E-T-154: Online Dose Verification with Gafchromic Film for Fixed-Gantry and Rotational Intensity Modulated Radiation Therapy: A Phantom Study

PURPOSE

The patient specific quality assurance (QA) measurements for fixed-gantry and rotational intensity modulated radiation therapy (IMRT and VMAT/RapidArc) are usually performed on a homogeneous phantom prior to the treatment. The purpose of this study is to develop an online method to verify the delivered dose to the patient on the treatment day.

METHODS

An anthropomorphic (Rando) head phantom was immobilized in treatment position with a thermoplastic mask to simulate a real patient. A sheet of gafchromic film (EBT2) was sandwiched between a 1-cm-thick solid water slab, which was fixed to the Type-S extension board, and the patient's head hold (a pillow used here). The CT images of the Rando phantom were acquired and exported to the treatment planning systems. One step-and-shot fixed-gantry IMRT plan and one RapidArc plan were generated and the dose distributions on the film plane were calculated. The two plans were delivered to the patient (Rando phantom in this study) in the treatment position on a Varian Trilogy linear accelerator with two new films. The films were scanned, and the measurements were compared with the planned doses.

RESULTS

The composite dose distributions measured on the film plane were the actual delivered dose for the treatment. The comparison between the measurement and planned dose profiles shows an agreement within 3% because of the good reproducibility of phantom positioning. Gamma pass rates (using 3mm and 3% criteria) for the IMRT and RapidArc plan were found to be 95% and 94%, respectively.

CONCLUSIONS

The phantom study has demonstrated the feasibility of using gafchromic film for online dose verification. This simple method takes into account the patient heterogeneity and the treatment associated uncertainties such as setup error, intrafraction motions and machine related variations. It can be implemented as an online physics and/or clinical QA tool without taking additional machine time.

Lung spirometry parameters and diffusion capacity are decreased in patients with Type 2 diabetes

AIMS

In cohort studies, Type 2 diabetes mellitus has been associated with decreased forced 1 s expiratory volume and forced vital capacity. We examined if forced vital capacity, forced 1 s expiratory volume and diffusion lung capacity correlate with diabetes mellitus across different races in a clinical setting.

METHODS

We examined the medical records of 19,882 adults 18-97 years of age in our centre from 1 January 2000 to 1 May 2009. After excluding patients with diseases causing abnormal lung function, 4164 subjects were available for analysis. We used multiple linear regressions to examine cross-sectional differences in forced vital capacity, forced 1 s expiratory volume and carbon monoxide diffusing capacity between patients with and without diabetes mellitus, after adjustment for age, sex, race, height, smoking, BMI and heart failure.

RESULTS

Patients with diabetes (n = 560) were older (62 ± 12 vs. 55 ± 16 years), more likely to be men (56 vs. 43%), overweight (BMI 31.7 ± 8.5 vs. 27.3 ± 6.7 kg/m2 ), have heart failure (33 vs. 14%) and less likely to be Caucasians (65 vs. 76%) and never smokers (66 vs. 72%) compared with patients without diabetes (n = 3604). The mean unadjusted values in patients with diabetes vs. those without were: forced vital capacity 2.78 ± 0.91 vs. 3.19 ± 1.03 l; forced 1 s expiratory volume 2.17 ± 0.74 vs. 2.49 ± 0.0.83; and carbon monoxide diffusing capacity 16.67 ± 5.53 vs. 19.18 ± 6.72 ml(-1) min(-1) mmHg, all P < 0.0001. These differences remained significant after adjustment for covariates. After race stratification, only Caucasians with diabetes had a significant decrease in all lung function measures.

CONCLUSIONS

Patients with diabetes have decreased lung function compared with those without diabetes. Caucasians with diabetes have more global lung function impairment compared with African-Americans and Hispanics.

Microarray profiling analysis uncovers common molecular mechanisms of rubella virus, human cytomegalovirus, and herpes simplex virus type 2 infections in ECV304 cells

To study the common molecular mechanisms of various viruses infections that might result in congential cardiovascular diseases in perinatal period, changes in mRNA expression levels of ECV304 cells infected by rubella virus (RUBV), human cytomegalovirus (HCMV), and herpes simplex virus type 2 (HSV-2) were analyzed using a microarray system representing 18,716 human genes. 99 genes were found to exhibit differential expression (80 up-regulated and 19 down-regulated). Biological process analysis showed that 33 signaling pathways including 22 genes were relevant significantly to RV, HCMV and HSV-II infections. Of these 33 biological processes, 28 belong to one-gene biological processes and 5 belong to multiple-gene biological processes. Gene annotation indicated that the 5 multiple-gene biological processes including regulation of cell growth, collagen fibril organization, mRNA transport, cell adhesion and regulation of cell shape, and seven down- or up-regulated genes [CRIM1 (cysteine rich transmembrane BMP regulator 1), WISP2 (WNT1 inducible signaling pathway protein 2), COL12A1 (collagen, type XII, alpha 1), COL11A2 (collagen, type XI, alpha 2), CNTN5 (contactin 5), DDR1 (discoidin domain receptor tyrosine kinase 1), VEGF (vascular endothelial growth factor precursor)], are significantly correlated to RUBV, HCMV and HSV-2 infections in ECV304 cells. The results obtained in this study suggested the common molecular mechanisms of viruses infections that might result in congential cardiovascular diseases.

P3-16-17: The Identification of Novel Microtubule Stabilizing Taccalonolides

Microtubule stabilizing agents, including the taxanes and epothilones, are some of the most important drugs used in the treatment of cancer. All of the microtubule stabilizers used clinically bind within the taxane site on microtubules and work through a similar mechanism of action. We have identified a new class of microtubule stabilizers, the taccalonolides, from plants of the genus Tacca. The most abundant taccalonolides, A and E, are classified as microtubule stabilizers due to their ability to disrupt both interphase and mitotic cellular microtubules, leading to mitotic arrest and apoptosis. However, they are unique from all other microtubule stabilizers in that they do not bind directly to microtubules or stimulate the polymerization of tubulin in biochemical preparations. The taccalonolide structure is characterized by a highly acetylated pentacyclic steroidal skeleton, which is also structurally distinct from all other microtubule targeted agents. The unique structure and mechanism of action of the taccalonolides, together with their ability to circumvent clinically relevant forms of taxane resistance, prompted our efforts to explore the structure-activity relationship of this class of molecules. We have isolated several novel taccalonolides, designated Z, AA, AB, AC, AF and AG, as well as multiple known taccalonolides. Each of these taccalonolides exhibited cellular microtubule stabilizing activity and antiproliferative actions against breast cancer cells. However, profound differences in potencies were noted with IC50 values ranging from 32 nM to 13 μM. These studies demonstrate that microtubule stabilizing activity is a shared trait among this class of molecules and that significant structure-activity relationships exist. Additionally, in vivo antitumor evaluations of taccalonolides A, E and N demonstrate that each of these molecules has activity in vivo and that taccalonolide A is the most effective against a syngeneic mammary model of breast cancer.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-16-17.

Polygamain, a new microtubule depolymerizing agent that occupies a unique pharmacophore in the colchicine site

Bioassay-guided fractionation was used to isolate the lignan polygamain as the microtubule-active constituent in the crude extract of the Mountain torchwood, Amyris madrensis. Similar to the effects of the crude plant extract, polygamain caused dose-dependent loss of cellular microtubules and the formation of aberrant mitotic spindles that led to G(2)/M arrest. Polygamain has potent antiproliferative activities against a wide range of cancer cell lines, with an average IC(50) of 52.7 nM. Clonogenic studies indicate that polygamain effectively inhibits PC-3 colony formation and has excellent cellular persistence after washout. In addition, polygamain is able to circumvent two clinically relevant mechanisms of drug resistance, the expression of P-glycoprotein and the βIII isotype of tubulin. Studies with purified tubulin show that polygamain inhibits the rate and extent of purified tubulin assembly and displaces colchicine, indicating a direct interaction of polygamain within the colchicine binding site on tubulin. Polygamain has structural similarities to podophyllotoxin, and molecular modeling simulations were conducted to identify the potential orientations of these compounds within the colchicine binding site. These studies suggest that the benzodioxole group of polygamain occupies space similar to the trimethoxyphenyl group of podophyllotoxin but with distinct interactions within the hydrophobic pocket. Our results identify polygamain as a new microtubule destabilizer that seems to occupy a unique pharmacophore within the colchicine site of tubulin. This new pharmacophore will be used to design new colchicine site compounds that might provide advantages over the current agents.

Detection of incidental colorectal tumours with 18F-labelled 2-fluoro-2-deoxyglucose positron emission tomography/computed tomography scans: results of a prospective study

AIM

This study assessed the clinical significance of incidental colorectal 2-fluoro-2-deoxyglucose (FDG) uptake using (18) F-FDG positron emission tomography/computed tomography (PET/CT) scans and evaluated the importance of colonoscopy when incidental colorectal FDG uptake was observed.

METHOD

A prospective study was designed and conducted at a single institution over a 2-year period. In patients undergoing PET/CT scans, all with FDG uptake in the colorectum were assigned to have colonoscopy and biopsy. The value of PET/CT scanning was studied by comparison with the colonoscopy and biopsy results.

RESULTS

Among 10,978 PET/CT scans, one or more focal uptakes of FDG in the colorectum were observed in 148 (1.35%) patients. In 136 valid patients, malignant colorectal tumours and polyps were found in 23.5% and 20.5%, respectively,, while the colon in the other 56% was normal. A higher false-positive rate was found in the right colon compared with the distal colorectum (66.2%vs 36.7%, P = 0.004). A significant increase of the maximum standardized uptake (SUVmax) value was found among normal, polyps and cancer groups. Multivariate analysis revealed that SUVmax was the risk factor for predicting colorectal cancer or polyps and FDG uptake in the right colon was a negative predictive factor for finding cancers or polyps.

CONCLUSIONS

Our study proves the necessity of colonoscopy when incidental FDG uptake is found on PET/CT imaging. The false-positive FDG uptake is more commonly observed in the right colon. Although the SUVmax value is higher in cancer patients, a high SUVmax value does not necessarily result in malignancies.

Emu model of full-range femoral head osteonecrosis induced focally by an alternating freezing and heating insult

The emu, a large bipedal bird with hip joint biomechanics similar to humans, was used to establish an experimental model of femoral head osteonecrosis and subsequent femoral head collapse. Focal lesions were induced in 20 adult male emus using an alternating liquid nitrogen freezing and radiofrequency heating insult. At 2, 4, 8, 12 and 16 weeks post-surgery, hip magnetic resonance imaging (MRI) was performed. Before the emus were sacrificed, barium sulphate was infused to the lower extremity to study blood vessel distribution patterns. Femoral samples were scanned by micro-computed tomography (micro-CT) and evaluated histologically. Hip MRI showed changes from broad oedema to femoral head collapse. Emus developed a crippled gait from post-operative week 6. Micro-CT scans and histology showed human-like osteonecrotic changes with an impaired local blood supply. The protocol resulted in consistent full-range osteonecrosis of the femoral head that may serve as a model for testing potential treatments.

Antimagnetic rotation band in nuclei: a microscopic description

Covariant density functional theory and the tilted axis cranking method are used to investigate antimagnetic rotation (AMR) in nuclei for the first time in a fully self-consistent and microscopic way. The experimental spectrum as well as the B(E2) values of the recently observed AMR band in (105)Cd are reproduced very well. This gives a further strong hint that AMR is realized in specific bands in nuclei.

Access to thalidomide for the treatment of multiple myeloma in Canada: physician behaviours and ethical implications

BACKGROUND

Multiple myeloma is an incurable malignancy. Since the late 1990s, its management has changed with the introduction of novel agents. Thalidomide, which is often called a "novel" therapy, has significantly prolonged survival in multiple myeloma and is considered worldwide to be part of standard of care in this disease. However, thalidomide is not approved in Canada, leading to problems with drug access for patients.

METHODS

Our study surveyed Canadian hematologists on their thalidomide prescribing practices and difficulties with drug access. We address some of the ethical issues facing patients and their doctors who are unable to obtain or afford the drug, and who therefore resort to alternative means such as illegal importation.

RESULTS

Of the 411 Canadian hematologists contacted, 122 completed the survey, 97 reported that they did not treat myeloma, and 192 did not respond. Assuming that all non-responders treat myeloma, our estimated overall response rate from physicians who treat this disease was 39%. Survey participants indicated that, in Canada, access to thalidomide is a major issue for physicians and myeloma patients alike, and that 81% of respondents are dissatisfied or very dissatisfied with the drug access process. Many physicians felt that the special access process for thalidomide is unduly onerous, influences treatment decisions, and invades patient privacy. We found that 20% of physicians were unaware of the legal implications of obtaining thalidomide from other countries and that at least 23% overtly or covertly support patients in obtaining the drug from a non-Health-Canada-approved source.

CONCLUSIONS

The current lack of access to thalidomide in Canada is a concerning problem for patients and health care providers dealing with myeloma. Regulatory changes at the federal level (Health Canada) need to be re-examined to promptly resolve this issue.

Herbivore-induced volatiles of cabbage (Brassica oleracea) prime defence responses in neighbouring intact plants

When attacked by herbivores, plants release herbivore-induced plant volatiles (HIPV) that may function in direct defence by repelling herbivores or reducing their growth. Emission of HIPV may also contribute to indirect defence by attracting natural enemies of the herbivore. Here, cabbage (Brassica oleracea L.) plants (receiver plants) previously exposed to HIPV and subsequently induced through feeding by five Pieris brassicae L. caterpillars attracted more Cotesia glomerata L. parasitoids than control plants. HIPVs to which receiver plants had been exposed were emitted by B. oleracea infested with 50 P. brassicae caterpillars. Control plants had been exposed to volatiles from undamaged plants. In contrast, there were no differences in the attraction of wasps to receiver plants induced through feeding of one or ten larvae of P. brassicae compared to control plants. In addition, RT-PCR demonstrated higher levels of LIPOXYGENASE (BoLOX) transcripts in HIPV-exposed receiver plants. Exposure to HIPV from emitter plants significantly inhibited the growth rate of both P. brassicae and Mamestra brassicae caterpillars compared to growth rates of caterpillars feeding on control receiver plants. Our results demonstrate plant-plant signalling leading to priming of both indirect and direct defence in HIPV-exposed B. oleracea plants.

Prevalence and characteristics of psoriatic arthritis in Chinese patients with psoriasis

BACKGROUND

The prevalence and clinical characteristics of psoriatic arthritis (PsA) in patients with psoriasis vary widely in different countries and studies on Chinese population are rarely reported.

OBJECTIVE

The aim of this study was to evaluate the prevalence and clinical characteristics of PsA in a Chinese population of patients with psoriasis.

METHODS

A large cross-sectional observational study was conducted in our outpatient dermatology department and consecutive psoriatic patients were evaluated for PsA according to Classification of Psoriatic arthritis (CASPAR) criteria. Demographic and medical parameters were recorded.

RESULTS

Among 1928 patients with psoriasis, 112 patients (5.8%) had PsA, of which 92% was newly diagnosed. Oligoarthritis (48.2%) was the most common manifestation pattern, followed by spondylitis (26.8%), polyarthritis (19.6%) and classic distal interphalangeal (DIP) arthritis (5.4%). Enthesitis was present in 26.8% and dactylitis in 13.4% of the patients. Compared with patients without PsA, patients with PsA had more severe skin disease (mean PASI 9.7 vs. 6.0), higher frequency of nail changes (46.4% vs. 21.0%) and scalp involvement (90.2% vs. 76.4%).

CONCLUSION

The findings are consistent with a low prevalence of PsA among patients with psoriasis in Asia and confirm a high percentage of undiagnosed cases with active arthritis among PsA patients in dermatologist's office. Dermatologists should screen for PsA in their patients, especially those with risk characteristics and early signs.

Prognostic analysis for carcinoid tumours of the rectum: a single institutional analysis of 106 patients

AIM

Rectal carcinoid is a rare rectal tumour with a good prognosis. The aim of this study was to assess its clinicopathological characteristics and prognostic factors in a single institution.

METHOD

Clinical and pathological information was retrospectively collected in a single institution, and patients' outcomes were determined. Multivariate analyses were performed to find independent prognostic factors attributed to overall survival.

RESULTS

A total of 106 patients with rectal carcinoid were included. In all, 66% of the patients underwent transanal local excision and 34% had transabdominal surgery. The 5-year survival rate was 87%. Muscularis invasion was the only independent prognostic factor for predicting 5-year survival (P = 0.00046). Tumour size was found to be significantly associated with muscular invasion (P = 0.00003). The area under the curve of tumour size in the receiver operating characteristic curve for predicting muscular invasion was 0.92.

CONCLUSION

Patients with rectal carcinoid have a good prognosis. Muscular invasion is an independent risk factor of survival.

The clinical values of methylation status of P16 and APC genes in bile in diagnosis of malignant obstructive jaundice

171

Background: Preoperative definitive diagnosis of malignant obstructive jaundice caused by biliary and pancreatic carcinomas still remains a major challenge. Hypermethylation of tumor suppressor genes have been implied in carcinogenesis of biliary and pancreatic malignancies. The diagnostic values of methylation status of tumor suppressor genes in bile in malignant obstructive jaundice have not been well-documented.

Methods: Bile was prospectively collected from 70 patients with obstructive jaundice treated at our hospital between November 2008 and Sepetember 2009. Forty-eight of them were proved to be malignant obstructive jaundice (biliary carcinoma in 36, pancreatic carcinoma in 8 and duodenal carcinoma in 4) by pathological examination, and 22 were benign obstructive jaundice caused by cholelithiasis. DNA was extracted from bile and modified by sodium bisulfite. Methylation-specific PCR was run to detect methylation status of P16 and APC gene promoters. Their diagnostic values in malignant obstructive jaundice were assessed.

Results: Hypermethylation of P16 promoter was presented in 72.9% (35/48) malignant obstructive jaundice, and 9% (2/22) bengin obstructive jaundice (p<0.05). Hypermethylation of APC promoter was presented in 56.2% (27/48) malignant obstructive jaundice, and 9% (2/22) bengin obstructive jaundice (p<0.05). With respect to their diagnostic values in malignant obstructive jaundice, sensitivity, specificity, positive predictivity and negative predictivity were 72.9%, 90.9%, 94.6% and 60.6%, respectively, for P16 gene; 56.2%, 90.9%, 93.1%, 48.8%, respectively, for APC gene.

Conclusions: Methylation status of P16 and APC gene promoters in bile was valuable in diagnosis of malignant obstructive jaundice, with an excellent specificity. P16 gene had a higher sensitivity than APC gene.

No significant financial relationships to disclose.

Oncological outcome of T1 rectal cancer undergoing standard resection and local excision

AIM

We studied the outcome and prognostic factors for T1 rectal cancer patients undergoing standard resection or transanal excision.

METHOD

One hundred and twenty-four patients with T1 rectal cancer were included in the study, of whom 66 (53.2%) underwent standard resection and 58 (46.8%) underwent transanal excision. Survival analysis was performed to compare the outcome.

RESULTS

The 5-year local recurrence rate was 11.0% in the transanal excision group versus 1.6% in the standard resection group (P = 0.031) but the 5-year disease-free survival and overall survival rates were not significantly different between the two groups. Multivariate analysis suggested that a high tumour grade and perineural or lymphovascular invasion were independent risk factors for local recurrence and recurrence-free survival. For high-risk patients (with at least one of the above risk factors), the 5-year local recurrence and 10-year recurrence-free survival rates were 21.2% and 74.5%, versus 1.2% and 92.0% in low-risk patients (P = 0.00003 and P = 0.003). In patients undergoing transanal excision, none in the low-risk group had local recurrence during follow up, while 40% (6 of 15) of patients in the high-risk group developed local recurrence within 5 years after surgery. The 5-year local recurrence rate was 45.0%.

CONCLUSION

Transanal excision in T1 rectal cancer may result in a high rate of local failure for patients with a high-grade tumour, or perineural or lymphovascular invasion. Local excision should be avoided as a curative treatment in high-risk patients.