Intensity-modulated radiation therapy (IMRT): Differences in target volumes and improvement in clinically relevant doses to small bowel in rectal carcinoma

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Background: In the treatment of rectal cancer, a strong dose-volume relationship exists between the amount of small bowel receiving low- to intermediate-doses of radiation and the rates of acute, severe gastrointestinal toxicity. Highly conformal treatment approaches, such as intensity-modulated radiation therapy (IMRT), may reduce dose to adjacent organs-at-risk (OAR). We performed a dosimetric evaluation of IMRT compared to 3-dimensional conformal radiation therapy (3DCRT) in standard, preoperative treatment for rectal cancer.

Methods: Using RTOG consensus contouring atlas, treatment volumes were generated for ten patients treated preoperatively, with IMRT plans compared to 3DCRT plans derived from classic anatomic landmarks, as well as modified 3DCRT plans treating the RTOG consensus volume. The patients were all T3, were node-negative (N=1) or node–positive (N=9), and were planned to a total dose of 45-Gy. Bowel displacement was achieved using a carbon-fiber bellyboard apparatus with prone positioning.

Results: IMRT plans had superior PTV coverage, dose homogeneity, and conformality in treatment of the gross disease and at-risk nodal volume, in comparison to 3DCRT. Additionally, in comparison to the modified 3DCRT plans, IMRT achieved a concomitant reduction in doses to the bowel, bladder, pelvic bones, and femoral heads, with an improvement in absolute volumes of small bowel receiving dose levels known to induce clinically-relevant acute toxicity. In the six patients with the highest volume of small bowel (range: 209-537-cc), the volume of bowel receiving 15-Gy was reduced from a median of 224-cc in the modified 3DCRT plans to 185-cc with IMRT. Also, the IMRT volumes were typically larger than that covered by classic 3DCRT fields, without incurring penalty with respect to adjacent OAR.

Conclusions: For rectal carcinoma, IMRT, compared to 3DCRT, yielded plans with superior target coverage, homogeneity, and conformality, while lowering dose to adjacent OAR. This is despite treating larger volumes, raising the possibility of a clinically-relevant improvement in the therapeutic ratio through the use of IMRT with a belly-board apparatus.

No significant financial relationships to disclose.

Study of genotypic variations and protein expression of the xCT subunit of cystine/glutamate transporter in pancreatic cancer

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Background: The plasma membrane xCT cystine-specific subunit of the cystine/glutamate transporter contributes to chemotherapy resistance in pancreatic cancer by regulating intracellular glutathione levels and protecting cancer cells against oxidative stress. We previously noted that the rs7674870 single nucleotide polymorphism (SNP) of xCT correlated with overall survival in pancreatic cancer and may be predictive of platinum resistance. There are no data regarding xCT protein expression in pancreatic cancer or the functional significance of this SNP.

Methods: Paraffin-embedded core and surgical biopsy tumor specimens from 49 patients with metastatic pancreatic adenocarcinoma were analyzed by immunohistochemistry (IHC) using an xCT specific antibody (Novus Biologicals). xCT protein IHC expression scores (product of intensity and percentage of staining cells) were analyzed in relation to overall survival and genotype of the patients using the one factor ANOVA test, Kaplan-Meier plot, log-rank test, and Cox regression analysis. Overall survival was measured from the date of diagnosis to the date of death or last follow-up.

Results: Positive xCT expression was detected in 38 (78%) of the 49 samples, and 9 (18%) patients had high levels of expression. High xCT expression was associated with lower overall survival as compared with low expression (5.1 months versus 8.8 months; p = 0.119). In a multivariate Cox regression model with adjustment for prognostic parameters of age, sex, performance status and CA19-9 level, high xCT expression was associated with a 2.1-fold increased risk of death (p = 0.096). Performance status also correlated with overall survival (p = 0.027). Preliminary analysis on the genotype-phenotype association (n = 12) indicated that xCT expression was higher with the TT genotype than the TC/CC genotype (p = 0.115), which is consistent with the previous observation that the TT genotype was associated with reduced survival.

Conclusions: These data provide supporting evidence for a possible role of cystine/glutamate transporter xCT subunit in pancreatic cancer progression and survival. Further pharmacogenomic and clinicopathologic studies are ongoing.

No significant financial relationships to disclose.

Use of DPC-4 immunostaining of diagnostic cytology specimens to predict the pattern of tumor progression in locally advanced pancreatic cancer patients (LAPC)

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Background: An autopsy study has identified DPC-4 as a potential biomarker of the pattern of disease spread in pancreatic cancer patients (Iacobuzio-Donahue et al, JCO, 2009). We sought to determine whether DPC-4 expression determined by immunohistochemistry (IHC) staining of primary tumor cytology specimens correlates with the clinical pattern of progression in patients with locally advanced pancreatic cancer (LAPC).

Methods: LAPC patients with ECOG 0-1 PS were treated with gemcitabine (1000 mg/m2), oxaliplatin (100 mg/m2), and cetuximab for (500mg/m2) q2wks for 4 doses followed by XRT (50.4 Gy to the gross tumor only) with capecitabine (825 mg/m2 twice daily, days of radiation) and cetuximab on a multiinstitutional trial. Forty-one of 58 patients treated at our institution had cytology specimens suitable for IHC staining. The patterns of progression were determined based on radiographic studies and clinical symptoms. Findings were blinded from the IHC results. Patients were categorized as 1) local disease dominant, 2) distant disease dominant, 3) indeterminate pattern, and 4) no progression. The IHC scoring of DPC-4 was determined by an experienced cytopathologist who was blinded from the clinical data.

Results: Median, 1yr and 3yr actuarial OS are 18.2 months, 67.2% and 18.5%. Dominant progression pattern was local (n=15), distant (n=14), indeterminate (n=8), and no progression (n=4). Intact DPC expression correlated with local dominant progression (11/15) and DPC-4 loss correlated with distant dominant progression (10/14), p=0.016. The median DM free survival rate was 18.0 for intact DPC-4 versus 12.5 mo for DPC-4 loss patients (p=NS). There was no significant difference in overall survival based on DPC-4 status.

Conclusions: Determination of DPC-4 expression from cytology specimens is feasible. DPC-4 expression correlated with the pattern of progression and is consistent with previous autopsy data. DPC-4 expression does not appear to be predictive or prognostic. Prospective validation of DPC-4 as a biomarker of disease progression is warranted and may lead to personalized treatment strategies for patients with LAPC.

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Dose-escalated external beam radiotherapy in unresectable hepatocellular carcinoma

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Background: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Data regarding the use of external beam radiotherapy is limited in patients from populations without endemic viral hepatitis. We examine the outcomes for patients treated with external beam radiotherapy in the modern era at a single institution.

Methods: A total of 29 patients with localized HCC treated from 2000 to 2009 were reviewed. Patients with metastatic disease at the time of radiation were excluded. Median radiation dose was 50 Gy (range 30-75 Gy) with a median biologically effective dose (BED) of 80.6 (range 60-138.6). Median tumor size at the time of radiation was 5.2 cm (range 2-25 cm).

Results: Median residual tumor following radiation was 80% (range 27%-278%), with a median residual α-fetoprotein of 47% (range 0.8%-8240%). Estimated one-year overall survival (OS) and in-field progression-free survival (PFS) rates for the study population were 56% and 79%, respectively. One year OS in patients treated to a BED <75 was 18% vs. 69% in patients treated to a BED ≥75 (p=0.002). One year in-field PFS rate (60% vs. 88%, p=0.023) and biochemical PFS duration (median 6.5 vs. 1.6 mos., p=0.001) were also significantly improved in patients treated to a BED ≥75. Grade 3 toxicity was seen in only 13.8% of patients.

Conclusions: In a population without endemic viral hepatitis, unresectable HCC demonstrates significant response toexternal beam radiotherapy with minimal toxicity. Furthermore, our findings suggest that increased BED is associated with improved survival and local tumor control.

No significant financial relationships to disclose.

Electrochemical oxidation and reuse of tannery saline wastewater

In this present work, electrochemical treatment of saline wastewater with organic (protein) load was studied. The influence of the critical parameters of electro-oxidation such as pH, period, salt concentration and current density on the reduction of organic load was studied using graphite electrodes. It was found that current density of 0.024 A/cm(2) for a period of 2 h at pH 9.0 rendered best results in terms of reduction in COD and TKN. The energy requirement for the reduction of 1 kg of TKN and 1 kg of COD are 22.45 kWh and 0.80 kWh respectively at pH 9 and 0.024 A/cm(2). Reuse experiments were conducted at commercial scale. One of the saline waste streams in leather manufacturing process, pickling was treated and reused continuously thrice. The characteristics of the waste stream and the quality of the leathers indicate that the reuse of saline streams with intermittent electrochemical treatment is feasible.

Automated detection of tuberculosis in Ziehl-Neelsen-stained sputum smears using two one-class classifiers

Screening for tuberculosis in high-prevalence countries relies on sputum smear microscopy. We present a method for the automated identification of Mycobacterium tuberculosis in images of Ziehl-Neelsen-stained sputum smears obtained using a bright-field microscope. We use two stages of classification. The first comprises a one-class pixel classifier for object segmentation. Geometric transformation invariant features are extracted for implementation of the second stage, namely one-class object classification. Different classifiers are compared; the sensitivity of all tested classifiers is above 90% for the identification of a single bacillus object using all extracted features. The mixture of Gaussians classifier performed well in both stages of classification. This method may be used as a step in the automation of tuberculosis screening, in order to reduce technician involvement in the process.

Spectroscopic investigations and structural confirmation studies on thiourea

The Fourier transform infrared and Raman spectra of thiourea have been studied in the region 4000-400 and 4000-10 cm(-1), respectively. A complete vibrational analysis on the molecular structure of thiourea has been made on the basis of C(2upsilon) point group symmetry. The validity of the vibrational assignments on the structure of thiourea is supported by evaluating the molecular constants and the potential energy distribution.

Application of empirical mode decomposition and Teager energy operator to EEG signals for mental task classification

This paper presents a novel method for mental task classification from EEG signals using Empirical Mode Decomposition and Teager energy operator techniques on EEG data. The efficacy of these techniques for non-stationary and non-linear data has already been demonstrated, which therefore lend themselves well to EEG signals, which are also non-stationary and non-linear in nature. The method described in this paper decomposed the EEG signals (6 EEG signals per task per subject, for a total of 5 tasks over multiple trials) into their constituent oscillatory modes, called intrinsic mode functions, and separated out the trend from the signal. Teager energy operator was used to calculate the average energy of both the detrended signal and the trend. The average energy was used to construct separate feature vectors with a small number of parameters for the detrended signal and the trend. Based on these parameters, one-versus-one classification of mental tasks was performed using Linear Discriminant Analysis. Using both feature vectors, an average correct classification rate of more than 85% was achieved, demonstrating the effectiveness of the method used. Furthermore, this method used all the intrinsic mode functions, as opposed to similar studies, demonstrating that the trend of the EEG signal also contains important discriminatory information.

Hyperthermia Sensitizes Breast Cancer Stem Cells to Radiation Therapy

Background In cancer, metastatic disease and recurrence are hypothesized to result, at least in part, from the residual cancer stem cells (CSCs), also referred to as tumor-initiating cells(TICs), which evade initial treatment. In several genetically engineered mouse models that resemble human breast cancer, the tumor subpopulation CD29+/CD24+/lin- has been shown to be more tumorigenic as compared to other subpopulations by in vitro and in vivo assays. We and others have demonstrated that the tumorigenic CD29+/CD24+/lin- subpopulation repairs radiation-induced DNA strand breaks more efficiently than the other subpopulations. Therefore, we hypothesized that hyperthermia, a documented means of inhibiting DNA repair, may radiosensitize CSCs to radiation therapy(RT) by delaying and inhibiting the repair of DNA strand breaks. Methods To test this hypothesis, we assayed for tumorigenic CD29+/CD24+/lin- cells in p53null mouse mammary tumor model with and without radiation, and in combination with hyperthermia (42°C) administered as optically-activated gold nanoparticles. We then determined if there was a decrease in functional CSCs by FACS analysis and limiting dilution transplantation assays. Results These studies confirmed that CD29+/CD24+/lin- cells were more radiation resistant and that their relative proportion was increased after RT, as compared to the other cell populations. However, the addition of hyperthermia increased the sensitivity of the CD29+/CD24+/lin- subpopulation to radiation. Radiation treatment alone in vivo resulted in a decrease in tumor size, but the percentage of tumorigenic cells increased as compared to untreated controls. In contrast, following post-treatment with 20 minutes of local hyperthermia, using intravenously administered optically activated gold nanoparticles, a larger regression in tumor size was observed, without a concomitant increase in the percentage of CD29+/CD24+/lin- tumorigenic cells. Using the functional limiting dilution transplantation assay to assay for CSCs, we showed that 48 hours after treatment cells derived from tumors treated with RT exhibited an increased frequency of TICs as compared to untreated controls, and tumors treated with radiation and hyperthermia. In addition, clonogenic survival assays of this tumorigenic subpopulation had consistent results with the in vivo data. Conclusion These results suggest that localized hyperthermia serves as a simple strategy to selectively sensitize the radioresistant subpopulation of CSCs to enhance their response to radiation therapy. The mechanisms responsible for these effects of hyperthermia are currently under investigation. Supported by grant NCI R01 CA112305 and CA16303.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 506.