Arabidopsis ecotype Ct-1, with its altered nitrate sensing ability, exhibits enhanced growth under low nitrate conditions in comparison to Col-0

To address the urgent need for sustainable solutions to the increased use of nitrogen fertilizers in agriculture, it is imperative to acquire an in-depth comprehension of the intricate interplay between plants and nitrogen. In this context, our research aimed to elucidate the molecular mechanism behind NO3- sensing/signaling in plants, which can enhance nitrogen utilization efficiency. Previous reports have revealed that the density and quantity of root hairs exhibit responsive behavior to varying levels of NO3-, while the precise molecular mechanisms governing these changes remain elusive. To further investigate this phenomenon, we specifically selected the Ct-1 ecotype, which manifested a greater abundance of root hairs compared to the Col-0 ecotype under conditions of low NO3-. Our investigations unveiled that the dissimilarities in the amino acid sequence of NRT1.1, a transceptor responsible for regulating nitrate signaling and transport, accounted for the observed variation in root hair numbers. These results suggest that NRT1.1 represents a promising target for gene editing technology, offering potential applications in enhancing the efficiency of nitrogen utilization in agricultural crops.

Hearing Outcomes in Cisplatin or Cetuximab Combined with Radiation for Patients with HPV-Associated Oropharyngeal Cancer in NRG/RTOG 1016

PURPOSE/OBJECTIVE(S)

NRG/RTOG 1016 was a noninferiority phase 3 trial comparing the efficacy of radiation with either cisplatin (RT+Cisp) or cetuximab (RT+Cetux) for patients with HPV+ oropharyngeal cancer (OPC). Perceived hearing handicap was included as a patient-reported outcome (PRO) secondary endpoint. The primary hypothesis was that perceived hearing handicap would be greater for patients receiving RT+Cisp compared to RT+Cetux.

MATERIALS/METHODS

Perceived hearing handicap was measured at baseline, end of treatment, 3, 6, and 12-months post-treatment using the Hearing Handicap Inventory for Adults Screening Version (HHIA-S), a 10-item self-assessment questionnaire designed to measure patients' reactions to their hearing loss. Total HHIA-S scores range from 0 to 40; higher total score indicates more severe perceived hearing handicap. Hearing handicap categories (none, mild/moderate, and severe) were also analyzed. Mixed ordinal logistic models were used to analyze the raw HHIA-S scores and handicap categories (2-sided alpha 0.05).

RESULTS

Participation in the PRO assessments was optional, with 368 patients participating in the hearing PRO. No significant differences in patient/tumor characteristics were found between PRO participants/non-participants. Pre-treatment (mean [SD]) HHIA-S scores were not different for RT+Cisp (3.23 [6.28]) and RT+Cetux (4.77 [8.14]) groups. Post-treatment HHIA-S scores increased for RT+Cisp, and remained stable at the later follow-up time points. RT+Cetux scores remained stable from baseline. Change score from pre- to post-treatment was higher for RT+Cisp (4.32, 95% CI = [2.57, 6.07]) than RT+Cetux (0.08, 95% CI = [-1.15, 1.31]; p < 0.001). For hearing handicap category, post-treatment RT+Cisp had a significantly higher percentage of mild/moderate and severe cases (32%) compared to RT+Cetux (20%). From pre- to post-treatment, worsening of hearing handicap category from normal to mild/moderate or severe was greater for RT+Cisp (24%) than for RT+Cetux (9%). The conditional odds of being in a higher self-perceived hearing handicap category in the RT+Cisp arm were 3.57 (95% CI [2.04, 6.25]) times that in the RT+Cetux arm. Averaging over patients, the marginal odds ratio was 2.46 (95% CI [1.65, 3.66]).

CONCLUSION

Patients receiving concurrent RT+Cisp for HPV-associated OPC have significantly higher odds of worsening self-perceived hearing handicap after treatment than with RT+Cetux. This was consistent across time through one-year post-treatment. These findings inform hearing-related outcomes for patients with HPV-associated OPC.

Reinforcement Learning Powered Station Parameter Optimized Radiation Therapy (SPORT): A Novel Treatment Planning and Beam Delivery Technique

PURPOSE/OBJECTIVE(S)

Conventional intensity modulated radiation therapy (IMRT) with a typical 5-20 fixed beams often does not provide sufficient angular sampling required for conformal dose shaping, whereas current volumetric modulated arc therapy (VMAT) discretizes the angular space into equally spaced control points without considering the differential need for intensity modulation of different angles, leading to undersampling at some angles while oversampling at some other angles. Our goal is to develop a node or station parameter optimized radiation therapy (SPORT) strategy with simultaneously optimized angular sampling and beam modulation by leveraging state-of-the-art reinforcement learning and the unique capability of modern digital LINACs in dose delivery through programmable nodal points.

MATERIALS/METHODS

We developed a SPORT optimization framework, in which, the process of programming control points (or station parameters) was formulated as a stochastic dynamic programming problem, which was solved by a reinforcement learning-based algorithm. On-policy reinforcement learning method, namely, state-action-reward-state-action (SARSA) was integrated with deep convolutional neural network to predict station parameters by utilizing the patient's anatomical structures meanwhile considering the delivery capability of a typical digital LINAC machine. Here, the deep convolutional neural network estimated the state-action value by using the quality of the plan with current station parameters when a next potential station parameter was selected. The state-action value was then updated by SARSA learning. The quality of the plan was quantified by dosimetry constraints. The model was assessed by a retrospective study on a cohort of patients underwent head-and-neck radiation therapy. Dosimetric analysis and delivery efficiency comparisons were used to evaluate the performance of the proposed framework.

RESULTS

Our model was used to generate 16 plans unseen in the original training set. All the plans predicted by our model achieved better dose distributions without violating clinical planning constraints. Moreover, instead of using 4 full standard arcs in the original clinically used plans obtained via manual optimization, the predicted plans only used one full standard arc (about 178 control points) plus boost from a few sub-arcs (less than 30 degrees of gantry angles), which significantly improved the efficiency of the beam delivery. We are in the process of integrating the sub-arcs into the full arc by considering the programmable capability of modern LINACs.

CONCLUSION

We demonstrated that a machine learning-based SPORT framework capable of optimizing the spatial sampling and beam modulation simultaneously for modern radiation therapy. The framework not only significantly improves the quality and efficiency of beam delivery, but also has the potential to be incorporated into current clinical workflow to improve the efficiency of dose planning and delivery.

Local Cost-Effectiveness of Nasopharyngeal Carcinoma Screening Strategies in Southern China: Secondary Analysis of the PRO-NPC-001 Cluster-Randomized Trial

PURPOSE/OBJECTIVE(S)

Population-based screening for endemic nasopharyngeal carcinoma (NPC) detects most cases at an early stage. In a cluster-randomized trial conducted in Guangdong, a combination of Epstein-Barr Virus (EBV) anti-VCA/EBNA1 IgA serology and endoscopy reduced NPC mortality. We conducted a secondary analysis of this trial in conjunction with local incidence and cost data, hypothesizing that screening would be cost-effective in this region.

MATERIALS/METHODS

We estimated population-level NPC mortality reduction, resource utilization, and cost-effectiveness of 12 unique screening strategies in six populations in Guangdong/Guangxi using a previously-validated time-inhomogeneous decision-analytic cohort model. These 12 strategies evaluated combinations of serology, nasopharyngeal swab PCR (NP PCR), endoscopy, and head/neck MRI. Incidence data, screening costs, and healthcare costs were obtained from local cancer registries, laboratories conducting ELISA/PCR, and the Guangdong provincial healthcare system. We evaluated variable screening ages, sexes, intervals, and durations to identify optimal screening approaches from the perspective of the healthcare system in southern China. An incremental cost-effectiveness ratio (ICER) willingness-to-pay threshold of 1.50 times the per-capita GDP was considered cost-effective in southern China.

RESULTS

For the base strategy screening 50-year-old men and women using only serology and endoscopy, the average cost per screened subject for a single round of screening over a five-year cycle was ¥175.69. The addition of MRI improved sensitivity (76% vs. 62%) and approximately doubled screening costs. Triage with NP PCR was cost-neutral when used in conjunction with MRI and reduced endoscopy/MRI utilization by 37% with a 3-4% reduction in screening sensitivity. Among 50-year-old men and women, screening was cost-effective in all populations provided that medium-risk subjects were not referred for endoscopy/MRI (ICER/GDP 0.62-0.83). The use of NP PCR without MRI (ICER/GDP 0.83) was dominated by the base strategy (ICER/GDP 0.62) due to higher costs and NPC mortality. After a single five-year screening cycle, screening reduced population NPC mortality by 14% with serology + endoscopy and 21% with serology + endoscopy + MRI. Introduction of MRI with or without NP PCR could be cost-effective in all populations. For MRI-based strategies, the most efficient use of resources was deferral of endoscopy unless MRI was abnormal (ICER/GDP 0.67). Overall, the best-performing strategies balanced NPC mortality, screening costs, and MRI utilization.

CONCLUSION

EBV serology-based screening for endemic NPC is likely to be cost-effective among adult men and women in Guangdong and Guangxi. Referring medium-risk subjects for endoscopy/MRI should be avoided, and NP PCR should be used to triage individuals for MRI rather than endoscopy. These data may aid the design of population-based screening programs in this region.

Clinical Implementation of an Automated IMRT/VMAT Treatment Planning Tool

PURPOSE/OBJECTIVE(S)

To create an in-house automated treatment planning tool for IMRT/VMAT treatments and evaluate the dosimetric plan quality against manually generated plans.

MATERIALS/METHODS

A scripting application programming interface is employed to interact with a commercial treatment planning system (TPS) to implement automatic plan evaluation and update optimization parameters by mimicking the human planning process. The automated planning performs in an iterative fashion until reaching an acceptable tradeoff among target coverage/dose homogeneity and sparing of critical organs at risk. In each iteration, the dose constraints, priorities, and optimization structures for are automatically updated based on the results of the current iteration. Twenty previously treated plans (10 prostate and 10 head and neck), were preliminarily used to evaluate the performance of the automated planning tool. The differences in target and organ-at-risk metrics from the manually generated clinical plans were analyzed using paired t-test to evaluate clinical acceptability of tour automated planning tool. The current in-house-developed automated planning solution is able to create plans for different disease sites, including head & neck, prostate, pelvis, and lung. So far, the VMAT plans for more than 150 different cases have been generated with the tool. The results for these were also evaluated.

RESULTS

Compared to the manually generated clinical head and neck plans, all auto plans achieved PTV D95% coverage and critical organs at risk sparing without statistically significant change in average global Dmax (107.4% for manual vs 107.3% for automated plans). The auto-planning solution provided reduced maximum doses to brainstem and spinal cord (average reductions with standard deviations of 5.1 ± 2.6 Gy and 2.9 ± 1.4 Gy, respectively, all p <0.03), reduced average mean doses to contralateral parotid, ipsilateral parotid, contralateral submandibular gland, pharynx, esophagus, cochleae (reductions of 2.2 ± 2.9 Gy, 4.8 ± 4.7 Gy, 3.6 ± 5.2 Gy, 2.0 ± 7.1 Gy, 3.9 ± 2.6 Gy, 3.8 ± 5.0 Gy, respectively, all p < 0.045). Similar results were observed for the prostate plans. With the same PTV coverage and without statistically significant change in average global Dmax (106.5% for manual vs 106.8% for automated plans), the automated solution provided superior sparing for both bladder and rectum. Bladder V75, V70, V65 were reduced by 0.6% ± 2.1%, 0.8% ± 2.5%, and 0.9% ± 2.9% (all p <0.04), respectively. Rectum V75, V70, V65, V60 were reduced by 1.0% ± 2.3%, 1.2% ± 2.8%, 1.3% ± 3.2%, 1.6% ± 3.6% (all p < 0.01), respectively.

CONCLUSION

Our automated treatment planning solution is capable of efficiently generating VMAT plans for different disease sites with superior dosimetric indices compared to manually generated plans. Our tool is integrated within a commercial TPS platform, so it has the advantage of seamless adoption into the standard workflow to improve plan quality and treatment planning efficiency in our clinic.

The KRAS-Variant and Cetuximab in HPV-Positive Oropharyngeal Cancer in NRG/RTOG 1016

PURPOSE/OBJECTIVE(S)

NRG/RTOG 1016 was a non-inferiority phase III trial comparing radiation with cisplatin versus cetuximab monotherapy for patients with HPV-positive oropharyngeal squamous cell carcinoma (SCC). The trial did not meet the non-inferiority criteria for overall survival (OS) and had significantly worse progression-free survival (PFS) and locoregional failure (LRF) in patients treated with cetuximab. Based on prior evidence that HNSCC patients with a germ-line mutation in KRAS (the KRAS-variant) had a positive response to radiation with cisplatin plus cetuximab without increased toxicity, samples from RTOG 1016 were used to test the protocol-specified hypothesis that KRAS-variant patients will have better outcomes when receiving IMRT + cetuximab monotherapy compared to IMRT + cisplatin.

MATERIALS/METHODS

The KRAS-variant was tested in 562 samples at MiraDx, a CLIA-certified laboratory. OS, PFS, LRF, and distant metastases (DM) were as defined per the RTOG 1016 protocol, and hazard ratios (HRs) were estimated by (cause-specific) Cox models. Negative binomial regression was used to model the number of treatment-related acute and late (≤ and > 180 days from end of treatment, respectively) grade 3-5 adverse events. To assess the predictive role of the KRAS-variant, all models included KRAS, assigned treatment, and their interaction, with the interaction tested at two-sided 0.05. HRs and toxicity ratios are expressed as IMRT + cetuximab / IMRT + cisplatin.

RESULTS

The prevalence of the KRAS-variant was 16% with similar patient and tumor characteristics and well-balanced treatment arms for variant and non-variant patients. Median follow-up was 8.6 years. There was no significant interaction between KRAS and treatment for OS (p = 0.99), PFS (p = 0.56), LRF (p = 0.09), or DM (p = 0.19) (Table 1). In KRAS-variant patients the mean acute and late toxicity ratios were 0.53 (95% CI 0.36, 0.80) and 1.62 (95% CI 0.57, 4.62). In non-variant patients, the mean acute and late toxicity ratios were 0.80 (95% CI 0.67, 0.95) and 0.55 (95% CI 0.35, 0.87), respectively. The interaction of KRAS and treatment was not significant for acute (p = 0.07) or late toxicity (p = 0.07).

CONCLUSION

While this study does not directly refute prior evidence that KRAS-variant patients benefit from radiation + cisplatin and cetuximab, this study does not support the hypothesis that the KRAS-variant is a predictive biomarker of improved outcome in HPV+ oropharyngeal SCC patients treated with IMRT + cetuximab alone, and suggests that for KRAS-variant patients, potential benefits in LRF and acute toxicity with cetuximab may be offset by worse DM and worse late toxicity.

Prospective Clinical Adoption of Artificial Intelligence for Organ Contouring in Head and Neck Radiation Treatment Planning

PURPOSE/OBJECTIVE(S)

Patients that undergo head and neck (H&N) radiation therapy (RT) require laborious delineation of organs-at-risk (OARs) on computed tomography (CT) scans in a treatment planning system (TPS) to minimize radiation to normal tissue. This task can be completed rapidly and accurately with recently developed artificial intelligence-based semantic segmentation models. The current study aims to deploy and evaluate a strategy for improving clinical practice with this technology.

MATERIALS/METHODS

Deep learning models were trained and tested with CT scans and OAR contours from previous H&N RT cases at our clinic. Two medical physicists vetted the models and selected a 2.5D U-Net for further implementation. The model was embedded in a dedicated server at the hospital, programmed to read H&N CT scans staged for import into the TPS, generate auto-contours, and write them into a TPS-compatible format made available alongside the scan. In the pilot implementation, the auto-contouring service was utilized for more than 60 cases, prospectively. The auto-contours were quantitatively evaluated against the treatment-approved contours to determine how much modification was performed by the clinical team.

RESULTS

The 2.5D U-Net selected for clinical integration segments 21 OARs in less than 3 minutes per scan. Across all the prospective cases, the mean Dice score and mean 95th percentile Hausdorff distance (mm) between the auto-contour and treatment-approved contour for each of the 21 OARs were as follows, respectively: brainstem (0.93, 1.94), optic chiasm (0.70, 2.96), left cochlea (0.69, 2.37), right cochlea (0.68, 2.44), esophagus (0.88, 2.46), left globe (0.93, 1.50), right globe (0.93, 1.63), glottis (0.91, 2.13), larynx (0.93, 2.76), mandible (0.90, 4.86), left optic nerve (0.78, 1.64), right optic nerve (0.82, 1.65), oral cavity (0.86, 8.46), left parotid gland (0.91, 2.78), right parotid gland (0.91, 2.39), pharynx (0.85, 2.39), spinal cord (0.87, 2.27), left submandibular gland (0.85, 3.46), right submandibular gland (0.83, 3.69), left temporal lobe (0.94, 2.20), and right temporal lobe (0.95, 2.09). The auto-contours for the optic chiasm, optic nerves, cochleas, and submandibular glands differed substantially from the final contours, a finding corroborated by the clinical team; the rest were clinically acceptable with minor or no edits necessary.

CONCLUSION

The proposed strategy provides a sophisticated starting point for treatment planning that has garnered overall favorable feedback from the participating radiation oncologists and dosimetrists. Consequently, the technique is being extended to other treatment sites.

Enhanced growth performance of abi5 plants under high salt and nitrate is associated with reduced nitric oxide levels

Numerous environmental stresses have a significant impact on plant growth and development. By 2050, it is anticipated that high salinity will destroy more than fifty percent of the world's agricultural land. Understanding how plants react to the excessive use of nitrogen fertilizers and salt stress is crucial for enhancing crop yield. However, the effect of excessive nitrate treatment on plant development is disputed and poorly understood; so, we evaluated the effect of excessive nitrate supply and high salinity on abi5 plant growth performance. We demonstrated that abi5 plants are tolerant to the harmful environmental conditions of excessive nitrate and salt. abi5 plants have lower amounts of endogenous nitric oxide than Arabidopsis thaliana Columbia-0 plants due to their decreased nitrate reductase activity, caused by a decrease in the transcript level of NIA2, a gene encoding nitrate reductase. Nitric oxide appeared to have a critical role in reducing the salt stress tolerance of plants, which was diminished by an excess of nitrate. Discovering regulators such as ABI5 that can modulate nitrate reductase activity and comprehending the molecular activities of these regulators are crucial for the application of gene-editing techniques. This would result in the appropriate buildup of nitric oxide to increase the production of crops subjected to a variety of environmental stresses.

The Plastidial DIG5 Protein Affects Lateral Root Development by Regulating Flavonoid Biosynthesis and Auxin Transport in Arabidopsis

To reveal the mechanisms underlying root adaptation to drought stress, we isolated and characterized an Arabidopsis mutant, dig5 (drought inhibition of lateral root growth 5), which exhibited increased sensitivity to the phytohormone abscisic acid (ABA) for the inhibition of lateral root growth. The dig5 mutant also had fewer lateral roots under normal conditions and the aerial parts were yellowish with a lower level of chlorophylls. The mutant seedlings also displayed phenotypes indicative of impaired auxin transport, such as abnormal root curling, leaf venation defects, absence of apical hook formation, and reduced hypocotyl elongation in darkness. Auxin transport assays with [3H]-labeled indole acetic acid (IAA) confirmed that dig5 roots were impaired in polar auxin transport. Map-based cloning and complementation assays indicated that the DIG5 locus encodes a chloroplast-localized tRNA adenosine deaminase arginine (TADA) that is involved in chloroplast protein translation. The levels of flavonoids, which are naturally occurring auxin transport inhibitors in plants, were significantly higher in dig5 roots than in the wild type roots. Further investigation showed that flavonoid biosynthetic genes were upregulated in dig5. Introduction of the flavonoid biosynthetic mutation transparent testa 4 (tt4) into dig5 restored the lateral root growth of dig5. Our study uncovers an important role of DIG5/TADA in retrogradely controlling flavonoid biosynthesis and lateral root development. We suggest that the DIG5-related signaling pathways, triggered likely by drought-induced chlorophyll breakdown and leaf senescence, may potentially help the plants to adapt to drought stress through optimizing the root system architecture.

The Loss of Function of the NODULE INCEPTION-Like PROTEIN 7 Enhances Salt Stress Tolerance in Arabidopsis Seedlings

Plants acquire nitrogen, an essential macronutrient, from the soil as nitrate. Since nitrogen availability is a major determinant of crop productivity, the soil is amended with nitrogenous fertilizers. Extensive use of irrigation can lead to the accumulation of salt in the soil, which compromises crop productivity. Our characterization of NODULE INCEPTION (NIN)-like PROTEIN 7 (NLP7), a transcription factor regulating the primary response to nitrate, revealed an intersection of salt stress and nitrate metabolism. The growth of loss-of-function mutant nlp7 was tolerant to high salinity that normally reduces the fresh weight and chlorophyll and protein content of wild type (Col-0). On a medium with high salinity, the nlp7 experienced less stress, accumulating less proline, producing less nitric oxide (NO) and reactive oxygen species (ROS), and expressing lower transcript levels of marker genes, such as RD29A and COR47, than Col-0. Nevertheless, more sodium ions were translocated to and accumulated in the shoots of nlp7 than that of Col-0. Since nlp7 also expressed less nitrate reductase (NR) activity, nitrate accumulated to abnormally high levels with or without salinity. We attributed the enhanced salt tolerance of nlp7 to the balanced accumulation of nitrate anions and sodium cations. Our results suggest that nitrate metabolism and signaling might be targeted to improve salt tolerance.

Growth Performance Can Be Increased Under High Nitrate and High Salt Stress Through Enhanced Nitrate Reductase Activity in Arabidopsis Anthocyanin Over-Producing Mutant Plants

Nitrogen is one of the most important macro-nutrients for plant growth and crop productivity. The amount of synthetic nitrogen fertilizers supplied to crops has dramatically increased, leading to a notable rise in crop yields. However, excessive nitrogen use has an enormous negative impact on ecosystems and human health through the emission of intense greenhouse gases, such as nitric oxide derived from the nitrate (NO₃ ^-) assimilation cascade. Additionally, owing to the development of extensive irrigation in agriculture, crops are known to suffer from high salt stress. The effect of excessive nitrogen fertilizer application has been studied in some crops, but the effect of high nitrate level and salt stress on plant stress tolerance has not been studied in detail. Therefore, in this study we aimed to study the effects of high concentrations of NO₃ ^- on salt stress tolerance in Arabidopsis. In addition, since anthocyanin functions as a reactive oxygen species (ROS) scavenger under abiotic stress conditions, we investigated whether enhanced anthocyanin content helps Arabidopsis to withstand higher salt stress levels under high NO₃ ^- concentrations by using pap1-D/fls1ko double mutant plants, which accumulate excessive amount of anthocyanin. We found that Col-0 plants are more sensitive to salt stress under high NO₃ ^- concentrations. Although both the pap1-D/fls1ko and fls1ko plants accumulated higher anthocyanin levels and radical scavenging activities than Col-0 plants under both normal and salt stress conditions, the fls1ko plants exhibited much better growth than the pap1-D/fls1ko plants. It appears that the enhanced NR activities and transcript levels of NIA1 and NIA2 in pap1-D/fls1ko and fls1ko plants led to an increase in the synthesis of proteins and proline, which increases osmolytes against salt stress. Our results demonstrate that optimal levels of anthocyanin accumulation can enhance growth performance of plants under high NO₃ ^- and salt stress conditions.

Characterization of the Transglycosylation Reaction of 4-α-Glucanotransferase (MalQ) and Its Role in Glycogen Breakdown in Escherichia coli

We first confirmed the involvement of MalQ (4-α-glucanotransferase) in Escherichia coli glycogen breakdown by both in vitro and in vivo assays. In vivo tests of the knock-out mutant, ΔmalQ, showed that glycogen slowly decreased after the stationary phase compared to the wild-type strain, indicating the involvement of MalQ in glycogen degradation. In vitro assays incubated glycogen-mimic substrate, branched cyclodextrin (maltotetraosyl-β-CD: G4- β-CD) and glycogen phosphorylase (GlgP)-limit dextrin with a set of variable combinations of E. coli enzymes, including GlgX (debranching enzyme), MalP (maltodextrin phosphorylase), GlgP and MalQ. In the absence of GlgP, the reaction of MalP, GlgX and MalQ on substrates produced glucose-1-P (glc-1-P) 3-fold faster than without MalQ. The results revealed that MalQ led to disproportionate G4 released from GlgP-limit dextrin to another acceptor, G4, which is phosphorylated by MalP. In contrast, in the absence of MalP, the reaction of GlgX, GlgP and MalQ resulted in a 1.6-fold increased production of glc-1-P than without MalQ. The result indicated that the G4-branch chains of GlgP-limit dextrin are released by GlgX hydrolysis, and then MalQ transfers the resultant G4 either to another branch chain or another G4 that can immediately be phosphorylated into glc-1-P by GlgP. Thus, we propose a model of two possible MalQ-involved pathways in glycogen degradation. The operon structure of MalP-defecting enterobacteria strongly supports the involvement of MalQ and GlgP as alternative pathways in glycogen degradation.

Influence of external cooling on the femtosecond laser ablation of dentin

In the present work, the influence of external cooling on the temperature rise in the tooth pulpal chamber during femtosecond laser ablation was investigated. The influence of the cooling method on the morphology and constitution of the laser-treated surfaces was studied as well. The ablation experiments were performed on dentin specimens using an Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs, 1030 nm). Cavities were created by scanning the specimens at a velocity of 5 mm/s while pulsing the stationary laser beam at 1 kHz and with fluences in the range of 2-14 J/cm². The experiments were performed in air and with surface cooling by a lateral air jet and by a combination of an air jet and water irrigation. The temperature in the pulpal chamber of the tooth was measured during the laser experiments. The ablation surfaces were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The temperature rise reached 17.5 °C for the treatments performed with 14 J/cm² and without cooling, which was reduced to 10.8 ± 1.0 and 6.6 ± 2.3 °C with forced air cooling and water cooling, respectively, without significant reduction of the ablation rate. The ablation surfaces were covered by ablation debris and resolidified droplets containing mainly amorphous calcium phosphate, but the amount of redeposited debris was much lower for the water-cooled specimens. The redeposited debris could be removed by ultrasonication, revealing that the structure and constitution of the tissue remained essentially unaltered. The present results show that water cooling is mandatory for the femtosecond laser treatment of dentin, in particular, when high fluences and high pulse repetition rates are used to achieve high material removal rates.

Sendai virus infection up-regulates trypsin I and matrix metalloproteinase-9, triggering viral multiplication and matrix degradation in rat lungs and lung L2 cells

To elucidate the virus-host cell interaction, we analyzed quantitatively the expression of various cellular proteases and tumor necrosis factor-alpha (TNF-alpha) after Sendai virus infection in rat lungs and lung L2 cells. After infection, TNF-alpha mRNA levels increased rapidly to a peak on day one, and then trypsin I and matrix metalloproteinase (MMP)-9, but not MMP-2, were significantly up-regulated with a peak on day 2 in vivo. These up-regulations were confirmed in L2 cells. Up-regulation of proMMP-9 and its active convertase trypsin I seems to synergistically enhance virus multiplication and the destruction of lung matrix, resulting in the progression of pneumonia.

Double-layer fluorescent zymography for processing protease detection

We have developed a novel double-layer zymographic method for the detection of specific processing proteases of a target proprotease using a specific fluorescent substrate. The target processing proteases were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the gel was subsequently incubated with the target proenzyme used as the substrate. A cellulose acetate membrane was immersed in 10% glycerol and then soaked in the fluorescent substrate solution. The slab gel of the processing protease was covered with the fluorescent substrate membrane, making a double layer. The double layer was incubated at 37 degrees C, and the released fluorescent band, in which the processing protease was located, was detected using UV light. The advantages of the double-layer fluorescent zymographic method are as follows: (i) the specific detection of target proprotease using a specific substrate, (ii) a relatively rapid and sensitive method, (iii) effective detection using small amounts of crude material, and (iv) wide applications that include the detection of processing proteases and activators for target proteases. Typical examples used for the detection of the processing proteases, such as plasminogen activator, chymotrypsinogen activator, procaspase-3 processing protease and caspase-3 activators, using this new method are described in this article.

Detection of protease inhibitors by a reverse zymography method, performed in a tris(hydroxymethyl)aminomethane–Tricine buffer system

A new detecting method for protease inhibitors, especially for low-molecular-weight inhibitors, is reported. Inhibitor samples were separated on a protein substrate-SDS-polyacrylamide gel in a Tris-Tricine buffer system that improves the separation and identification of peptides and low-molecular-weight proteins. After electrophoresis, the gel was incubated with the target proteases to hydrolyze the background protein substrate. The inhibitor bands, which were protected from proteolysis by the target proteases, were stained. Standard low-molecular-weight inhibitors, such as pepstatin A for pepsin or matrix metalloproteases inhibitor I for collagenase, as well as larger inhibitors, such as soybean trypsin inhibitor or aprotinin for tryspin and cystatin C for papain, were demonstrated by this method and showed clear blue inhibitor bands in the white background when the gels were treated with the target proteases. Some significant applications of this method are introduced. This method is an ideal system for discovering new protease inhibitors in small natural samples.

New functions of lactoferrin and beta-casein in mammalian milk as cysteine protease inhibitors

We found new inhibitory function of lactoferrin and beta-casein in milk against cysteine proteases using reverse zymography. The inhibition of cathepsin L by lactoferrin was strongest and the inhibition kinetics were of a non-competitive type. Heat denatured lactoferrin lost the inhibitory activity completely, therefore the tertiary structure is essential to show the inhibition. Native lactoferrin was not degraded by papain during the assay condition. The intramolecular peptide, Y(679)-K(695), of lactoferrin is an active domain and the synthesized peptide inhibited cysteine proteases. The Y(679)-K(695) peptide showed 90% homology with the sequences of a common active site of cystatin family. beta-Casein and the active domain, synthesized L(133)-Q(151), peptide inhibited cysteine proteases. Lactoferrin and beta-casein in milk might play a role in antiseptic and antiinfectious functions due to cysteine protease inhibition of bacteria and viruses.

Image-guided radiosurgery in the treatment of spinal metastases

Object

The authors describe a new method for treating metastatic spinal tumors in which noninvasive, image-guided, frameless stereotactic radiosurgery is performed. Stereotactic radiosurgery delivers a high dose of radiation in a single or limited number of fractions to a lesion while maintaining delivery of a low dose to adjacent normal structures.

Methods

Image-guided radiosurgery was developed by coupling an orthogonal pair of real-time x-ray cameras to a dynamically manipulated robot-mounted linear accelerator that guides the radiation beam to treatment sites associated with radiographic landmarks. This procedure can be conducted in an outpatient setting without the use of frame-based skeletal fixation. The system relies on skeletal landmarks or implanted fiducial markers to locate treatment targets. Four patients with spinal metastases underwent radiosurgery with total prescription doses of 1000 to 1600 cGy in one or two fractions. Alignment of the treatment dose with the target volume was accurate to within 1.5 mm. During the course of each treatment fraction, patient movement was less than 0.5 mm on average. Dosimetry was highly conformal, with a demonstrated ability to deliver 1600 cGy to the perimeter of an irregular target volume while keeping exposure to the cord itself below 800 cGy.

Conclusions

These experiences indicate that frameless radiosurgery is a viable therapeutic option for metastatic spine disease.

Image-guided hypo-fractionated stereotactic radiosurgery to spinal lesions

OBJECTIVE

This article demonstrates the technical feasibility of noninvasive treatment of unresectable spinal vascular malformations and primary and metastatic spinal tumors by use of image-guided frameless stereotactic radiosurgery.

METHODS

Stereotactic radiosurgery delivers a high dose of radiation to a tumor volume or vascular malformation in a limited number of fractions and minimizes the dose to adjacent normal structures. Frameless image-guided radiosurgery was developed by coupling an orthogonal pair of x-ray cameras to a dynamically manipulated robot-mounted linear accelerator that guides the therapy beam to treatment sites within the spine or spinal cord, in an outpatient setting, and without the use of frame-based fixation. The system relies on skeletal landmarks or implanted fiducial markers to locate treatment targets. Sixteen patients with spinal lesions (hemangioblastomas, vascular malformations, metastatic carcinomas, schwannomas, a meningioma, and a chordoma) were treated with total treatment doses of 1100 to 2500 cGy in one to five fractions by use of image-guided frameless radiosurgery with the CyberKnife system (Accuray, Inc., Sunnyvale, CA). Thirteen radiosurgery plans were analyzed for compliance with conventional radiation therapy.

RESULTS

Tests demonstrated alignment of the treatment dose with the target volume within +/-1 mm by use of spine fiducials and the CyberKnife treatment planning system. Tumor patients with at least 6 months of follow-up have demonstrated no progression of disease. Radiographic follow-up is pending for the remaining patients. To date, no patients have experienced complications as a result of the procedure.

CONCLUSION

This experience demonstrates the feasibility of image-guided robotic radiosurgery for previously untreatable spinal lesions.

Morphology and current-voltage characteristics of nanostructured pentacene thin films probed by atomic force microscopy

Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene.

Treatment results and prognostic factors of advanced T3--4 laryngeal carcinoma: the University of California, San Francisco (UCSF) and Stanford University Hospital (SUH) experience

PURPOSE

To review the UCSF-SUH experience in the treatment of advanced T3--4 laryngeal carcinoma and to evaluate the different factors affecting locoregional control and survival.

METHODS AND MATERIALS

We reviewed the records of 223 patients treated for T3--4 squamous cell carcinoma of the larynx between October 1, 1957, and December 1, 1999. There were 187 men and 36 women, with a median age of 60 years (range, 28--85 years). The primary site was glottic in 122 and supraglottic in 101 patients. We retrospectively staged the patients according to the 1997 AJCC staging system. One hundred and twenty-seven patients had T3 lesions, and 96 had T4 lesions; 132 had N0, 29 had N1, 45 had N2, and 17 had N3 disease. The overall stage was III in 93 and IV in 130 patients. Seventy-nine patients had cartilage involvement, and 144 did not. Surgery was the primary treatment modality in 161 patients, of which 134 had postoperative radiotherapy (RT), 11 had preoperative RT, 7 had surgery followed by RT and chemotherapy (CT), and 9 had surgery alone. Forty-one patients had RT alone, and 21 had CT with RT. Locoregional control (LRC) and overall survival (OS) were estimated using the Kaplan--Meier method. Log-rank statistics were employed to identify significant prognostic factors for OS and LRC.

RESULTS

The median follow-up was 41 months (range, 2--367 months) for all patients and 78 months (range, 6--332 months) for alive patients. The LRC rate was 69% at 5 years and 68% at 10 years. Eighty-four patients relapsed, of which 53 were locoregional failures. Significant prognostic factors for LRC on univariate analysis were primary site, N stage, overall stage, the lowest hemoglobin (Hgb) level during RT, and treatment modality. Favorable prognostic factors for LRC on multivariate analysis were lower N stage and primary surgery. The overall survival rate was 48% at 5 years and 34% at 10 years. Significant prognostic factors for OS on univariate analysis were: primary site, age, overall stage, T stage, N stage, lowest Hgb level during RT, and treatment modality. Favorable prognostic factors for OS on multivariate analysis were lower N stage and higher Hgb level during RT.

CONCLUSION

Lower N-stage was a favorable prognostic factor for LRC and OS. Hgb levels > or = 12.5 g/dL during RT was a favorable prognostic factor for OS. Surgery was a favorable prognostic factor for LRC but did not impact on OS. Correcting the Hbg level before and during treatment should be investigated in future clinical trials as a way of improving therapeutic outcome in patients with advanced laryngeal carcinomas.

Role of beam orientation optimization in intensity-modulated radiation therapy

PURPOSE

To investigate the role of beam orientation optimization in intensity-modulated radiation therapy (IMRT) and to examine the potential benefits of noncoplanar intensity-modulated beams.

METHODS AND MATERIALS

A beam orientation optimization algorithm was implemented. For this purpose, system variables were divided into two groups: beam position (gantry and table angles) and beam profile (beamlet weights). Simulated annealing was used for beam orientation optimization and the simultaneous iterative inverse treatment planning algorithm (SIITP) for beam intensity profile optimization. Three clinical cases were studied: a localized prostate cancer, a nasopharyngeal cancer, and a paraspinal tumor. Nine fields were used for all treatments. For each case, 3 types of treatment plan optimization were performed: (1) beam intensity profiles were optimized for 9 equiangular spaced coplanar beams; (2) orientations and intensity profiles were optimized for 9 coplanar beams; (3) orientations and intensity profiles were optimized for 9 noncoplanar beams.

RESULTS

For the localized prostate case, all 3 types of optimization described above resulted in dose distributions of a similar quality. For the nasopharynx case, optimized noncoplanar beams provided a significant gain in the gross tumor volume coverage. For the paraspinal case, orientation optimization using noncoplanar beams resulted in better kidney sparing and improved gross tumor volume coverage.

CONCLUSION

The sensitivity of an IMRT treatment plan with respect to the selection of beam orientations varies from site to site. For some cases, the choice of beam orientations is important even when the number of beams is as large as 9. Noncoplanar beams provide an additional degree of freedom for IMRT treatment optimization and may allow for notable improvement in the quality of some complicated plans.

Treatment results of carcinoma in situ of the glottis: an analysis of 82 cases

OBJECTIVES

To evaluate the results of different treatment modalities for carcinoma in situ of the glottis, and to identify important prognostic factors for outcome.

DESIGN

Review of 82 cases treated definitively for glottic carcinoma in situ between 1958 and 1998. The median follow-up for all patients was 112 months, and 90% had more than 2 years of follow-up.

SETTING

Academic tertiary care referral centers.

INTERVENTION

Fifteen patients were treated with vocal cord stripping (group 1), 13 with more extensive surgery (group 2) including endoscopic laser resection (11 patients) and hemilaryngectomy (2 patients), and 54 with radiotherapy (group 3). Thirty patients had anterior commissure involvement and 9 had bilateral vocal cord involvement. Radiotherapy was delivered via opposed lateral fields at 1.5 to 2.4 Gy per fraction per day (median fraction size, 2 Gy), 5 days per week. The median total dose was 64 Gy, and the median overall time was 47 days.

MAIN OUTCOME MEASURES

Initial locoregional control (LRC), ultimate LRC, and larynx preservation.

RESULTS

The 10-year initial LRC rates were 56% for group 1, 71% for group 2, and 79% for group 3. Of those who failed, the median time to relapse was 11 months for group 1, 17 months for group 2, and 41 months for group 3. Univariate analysis showed that the difference in initial LRC rates between groups 1 and 3 was statistically significant (P =.02), although it was not statistically significant on multivariate analysis (P =.07). Anterior commissure involvement was an important prognostic factor for LRC on both univariate (P =.03) and multivariate (P =.04; hazard ratio, 1.6) analysis, and its influence appeared to be mainly confined to the surgically treated patients (groups 1 and 2). The 10-year larynx preservation rates were 92% for group 1, 70% for group 2, and 85% for group 3. Anterior commissure involvement was the only important prognostic factor for larynx preservation (P =. 01) on univariate analysis. All but 2 patients in whom treatment failed underwent successful salvage surgery. Voice quality was deemed good to excellent in 73% of the patients in group 1, 40% in group 2, and 68% in group 3.

CONCLUSIONS

Treatment of carcinoma in situ of the glottis with vocal cord stripping or more extensive surgery or radiotherapy provided excellent ultimate LRC and comparable larynx preservation rates. Anterior commissure involvement was associated with poorer initial LRC and larynx preservation, particularly in the surgically treated patients. The choice of initial treatment should be individualized, depending on patient age, reliability, and tumor extent. Pretreatment and posttreatment objective evaluation of voice quality should be helpful in determining the best therapy for these patients.

Pancreatic tumors show high levels of hypoxia

PURPOSE

Because of the dismal outcomes of conventional therapies for pancreatic carcinomas, we postulated that hypoxia may exist within these tumors.

METHODS AND MATERIALS

Seven sequential patients with adenocarcinomas of the pancreas consented to intraoperative measurements of tumor oxygenation using the Eppendorf (Hamburg, Germany) polargraphic electrode.

RESULTS

All 7 tumors demonstrated significant tumor hypoxia. In contrast, adjacent normal pancreas showed normal oxygenation.

CONCLUSION

Tumor hypoxia exists within pancreatic cancers.

Head and neck cancer in cardiothoracic transplant recipients

INTRODUCTION

There is an increased incidence of cancer in patients after organ transplantation. We reviewed a large series of cardiothoracic transplant recipients to determine the incidence and natural history of head and neck malignancy.

METHODS

A total of 1069 heart (n = 855), heart/lung (n = 111), and lung (n = 103) transplants were performed at Stanford University from January 1968 to February 1998. Demographic data, risk factors, and disease course were evaluated in patients who developed cancer. The mean length of follow-up was 8.9+/-5.2 years.

RESULTS

One hundred twenty patients (11.2%) developed 547 non-lymphomatous malignancies. The mean number of malignancies per cancer patient was 4.6. The average time from transplantation to development of cancer was 63.1 months. A total of 50.5% of malignancies presented in the head and neck; 96.4% of these were cutaneous in origin and 3.6% were noncutaneous. Of cutaneous malignancies, 79.3% were squamous cell carcinoma and 15.9% were basal cell carcinoma Cutaneous malignancies most commonly presented on the scalp, cheek, lip, and neck. Noncutaneous malignancies involved the oral cavity (5), thyroid (4), and parotid (1). Thirteen percent of cutaneous head and neck cancers behaved aggressively, requiring extensive management including radical surgery, radiation, and/or chemotherapy. A total of 34.2% of cancer patients developed metastases and 54.9% of cancer patients died as a direct result of cancer. A total of 68% of cancer patients were smokers and 23.8% had significant alcohol use.

CONCLUSION

Transplant recipients have an increased incidence of cancer presenting in the head and neck. Malignancies in transplant patients behave more aggressively than in the general population. Recognition of this aggressive biological behavior and heightened cancer surveillance should result in improved outcomes.

Dosimetric effects of patient displacement and collimator and gantry angle misalignment on intensity modulated radiation therapy

PURPOSE AND OBJECTIVE

The primary goal of this study was to examine systematically the dosimetric effect of small patient movements and linear accelerator angular setting misalignments in the delivery of intensity modulated radiation therapy. We will also provide a method for estimating dosimetric errors for an arbitrary combination of these uncertainties.

MATERIALS AND METHODS

Sites in two patients (lumbar-vertebra and nasopharynx) were studied. Optimized intensity modulated radiation therapy treatment plans were computed for each patient using a commercially available inverse planning system (CORVUS, NOMOS Corporation, Sewickley, PA). The plans used nine coplanar beams. For each patient the dose distributions and relevant dosimetric quantities were calculated, including the maximum, minimum, and average doses in targets and sensitive structures. The corresponding dose volumetric information was recalculated by purposely varying the collimator angle or gantry angle of an incident beam while keeping other beams unchanged. Similar calculations were carried out by varying the couch indices in either horizontal or vertical directions. The intensity maps of all the beams were kept the same as those in the optimized plan. The change of a dosimetric quantity, Q, for a combination of collimator and gantry angle misalignments and patient displacements was estimated using Delta=Sigma(DeltaQ/Deltax(i))Deltax(i). Here DeltaQ is the variation of Q due to Deltax(i), which is the change of the i-th variable (collimator angle, gantry angle, or couch indices), and DeltaQ/Deltax(i) is a quantity equivalent to the partial derivative of the dosimetric quantity Q with respect to x(i).

RESULTS

While the change in dosimetric quantities was case dependent, it was found that the results were much more sensitive to small changes in the couch indices than to changes in the accelerator angular setting. For instance, in the first example in the paper, a 3-mm movement of the couch in the anterior-posterior direction can cause a 38% decrease in the minimum target dose or a 41% increase in the maximum cord dose, whereas a 5 degrees change in the &theta;(1)=20 degrees beam only gave rise to a 1.5% decrease in the target minimum or 5.1% in the cord maximum. The effect of systematic positioning uncertainties of the machine settings was more serious than random uncertainties, which tended to smear out the errors in dose distributions.

CONCLUSIONS

The dose distribution of an intensity modulated radiation therapy (IMRT) plan changes with patient displacement and angular misalignment in a complex way. A method was proposed to estimate dosimetric errors for an arbitrary combination of uncertainties in these quantities. While it is important to eliminate the angular misalignment, it was found that the couch indices (or patient positioning) played a much more important role. Accurate patient set-up and patient immobilization is crucial in order to take advantage fully of the technological advances of IMRT. In practice, a sensitivity check should be useful to foresee potential IMRT treatment complications and a warning should be given if the sensitivity exceeds an empirical value. Quality assurance action levels for a given plan can be established out of the sensitivity calculation.

Analysis of titanium dental implants after failure of osseointegration: combined histological, electron microscopy, and X-ray photoelectron spectroscopy approach

A multitechnique approach has been used to characterize the surface of nonosseointegrated titanium implants and the surrounding biological tissues. Five pure titanium dental implants were used as reference, and 25 removed implants were studied. Surface and in-depth chemical compositions of the implants (from a total of 16 patients) were investigated by X-ray photoelectron spectroscopy (XPS). Histological slides of the surrounding tissues were examined by light microscopy, XPS, and electron microprobe analysis. None of the failed implants presented the regular surface composition and depth profile of the TiO2 overlayer; foreign elements (Ca, Na, P, Si, Cl, Zn, Pb, and Al) were observed on some implants. Fibrosis, lymphocytic and plasmocytic infiltrates, and granulomatous lesions were detected in the surrounding tissues. XPS and electron microprobe analysis indicated the presence of Zn, Fe, Sn, and Ti in the tissues. As a possible scenario for implant failure, we propose and discuss a oxidoreduction mechanism, leading to a partial dissolution or the complete dissociation of the protective titanium dioxide overlayer and to ion diffusion through the surrounding tissues.

Candidate genes for the hypoxic tumor phenotype

In this study, we have analyzed changes induced by hypoxia at the transcriptional level of genes that could be responsible for a more aggressive phenotype. Using a series of DNA array membranes, we identified a group of hypoxia-induced genes that included plasminogen activator inhibitor-1 (PAI-1), insulin-like growth factor-binding protein 3 (IGFBP-3), endothelin-2, low-density lipoprotein receptor-related protein (LRP), BCL2-interacting killer (BIK), migration-inhibitory factor (MIF), matrix metalloproteinase-13 (MMP-13), fibroblast growth factor-3 (FGF-3), GADD45, and vascular endothelial growth factor (VEGF). The induction of each gene was confirmed by Northern blot analysis in two different squamous cell carcinoma-derived cell lines. We also analyzed the kinetics of PAI-1 induction by hypoxia in more detail because it is a secreted protein that may serve as a useful molecular marker of hypoxia. On exposure to hypoxia, there was a gradual increase in PAI-1 mRNA between 2 and 24 h of hypoxia followed by a rapid decay after 2 h of reoxygenation. PAI-1 levels were also measured in the serum of a small group of head and neck cancer patients and were found to correlate with the degree of tumor hypoxia found in these patients.

Lymph node metastasis in maxillary sinus carcinoma

PURPOSE

To evaluate the incidence and prognostic significance of lymph node metastasis in maxillary sinus carcinoma.

METHODS AND MATERIALS

We reviewed the records of 97 patients treated for maxillary sinus carcinoma with radiotherapy at Stanford University and at the University of California, San Francisco between 1959 and 1996. Fifty-eight patients had squamous cell carcinoma (SCC), 4 had adenocarcinoma (ADE), 16 had undifferentiated carcinoma (UC), and 19 had adenoid cystic carcinoma (AC). Eight patients had T2, 36 had T3, and 53 had T4 tumors according to the 1997 AJCC staging system. Eleven patients had nodal involvement at diagnosis: 9 with SCC, 1 with UC, and 1 with AC. The most common sites of nodal involvement were ipsilateral level 1 and 2 lymph nodes. Thirty-six patients were treated with definitive radiotherapy alone, and 61 received a combination of surgical and radiation treatment. Thirty-six patients had neck irradiation, 25 of whom received elective neck irradiation (ENI) for N0 necks. The median follow-up for alive patients was 78 months.

RESULTS

The median survival for all patients was 22 months (range: 2.4-356 months). The 5- and 10-year actuarial survivals were 34% and 31%, respectively. Ten patients relapsed in the neck, with a 5-year actuarial risk of nodal relapse of 12%. The 5-year risk of neck relapse was 14% for SCC, 25% for ADE, and 7% for both UC and ACC. The overall risk of nodal involvement at either diagnosis or on follow-up was 28% for SCC, 25% for ADE, 12% for UC, and 10% for AC. All patients with nodal involvement had T3-4, and none had T2 tumors. ENI effectively prevented nodal relapse in patients with SCC and N0 neck; the 5-year actuarial risk of nodal relapse was 20% for patients without ENI and 0% for those with elective neck therapy. There was no correlation between neck relapse and primary tumor control or tumor extension into areas containing a rich lymphatic network. The most common sites of nodal relapse were in the ipsilateral level 1-2 nodal regions (11/13). Patients with nodal relapse had a significantly higher risk of distant metastasis on both univariate (p = 0.02) and multivariate analysis (hazard ratio = 4.5, p = 0.006). The 5-year actuarial risk of distant relapse was 29% for patients with neck control versus 81% for patients with neck failure. There was also a trend for decreased survival with nodal relapse. The 5-year actuarial survival was 37% for patients with neck control and 0% for patients with neck relapse.

CONCLUSION

The overall incidence of lymph node involvement at diagnosis in patients with maxillary sinus carcinoma was 9%. Following treatment, the 5-year risk of nodal relapse was 12%. SCC histology was associated with a high incidence of initial nodal involvement and nodal relapse. None of the patients presenting with SCC histology and N0 necks had nodal relapse after elective neck irradiation. Patients who had nodal relapse had a higher risk of distant metastasis and poorer survival. Therefore, our present policy is to consider elective neck irradiation in patients with T3-4 SCC of the maxillary sinus.

Estimation theory and model parameter selection for therapeutic treatment plan optimization

Treatment optimization is usually formulated as an inverse problem, which starts with a prescribed dose distribution and obtains an optimized solution under the guidance of an objective function. The solution is a compromise between the conflicting requirements of the target and sensitive structures. In this paper, the treatment plan optimization is formulated as an estimation problem of a discrete and possibly nonconvex system. The concept of preference function is introduced. Instead of prescribing a dose to a structure (or a set of voxels), the approach prioritizes the doses with different preference levels and reduces the problem into selecting a solution with a suitable estimator. The preference function provides a foundation for statistical analysis of the system and allows us to apply various techniques developed in statistical analysis to plan optimization. It is shown that an optimization based on a quadratic objective function is a special case of the formalism. A general two-step method for using a computer to determine the values of the model parameters is proposed. The approach provides an efficient way to include prior knowledge into the optimization process. The method is illustrated using a simplified two-pixel system as well as two clinical cases. The generality of the approach, coupled with promising demonstrations, indicates that the method has broad implications for radiotherapy treatment plan optimization.

Treatment of maxillary sinus carcinoma: a comparison of the 1997 and 1977 American Joint Committee on cancer staging systems

BACKGROUND

This study was conducted to assess the effectiveness of the 1997 American Joint Committee on Cancer (AJCC) staging system to predict survival and local control of patients with maxillary sinus carcinoma and to identify significant factors for overall survival, local control, and distant metastases in patients with these tumors.

METHODS

Ninety-seven patients with maxillary sinus carcinoma were treated with radiotherapy at Stanford University and the University of California, San Francisco between 1959-1996. The histologic type of carcinoma among the 97 patients were: 58 squamous cell carcinomas, 4 adenocarcinomas, 16 undifferentiated carcinomas, and 19 adenoid cystic carcinomas. All patients were restaged clinically according to the 1977 and 1997 AJCC staging systems. The T classification of the tumors of the patients was as follows: 8 with T2, 18 with T3, and 71 with T4 according to the 1977 system and 8 with T2, 36 with T3, and 53 with T4 according to the 1997 system. Eleven patients had lymph node involvement at diagnosis. Thirty-six patients were treated with radiotherapy alone and 61 received a combination of surgical and radiation treatments. The median follow-up for surviving patients was 78 months.

RESULTS

The 5-year and 10-year actuarial survival rates for all patients were 34% and 31%, respectively. The 5-year survival estimate by the 1977 AJCC system (P = 0.06) was 75% for Stage II, 19% for Stage III, and 34% for Stage IV and by the 1997 AJCC system (P = 0.006) was 75% for Stage II, 37% for Stage III, and 28% for Stage IV. Significant prognostic factors for survival by multivariate analysis included age (favoring younger age, P<0.001), 1997 T classification (favoring T2-3, P = 0. 001), lymph node involvement at diagnosis (favoring N0, P = 0.002), treatment modality of the primary tumor site (favoring surgery and radiotherapy, P = 0.009), and gender (favoring female patients, P = 0.04). The overall radiation time was of borderline significance (favoring shorter time, P = 0.06). The actuarial 5-year local control rate was 43%. By the 1977 AJCC system (P = 0.78) it was 62% with T2, 36% with T3, and 45% with T4 and using the 1997 AJCC system (P = 0.29) it was 62% with T2, 53% with T3, and 36% with T4. The only significant prognostic factor for local control for all patients by multivariate analysis was local therapy, favoring surgery and radiotherapy over radiotherapy alone (P< 0.001). For patients treated with surgery, pathologic margin status correlated with local control (P = 0.007) and for patients treated with radiation alone, higher tumor dose (P = 0.007) and shorter overall treatment time (P = 0.04) were associated with fewer local recurrences. The 5-year estimate of freedom from distant metastases was 66%. The 1997 T classification, N classification, and lymph node recurrence were adverse prognostic factors for distant metastases on multivariate analysis. There were 22 complications in 16 patients, representing a 30% actuarial risk of developing late complications at 10 years.

CONCLUSIONS

The 1997 AJCC staging system was found to be superior to the 1977 AJCC staging system in predicting both survival and local control in this patient population. Combined surgical and radiation treatment to the primary tumor yielded higher survival and local control than radiotherapy alone. Other significant prognostic factors for survival were patient age, gender, and lymph node (N) classification. Prolonged overall radiation time was associated with poorer survival and local control. Late severe toxicity from the treatment of these tumors was a significant problem in long term survivors. Improved radiotherapy techniques should lead to decreased injury to the surrounding normal tissues. (c) 1999 American Cancer Society.

DNA damage measured by the comet assay in head and neck cancer patients treated with tirapazamine

Tirapazamine (TPZ) [3-amino-1,2,4-benzotriazine 1,4-dioxide, SR4233, WIN 59075, and Tirazone] is a novel anticancer drug that is selectively activated by the low oxygen environment in solid tumors. By killing the radioresistant hypoxic cells, TPZ potentiates the antitumor efficacy of fractionated irradiation of transplanted tumors in mice. As this cell kill is closely correlated with TPZ-induced DNA damage, we investigated whether human head and neck cancers would show DNA damage similar to that seen in mouse tumors following TPZ administration. TPZ-induced DNA damage in both transplanted tumors in mice and in neck nodes of 13 patients with head and neck cancer was assessed using the alkaline comet assay on cells obtained from fine-needle aspirates. The oxygen levels of the patients' tumors were also measured using a polarographic oxygen electrode. Cells from the patients' tumors showed DNA damage immediately following TPZ administration that was comparable to, or greater than, that seen with transplanted mouse tumors. The heterogeneity of DNA damage in the patients' tumors was greater than that of individual mouse tumors and correlated with tumor hypoxia. The similarity of TPZ-induced DNA damage in human and rodent tumors suggests that tirapazamine should be effective when added to radiotherapy or to cisplatin-based chemotherapy in head and neck cancers.

Optimization of importance factors in inverse planning

Inverse treatment planning starts with a treatment objective and obtains the solution by optimizing an objective function. The clinical objectives are usually multifaceted and potentially incompatible with one another. A set of importance factors is often incorporated in the objective function to parametrize trade-off strategies and to prioritize the dose conformality in different anatomical structures. Whereas the general formalism remains the same, different sets of importance factors characterize plans of obviously different flavour and thus critically determine the final plan. Up to now, the determination of these parameters has been a 'guessing' game based on empirical knowledge because the final dose distribution depends on the parameters in a complex and implicit way. The influence of these parameters is not known until the plan optimization is completed. In order to compromise properly the conflicting requirements of the target and sensitive structures, the parameters are usually adjusted through a trial-and-error process. In this paper, a method to estimate these parameters computationally is proposed and an iterative computer algorithm is described to determine these parameters numerically. The treatment plan selection is done in two steps. First, a set of importance factors are chosen and the corresponding beam parameters (e.g. beam profiles) are optimized under the guidance of a quadratic objective function using an iterative algorithm reported earlier. The 'optimal' plan is then evaluated by an additional scoring function. The importance factors in the objective function are accordingly adjusted to improve the ranking of the plan. For every change in the importance factors, the beam parameters need to be re-optimized. This process continues in an iterative fashion until the scoring function is saturated. The algorithm was applied to two clinical cases and the results demonstrated that it has the potential to improve significantly the existing method of inverse planning. It was noticed that near the final solution the plan became insensitive to small variations of the importance factors.

Postoperative irradiation of minor salivary gland malignancies of the head and neck

OBJECTIVES

(1) To review the Stanford experience with postoperative radiotherapy for minor salivary gland carcinomas of the head and neck. (2) To identify patterns of failure and prognostic factors for these tumors.

MATERIALS AND METHODS

Fifty-four patients with localized tumors were treated with curative intent at Stanford University between 1966 and 1995. The 1992 AJCC staging for squamous cell carcinomas was used to retrospectively stage these patients. Thirteen percent had stage I, 22% stage II, 26% stage III, and 39% stage IV neoplasms. Thirty-two patients (59%) had adenoid cystic carcinoma, 15 (28%) had adenocarcinoma, and seven (13%) had mucoepidermoid carcinoma. Thirty (55%) had positive surgical margins and seven (13%) had cervical lymph node involvement at diagnosis. The median follow-up for alive patients was 7.8 years (range: 25 months-28.9 years).

RESULTS

The 5- and 10-year actuarial local control rates were 91 and 88%, respectively. Advanced T-stage (T3-4), involved surgical margins, adenocarcinoma histology, and sinonasal and oropharyngeal primaries were associated with poorer local control. The 5- and 10-year actuarial freedom from distant metastasis were 86 and 81%, respectively. Advanced T-stage (T3-4), lymph node involvement at diagnosis, adenoid cystic and high-grade mucoepidermoid histology were associated with a higher risk of distant metastases. The 10-year cause-specific survival (CSS) and overall survival (OS) were 81 % and 63%, respectively. On multivariate analysis, prognostic factors affecting survival were T-stage (favoring T1-2), and N-stage (favoring NO). When T- and N-stage were combined to form the AJCC stage, the latter became the most significant factor for survival. The 10-year OS was 86% for stage I-II vs. 52% for stage III-IV tumors. Late treatment-related toxicity was low (3/54); most complications were mild and no cranial nerve damage was noted.

CONCLUSIONS

Surgical resection and carefully planned post-operative radiation therapy for minor salivary gland tumors is well tolerated and effective with high local control rates. AJCC stage was the most significant predictor for survival and should be used for staging minor salivary gland carcinomas.

Cell cycle proteins and the development of oral squamous cell carcinoma

Expression of cell cycle regulatory proteins was evaluated in premalignant and malignant oral epithelial lesions, to test the hypothesis that protein regulation of the cell cycle may be altered in the development of oral squamous cell carcinoma. Archived paraffin-embedded specimens (n = 90) from 25 patients with recurrent or persistent lesions were evaluated in immunohistochemically stained sections for cell cycle regulatory proteins p53, Rb, Cyclin D1, p27, and p21. The cell cycle was also evaluated by expression of nuclear protein Ki 67. Sections were graded semiquantitatively using a 0-3 + scale to indicate the percentage of positively stained cells. The initial histologic diagnosis for 17/25 patients was either focal keratosis, mild dysplasia, or moderate dysplasia; the initial diagnosis for the remaining eight patients ranged from severe dysplasia to moderately differentiated squamous cell carcinoma. Thirty-three of 90 specimens showed positive p53 expression, 11 of which were dysplasias. Eighty-nine of 90 specimens, from all stages of disease, showed positive Rb expression. Twenty-three of 90 specimens showed positive Cyclin D1 expression, typically in the later stages (carcinoma) of a patient's disease. Eighty-four of 90 specimens showed positive p21 expression; while 55 of 90 specimens were positive for p27. In control mucosa, p27 was highly expressed, while Rb and p21 proteins were expressed at relatively low levels; p53 and Cyclin D1 proteins were largely absent. Generally, staining of p53, Rb, p21, and Ki 67 increased with time in serial biopsies, while p27 showed decreased staining with disease progression. These data show that cell cycle regulatory proteins are altered in both premalignant and malignant disease, and that protein phenotypes are heterogeneous. P53 expression is seen early, and Cyclin D1 expression is seen late in the development of oral premalignant and malignant disease. Expression of p53, Rb, p21 and Ki67 increased, while p27 decreased, with disease progression.

Apoptosis-associated proteins and the development of oral squamous cell carcinoma

Expression of apoptosis-associated proteins was evaluated in premalignant and malignant oral epithelial lesions, to test the hypothesis that protein regulation of apoptosis may be altered in the development of oral squamous cell carcinoma. Ninety archived paraffin-embedded specimens from 25 patients (two or more sequential biopsies each) and eight control specimens were evaluated in immunohistochemically stained sections for tumor suppressor protein p53, p53 binding protein mdm-2, and apoptosis regulatory proteins Bcl-2, Bcl-X, Bax, and Bak. The initial histologic diagnosis for 17/25 patients was either focal keratosis, mild dysplasia, or moderate dysplasia; the initial diagnosis for the remaining eight patients ranged from severe dysplasia to moderately differentiated squamous cell carcinoma. Thirty of 90 specimens showed positive p53 expression, nine of which were dysplasias. In patients with one or more lesions displaying p53 expression, there was increased intensity of staining with disease progression. Bak was expressed in 57/90 specimens, including 27 dysplasias of various grades. There was also a significantly increased intensity of Bak staining with disease progression, which did not appear to be dependent upon p53 status. Bcl-X was expressed in 73/90 specimens, with staining displayed earlier in premalignant lesions than either p53 or Bak. Ten of 90 specimens were positive for Bcl-2 (all were dysplasias or carcinomas), and only 2/90 specimens were positive for Bax. Eleven of 90 specimens were positive for mdm-2; six of which were also positive for p53. These data show that apoptosis-associated proteins are altered in variable patterns in both premalignant and malignant oral epithelial lesions. p53 and especially Bak and Bcl-X are expressed early; Bax is largely absent; and Bcl-2 and mdm-2 show sporadic expression in the development of oral premalignant and malignant disease.

The etiology of bacterial pneumonia and meningitis in Vietnam

BACKGROUND

To date no studies on the incidence of Haemophilus influenzae type b (Hib) disease, Hib carrier rates in infants and children or the proportion of bacterial meningitis cases caused by Hib in Vietnam have been performed. The availability of safe and highly effective Hib vaccines makes such information important.

METHODS

The bacterial etiology of a sample of infants and children with pneumonia and meningitis seen at Pediatric Hospital No. 1 in Ho Chi Minh City was studied by culture and latex agglutination of blood, cerebrospinal fluid, urine and pleural fluid. The carriage rate of pneumococci and Hib was studied in a sample of outpatient children.

RESULTS

Hib caused 53% of 34 culture-proven bacterial meningitis cases and pneumococci caused 18%. Of 31 meningitis cases diagnosed by latex agglutination, 39% were caused by Hib and 55% by pneumococci. Ninety percent of cases of Hib meningitis occurred in children <1 year of age. Fifty percent of meningitis cases were associated with acute respiratory infection. In 213 bacteremic pneumonia cases 92.5% of blood cultures grew Streptococcus pneumoniae and only 1% grew Hib. The carrier rate of Hib in outpatients <5 years of age with upper respiratory tract infection increased from 2% to 7.6% between 1993 and 1996.

CONCLUSION

Hib is the most frequent cause of meningitis in infants and children admitted to hospitals in South Vietnam. Ninety percent of Hib meningitis cases occur in patients < 1 year of age. Bacteremic Hib pneumonia in Vietnam is rare. The results suggest that Hib is the major cause of meningitis in Vietnam but do not permit conclusions regarding its true incidence. The carrier rate of Hib in children <5 years of age in Vietnam has increased to approximately 7% since 1993.

Influence of fraction size, total dose, and overall time on local control of T1-T2 glottic carcinoma

PURPOSE

To evaluate the influence of fraction size, overall time, total dose, and other prognostic factors on local control of T1 and T2 glottic carcinomas.

METHODS AND MATERIALS

Between 1956 and 1995, 398 consecutive patients with early glottic carcinoma (315 T1 and 83 T2) were treated with once-a-day definitive radiotherapy at the University of California, San Francisco, and associated institutions. Treatment was delivered 5 days per week. Minimum tumor dose ranged from 46.6 to 77.6 Gy (median: 63 Gy). The fraction size was < 1.8 Gy in 146; 1.8-1.99 Gy in 128; 2.0-2.24 Gy in 62, and > or = 2.25 Gy in 62 patients. Overall time ranged from 34 to 75 days (median: 50 days). The majority of patients treated with a fraction size of 2.25 Gy completed therapy within 43 days. Median follow-up of all alive patients was 116 months (range 3-436 months).

RESULTS

Five-year local control was 85% for T1 and 70% for T2 glottic carcinomas (p = 0.0004). For T1 lesions, within the dose and time range evaluated, there was no apparent relationship between fraction size, overall time, total dose, and local control on multivariate analysis. Treatment era was the only significant prognostic factor (p = 0.02), and anterior commissure (AC) involvement was of borderline significance (p = 0.056). Five-year local control was 77% for patients treated between 1956-1970, 89% for between 1971-1980, and 91% for between 1981-1995; 80% for patients with AC involvement and 88% for those without. For T2 lesions, prognostic factors for local control on multivariate analysis were: overall time (p = 0.003), fraction size (p = 0.003), total dose (p = 0.01), impaired vocal cord mobility (p = 0.02), and subglottic extension (p = 0.04). Five-year local control was 100% for T2 lesions treated with overall time < or = 43 days vs. 84% for overall time > 43 days; 100% for fraction size > or = 2.25 Gy vs. 44% for fraction size < 1.8 Gy; 78% for total dose > 65 Gy vs. 60% for total dose < or = 65 Gy; 79% for normal cord mobility vs. 45% for impaired cord mobility, and 58% for lesions with subglottic extension vs. 77% for those without. The severe complication rate for the entire group was low: 1.8%.

CONCLUSIONS

Total dose, fraction size, and overall time were significant factors for local control of T2 but not T1 glottic carcinomas. Anterior commissure involvement was associated with decreased local control for T1 but not T2 lesions. For T1 lesions, local control improved over the treatment era. For T2 lesions, local control decreased with impaired cord mobility and subglottic extension.

Adult medulloblastoma: an analysis of survival and prognostic factors

PURPOSE

This analysis aimed to review the experience in the management of adult medulloblastoma at the University of California, San Francisco, and to identify important prognostic factors for survival and posterior fossa control.

PATIENTS AND METHODS

We performed a retrospective review of 34 adult patients, age > or = 15, with cerebellar medulloblastoma treated with radiotherapy at the University of California, San Francisco from 1970 to 1994. All patients underwent a surgical procedure (complete resection in 17, subtotal resection in 10, and biopsy alone in seven), followed by craniospinal irradiation. Most patients treated after 1979 also received chemotherapy. Twenty were classified as poor-risk due to either incomplete resection or evidence of disease outside of the posterior fossa at diagnosis.

RESULTS

The 5-year posterior fossa control and overall survival rates were 61% and 58%, respectively. The majority of relapses occurred in the posterior fossa (14 of 17). Multivariate analysis revealed that age (favoring older patients), gender (favoring female patients), and extent of disease at diagnosis (favoring localized disease) were important prognostic factors for posterior fossa control. There was a trend toward improved posterior fossa control with higher radiation dose to the posterior fossa in patients with a complete resection. Gender and extent of disease at presentation were significant prognostic factors for survival. The 5-year survival rates were 92% for female patients versus 40% for male patients, and 67% for patients with localized disease versus 25% for those with disseminated disease. The prognosis following recurrence was poor; all died of the disease.

DISCUSSION

Survival for adult medulloblastoma was comparable to its pediatric counterpart. In patients with localized disease at presentation, gender (favoring female patients) and age (favoring older patients) were important prognostic factors for posterior fossa control and survival. In patients with disseminated disease at presentation, the prognosis is poor, and innovative therapy is needed to improve survival.

Prognostic factors in adult soft-tissue sarcomas of the head and neck

PURPOSE

The main objectives of this study were (a) to review the treatment results of primary head and neck soft-tissue sarcoma at our institution, (b) to identify important prognostic factors in local control and survival, and (c) to assess the efficacy of salvage therapy.

METHODS AND MATERIALS

Sixty-five patients were treated at the University of California, San Francisco, between 1961 and 1993. Seventeen patients (27%) had low-grade, 10 (15%) had intermediate-grade, and 38 (58%) had high-grade sarcomas. Tumors were > 5 cm in 35 patients. Local management consisted of surgery alone in 14 patients (22%), surgery and radiotherapy in 40 (61%), and radiotherapy alone in 11 (17%) patients. The median follow-up was 64 months.

RESULTS

The 5-year actuarial local control rate of the entire group was 66%. Tumor size and grade were important predictors for local control on multivariate analysis. The actuarial local control rate at 5 years was 92% for T1 vs. 40% for T2 primaries (p = 0.004), and 80% for Grade 1-2 vs. 48% for Grade 3 tumors (p = 0.01). None of the patients treated with radiotherapy alone with a dose of 50-65 Gy were controlled locally. Combined radiotherapy and surgery appeared to yield superior local control compared to surgery alone (77% vs. 59%); however, the difference was not statistically significant. The 5-year actuarial overall and cause-specific survivals were 56% and 60%, respectively. Unfavorable prognostic factors for cause-specific survival on multivariate analysis were age > 55 (p = 0.009), high tumor grade (p = 0.0002), inadequate surgery (p = 0.008), and positive surgical margins (p = 0.0009). In patients who underwent salvage therapy for treatment failure, the 5-year actuarial survival after salvage treatment was 26%.

CONCLUSION

Tumor size and grade were important predictors for local control. Age, grade, adequacy of surgery, and status of surgical margins were significant prognostic factors for survival. There was a trend of improved local control with combined surgery and radiotherapy compared to either modality alone for high-risk patients. Radiotherapy alone with doses < or = 65 Gy was insufficient for control of gross disease. Aggressive salvage therapy was worthwhile in patients whose disease was uncontrolled after the initial treatment.

Pattern of recurrence of medulloblastoma after low-dose craniospinal radiotherapy

PURPOSE

We retrospectively evaluated relapse of medulloblastoma after low- or high-dose craniospinal radiotherapy, and after conventional or hyperfractionated posterior fossa irradiation.

METHODS AND MATERIALS

Ninety-two pediatric patients were treated postoperatively since 1970 at the University of California, San Francisco. Until 1989, we employed conventional fractionation with low (< or = 30 Gy) or high-dose craniospinal fields and low-dose (< or = 56 Gy) posterior fossa boosts. Recently, hyperfractionation delivered low- or high-dose to the craniospinal axis and high-dose to the posterior fossa. Most patients treated after 1979 received chemotherapy.

RESULTS

Median follow-up was 70 months. Five-year disease-free survival was 36% (22% for poor-risk vs. 59% for good-risk patients). Five-year overall survival was 52% (43% for poor vs. 68% for good-risk). Neither the dose to the posterior fossa nor the craniospinal axis was statistically related to recurrence. Failure in the posterior fossa occurred despite boosts greater than 56 Gy. Females, over the age of 6 years, had significantly better relapse-free survival than males of the same age. Six of the 54 patients who relapsed were long-term survivors.

CONCLUSIONS

Low-dose craniospinal radiotherapy, where the majority of patients received chemotherapy, was not associated with increased failure. High-dose posterior fossa hyperfractionation did not improve control. Long-term survival was noted in a number of patients after relapse. We recommend 60 Gy or greater with conventional fractions to the primary area, and continued study of low-dose craniospinal irradiation with adjuvant chemotherapy.