Multi-institutional consensus on machine QA for isochronous cyclotron-based systems delivering ultra-high dose rate (FLASH) pencil beam scanning proton therapy in transmission mode.

BACKGROUND: The first clinical trials to assess the feasibility of FLASH radiotherapy in humans have started (FAST-01, FAST-02) and more trials are foreseen. To increase comparability between trials it is important to assure treatment quality and therefore establish a standard for machine quality assurance (QA). Currently, the AAPM TG-224 report is considered as the standard on machine QA for proton therapy, however, it was not intended to be used for ultra-high dose rate (UHDR) proton beams, which have gained interest due to the observation of the FLASH effect. PURPOSE: The aim of this study is to find consensus on practical guidelines on machine QA for UHDR proton beams in transmission mode in terms of which QA is required, how they should be done, which detectors are suitable for UHDR machine QA, and what tolerance limits should be applied. METHODS: A risk assessment to determine the gaps in the current standard for machine QA was performed by an international group of medical physicists. Based on that, practical guidelines on how to perform machine QA for UHDR proton beams were proposed. RESULTS: The risk assessment clearly identified the need for additional guidance on temporal dosimetry, addressing dose rate (constancy), dose spillage, and scanning speed. In addition, several minor changes from AAPM TG-224 were identified; define required dose rate levels, the use of clinically relevant dose levels, and the use of adapted beam settings to minimize activation of detector and phantom materials or to avoid saturation effects of specific detectors. The final report was created based on discussions and consensus. CONCLUSIONS: Consensus was reached on what QA is required for UHDR scanning proton beams in transmission mode for isochronous cyclotron-based systems and how they should be performed. However, the group discussions also showed that there is a lack of high temporal resolution detectors and sufficient QA data to set appropriate limits for some of the proposed QA procedures.

Design of optical notch filters using apodized thickness modulation.

An apodized thickness design method for discrete layer notch filters is presented. The method produces error tolerant designs with low ripple in the passband regions without any additional numerical optimization. Several apodization functions including Gaussian, cosine squared, as well as quintic are considered. Theoretical and experimental results from ion beam deposited sample designs for single-notch as well as multinotch filters are presented. Good agreement is observed between the theoretical design and the experimental measurement even when the deposition process is only controlled on time. This demonstrates the low layer error sensitivity of the apodized designs.

Cyclopropyl- and methyl-containing inhibitors of neuronal nitric oxide synthase.

Inhibitors of neuronal nitric oxide synthase have been proposed as therapeutics for the treatment of different types of neurological disorders. On the basis of a cis-3,4-pyrrolidine scaffold, a series of trans-cyclopropyl- and methyl-containing nNOS inhibitors have been synthesized. The insertion of a rigid electron-withdrawing cyclopropyl ring decreases the basicity of the adjacent amino group, which resulted in decreased inhibitory activity of these inhibitors compared to the parent compound. Nonetheless, three of them exhibited double-digit nanomolar inhibition with high nNOS selectivity on the basis of in vitro enzyme assays. Crystal structures of nNOS and eNOS with these inhibitors bound provide a basis for detailed structure-activity relationship (SAR) studies. The conclusions from these studies will be used as a guide in the future development of selective NOS inhibitors.

Predictors of pathologic complete response after standard neoadjuvant chemotherapy in triple-negative breast carcinoma.

The objective of this study was to identify predictors of pathologic complete response and tumor volume reduction in triple-negative breast carcinomas. Consecutive cases of 101 triple-negative carcinomas within the last 3 years treated with standard neoadjuvant chemotherapy were identified. However, 56 cases with sufficient material available (for tissue microarray construction) in the pretherapy core biopsy tissue blocks formed the basis of this study. The pretherapy tumor core biopsy slides were examined for various morphologic features including tumor grade. The tumors were immunohistochemically examined for basal phenotype markers (CK5, CK14, CK17, epidermal growth factor receptor), cell adhesion marker E-cadherin, and proliferation marker Ki-67. The overall rate of pathologic complete response was 34% (19 of 56). Neither any morphologic feature nor any basal marker reactivity predicted for pathologic complete response or >50% tumor volume reduction. Ki-67 proliferation index also failed as a predictive marker. Reduced E-cadherin expression (defined as H score ≤200) was initially seen in 47% of cases with pathologic complete response and in only 6% of cases that failed to achieve pathologic complete response (P=0.001); however, in additional 20 cases from a separate validation set, no such difference was identified. Basal marker reactivity in triple-negative breast carcinomas does not predict pathologic complete response after neoadjuvant chemotherapy. As vast majority of triple-negative tumors are highly proliferative, Ki-67 proliferation index appears to have negligible clinical value in predicting pathologic complete response. E-cadherin expression as a predictor of pathologic complete response in triple-negative tumors should be further assessed on larger number of cases.

Intramolecular hydrogen bonding: a potential strategy for more bioavailable inhibitors of neuronal nitric oxide synthase.

Selective neuronal nitric oxide synthase (nNOS) inhibitors have therapeutic applications in the treatment of numerous neurodegenerative diseases. Here we report the synthesis and evaluation of a series of inhibitors designed to have increased cell membrane permeability via intramolecular hydrogen bonding. Their potencies were examined in both purified enzyme and cell-based assays; a comparison of these results demonstrates that two of the new inhibitors display significantly increased membrane permeability over previous analogs. NMR spectroscopy provides evidence of intramolecular hydrogen bonding under physiological conditions in two of the inhibitors. Crystal structures of the inhibitors in the nNOS active site confirm the predicted non-intramolecular hydrogen bonded binding mode. Intramolecular hydrogen bonding may be an effective approach for increasing cell membrane permeability without affecting target protein binding.

High yielding allylation of a chiral secondary alcohol containing base sensitive functional groups.

Inhibitors of neuronal nitric oxide synthase, based on a chiral pyrrolidine scaffold, show promise for the treatment of certain neurodegenerative diseases. We recently reported the synthesis of a series of selective inhibitors, but the method was limited at a key step of formingan allyl ether intermediate. Yields for this step were very inconsistent, and the presence of base sensitive functional groups limited the range of available methods for forming this ether bond. This work describes a novel application of palladium catalyzed decarboxylativeallylation, consistently resulting in 90% isolated yields, which is crucial for the synthesis of the critical allyl ether late stage intermediate. We also report a new quantitative yielding and straightforward synthesis of the allyl-t-butylcarbonate precursor.

Semi-quantitative immunohistochemical assay versus oncotype DX(®) qRT-PCR assay for estrogen and progesterone receptors: an independent quality assurance study.

Estrogen receptor (ER) status is a strong predictor of response to hormonal therapy in breast cancer patients. Presence of ER and level of expression have been shown to correlate with time to recurrence in patients undergoing therapy with tamoxifen or aromatase inhibitors. Risk reduction is also known to occur in ER-negative, progesterone receptor (PR)-positive patients treated with hormonal therapy. Since the 1990s, immunohistochemistry has been the primary method for assessing hormone receptor status. Recently, as a component of its oncotype DX(®) assay, Genomic Health began reporting quantitative estrogen and PR results determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). As part of an ongoing quality assurance program at our institution, we reviewed 464 breast cancer cases evaluated by both immunohistochemistry and oncotype DX(®) assay for estrogen and PR. We found good correlation for ER status between both assays (98.9% concordance), with immunohistochemistry being slightly more sensitive. Concordance for PR was 94.2% between immunohistochemistry and qRT-PCR with immunohistochemistry again more sensitive than RT-PCR. The results also showed linear correlation between immunohistochemistry H-scores and qRT-PCR expression values for ER (correlation coefficient of 0.579), and PR (correlation coefficient of 0.685). Due to the higher sensitivity of hormone receptor immunohistochemistry and additional advantages (ie preservation of morphology, less expensive, faster, more convenient), we conclude immunohistochemistry is preferable to qRT-PCR for determination of estrogen and PR expression.

Improved synthesis of chiral pyrrolidine inhibitors and their binding properties to neuronal nitric oxide synthase.

We report an efficient synthetic route to chiral pyrrolidine inhibitors of neuronal nitric oxide synthase (nNOS) and crystal structures of the inhibitors bound to nNOS and to endothelial NOS. The new route enables versatile structure-activity relationship studies on the pyrrolidine-based scaffold, which can be beneficial for further development of nNOS inhibitors. The X-ray crystal structures of five new fluorine-containing inhibitors bound to nNOS provide insights into the effect of the fluorine atoms on binding.

Polyradiculopathies from schwannomatosis.

We describe a case of schwannomatosis presenting as radicular pain and numbness in multiple radicular nerve distributions. There were multiple peripheral nerve tumors detected by magnetic resonance imaging (MRI) at the left vestibular nerve, cauda equina, right radial nerve, thoracic paraspinal nerve, and brachial plexi. Several resected tumors have features of schwannomas, including hypercellular Antoni A areas, hypocellular Antoni B areas, Verocay bodies, and hyalinized blood vessels. The specimens are also positive for immunohistochemical staining for INI1 with diffuse nuclear staining. The findings are consistent with sporadic form of schwannomatosis. This case highlights the importance of using MRI and INI1 immunohistochemistry to differentiate familial schwannomatosis, neurofibromatosis 2 (NF2)-associated schwannomatosis, and sporadic schwannomatosis.

Comparison of preoperative computed tomography and surgical findings in maxillofacial infections.

PURPOSE: To examine the accuracy of computed tomography (CT) in predicting the presence of surgically confirmed abscess in patients presenting with deep maxillofacial infections (DMIs). MATERIALS AND METHODS: The medical records of 36 patients with clinically suspected DMI were reviewed. All patients underwent preoperative CT scan to determine whether abscess or cellulitis was present. The operative reports of all patients were compared with their preoperative CT scan findings. RESULTS: Of 36 patients, 30 had abscess predicted by preoperative CT scan. The positive predictive value for DMI based on CT findings interpreted by an oral surgeon and confirmed as an abscess at operation was 90%, whereas the negative predictive value was 33%. When findings were interpreted by a radiologist, the positive predictive value was 94.1% whereas the negative predictive value was 26.3%. Thirty patients had abscess predicted by preoperative CT scan when interpreted by an oral surgeon, whereas seventeen had abscess predicted by a radiologist. At operation, 3 of 30 patients had cellulitis whereas 27 had abscess, for a false-positive rate of 60% and false-negative rate of 12.9%. On the basis of preoperative radiography, 1 of 17 patients had cellulitis whereas 16 had abscess, for a false-positive rate of 16.7% and a false-negative rate of 46.7%. The agreement between CT and operative findings in predicting abscess by an oral surgeon was 80.6% and by a radiologist was 58.3%. CONCLUSION: CT yielded high sensitivity for the detection of DMI abscess but poor specificity, likely because of the paucity of cellulitis.

Vocal cord paralysis following orthognathic surgery intubation.

The incidence of recurrent laryngeal nerve paralysis following short-term oro-endotracheal intubation for any surgical procedure is very rare. The diagnosis becomes very difficult if the surgical procedure may alter the vocal characteristics following surgery. We report a case of a 24 year-old healthy male patient who developed prolonged hoarseness which developed after having undergone a bimaxillary orthognathic surgical procedure. Following surgery, the patient's complaints of hoarseness and mild coughing on taking thin liquids were investigated with the assistance of the otolarynology voice department. A flexible fiberoptic laryngoscopy and videostroboscopy showed a partial paralysis of the left vocal cord suggesting damage to the left recurrent laryngeal nerve. The recovery was gradual and resolved without any intervention in approximately 6 weeks. Prolonged change or loss of voice quality following an orthognathic surgical procedure, as discussed in this case, when associated with difficulty in swallowing thin or thick liquids warrants a thorough investigation and can be managed at times with observation alone.

Comparison of treatment outcomes associated with early versus late treatment of mandible fractures: a retrospective chart review and analysis.

PURPOSE: We conducted outcomes assessment for all patients who had undergone treatment of mandible fractures at Tufts Medical Center across the 2 specialties of oral and maxillofacial surgery and otolaryngology. The aim of the present study was to determine whether a correlation existed between the development of postoperative complications and late treatment of mandible fractures (defined as treatment provided >48 hours after the time of injury). PATIENTS AND METHODS: All patients with mandible fractures treated at Tufts Medical Center between January 1, 2003 and January 1, 2008, underwent chart review to document the relevant data, including the time of fracture, time of treatment, and complications recorded during postoperative follow-up. The only patients included in the review were those who had follow-up data with good documentation. RESULTS: Our dataset included 92 patients, with a mean age of 28.74 years. The injury scores, compared between the early and late treatment and complication and noncomplication groups, were equivocal. Of our 92 treated patients, 19 (20.7%) had ≥1 postoperative complication. Of the 19 patients with any complication, 10 had undergone early treatment and 9 had been treated after 48 hours. Of our late treatment group, 25% developed ≥1 complication. The overall complication rate for the early group was 18%. CONCLUSIONS: Our study did not reveal a statistically significant difference in the development of postoperative complications after mandible fracture repair between the early and late treatment groups. Our study seemed to have a result similar to that of some of the earlier studies investigating the same variable.

The relationship between papillary infarction and microinvasion in ovarian atypical proliferative ("borderline") serous and seromucinous tumors.

Papillary infarction is commonly observed in ovarian atypical proliferative serous and seromucinous tumors (APST/APSMT), but there are no published data on its significance. This study characterizes the features associated with papillary infarcts and microinvasion to further understand these phenomena. From consecutive hospital-based cases, 32 APST/APSMT in 26 patients (6 bilateral) were reviewed and evaluated for papillary infarcts, microinvasion (<5 mm), and other histologic features. Among the tumors, 69% were APSTs and 31% APSMTs. Infarcts were identified in 46% of patients, and microinvasion in 27%. Microinvasion was significantly more common in tumors with infarcts (50%) than in those without (7%; P=0.0261). Papillary infarcts were significantly more common in APSTs (61%) than in APSMTs (13%; P=0.0357). The microinvasive tumors were significantly more likely to be bilateral (57% vs. 11%, P=0.0278). The mean infarct size in the presence of microinvasion was 5.9 mm, and in the absence of microinvasion, 2.2 mm (not significant). The infarcts were topographically separate from the foci of microinvasion. Other features evaluated showed no meaningful correlations with microinvasion or infarction. Proliferative noninvasive serous tumors with papillary infarcts are significantly more likely to have microinvasion, and papillary infarcts are more common in APSTs than in APSMTs. APSTs with microinvasion are more common than earlier appreciated. Whether papillary infarction is pathogenetically related to microinvasion is unknown and warrants further investigation.

Second generation analogues of the cancer drug clinical candidate tipifarnib for anti-Chagas disease drug discovery.

We previously reported that the cancer drug clinical candidate tipifarnib kills the causative agent of Chagas disease, Trypanosoma cruzi, by blocking ergosterol biosynthesis at the level of inhibition of lanosterol 14alpha-demethylase. Tipifarnib is an inhibitor of human protein farnesyltransferase. We synthesized tipifarnib analogues that no longer bind to protein farnesyltransferase and display increased potency for killing parasites. This was achieved in a structure-guided fashion by changing the substituents attached to the phenyl group at the 4-position of the quinoline ring of tipifarnib and by replacing the amino group by OMe. Several compounds that kill Trypanosoma cruzi at subnanomolar concentrations and are devoid of protein farnesyltransferase inhibition were discovered. The compounds are shown to be advantageous over other lanosterol 14alpha-demethylase inhibitors in that they show only modest potency for inhibition of human cytochrome P450 (3A4). Since tipifarnib displays high oral bioavailability and acceptable pharmacokinetic properties, the newly discovered tipifarnib analogues are ideal leads for the development of drugs to treat Chagas disease.

Structurally simple inhibitors of lanosterol 14alpha-demethylase are efficacious in a rodent model of acute Chagas disease.

We report structure-activity studies of a large number of dialkyl imidazoles as inhibitors of Trypanosoma cruzi lanosterol-14alpha-demethylase (L14DM). The compounds have a simple structure compared to posaconazole, another L14DM inhibitor that is an anti-Chagas drug candidate. Several compounds display potency for killing T. cruzi amastigotes in vitro with values of EC(50) in the 0.4-10 nM range. Two compounds were selected for efficacy studies in a mouse model of acute Chagas disease. At oral doses of 20-50 mg/kg given after establishment of parasite infection, the compounds reduced parasitemia in the blood to undetectable levels, and analysis of remaining parasites by PCR revealed a lack of parasites in the majority of animals. These dialkyl imidazoles are substantially less expensive to produce than posaconazole and are appropriate for further development toward an anti-Chagas disease clinical candidate.

Rational modification of a candidate cancer drug for use against Chagas disease.

Chagas disease is one of the major neglected diseases of the world. Existing drug therapies are limited, ineffective, and highly toxic. We describe a novel strategy of drug discovery of adapting an existing clinical compound with excellent pharmaceutical properties to target a pathogenic organism. The protein farnesyltransferase (PFT) inhibitor tipifarnib, now in phase III anticancer clinical trials, was previously found to kill Trypanosoma cruzi by blocking sterol 14 alpha-demethylase (14DM). We rationally developed tipifarnib analogues that display reduced affinity for human PFT to reduce toxicity while increasing affinity for parasite 14DM. The lead compound has picomolar activity against cultured T. cruzi and is efficacious in a mouse model of acute Chagas disease.