Intensity-Modulated Proton Therapy (IMPT) Offered Advantageous Dosimetry Compared to Volumetric Arc Therapy (VMAT) or Helical Tomotherapy (HT) in Patients with Synchronous Bilateral Breast Cancer

PURPOSE/OBJECTIVE(S)

Radiotherapy of synchronous bilateral breast cancer poses some technical challenges with regards to dose coverage and sparing of organs at risk (OAR). In this study, we aimed to evaluate dosimetric characteristics of 3 different techniques, IMPT vs photon (VMAT and HT). We hypothesized that IMPT would result in lower doses to organs at risk, as compared to the other 2 techniques.

MATERIALS/METHODS

A total of 10 patients with synchronous bilateral breast cancer who were treated with VMAT at our institution were retrospectively analyzed. Clinical target volume (CTV) included chest wall and regional nodes (supraclavicular fossa and internal mammary chain) and prescription dose was 40.05 Gy in 15 daily fractions. HT and IMPT plans were generated for each patient. Dose-volume statistics, including planning target volume (PTV) coverage and dose to OAR: lungs, heart, thyroid, spinal cord, brachial plexus and esophagus, were compared between modalities using a paired T-test.

RESULTS

Mean age of patients was 61 years (43-84). Majority of the patients (80%) were ER+ PR+ and HER2-. 40% of patients underwent breast reconstruction following surgery. All 3 techniques provided adequate target volume distribution and OAR sparing. Compared to VMAT and HT plans, IMPT had better heart and lung sparing effects, resulting in lower mean and V25 Gy heart dose; mean, V20 Gy and V5 Gy lung dose (p<0.0001). There was no significant difference in VMAT and HT plans for mean heart and lung dose. VMAT plans showed significantly lower V25 Gy heart dose on average (p = 0.04). V5 Gy lung dose was slightly lower in HT compared to VMAT plans, approaching statistical significance (p = 0.08). PTV coverage was adequate for all 3 techniques. All techniques fulfilled cord, esophagus, thyroid and brachial plexus constraints.

CONCLUSION

IMPT plans showed significantly better OAR sparing compared to photon techniques. All 3 techniques met OAR constraints, and resulted in adequate target volume coverage. As IMPT is significantly more costly than VMAT or HT techniques, appropriate patient selection is important to deliver treatment in the most resource-effective manner for patients who would derive the most benefit, for example those with young age or existing heart or lung comorbidities.

Insulin-induced hypoglycaemia suppresses pulsatile luteinising hormone secretion and arcuate Kiss1 cell activation in female mice

Stress suppresses pulsatile luteinising hormone (LH) secretion in a variety of species, although the mechanism underlying this inhibition of reproductive function remains unclear. Metabolic stress, particularly hypoglycaemia, is a clinically-relevant stress type that is modelled with bolus insulin injection (insulin-induced hypoglycaemia). The present study utilised ovariectomised C57BL/6 mice to test the hypothesis that acute hypoglycaemia suppresses pulsatile LH secretion via central mechanisms. Pulsatile LH secretion was measured in 90-minute sampling periods immediately prior to and following i.p. injection of saline or insulin. The secretion of LH was not altered over time in fed animals or acutely fasted (5 hours) animals following an i.p. saline injection. By contrast, insulin elicited a robust suppression of pulsatile LH secretion in fasted animals, preventing LH pulses in five of six mice. To identify the neuroendocrine site of impairment, a kisspeptin challenge was performed in saline or insulin pre-treated animals in a cross-over design. LH secretion in response to exogenous kisspeptin was not different between animals pre-treated with saline or insulin, indicating normal gonadotrophin-releasing hormone cell and pituitary responses during acute hypoglycaemia. Based on this finding, the effect of insulin-induced hypoglycaemia on arcuate kisspeptin (Kiss1) cell function was determined using c-Fos as a marker of neuronal activation. Insulin caused a significant suppression in the percentage of Kiss1 cells in the arcuate nucleus that contained c-Fos compared to saline-injected controls. Taken together, these data support the hypothesis that insulin-induced hypoglycaemia suppresses pulsatile LH secretion in the female mouse via predominantly central mechanisms, which culminates in the suppression of the arcuate Kiss1 population.

Letrozole treatment of pubertal female mice results in activational effects on reproduction, metabolism and the gut microbiome

Polycystic ovary syndrome (PCOS) is a common endocrine disorder in reproductive-aged women that is comprised of two out of the following three features: hyperandrogenism, oligo- or amenorrhea, or polycystic ovaries. In addition to infertility, many women with PCOS have metabolic dysregulation that increases the risk of developing type 2 diabetes, hypertension, and non-alcoholic fatty liver disease. Changes in the gut microbiome are associated with PCOS and gut microbes may be involved in the pathology of this disorder. Since PCOS often manifests in the early reproductive years, puberty is considered to be a critical time period for the development of PCOS. Exposure to sex steroid hormones during development results in permanent, organizational effects, while activational effects are transient and require the continued presence of the hormone. Androgens exert organizational effects during prenatal or early post-natal development, but it is unclear whether androgen excess results in organizational or activational effects during puberty. We recently developed a letrozole-induced PCOS mouse model that recapitulates both reproductive and metabolic phenotypes of PCOS. In this study, we investigated whether letrozole treatment of pubertal female mice exerts organizational or activational effects on host physiology and the gut microbiome. Two months after letrozole removal, we observed recovery of reproductive and metabolic parameters, as well as diversity and composition of the gut microbiome, indicating that letrozole treatment of female mice during puberty resulted in predominantly activational effects. These results suggest that if exposure to excess androgens during puberty leads to the development of PCOS, reduction of androgen levels during this time may improve reproductive and metabolic phenotypes in women with PCOS. These results also imply that continuous letrozole exposure is required to model PCOS in pubertal female mice since letrozole exerts activational rather than organizational effects during puberty.

Exposure to a Healthy Gut Microbiome Protects Against Reproductive and Metabolic Dysregulation in a PCOS Mouse Model

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting ∼10% to 15% of reproductive-aged women worldwide. Diagnosis requires two of the following: hyperandrogenism, oligo-ovulation or anovulation, and polycystic ovaries. In addition to reproductive dysfunction, many women with PCOS display metabolic abnormalities associated with hyperandrogenism. Recent studies have reported that the gut microbiome is altered in women with PCOS and rodent models of the disorder. However, it is unknown whether the gut microbiome plays a causal role in the development and pathology of PCOS. Given its potential role, we hypothesized that exposure to a healthy gut microbiome would protect against development of PCOS. A cohousing study was performed using a letrozole-induced PCOS mouse model that recapitulates many reproductive and metabolic characteristics of PCOS. Because mice are coprophagic, cohousing results in repeated, noninvasive inoculation of gut microbes in cohoused mice via the fecal-oral route. In contrast to letrozole-treated mice housed together, letrozole mice cohoused with placebo mice showed significant improvement in both reproductive and metabolic PCOS phenotypes. Using 16S rRNA gene sequencing, we also observed that the overall composition of the gut microbiome and the relative abundance of Coprobacillus and Lactobacillus differed in letrozole-treated mice cohoused with placebo mice compared with letrozole mice housed together. These results suggest that dysbiosis of the gut microbiome may play a causal role in PCOS and that modulation of the gut microbiome may be a potential treatment option for PCOS.

Letrozole treatment of adult female mice results in a similar reproductive phenotype but distinct changes in metabolism and the gut microbiome compared to pubertal mice

BACKGROUND

A majority of women with polycystic ovary syndrome (PCOS) have metabolic dysfunction that results in an increased risk of type 2 diabetes. We previously developed a pubertal mouse model using the aromatase inhibitor, letrozole, which recapitulates many of the reproductive and metabolic features of PCOS. To further our understanding of the effects of androgen excess, we compared the effects of letrozole treatment initiated in puberty versus adulthood on reproductive and metabolic phenotypes as well as on the gut microbiome.

RESULTS

Letrozole treatment of both pubertal and adult female mice resulted in reproductive hallmarks of PCOS, including hyperandrogenemia, anovulation and polycystic ovaries. However, unlike pubertal mice, treatment of adult female mice resulted in modest weight gain and abdominal adiposity, minimal elevation in fasting blood glucose and insulin levels, and no detectable insulin resistance. In addition, letrozole treatment of adult mice was associated with a distinct shift in gut microbial diversity compared to letrozole treatment of pubertal mice.

CONCLUSIONS

Our results indicate that dysregulation of metabolism and the gut microbiome in PCOS may be influenced by the timing of androgen exposure. In addition, the minimal weight gain and lack of insulin resistance in adult female mice after letrozole treatment indicates that this model may be useful for investigating the effects of hyperandrogenemia on the hypothalamic-pituitary-gonadal axis and the periphery without the influence of substantial metabolic dysregulation.

In vitro effects of local anaesthetics on the thromboelastographic profile of parturients

BACKGROUND

Post-dural puncture headache can be an incapacitating complication of obstetric epidural analgesia/anaesthesia and early or prophylactic epidural blood patch (EBP) is one of the treatment options. Although local anaesthetic (LA) agents have been shown to have anticoagulation effects in vitro, peri-partum women are known to be hypercoagulable. We postulated that the presence of residual LA might not result in impaired haemostasis of the EBP in parturients.

METHODS

Blood samples from 10 healthy term parturients were subjected to thromboelastography after the addition of four different LA (lidocaine, bupivacaine, levobupivacaine, and ropivacaine) preparations.

RESULTS

There was a significant reduction in reaction (R) and coagulation (K) time (P<0.001, P<0.05) and an increase in alpha degrees angle (P<0.01) when comparing undiluted blood with the saline control group. Maximum amplitude (MA) and clot lysis (Ly30) did not change significantly despite the 50% dilution. The thromboelastographic parameters of all four LA-treated groups were no different from their saline controls and from each other.

CONCLUSION

At clinical dosages, LA did not cause any hypocoagulable changes on the thromboelastographic profile of healthy parturients.

Teaching first-year medical students physiology: does the human patient simulator allow for more effective teaching?

BACKGROUND

Although the Human Patient Simulator (HPS) is an effective teaching tool in many medical fields, literature supporting its use in the teaching of physiology to medical students is lacking. This study investigated the effectiveness of HPS-based teaching of cardiovascular physiology to first-year medical students.

METHODS

Two hundred and ten first-year medical students were scheduled to our HPS laboratory with the purpose of demonstrating "physiology in action". Students were divided into groups of 19-25 each, and attended a lecture followed by a HPS session. Using a theatre-type simulator complete with mannequin, anaesthesia machine and monitors (METI, Sarasota FL), the scenarios of hypovolaemia, sepsis, and cardiac failure were run to demonstrate the physiological changes that occur with changes in preload, afterload, and cardiac contractility. Each student was given a true/false test before, and again after the HPS session, followed by a survey of their learning experience.

RESULTS

There was marked improvement in test scores after the HPS session (82.1% vs. 64.6%, P < 0.001). Most of the students felt that HPS was a better teaching tool (94.5%) and raised more questions (76.5%) than lectures. They wanted more topics to be taught this way (96%), as they could apply and re-enforce textbook knowledge, and visualise real-time changes. However, they felt that their experience could have been enhanced with more time and smaller groups.

DISCUSSION

HPS is an excellent teaching tool as it stimulates student curiosity and makes knowledge acquisition and understanding easier. It is highly desirable to be incorporated into the teaching of physiology.

Duplex PCR system for simultaneous detection of Neisseria gonorrhoeae and Chlamydia trachomatis in clinical specimens

AIMS

To evaluate the use of a duplex polymerase chain reaction (PCR) assay for the simultaneous detection of Neisseria gonorrhoeae and Chlamydia trachomatis in clinical samples.

METHODS

Genital swab specimens were obtained from both China (203 swabs) and Hong Kong (202 swabs). N gonorrhoeae and C trachomatis were detected in each specimen with a number of tests including enzyme immunoassays (IDEIA) and PCR assays using both single and double primer pairs. The primer pair for N gonorrhoeae was derived from the cppB gene on its cryptic plasmid and the PCR product was 390 base pairs long. For C trachomatis, the PCR product was 473 base pairs long, resulting from amplification of a sequence in the common 7.4 kilobase plasmid present in all serovars. For N gonorrhoeae, PCR results were also compared with those obtained by culture and Gram's smear of the discharges.

RESULTS

For the 203 specimens collected in China, similar numbers of positive results (177) were obtained by both Gonozyme and duplex PCR for the detection of N gonorrhoeae. No discrepant results were found among the cultured specimens when Gonozyme and duplex PCR were compared. C trachomatis was detected in 47 specimens by duplex PCR, but was detected in only 28 by IDEIA. Of the 202 Hong Kong specimens, 46 were positive for N gonorrhoeae, detected by both Gonozyme and duplex PCR; 34 were positive for C trachomatis, 25 of which were detected by IDEIA and the remainder by duplex PCR.

CONCLUSIONS

The duplex PCR assay is a satisfactory diagnostic tool for the simultaneous detection of N gonorrhoeae and C trachomatis in clinical swab samples. Further evaluation is suggested.

Diagnosis of urogenital gonorrhoea: evaluation of an enzyme immunoassay and use of urine as a non-invasive specimen

Urethral swabs and urine samples were collected from 42 male patients attending a social hygiene clinic in Hong Kong and used for gonococcal culture and detection of antigens by enzyme immunoassay. Of the patients, 21 were suffering from gonorrhoea as indicated by positive gonococcal culture from both urethral swabs and urine. Twenty of the positive cases were detected by both swab and urine specimens using Gonozyme, an enzyme immunoassay kit. One culture-positive case failed detection by both swab and urine specimens. Gonozyme showed sensitivity and specificity of 95.2% and 100% respectively. With male patients, the use of urine as an alternative specimen to urethral swabs appears to have potential value for both culture and Gonozyme testing. Genital swabs and urine samples were subsequently collected from 108 patients (89 male, 19 female) attending the sexually transmitted disease monitoring centre in Guangzhou, China. Gonozyme tests were performed on both types of specimen, while only swabs were cultivated. When compared with swab culture, Gonozyme had sensitivity and specificity of 100% and 89.2% for males, and 100% and 90.9% for females, respectively. When urine was compared with swabs in the Gonozyme test, urine had sensitivity and specificity of 83.6% and 89.2% for males, and 62.5% and 81.8% for females, respectively. Hence, Gonozyme merits further investigation as an acceptable rapid diagnostic method for detection of Neisseria gonorrhoeae, especially when using urine as an alternative non-invasive specimen from male patients.

Development of a specific probe for the aminoglycoside-(3)-N-acetyltransferase resistance gene

Aminoglycoside-(3)-N-acetyltransferase isoenzyme V (AAC(3)V) is produced by > 90% of aminoglycoside-resistant Escherichia coli isolates from Hong Kong. A gentamicin resistance determinant from a conjugative plasmid carried by one of these E. coli strains producing AAC(3)V was cloned as a 6-kb fragment in the PstI site of the Bluescript II KS-phagemid vector. A 0.8-kb SphI-SalI fragment from the cloned insert was used as a probe in an epidemiological study. The specificity of this probe was evaluated by colony hybridization with 17 control strains producing different known aminoglycoside resistance enzymes. Hybridization was observed only with strains producing AAC(3)V. The probe demonstrated the presence of the AAC(3)V gene in 95.5% to 133 gentamicin-resistant E. coli isolates. This result agreed with the earlier data on the distribution of this enzyme that were based on the susceptibility profile.

Use of PCR in routine diagnosis of treated and untreated pulmonary tuberculosis

AIMS

To assess the routine use of a polymerase chain reaction (PCR) assay for the direct detection of Mycobacterium tuberculosis in expectorated sputum specimens.

METHODS

A pair of primers (20-mer) were designed to amplify the 38 kilodalton protein of M tuberculosis. The specificity of the assay was evaluated in 31 M tuberculosis strains, 15 atypical mycobacterium species, and several commensal bacteria of the upper respiratory tract. The assay was subsequently applied to 519 sputum specimens from 85 inpatients of a chest hospital in Hong Kong.

RESULTS

An amplified product of 239 base pairs was found in all M tuberculosis strains, standard strains of M bovis, and M africanum but not in the other bacterial strains tested. For the 51 patients with pulmonary radiographic lesions, the diagnosis of pulmonary tuberculosis was subsequently confirmed by both culture and PCR in 41 of them. Five patients who were treated before admission were positive by PCR alone. All but one patient in the control group (patients with acute exacerbation of chronic obstructive airway diseases) or those with atypical mycobacterial diseases were PCR negative. The PCR remained positive after four weeks of anti-tuberculosis treatment in 29 patients, 16 of whom had become culture negative.

CONCLUSION

This PCR assay is a useful technique for the diagnosis of untreated and recently treated cases of pulmonary tuberculosis.

Polymerase chain reaction for the detection of Neisseria gonorrhoeae in clinical samples

AIMS

To evaluate the use of a cppB gene derived polymerase chain reaction (PCR) assay for direct detection of Neisseria gonorrhoeae in clinical samples.

METHODS

A PCR assay was performed on 33 N gonorrhoeae strains and 12 other Neisseria species and other normal genital flora to evaluate the specificity of the chosen cppB primers. The assay was subsequently evaluated with 52 clinical swab samples collected from China.

RESULTS

An amplified product of 390 base pairs (bp) was observed with all the N gonorrhoeae strains, each of these products on digestion with the restriction enzyme MspI produced two bands of 250 bp and 140 bp respectively. This set of primers did not produce any amplified product of the expected length with the other non-gonococcal strains tested. For the 52 clinical swabs, 34 were culture positive and PCR successfully detected all these positives. In addition the PCR was positive for two swabs which were culture negative but positive for N gonorrhoeae antigens when tested with the ELISA method (Gonozyme).

CONCLUSIONS

This PCR assay is a promising diagnostic tool for detection of gonococci directly from clinical swab samples. Further evaluation is necessary.

A one-year survey of campylobacter enteritis and other forms of bacterial diarrhoea in Hong Kong

The following enteropathogens were isolated from the faeces of 769 (10.2%) of 7,545 patients of whom 5,704 had diarrhoea or abdominal pain, attending a teaching hospital in Hong Kong during one year: salmonellae 458 (6.1%); Vibrio parahaemolyticus 125 (1.7%); campylobacters 108 (1.4%); shigellae 83 (1.1%); others 19 (0.3%). Further identification of the campylobacter isolates showed that 63 (58%) were Campylobacter jejuni biotype 1, 44 (41%) were C. coli and only one was C. jejuni biotype 2. Seventy-five (69%) of the 108 campylobacters were isolated from children under two years of age, mostly during the second year of life. Faecal specimens from 1,841 children under the age of two years without gastrointestinal symptoms yielded almost the same percentages of salmonellae, campylobacters and shigellae as children with diarrhoea. Salmonellae, shigellae and vibrios were isolated most often in the hot late summer months (August to October), but, contrary to the pattern in Europe and North America, both C. jejuni and C. coli were most prevalent in the coolest months of the year (January to March). The reasons for this "reversed' trend are unknown.