Probabilistic exposure assessment of operator and residential exposure; a Canadian regulatory perspective

An overview of the considerations central to selection of probabilistic versus deterministic approaches to assessment of operator and residential exposure are provided. From a regulatory perspective, the decision to use probabilistic over deterministic assessments should include consideration of factors such as the nature of the populations being assessed, including the expected duration and frequency of their exposures, as well as an understanding of the toxicity endpoints that the exposure assessment will be linked to during risk assessment. In situations where there is an identifiable need to characterize variability and uncertainty and/or quantify the exposure that will represent most of the exposed population, and where there are adequate data to characterize input parameters, probabilistic assessments may be appropriate. Issues with respect to probabilistic assessments for which detailed, harmonized guidance are required are outlined. These issues are discussed within the context of a tiered approach to exposure and risk assessment.

Unequal homologous recombination of human DNA on a yeast artificial chromosome

We examined unequal homologous DNA recombination between human repetitive DNA elements located on a yeast artificial chromosome (YAC) and transforming plasmid molecules. A plasmid vector containing an Alu element, as well as a sequence identical to a unique site on a YAC, was introduced into yeast and double recombinant clones analyzed. Recombination occurs between vector and YAC Alu elements sharing as little as 74% identity. The physical proximity of an Alu element to the unique DNA segment appears to play a significant role in determining the frequency with which that element serves as a recombination substrate. In addition, cross-over points of the recombination reaction are largely confined to the ends of the repetitive element. Since a similar distribution of crossover sites occurs during unequal homologous recombination in human germ and somatic tissue, we propose that similar enzymatic processes may be responsible for the events observed in our system and in human cells. This suggests that further examination of the enzymology of unequal homologous recombination of human DNA within yeast may yield a greater understanding of the molecular events which control this process in higher eukaryotes.

Abstract P4-21-09: Cardiac biomarkers for early detection and prediction of trastuzumab and/or lapatinib-induced cardiotoxicity in patients with HER2 positive early breast cancer (BIG 1-06)

Background:Anti-HER2 agents are associated with an increased risk of cardiotoxicity, occurring mostly during treatment and being generally reversible. To date, no cardiac biomarkers have been validated as predictive markers of cardiotoxicity in patients (pts) receiving anti-HER2 therapies. We evaluated high sensitivity (HS) troponin T (TnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) in pts treated with neoadjuvant anti-HER2 therapies to evaluate if early elevation of cardiac biomarkers predicts early or late cardiac events.

Material and Methods: 455 pts were randomized to receive either lapatinib (154 pts), trastuzumab weekly (149 pts), or lapatinib with trastuzumab for a total of 6 weeks (152 pts). After this biological window, pts continued on the same targeted therapy plus 12-weekly paclitaxel until definitive surgery. After surgery, patients received adjuvant FEC (3x) followed by the same HER2 therapy as in the neoadjuvant phase for further 34 weeks (to complete 52 weeks in total). Eligible pts had an LVEF ≥50%. Cardiac biomarkers were centrally tested in plasma samples collected at baseline, week 2 (W2) and at surgery. Elevated biomarker was defined as either TNT >0.015 μg/L or NT-proBNP >125 pg/mL. The small number of pts and rarity of marker elevations allowed only descriptive analyses.

Results: At a median follow-up of 3.8 years, 280 pts had cardiac biomarkers tested at baseline (61.5%) and NT-proBNP was elevated in 39 pts (13.9%) while TNT was elevated in only 1 pt (0.35%). From those 39 pts with NT-proBNP elevated at baseline, only 1 pt experienced a cardiac event. Also, hypertension was presented in 14 pts (24.5%) with elevated NT-proBNP.

Serial measurements were available in 173 pts (61.7%) and NT-proBNP was elevated in 25, 10 and 21 pts at baseline, W2 and at surgery, respectively, while among 171 pts (61%) TNT was elevated in 1, 1 and 5 pts, respectively.

There were 13 cardiac events in 11 pts in the entire trial. Five of these pts had a measurement of cardiac biomarkers at baseline (non-elevated NT-prBNP and TNT were observed in 4 and 5 pts), 9 of them had a measurement at week 2 (non-elevated NT-prBNP and TNT were observed in 8 and 9 pts) and 3 of them at surgery (non-elevated NT-prBNP and TNT were observed in 3 and 3 pts), respectively. The following table show the low specificity of the cardiac biomarkers.

 Patients without cardiac event (N)Patients with cardiac event (N)Patients with elevated markerElevated NT-proBNP   Baseline38139Week 229130Surgery40040Elevated TNT   Baseline101Week 2101Surgery606

During adjuvant phase, 13 pts experienced LVEF drop to <50% and none had either NT-proBNP elevated or TNT at surgery.

Conclusions: Despite the small sample size, we demonstrated that cardiac biomarkers are rarely elevated in pts receiving anti-HER2 therapies, which is probably due to the absence of myocyte necrosis with respect to TNT, and the lack of chamber dilation in the case of NT-proBNP after exposure to these drugs. In addition, few cardiac events were present in this population not previously exposed to anthracycline-based chemotherapy; therefore the use of cardiac biomarkers in this population may be unnecessary.

Citation Format: de Azambuja E, Bradbury I, Ewer M, Campbell C, Zardavas D, Ameels H, Baselga J, Huober J, Izquierdo M, Bozovic-Spasojevic I, Maetens M, Harbeck N, Pusztai L, Piccart M, Rodeheffer R, Sutter T. Cardiac biomarkers for early detection and prediction of trastuzumab and/or lapatinib-induced cardiotoxicity in patients with HER2 positive early breast cancer (BIG 1-06) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-09.

[Guidance to parent of black babies with a cleft lip and palate]

There are indications that the parents of babies with a cleft lip and palate often require more information regarding their baby's birth defect than what is given to them. In South Africa shortcomings exist in the literature covering the specific requirements of parents of black cleft lip and palate babies. In this study the unique requirements of parents of black cleft lip and palate babies was determined and, based on these results, an information pamphlet was prepared for this population group. Based on the results obtained with the help of fifteen participants it was established, firstly, that the needs of black South-African parents of children with a cleft lip and palate are similar to the needs of parents of babies with the same birth defect world-wide. Secondly, it was established that the information pamphlet which was compiled as part of the study made a positive contribution to parent guidance conducted with the participants. Important therapeutic implications were also reflected by the results.

Short term neonatal starvation altered cholera toxin binding in rabbits

Acute neonatal malnutrition alters lumenal glycoproteins as demonstrated by altered lectin binding. To determine the effect of a 72-h fast on lumenal glycolipids, specifically the monosialoganglioside GM1, we quantitated cholera toxin (CT) binding and adenylate cyclase activity. The calculated number of specific sites for CT binding to microvillus membrane (MVM) from newborn rabbits fasted for 72 h was decreased in MVM from proximal small bowel (7 +/- 0.8 x 10(8)/micrograms protein) compared to 72-h control neonatal rabbits (18 +/- 3.3 x 10(8) micrograms protein). In distal small bowel there was no difference in the calculated receptor sites/micrograms MVM protein between fasted (8 +/- 1.7 x 10(8)) and fed (11 +/- 4 x 10(8)) groups. MVM prepared from proximal small bowel of fed animals bound significantly more CT than MVM prepared from distal small bowel of fed animals. The affinity for CT was the same in all MVM preparations. Neuraminidase treatment of MVM resulted in increased CT binding in fed and fasted rabbit proximal and distal MVM preparations, but the greatest increase occurred in MVM prepared from proximal small bowel from fasted animals. There was no difference in adenylate cyclase activity in fed, fasted, and proximal or distal small bowel crude membrane preparations. Refeeding (120 h) resulted in normalization of CT binding in MVM from proximal small bowel of fasted animals. We conclude a 72-h fast in neonatal rabbits resulted in decreased regional CT binding in MVM prepared from proximal small bowel of fasted animals, but no change in adenylate cyclase activity. Refeeding reverses CT binding abnormalities.