Do surgical margins matter after mastectomy? A systematic review.

BACKGROUND: No consensus exists regarding adequacy of margins after mastectomy. To determine if pathological margin proximity is associated with local (LR) or distant recurrence after mastectomy for early invasive breast cancer or ductal carcinoma in situ. METHODS: A systematic review of literature published from 1980 to 2019 and meta-analysis was conducted. Unpublished data were sought from authors (PROSPERO (CRD42019127541)). Thirty-four studies comprising 34,833 breast cancer patients were included in the quantitative synthesis. Eligible studies reported on patients undergoing curative mastectomy for cancer allowing estimation of outcomes in relation to margin status/width. The association between pathological margin status and local (LR) and distant recurrence was considered using random effects modelling. PRISMA guidelines were followed. RESULTS: Positive margins were associated with increased LR on multivariable analyses (HR, 2·64, (95%CI 2·01-3·46)) and LR was higher regardless of the distance of tumour from the margin defined as positive. After skin-sparing mastectomy, positive margins were associated with increased LR (HR 3·40, (95%CI 1·9-6·2)). In the 4 studies reporting distant recurrence, patients with involved margins had a higher risk (HR 1·53, (95%CI 1·03-2·25)). CONCLUSIONS: Failure to achieve clear margins after mastectomy may increase the risks of local and distant recurrence. Adequate margin clearance should be recommended to minimize recurrence after mastectomy in National and International Guidelines.

The effects of temperature on the biophysical properties of optic nerve F-fibres.

In multiple sclerosis, exacerbation of symptoms with rising body temperature is associated with impulse conduction failure. The mechanism is not fully understood. Remarkably, normal optic nerve axons also show temperature dependent effects, with a fall in excitability with warming. Here we show two properties of optic nerve axons, accommodation and inward rectification (Ih), respond to temperature changes in a manner consistent with a temperature dependent membrane potential. As we could find no evidence for the functional expression of KV7.2 in the axons, using the K+ channel blocker tetraethylammonium ions, we suggest this may explain the membrane potential lability. In order to understand how the axonal membrane potential may show temperature dependence, we have developed a hypothesis involving the electroneutral movement of Na+ ions across the axon membrane, that increases with increasing temperature with an appropriate Q10. Part, but probably not all, of the electroneutral Na+ movement is eliminated by removing extracellular Cl- or exposure to bumetanide, consistent with the involvement of the transporter NKCC1. Numerical simulation suggests a change in membrane potential of - 15-20 mV mimics altering temperature between room and physiological in the largest axons.