Abstract: We included 11 cohort studies, evaluating a total of 6502 participants undergoing 7018 procedures: 2529 underwent a nipple-sparing mastectomy (NSM), 818 underwent skin-sparing mastectomy (SSM) and 3671 underwent traditional mastectomy, also known as modified radical mastectomy (MRM). No participants underwent areola-sparing mastectomy. There was a high risk of confounding for all reported outcomes. For overall survival, the hazard ratio (HR) for NSM compared to SSM was 0.70 (95% CI 0.28 to 1.73; 2 studies; 781 participants) and the HR for NSM compared to MRM was 0.72 (95% CI 0.46 to 1.13; 2 studies, 1202 participants). Local recurrence was evaluated in two studies, the HR for NSM compared to MRM was 0.28 (95% CI 0.12 to 0.68; 2 studies, 1303 participants). The overall risk of complications was different in NSM when compared to other types of mastectomy in general (RR 0.10, 95% CI 0.01 to 0.82, 2 studies, P = 0.03; 1067 participants). With respect to skin necrosis, there was no evidence of a difference with NSM compared to other types of mastectomy, but the confidence interval was wide (RR 4.22, 95% CI 0.59 to 30.03, P = 0.15; 4 studies, 1948 participants). We observed no difference among the three types of mastectomy with respect to the risk of local infection (RR 0.95, 95% CI 0.44 to 2.09, P = 0.91, 2 studies; 496 participants). Meta-analysis was not possible when assessing cosmetic outcomes and quality of life, but in general the NSM studies reported a favourable aesthetic result and a gain in quality of life compared with the other types of mastectomy. The quality of evidence was considered very low for all outcomes due to the high risk of selection bias and wide confidence intervals. The findings from these observational studies of very low-quality evidence were inconclusive for all outcomes due to the high risk of selection bias.

Plain-language summary: The evidence is current to September 2014. We included 11 studies involving 6502 participants having 7018 surgical procedures (some participants had surgery on both breasts). Out of these, 2529 participants underwent nipple-sparing mastectomy, while there were no participants who had an areola-sparing mastectomy, 818 participants underwent skin-sparing mastectomy and 3671 underwent a traditional mastectomy. All participants in the studies were women and most of them (99.2%) had invasive breast cancer or ductal carcinoma in situ. We compared nipple-sparing mastectomy to conventional mastectomy and skin-sparing mastectomy in two different analyses. It was not possible to conclude whether or not survival following nipple-sparing mastectomy was similar to traditional mastectomy and skin-sparing mastectomy. Results were also inconclusive for differences in local recurrence and adverse events following different types of mastectomy. In practice the decision to select nipple-sparing mastectomy over other types of mastectomy should be done through shared decision making after extensive discussion of the risks and benefits. Generally the nipple-sparing mastectomy studies reported a favourable aesthetic result and a gain in quality of life compared with the other types of mastectomy. However, due to the lack of numerical data, it was not possible to pool the results of different studies. The quality of the evidence included in this review was very low. The studies had a number of methodological flaws. Poor reporting meant that the effect of the type of mastectomy on survival could not be determined for a number of studies. Also, differences between surgery groups in tumour stage and whether or not adjuvant radiotherapy was used may have affected the results. This is likely to have an impact on the findings and future research is likely to change the current findings.