Abstract: Five RCTs with 202 participants met the inclusion criteria. The women participants were typically in their 50s, and the majority of them (about 82%) received reconstructive surgery following breast cancer, while the others had reconstructive surgery after prophylactic mastectomy. The studies were heterogenous in terms of implant comparisons, which prevented us from pooling the data. The studies were judged as being at an unclear risk of bias for most risk of bias items owing to poor quality of reporting in the trial publications. Three of the five RCTs were judged to be at high risk of attrition bias, and one at high risk of detection bias. Textured silicone versus smooth silicone implants: textured implants were associated with worse outcomes when compared to smooth implants (capsular contracture: risk ratio (RR) 0.82, 95% CI 0.14 to 4.71; 1 study, 20 participants; very low quality evidence; reintervention: RR 0.82, 95% CI 0.14 to 4.71; 1 study, 20 participants; very low quality evidence). No results in this comparison were statistically significant. Silicone versus saline implants: saline-filled implants performed better than silicone-filled implants for some outcomes; specifically, they produced less severe capsular contracture (RR 3.25, 95% CI 1.24 to 8.51; 1 study, 60 participants; very low quality evidence) and increased patient satisfaction (RR 0.60, 95% CI 0.41 to 0.88; 1 study, 58 participants; very low quality evidence). However reintervention was significantly more frequent in the saline-filled implant group than in the silicone-filled group (OR 0.08, 95% CI 0.01 to 0.43; 1 study, 60 participants; very low quality evidence). Poly(N-vinyl-2-pyrrolidone) hydrogel-filled (PVP-hydrogel) versus saline-filled implants: PVP-hydrogel-filled implants were associated with worse outcomes when compared to saline-filled implants (capsular contracture: RR 3.50, 95% CI 0.83 to 14.83; 1 study, 40 participants; very low quality evidence; short-term complications: RR 2.10, 95% CI 0.21 to 21.39; 1 study, 41 participants; very low quality evidence). Anatomical versus round implants: anatomical implants were associated with worse outcomes than round implants (capsular contracture: RR 2.00, 95% CI 0.20 to 20.15; 1 study, 36 participants; very low quality evidence; short-term complications: RR 2.00, 95% CI 0.42 to 9.58; 1 study, 36 participants; very low quality evidence; reintervention: RR 1.50, 95% CI 0.51 to 4.43; 1 study, 36 participants; very low quality evidence). No results in this comparison were statistically significant. Variable-volume versus fixed-volume implants: data about one-stage reconstruction using variable-volume implants were compared with data about fixed-volume implants positioned during the second surgical procedure of two-stage reconstructions. Fixed-volume implant reconstructions were possibly associated with a greater number of women reporting that their reconstruction corresponded with expected results (RR 0.25, 95% CI 0.10 to 0.62; 1 study, 40 participants; very low quality evidence) and fewer reinterventions (RR 7.00, 95% CI 1.82 to 26.89; 1 study, 40 participants; very low quality evidence) when compared to variable-volume implants. A higher patient satisfaction level (rated from 1 to 6, with 1 being very bad and 6 being very good) was found with the fixed-volume implants for overall aesthetic result (mean difference (MD) -1.10, 95% CI -1.59 to -0.61; 1 study, 40 participants; very low quality evidence). There were no studies that examined the effects of recent (fifth) generation silicone implants versus previous generations or different implant manufacturing companies. Despite the central role of breast reconstruction in women with breast cancer, the best implants to use in reconstructive surgery have been studied rarely in the context of RCTs. Furthermore the quality of these studies and the overall evidence they provide is largely unsatisfactory. Some of our results can be interpreted as early evidence of potentially large differences between different surgical approaches, which should be confirmed in new high-quality RCTs that include a larger number of women. These days - even after a few million women have had breasts reconstructed - surgeons cannot inform women about the risks and complications of different implant-based breast reconstructive options on the basis of results derived from RCTs.

Plain-language summary: The evidence is current to July 2015. We conducted a review to compare short- and long-term surgical complications (such as scar tissue forming around the implant and squeezing it - referred to as 'capsular contracture', and 'implant rupture'), cosmetic outcomes, women's postoperative quality of life and satisfaction with different types of breast implants used in breast reconstruction. We found five randomised studies involving 202 women that provided data for five different comparisons: rough versus smooth surface, implant filler materials compared to each other (silicone versus saline, and hydrogel versus saline), anatomical versus round shape, and variable- versus fixed-volume. Four studies included women who received a mastectomy for breast cancer and one study included women who had bilateral mastectomies for preventive purposes. The authors of two studies reported that they did not have competing interests; the authors of three studies did not report this information. Three studies reported that their studies received financial support from research foundations; the other studies did not report any information regarding the source of their funding. Only two studies reported differences between types of implants for some of the outcomes we considered. One study on 65 women compared silicone-filled implants with saline-filled implants and showed that saline implants resulted in fewer cases of capsular contracture and a higher number of women who were satisfied with the reconstructed breast. However more women in the saline-filled implant group required further operations on the reconstructed breast than in the silicone-filled implant group. Another study on 40 women compared variable-volume implants (inserted in a single surgical procedure) with fixed-volume implants (inserted in the second of two separate surgical procedures) and showed that there were significantly higher satisfaction levels and significantly lower reoperation rates with the fixed-volume implants. The remaining three studies reported on the following comparisons: rough versus smooth silicone-filled implants (20 women), PVP-hydrogel versus saline-filled implants (41 women) and anatomically shaped versus round implants (36 women). These studies reported no differences between implant types for outcomes such as capsular contracture, other short-term complications or reoperation rates. There were no studies that compared recent generation silicone implants with earlier versions or implants from different manufacturing companies. The evidence we found was limited: only a negligible, tiny fraction of women who undergo breast reconstruction have been studied in randomised controlled trials. The quality of evidence is very low, as the studies we identified suffered from major methodological limitations. Despite the fact that several million women have had their breasts reconstructed over the last 20 years, the small number of studies and the low numbers of women included in these studies does not allow us to draw any definitive conclusions about the which is the best type of breast implant. This lack of evidence should be discussed when informing women about the risks and complications of different implant-based breast reconstruction options. There is a need for further studies, which include a larger number of women and compare different types of implants, to free women from decisions made on the basis of surgical opinion alone.