Efficacy of Long Term Trimethoprim & Sulfamethoxazole (Bactrim) Therapy in Prevention of Late Implant Infections in the Radiated Chest Wall
Michelle Lee, Seema S. Sonnad, PhD, Joseph M. Serletti, MD.
University of Pennsylvania, Philadelphia, PA, USA.
Background: Prosthetic implants are widely used in breast reconstruction. A significant post-operative complication is implant infection. Nahabedian et al. demonstrated that radiation therapy to the chest wall is the only statistically significant factor associated with implant infection. The issue of antimicrobial prophylaxis in the post-operative period remains controversial. The purpose of this study is to determine the efficacy of long term Trimethoprim & Sulfamethoxazole (Bactrim) therapy in preventing late implant infections in the radiated chest wall.
Methods: A retrospective review of 51 implant reconstructions by a single surgeon between 2005-2008 was performed. Only patients with previous radiation therapy to the chest wall and subsequent implant breast reconstruction were included. In 2007, the senior author changed his post-operative management: since then, all of his patients with previous radiation therapy to the chest wall and subsequent implant reconstruction have been placed on prophylactic TMP/SMX for 30 days post implant insertion. The study population was subdivided into 2 groups: 26 implant reconstructions without post-operative TMP/SMX prophylaxis (No TMP/SMX Group) and 25 implant reconstructions with 30 days of TMP/SMX prophylaxis (TMP/SMX Group). Population variables include age, BMI and past medical history - hypertension, diabetes, pre-operative and post-operative chemotherapy, and history of smoking. The operative variable is peri-operative antibiotic prophylaxis. The post-operative variable is the type of antibiotic prophylaxis. The outcome variable is implant infection. Statistical analysis included Chi-Squared Analysis and Kaplan Meier Estimator.
Results: A total of 51 post-radiation implant reconstructions were performed on 46 patients between 2005-2008. The mean age of the population was 47, range 23-70 years old. There was no difference in age, BMI, smoking history, pre-operative chemotherapy, hypertension and diabetes between No TMP/SMX Group and the TMP/SMX Group. The No TMP/SMX Group had a higher rate of implant infections (35% v 8%, p = 0.021). The No TMP/SMX Group was further subdivided into 2 groups: 19 implant reconstructions received short term (5-7 days) antibiotics prophylaxis consisting of mostly first generation cephalosporin (Other Antibiotics Group) and 7 received no post-operative antibiotic prophylaxis (No Antibiotics Group). The Other Antibiotics Group had a higher rate of infection than the TMP/SMX Group (42% v 8%, p = 0.0075).
Conclusion: Among patients with previous radiation to the chest wall, long term Trimethoprim & Sulfamethoxazole (Bactrim) prophylaxis is more effective in preventing late implant infections than other tested modalities. Specifically, it is more effective than short-term first generation cephalosporin, which is commonly used to prevent implant infection.