A Phase 2 interventional study of Cephalexin in Breast Cancer, Breast Cancer Female and Genetic Predisposition to Disease, sponsored by University of California, San Francisco. Recruiting at 1 site in United States. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-03-18.
Sponsored by University of California, San Francisco · Phase 2, Interventional, and Supportive care
The most common tissue expander-related infections are from Staphylococcus and Pseudomonas species. In addition, from breast tissue microbiome studies, Staphylococcus and Pseudomonas show variable abundance across samples. The investigator hypothesizes that participants undergoing mastectomy with high initial abundance of Staphylococcus and/or Pseudomonas are more likely to develop subsequent tissue expander-related infections from these respective organisms.
PRIMARY OBJECTIVE:
I. To determine the feasibility of breast microbiome sampling using the study techniques
SECONDARY OBJECTIVES:
I. To define the differences in the gut and breast microbiomes between participants undergoing mastectomy with implant-based reconstruction who develop post-operative implant infection and those who do not.
II. To determine the effects of post-operative antibiotics on the gut and breast microbiomes after mastectomy with implant-based reconstruction.
OUTLINE: Participants are randomized to 1 of 2 cohorts.
COHORT A: Participants receive postoperative antibiotics to take for at least 7 days post-operatively.
COHORT B: Participants receive no antibiotics post-operatively in the absence of clinical evidence of infection.
Participants are followed up for 90 days.
12,544 studies on the registry are indexed under Breast Neoplasms; 2,892 are open to participants now.
This study's planned enrollment of 200 is above the median of 72 across 9,303 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →University of California, San Francisco is the lead sponsor of 2,132 studies on the registry; 375 are open to participants now.
Of its 262 completed or terminated interventional studies of FDA-regulated products, 196 (75%) have results posted.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Receive standard pre-incision antibiotics and 24-hour perioperative antibiotics - Prescribed standard postoperative antibiotics to take for at least 7 days post-operatively
Drug: Cephalexin
Receive standard pre-incision antibiotics and 24-hour perioperative antibiotics - No antibiotics post-operatively, unless patient develops clinical evidence of infection
Given orally (PO)
Also known as: Keflex
Proportion of tissue samples obtained successfully over time
The feasibility of success in obtaining samples from breast tissue will be measured as a binary outcome (successful or not successful) over time (intra-operatively, week 1, week 2, week 3, and week 4). The investigators will assess and document success in obtaining a tissue sample immediately at the time of sampling of each participant.
Time frame: 90 days
Proportion of aspirate samples obtained successfully overall
The feasibility of success in obtaining samples from the tissue expander aspiration ports will be measured as a binary outcome (successful or not successful) over time (intra-operatively, week 1, week 2, week 3, and week 4). The investigators will assess and document success in obtaining a aspirate sample immediately at the time of sampling of each participant.
Time frame: 90 days
Proportion of tissue samples successfully producing microbiome data
Feasibility based off of the success rates in producing microbiome data from tissue samples in each patient will be measured as a binary outcome (successful or not successful) and will be reported.
Time frame: 90 days
Proportion of aspirate samples successfully producing microbiome data
Feasibility based off of the success rates in producing microbiome data from tissue samples in each patient will be measured as a binary outcome (successful or not successful) and will be reported.
Time frame: 90 days
Proportion of any samples successfully producing microbiome data
Feasibility based off of the success rates in producing microbiome data from tissue or aspirate samples in each patient will be measured as a binary outcome (successful or not successful) and will be reported.
Time frame: 90 days
Correlation of the change in breast microbiome over time with total duration of antibiotics (Cohort A only)
The investigators will analyze the microbiomes between groups, between microbiome environments (gut v. breast, inter-individual). The correlate of change in breast microbiome over time will be compared to the total duration of antibiotics for Cohort A only. The measure of association ranges from +1 to -1, with a value of zero equal to no association.
Time frame: 90 days
Proportion of participants with post-operative infection
Safety will be assessed by clinically assessing for signs of post-operative infection in each patient at each clinic visit. A post-operative infection is defined by clinical assessment of findings of surgical site erythema, tenderness, edema, and/or purulent drainage +/- fever. Proportion of participants with clinically diagnosed infection will be reported for each group and final diagnosis for analyses will be binary; a participant will either have a post-operative infection in the 90 day post-operative period or not have a post-operative infection in the 90 day post-operative period.
Time frame: 90 days
Shannon Diversity Index Score for species of microbiome
Alpha diversity will be evaluated for species richness by number of operational taxonomic units and for evenness using the Shannon Index. The Shannon diversity index (H) is an index that is commonly used to characterize species diversity in a community and accounts for both abundance and evenness of the species present. The proportion of species (i) relative to the total number of species (pi) is calculated, and then multiplied by the natural logarithm of this proportion (lnpi). The resulting product is summed across species, and multiplied by -1. Shannon's equitability (EH) can be calculated by dividing H by Hmax (here Hmax = lnS). Equitability assumes a value between 0 and 1 with 1 being complete evenness and the overall index score is represented by a percentage of the species.
Time frame: 90 days
Number of overall identified microbes
The investigators will evaluate microbial composition by grouping identified microbes into operational taxonomic units at the species, genera and phyla levels and will compare the relative abundances of these microbes between groups at the species, gene
Time frame: 90 days
Plan to share: No
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University of California, San Francisco