Factors influencing eligibility for breast boost using noninvasive image-guided breast brachytherapy

Noninvasive image-guided breast brachytherapy (NIBB) allows for accurate targeting of the tumor bed (TB) for breast boost by using breast immobilization and image guidance. However, not all patients are candidates for this technique.

Consecutive patients treated for breast cancer were evaluated. Patients with very small breast size (cup ≤ A) for whom immobilization could not be achieved were treated with electrons. All others underwent simulation for NIBB boost. The rate of eligibility for NIBB, reasons for ineligibility, and related patient and anatomic factors were analyzed.

Of 52 patients evaluated, 6 patients were ineligible for NIBB because of small breast size. Of the remaining patients who underwent simulation for NIBB boost, 33 patients (72%) were treated with NIBB. Reasons for ineligibility were the absence of identifiable TB (n = 5), inability to position patient/breast to adequately target the TB (n = 4), posterior TB location (n = 3), and discomfort during compression (n = 1). The likelihood of being eligible for NIBB boost was dependent on breast size: ≤A (0%), B (50%), C (71%), D-DD (77%), and >DD (80%) (p = 0.002). The presence of surgical clips also predicted eligibility for NIBB: 79% clips vs. 45% without clips (p = 0.05). A posterior TB location was not associated with ineligibility (p = 0.2).

NIBB boost is feasible in most patients. Patients with larger breast size are more likely to be good candidates. Posterior TB location can be challenging for NIBB, but most patients are still candidates. Surgical clips are very helpful in defining the TB and greatly increase the likelihood of eligibility for NIBB.