Five fraction accelerated partial breast irradiation using noninvasive image-guided breast brachytherapy: Feasibility and acute toxicity

PurposeTo improve efficiency, convenience, and cost, a prospective phase II trial was initiated to evaluate accelerated partial breast irradiation delivered with noninvasive image-guided breast brachytherapy (NIBB) via five once-daily fractions.Methods and MaterialsWomen ≥50 years old with early-stage breast cancer undergoing breast conserving surgery were enrolled. Eligibility criteria included invasive carcinoma ≤2.0 cm or ductal carcinoma in situ ≤3.0 cm, ER positive (if invasive), lymph node negative, LVI absent, and margins negative by 2 mm. Patients received a total dose of 28.5 Gy in five daily fractions. NIBB was delivered using two orthogonal axes for each fraction. Applicators were selected to encompass the lumpectomy cavity with a 1.0 cm clinical target volume margin and 0 to 0.5 cm planning target volume margin. Acute and late toxicity was assessed based on CTCAE v3.0.ResultsForty patients with a mean age of 67 years underwent protocol treatment. Mean tumor size was 1.0 cm (0.3–2.0 cm). Eighty percent had invasive carcinoma and the remainder had ductal carcinoma in situ. Mean tumor bed volume was 21 cc (5–79 cc) and mean breast volume was 1319 cc (499–3044 cc). Mean breast separation with compression was 6.7 cm (3.5–8.9 cm). All patients tolerated well. Median discomfort with compression was 1 (range: 0–7) on a 10-point pain scale. Acute skin reaction was Grade 0–1 in 70%, Grade 2 in 28%, and Grade 3 in 3%. Acute skin toxicity was not associated with breast size but was associated with larger breast separation with compression (p < 0.01) and larger applicator size (p < 0.01). No Grade 3+ late toxicity or local recurrences have been observed at a median followup of 14 months.ConclusionsAccelerated partial breast irradiation delivered using NIBB over five daily fractions is a convenient treatment option that is feasible and well tolerated.