Partial breast irradiation in breast conserving therapy by way of intersitial brachytherapy.

Objective: To examine early and late toxicities, evaluate cosmetic results, and determine the need for reoperation or additional diagnostic procedures in patients treated with accelerated partial breast irradiation (APBI) delivered by way of an interstitial implant in breast-conserving therapy.

Methods: A total of 199 patients with stage I or II breast cancer were managed with lumpectomy followed by radiation restricted to the tumor bed using an interstitial implant (APBI). Retrospective analyses were performed for early and late toxicities (infection, fat necrosis, breast pain, edema, erythema, fibrosis, pigmentation changes, and telangiectasias), need for reoperation or additional diagnostic procedures, cosmetic results, and local control. Patient selection criteria by the surgeon for referral to RT for APBI included age, tumor size, histology, nodal status, margin status, and absence of extensive intraductal component. Treatment was delivered with either a low-dose or high-dose rate implant. Median follow-up was 5.7 years, and 54% of the patients were followed-up for >7 years.

Results: Infections developed in 22 of 199 (11%) patients: 7% early (1 month after implant removal). Five of the 22 patients (2% of all patients) required operative intervention for the infection, either incision and drainage or debridement. There was a statistically significant difference between infection rates with open (8.5%) versus closed (2.5%) cavity placement of the interstitial needles (P = 0.005). There was no statistically significant difference between low-dose rate (inpatient) and high-dose rate (outpatient) treatment (P = 0.207). Forty-five patients (23%) had an additional diagnostic procedure to evaluate a suspicious or uncertain finding on physical examination or mammogram. Fibrosis and fat necrosis were found in 26 of the 45 patients. The incidence of fat necrosis increased with time. More patients were found to have fat necrosis after 5 years. One patient had fat necrosis diagnosed at <6 months; 8 patients (4% of total) at >/=6 months to <2 years; 10 patients (5% of total) at >/=2 years to <5 years; and 22 patients (11% of total) at >/=5 years. The majority of fat necrosis was detected on mammogram (80%) and was asymptomatic (78%). Cosmesis and toxicities were assessed at 3 defined time points: /=5 years of follow-up. Using Harvard criteria, good to excellent cosmetic results were observed in >90% of patients. Breast pain, edema, and erythema diminished with time. Of the 199 cases, there were only 5 ipsilateral breast failures, yielding a 5-year actuarial local recurrence rate of 1.2%. Of these 5 failures, 2 were true recurrences/marginal misses, yielding a 5-year actuarial true recurrence/marginal miss rate of 0.5%. The 5-year actuarial cause-specific survival rate was 99% for APBI patients.

Conclusions: In selected patients with early-stage breast cancer, APBI with targeted interstitial brachytherapy offers 5-year results comparable with conventional breast-conserving therapy employing whole-breast radiation therapy. Minimal long-term toxicities were noted, most of which demonstrated continued resolution over time. Acceptable acute (7%) and delayed (4%) infection rates were observed. Fat necrosis was identified with increasing frequency with time, but the majority was asymptomatic. Cosmetic results are good to excellent (>90%). Continued follow-up by the surgeon will be required to determine the long-term efficacy of this alternative treatment approach.