Interim Cosmetic Results And Toxicity Using 3d Conformal External Beam Radiation Therapy To Deliver Accelerated Partial Breast Irradiation In Patients With Early-Stage Breast Cancer

Concerns with the use of any form of APBI relate to the large fraction sizes administered and a possible increase in the rate of development of late effects. We analyzed toxicity and cosmetics results using three-dimensional conformal external beam radiation therapy (3D-CRT) to deliver accelerated partial breast irradiation in our phase III trial. One hundred patients undergoing breast-conserving surgery were randomized to receive WBRT (n = 51) or APBI (n = 49). The whole breast received 48 Gy with 2-Gy daily fractions, with or without additional 10 Gy irradiation to the tumor bed, depending on local recurrence risk factors. In APBI arm, patients received 37.5 Gy in 3.75 Gy/fraction delivered twice daily. Toxicity results were scored based on the RTOG Common Toxicity Criteria. Late skin toxicity was measured by Multi-Skin-Center MC-750-B2, CKelectronic-GmbH, which allow the users to put together measuring parameters for the skin: pigmentation (melanin), redness (erythema), TEWL (transepidermal waterloss index) and elasticity. Cosmetic results were rated as good/excellent, regular or poor cosmetic result by the treating radiation oncologist and every patient. With a median follow-up of 6 years, no local recurrences were developed. Acute skin effects were noted in 43/49 patients of APBI arm (69.4% grade I and 18.4% grade II) and in all patients of control arm (25.5% grade I, 62.7% grade II and 11.8% grade III). Only one case of grade II acute pneumonitis was noted and it was in one woman of the WBRT arm. As show in the Table, late skin toxicity was similar between two arms and only grades I and II late effects were reported. Elasticity was lower in highest doses area (boost or quadrant) than in ipsilateral breast. Taking into account only this area, elasticity was lower in WBRT arm than in APBI arm. Delivery of APBI with 3D-CRT resulted in minimal chronic (>6 months) toxicity to date with good/excellent cosmetic results. Additional follow-up is needed to assess the long-term efficacy of this form of APBI. Therefore, this noninvasive approach may increase the availability of APBI to patients with early-stage breast cancer.Oral Scientific Abstract 215; TableTOXICITYLATE TOXICITYWBRTN (%)APBIN (%)6 MONTHS Grade I6 (13)5(13) Grade II1(2)01 YEAR Grade I2(5.2)4(11.4) Grade II2 (5.2)0(0)2 YEARS Grade I1(3)2(6.7) Grade II01(3.3)3 YEARS Grade I1(4.2)4(14.3) Grade II00 Open table in a new tab