Comparison of Acute Skin Reaction between Short Course and Conventional Fractionation Radiotherapy in Breast Conserving Therapy with Skin Dose Measurement

Abstract

We have conducted a clinical trial to evaluate the short course whole breast irradiation to be equally effective and safe with conventional fractionation. In this study, we compared acute skin reactions in both arms with film dosimetry. The patients with stage 0 to II of breast cancer, after lumpectomy or quadrantectomy with sentinel lymph node biopsy or axillary node dissection, positive lymph nodes less than 3, and no concurrent chemotherapy were eligible for this study. Prior to the treatment, all patients were explained about the two treatment schedules and decided by the patient's free selection. The short course irradiation (SCI) consisted of 43.2Gy/16f to the whole breast with additional tumor bed boost of 8.1Gy/3f for positive or less than 5mm surgical margins. The conventional course irradiation (CCI) consisted of 50Gy/25f to the whole breast with additional tumor bed boost of 10Gy/5f for positive or less than 5mm surgical margins or 6Gy/3f in negative surgical margins which has been our standard of care. All breasts were irradiated with 4 MV photon, tangential fields using electronic tissue compensation. The acute adverse effects were observed weekly during treatment and 1 and 2 week after the completion of treatment and scored by CTCAE v3.0. Film dosimetry was performed using radiochromic film (Gafchromic EBT) at 3 settled points, point 1: 5cm away from nipple in upper-outer quadrant, point 2: 5cm away from nipple in inner-lower quadrant, point 3: just above nipple. The average doses of the points were calculated in each arm. BED was calculated using α/β ratio=10.6 in each arm (Zeman, 2007). Between 1st of April 2006 and 31st of December 2008, 767 cases were registered. Among them, 419 cases (54%) were SCI and 348 cases (46%) were CCI. The cases with tumor bed boost of 8.1Gy in SCI were 160 cases (38%), 6Gy and 10Gy were 159 cases (45%) and 189 cases (55%) in CCI, respectively. Grade 2 acute skin reactions were observed in 9 cases (2%) in SCI and 70 cases (20%) in CCI (p < 0.001). The factors affecting acute skin reactions were menopausal status (post was significantly low. p < 0.001). The average skin doses at point 1, 2, and 3 in 9 patients were 1.22Gy, 0.91Gy, 0.80Gy, and 0.87Gy in SCI and 1.09Gy and 1.18Gy in CCI, respectively. The CCI/SCI skin dose ratio at 3 points was 1.34, 1.36, and 1.35, respectively. Whole course BEDs of skin at point 1, 2 and 3 were 21.7Gy 19.1Gy, 21.0Gy in SCI and 24.8Gy, 21.5Gy, 23.6Gy in CCI, respectively. The BED differences between two arms were 3.0, 2.4, and 2.6 at each point. The short course whole breast irradiation is superior for less skin dose and less acute skin reaction.