Impact of Photon Beam Energy on Local Failure in Breast Cancer

Purpose: To compare the frequency of local failure between 60Co and 6MV after conservative and radical surgery from a large retrospective series of patients with breast carcinoma.Patients and methods: The criteria for selection from the Centre René Gauducheau database on breast cancer (Berenis) were: primary unilateral adenocarcinoma without detectable metastases; radiation therapy of the breast or chest wall +/− lymph node areas consisting of 45-50 Gy at 1.8-2 Gy/fraction plus a 10 to 15- Gy boost after lumpectomy; local failure within the breast or thoracic wall as first event since initial treatment.The role of beam energy (60Co Vs 6MV), young age ( < Vs> 35y), clinical tumor (cT) (T1 Vs T2 Vs T3 Vs T4), and lymph node (cN)(N0 Vs N1) stage, pathological tumor (pT) and lymph node (pN) stage, SBR grading (1-2 Vs 3), receptors and adjuvant hormonotherapy was evaluated after conservative and radical surgery. The Chi2 test was used for univariate analysis and logistic regression for multivariate analysis.Results: Between 01/85 and 12/97 a total of 1957 patients met the selection criteria including 1489 conservative and 468 radical treatment. Median age at diagnosis was 56 years. Prior to 1991 all patients were treated with 60Co and thereafter either with 60Co or RX 6 MV at the discretion of each physician, making a total of 1470 (76.1%) for 60Co (1156 conservative and 314 radical surgery) and 487 (23.9 %), for RX 6 MV (333 conservative and 154 radical surgery). Median follow-up was 4.9 years. For the entire group 5- year local failure- free survival was 85.2 % (83.1 % for conservative and 92.8 % for radical surgery), and- 5 year overall survival 86.3 % (89.5 % for conservative and 61.9 % for radical surgery). In univariate analysis factors negatively influencing 5 -year local failure- free survival were age < 35 y, cT, cN, pT, pN, SBR 3, ER -, no adjuvant hormonotherapy radical surgery and use of 6MV. In multivariate analysis, only pT, SBR 3, no adjuvant hormonotherapy, radical surgery and 6MV were significant.Despite a shorter follow-up, the local failure rate was significantly increased with RX 6 MV as compared to 60Co in the entire group ( OR = 1.56, p=0.008), mainly after conservative treatment (OR = 1.48, p=0.031). After radical surgery, a difference favoring 60Co was observed but was not significant (OR = 2.01, p=0.1).Conclusion: From this large retrospective study, it appears that local failure rate was increased with RX 6 MV as compared to 60Co. This results led us to recommend the use of the lowest available photon energy to treat breast carcinoma. Purpose: To compare the frequency of local failure between 60Co and 6MV after conservative and radical surgery from a large retrospective series of patients with breast carcinoma. Patients and methods: The criteria for selection from the Centre René Gauducheau database on breast cancer (Berenis) were: primary unilateral adenocarcinoma without detectable metastases; radiation therapy of the breast or chest wall +/− lymph node areas consisting of 45-50 Gy at 1.8-2 Gy/fraction plus a 10 to 15- Gy boost after lumpectomy; local failure within the breast or thoracic wall as first event since initial treatment. The role of beam energy (60Co Vs 6MV), young age ( < Vs> 35y), clinical tumor (cT) (T1 Vs T2 Vs T3 Vs T4), and lymph node (cN)(N0 Vs N1) stage, pathological tumor (pT) and lymph node (pN) stage, SBR grading (1-2 Vs 3), receptors and adjuvant hormonotherapy was evaluated after conservative and radical surgery. The Chi2 test was used for univariate analysis and logistic regression for multivariate analysis. Results: Between 01/85 and 12/97 a total of 1957 patients met the selection criteria including 1489 conservative and 468 radical treatment. Median age at diagnosis was 56 years. Prior to 1991 all patients were treated with 60Co and thereafter either with 60Co or RX 6 MV at the discretion of each physician, making a total of 1470 (76.1%) for 60Co (1156 conservative and 314 radical surgery) and 487 (23.9 %), for RX 6 MV (333 conservative and 154 radical surgery). Median follow-up was 4.9 years. For the entire group 5- year local failure- free survival was 85.2 % (83.1 % for conservative and 92.8 % for radical surgery), and- 5 year overall survival 86.3 % (89.5 % for conservative and 61.9 % for radical surgery). In univariate analysis factors negatively influencing 5 -year local failure- free survival were age < 35 y, cT, cN, pT, pN, SBR 3, ER -, no adjuvant hormonotherapy radical surgery and use of 6MV. In multivariate analysis, only pT, SBR 3, no adjuvant hormonotherapy, radical surgery and 6MV were significant. Despite a shorter follow-up, the local failure rate was significantly increased with RX 6 MV as compared to 60Co in the entire group ( OR = 1.56, p=0.008), mainly after conservative treatment (OR = 1.48, p=0.031). After radical surgery, a difference favoring 60Co was observed but was not significant (OR = 2.01, p=0.1). Conclusion: From this large retrospective study, it appears that local failure rate was increased with RX 6 MV as compared to 60Co. This results led us to recommend the use of the lowest available photon energy to treat breast carcinoma.