[10] Impact of radiation dose on local control, fibrosis and survival after breast conserving treatment: 10 years results of the EORTC trial 22881-10882.

Bartelink H, Horiot JC, Poortmans P, Struikmans H, van den Bogaert W, Barillot I, Fourquet A, Jager J, Hoogenraad W, Pierart M, Collette L.. The Netherlands Cancer Institute, Amsterdam, Netherlands; Centre Georges-Francois Leclerc, Dijon, France; Dr. Bernard Verbeeten Institute, Tilburg, Netherlands; University Hospital Utrecht, Utrecht, Netherlands; University Hospital Gasthuisberg, Leuven, Belgium; Institute Curie, Paris, France; Radiotherapeutic Institute Limburg, Heerlen, Netherlands; Joint Center for Radiotherapy Arnhem/Nijmegen, St. Radboud Hospital, Nijmegen, Netherlands; EORTC, Brussels, Belgium

Purpose: To investigate the long term impact of a boost radiation of 16 Gy on local control, fibrosis and survival for patients who underwent lumpectomy and whole breast irradiation as part of their breast conserving therapy (BCT) for stage I and II breast cancer.
Patients and methods: 5318 patients with microscopically complete excision followed by whole breast irradiation of 50 Gy were randomized between a boost dose of 16 Gy (2661 patients) and no boost dose (2657 patients). Survival and local control were compared by Logrank and Gray test, respectively (2-sided a=0.01), with a median follow-up of 10.75 years.
Results: The median age was 55 years. Patient and tumor characteristics are well balanced between the two groups, 90% of cases were cN0 and 78% were pN0.
Survival at 10 years was 82% in both arms and did not differ significantly (P=0.93). Local failure was reported as the first failure in 278 vs. 165 patients, regional recurrence as first event in 59 vs. 56, distant failure in 305 vs. 353, contralateral breast cancer recurrence in 120 vs. 136, 2nd primary cancer in 132 vs. 144 and death not due to BC in 93 vs. 85, in the no boost and the boost group, respectively. At 10 years, the cumulative incidence of local recurrence was 10.2% vs. 6.2 % for the no boost and the boost group, respectively (P<0.0001). The absolute risk reduction per age group at 10 years was from 23.9% to 13.5% (Gray test P=0.0014) in the 40year, from 12.5% to 8.7% (Gray test P=0.0099) in the 41-50 year, from 7.8% to 4.9% (Gray test P=0.0157) in the 51-60 year and from 7.3% to 3.8% in the >60 year old (Gray test P=0.0008). The cumulative incidence of severe fibrosis was statistically significant (P< 0.0001) increased in the boost group with 10-year rate of 4.4% versus 1.6% in the no boost group P<0.0001).
Conclusion: A boost irradiation of 16 Gy improved local control at the cost of a small increase of severe fibrosis, while no difference in survival was observed. The benefit in local control at 10 years amounts roughly 10% in patients 40years old or younger, 4% in patients aged 41-50 years, and 3% in patients older than 50 years.

Thursday, December 14, 2006 3:00 PM

General Session 2 (2:00 PM-3:30 PM)