• Ninja Antonini, Heather Jones, Jean Claude Horiot, Philip Poortmans, Henk Struikmans, Walter Van den Bogaert, Isabelle Barillot, Alain Fourquet, Jos Jager, Willem Hoogenraad, Laurence Collette, Marianne Pierart, Guus Hart, and Harry Bartelink.
• Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
• Radiother Oncol. 2007 Mar 1; 82 (3): 265-71.

PurposeTo determine whether the effect of an additional "boost" radiation after breast conservative therapy (BCT) on local control depends on age and evaluate the impact of a treatment policy with a threshold for age.Patients And MethodsWe used data from EORTC 22881-10882 trial, with median follow-up of 77.4 months. Patients receiving BCT and 50Gy whole breast irradiation were randomized to no boost and 16Gy boost (N=5318).ResultsIn univariate analysis, a boost reduced local failure by a factor of 2 (P<0.0001). Multivariate analysis showed local control increased with age (P=0.0003). There was no evidence that the relative effect of a boost on local control depends on age (P=0.97) However in younger patients the 5-year local failure was higher, therefore the absolute reduction was greater. If the threshold-age for boost treatment were set at 40 years, 8.4% of the study population would receive a boost, resulting in a 5-year local failure of 6.1% in the study population. Changing the threshold-age to 60 years, 67% of the study population would receive a boost and the 5-year local failure would be reduced to 4.4%.ConclusionsIn younger patients a boost dose resulted in a greater absolute reduction of local failure. The relative risk reduction was however similar for all ages. Applying a treatment policy with a threshold-age of 60 would result in 0.6% increase in local failure in the total study population, while sparing the boost to 1/3 of the patients.

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