Effect of age and radiation dose on local control after breast conserving treatment: EORTC trial 22881-10882.
OBJECTIVE
To 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.


METHODS
We 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).


RESULTS
In 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%.


CONCLUSIONS
In 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.
Antonini
Ninja
N
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Jones
Heather
H
Horiot
Jean Claude
JC
Poortmans
Philip
P
Struikmans
Henk
H
Van den Bogaert
Walter
W
Barillot
Isabelle
I
Fourquet
Alain
A
Jager
Jos
J
Hoogenraad
Willem
W
Collette
Laurence
L
Pierart
Marianne
M
Hart
Guus
G
Bartelink
Harry
H
D000328:Adult; D000367:Age Factors; D000971:Antineoplastic Combined Chemotherapy Protocols; D001943:Breast Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy; D003520:Cyclophosphamide; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005472:Fluorouracil; D006801:Humans; D015412:Mastectomy, Segmental; D008727:Methotrexate; D008875:Middle Aged; D015999:Multivariate Analysis; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D016016:Proportional Hazards Models; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D012306:Risk
D003520:Cyclophosphamide; D005472:Fluorouracil; D008727:Methotrexate