A Feasibility Study to Evaluate Intensity Modulated Radiation Therapy (IMRT) for Concomitant Boost Breast Radiotherapy (CBRT)
Rather than a sequential boost, we propose delivering a concomitant boost using intensity
modulated radiotherapy (IMRT). IMRT is a sophisticated technique deliberately using multiple
non-uniform beams, resulting in complex, conformal dose distributions. This technique offers
several advantages. A concomitant IMRT boost potentially offers improved dose distributions
by allowing more conformal doses around the boost volume and increased sparing of the
remaining breast and adjacent organs at risk. Several studies have shown better target dose
homogeneity resulting in less toxicity with adjuvant breast IMRT . One study found a
significant reduction in the rates of moist desquamation with IMRT compared to wedged
tangential fields (31% vs. 48%, P=0.0014).
Longer treatment duration increases the inconvenience and decreases patient compliance.
Furthermore, this places extra financial and emotional hardship on the patient and her
family, particularly if they must travel long distances between home and the treatment
centre. Studies have found 10-30% of patients do not receive adjuvant radiotherapy after
lumpectomy,placing these patients at higher risk for local recurrence and death from
disease. Radiobiologically, a boost increases the risk of late normal tissue effects. In the
EORTC study, they found significantly higher but limited rates of severe fibrosis at 10
years of 4.4% vs. 1.6% (p<0.0001) with the boost. No age effect was noted on the incidence
of fibrosis. One study compared a shorter hypofractionated schedule of 42.5 Gy/16 fractions
over 3.5 weeks with the standard schedule of 50 Gy/25 fractions over 5 weeks and observed
comparable 5 year local recurrence rates and cosmetic outcomes.
Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment
To evaluate the feasibility of delivering 42.5 Gy to the breast with a concomitant 10 Gy boost to the tumour bed in 16 fractions without major treatment deviation.
Fei-Fei Liu, MD
University Health Network, Princess Margaret Hospital
Canada: Ethics Review Committee
UHN REB 07-0594-C