Women under 35 years of age with breast cancer can have an almost 20% lower risk of their disease recurring if they are treated using a new radiotherapy regime. These were some of the results presented here today (Tuesday 26th October) by Prof. Harry Bartelink and his colleagues at the 23rd Meeting of the European Society for Therapeutic Radiology and Oncology.
The analyses were based on data from the EORTC (European Organisation for Research and Treatment of Cancer) 22881 trial with updated follow-up (median follow-up: > 6years). 5318 patients with microscopically complete excision of early breast cancer using breast-conserving surgery were randomly assigned to undergo 50Gy irradiation of the whole breast either with or without an additional 16Gy of radiotherapy to the tumour bed (radiotherapy boost). 362 local recurrences were observed: 232 in the no-boost group and 130 in the boost group, demonstrating a considerable improvement in recurrence rate in women treated with boost.
The effect of the boost treatment was of greatest benefit in the younger women, with a reduction in 5-year local disease recurrence rate from 26% to 8.5% in women under 35 years of age. In women over 60 the boost dose resulted in a reduction of 5-year local recurrence rate from 3.9% to 2.1%. The addition of a boost dose caused a slight increase in early and late side effects and increases the burden on already overstretched resources. A balance therefore needs to be struck between providing optimal care with acceptable side effects whilst taking into account the availability of resources.
The trial data was used to estimate the impact on the 5-year local recurrence rate of a treatment policy restricting boost irradiation to patients below a certain age threshold. If no patients received a boost then the overall local recurrence rate would be 6.5%, whilst treating all patients with a boost would result in a recurrence rate of 3.6%. A policy limiting the boost dose to patients 40 years old or younger (or 8.4% of the total) would result in an overall 5-year local recurrence of 5.7% in the whole population. By increasing the threshold to 50 years (boost given to 34% of the total) the 5-year local recurrence rate reduces further to 4.8% - equivalent to the local control achieved by mastectomy.
"This evidence suggests that a 16Gy boost is a tolerable and viable alternative to total mastectomy, achieving similar local recurrence rates as the latter whilst sparing patients the necessity of breast removal", said Prof. Bartelink. "These results are so conclusive that this new approach should be immediately implemented in cancer treatment centres as a new standard of care for women under 51 years old".
"Increasing the amount of radiation given in the boost dose for younger patients, those 50 years old or younger, may improve the results even further. This is currently being investigated in a new trial", said Prof. Bartelink. "Another trial, using microarray molecular technology, is also underway which aims to develop techniques which will predict how individual women will respond to radiotherapy and therefore predict which women should receive a boost dose".
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