Phase III randomised trial
Does an integrated boost increase acute toxicity in prone hypofractionated breast irradiation? A randomized controlled trial

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Abstract

Background and purpose

The safety of a simultaneous integrated boost (SIB) in combination with prone hypofractionated whole-breast irradiation (WBI) was investigated.

Materials and methods

167 patients were randomized between WBI with a sequential boost (SeB) or SIB. All patients were treated in prone position to 40.05 Gy in 15 fractions to the whole breast. In the control arm, a SeB of 10 Gy in 4 fractions (negative surgical margins) or 14.88 Gy in 6 fractions (transsection) was prescribed. In the experimental arm a SIB of 46.8 or 49.95 Gy (negative and positive surgical margins, respectively) was prescribed.

Results

Patient age was the only significantly different parameter between treatment arms with patients in the SIB arm being slightly older. In both arms, 6/83 patients developed moist desquamation. Grade 2/3 dermatitis was significantly more frequent in the SeB arm (38/83 vs 24/83 patients, p = 0.037). In the SIB and SeB arm, respectively, 36 patients (43%) and 51 patients (61%) developed pruritus (p = 0.015). The incidence of oedema was lower in the SIB arm (59 vs 68 patients), but not statistically significant (p = 0.071).

Conclusions

The primary endpoint, moist desquamation, was not significantly different between treatment arms.

Section snippets

Patients

As illustrated in the Consort diagram (Fig. 1), 168 patients were included after breast conserving surgery for early-stage breast carcinoma. 151 patients were treated at Ghent University Hospital (UZ Gent) and 17 at Liège University Hospital (CHU Liège). The study was approved by the Ethics Board of both hospitals and registered at clinicaltrials.gov (NCT01973634). Exclusion criteria were: mastectomy, lymph node irradiation, no boost dose planned according to the institution’s practice

Results

Patient and treatment characteristics of the 167 analysed patients are shown in Table 1. Patients in the control arm were slightly older (mean age 59.5 years versus 55.7 years in the experimental arm, p = 0.028). The other variables were not significantly different between treatment arms.

The analysis of dose parameters was done on 163 patients (80 patients in the control arm and 83 patients in the SIB arm). Reasons for excluding patients were electron boost (2), 3 different plans on 3 different CTs

Discussion

Strong evidence now exists that breast cancer cells are as sensitive to fraction size as healthy tissues [25], justifying the use of hypofractionation schemes lowering the total dose but increasing the dose per fraction. WBI in 15–16 fractions is standard practice in the United Kingdom for several years now. After publication of the 10 year results of the UK and Canadian randomized trials, showing excellent efficacy and less long-term side effects of these schemes compared to more protracted

Conclusion

No difference was observed between treatment arms in the rate of moist desquamation, the primary endpoint of the trial. A SIB in combination with prone hypofractionated WBI appears to be a safe treatment regarding acute toxicity, but long-term data have to be awaited.

Conflict of interest statement

The authors report no conflict of interest.

Acknowledgements

This work was financed through Cancer Plan Action 29 (project 015 and 008) by the Federal Public Service of Health, Food Chain Safety and Environment, Belgium. Liv Veldeman is funded by a grant of Kom op tegen Kanker (Clinical Mandate). Christel Monten and Tom Vercauteren are recipients of a grant from the Clinical Research Fund of Ghent University Hospital. Special thanks to Karolien Roelants who was responsible for the artwork.

References (32)

Cited by (27)

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    In the FAST-FORWARD trial, the boost was given in additional fractions after whole breast radiotherapy, adding at least one week to the treatment [10]. A further decrease in OTT can be achieved by a simultaneously integrated boost (SIB) to the tumor(bed) in the treatment without decreasing cosmesis or increasing acute and late toxicity [15–17]. Using NART in 5 fractions with SIB should result in even a shorter OTT, since the waiting time between surgery and RT is omitted.

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    The study by Paelinck et al concentrated on the development of moist desquamation as the primary endpoint after prone hypofractionated WBI with seqB or SIB, and similar to the current study, it reported no significant differences between the treatment arms.30 To date, only acute toxicity has been published to our knowledge, and results are difficult to compare, as all patients were treated in prone and not supine positions in all of the aforementioned studies.30 The largest prospective study tested hypofractionated radiation therapy with 40.5 Gy in 15 fractions 5 days per week to the whole breast, after randomization to a concomitant daily boost to the tumor bed of 0.5 Gy or a weekly boost of 2 Gy on Friday.32

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