Weekly Concomitant Boost in Adjuvant Radiotherapy for Patients with Early Breast Cancer: Preliminary Results on Feasibility

Abstract

Aims and background

Recent advances in the management of patients with breast cancer are focused toward the reduction of overall treatment time of radiotherapy by delivering a dose biologically equivalent to a standard schedule. The aim of the present study was to evaluate the feasibility and preliminary toxicity of a moderately hypofractionated whole breast irradiation schedule with the addition of a concomitant boost delivered to the tumor bed once-a-week in patients with early breast cancer submitted to conservative surgery.

Materials

We selected patients with pT1c and pT2 N0/N+ M0 carcinoma of the breast with negative surgical margins. The basic course consisted of 4600 cGy prescribed to the ICRU 50 reference point dose and delivered in 20 fractions, 4 times a week for 5 weeks. Once a week, immediately after whole breast irradiation, a concomitant photon boost of 120 cGy was delivered to the lumpectomy area. Overall, according to the linear-quadratic model, the schedule provides a biologically equivalent dose of 87 Gy for breast tumor (assuming α/β = 4 Gy), of 66 Gy for acute responding normal tissues (assuming α/β = 10 Gy), and 99 Gy for late responding normal tissues (assuming α/β = 3 Gy). Biologically, the schedule compares favorably with the 6-week conventional regimen consisting of 50 Gy, 2 Gy/fraction, followed by a 10 Gy boost (BED_tumor,90 Gy; BED_{acute effects}, 72 Gy, and BED_{late effects}, 100 Gy).

Results

From November 2004 to April 2007, we tested this radiotherapy schedule in 176 patients. All enrolled patients had achieved a minimum follow-up of 6 months and were considered in detail for the evaluation of feasibility. Three clinical examinations were performed by a group of independent physicians at treatment end, after 1 month and after 6 months. According to the RTOG/EORTC Toxicity Criteria, of the 176 assessable patients at the end of radiotherapy, 58% showed grade 0–1 skin toxicity, 30% grade 2 and 12% grade 3. At one month of follow-up, grade 0 toxicity was observed in 47% of cases, grade 1 in 46% and grade 2 in 7%. At 6 months, late (skin and subcutaneous tissue) toxicity was assessed with the following scores: grade 0 in 68%, grade 1 in 26% and grade 2 in 6% of the patients. At 6 months, cosmesis was excellent, good and fair in 71%, 24% and 5% of patients, respectively.

Conclusions

The explored adjuvant schedule planned to intensify the radiotherapy course for patients with early breast cancer by adding a weekly concomitant boost appears to be feasible and provides low local toxicity and excellent to good short-term cosmetic results.