Accelerated partial breast irradiation using 3D conformal radiotherapy: Toxicity and cosmetic outcome

Cosmetic Outcomes of a Phase 1 Dose Escalation Study of 5-Fraction Stereotactic Partial Breast Irradiation for Early Stage Breast Cancer

PURPOSE

Our purpose was to evaluate cosmetic changes after 5-fraction adjuvant stereotactic partial breast irradiation (S-PBI).

METHODS AND MATERIALS

Seventy-five women with in situ or invasive breast cancer stage 0, I, or II, with tumor size ≤3 cm, were enrolled after lumpectomy in a phase 1 dose escalation trial of S-PBI into cohorts receiving 30, 32.5, 35, 37.5, or 40 Gy in 5 fractions. Before S-PBI, 3 to 4 gold fiducial markers were placed in the lumpectomy cavity for tracking with the Synchrony respiratory tracking system. S-PBI was delivered with a CyberKnife robotic radiosurgery system. Patients and physicians evaluated global cosmesis using the Harvard Breast Cosmesis Scale. Eight independent panelists evaluated digital photography for global cosmesis and 10 subdomains at baseline and follow-up. McNemar tests were used to evaluate change in cosmesis, graded as excellent/good or fair/poor, from baseline to year 3. Wilcoxon signed rank tests were used to evaluate change in subdomains. Cohen's kappa (κ) statistic was used to estimate interobserver agreement (IOA) between raters, and Fleiss' κ was used to estimate IOA between panelists.

RESULTS

Median cosmetic follow-up was 5, 5, 5, 4, and 3 years for the 30, 32.5, 35, 37.5, and 40 Gy cohorts. Most patients reported excellent/good cosmesis at both baseline (86.3%) and year 3 (89.8%). No dose cohort had significantly worsened cosmesis by year 3 on McNemar analysis. No cosmetic subdomain had significant worsening by year 3. IOA was fair for patient-physician (κ = 0.300, P < .001), patient-panel (κ = 0.295, P < .001), physician-panel (κ = 0.256, P < .001), and individual panelists (Fleiss κ = 0.327, P < .001).

CONCLUSIONS

Dose escalation of S-PBI from 30 to 40 Gy in 5 fractions for early stage breast cancer was not associated with a detectable change in cosmesis by year 3. S-PBI is a promising modality for treatment of early stage breast cancer.

Comparison of Toxicity and Cosmetic Outcomes After Accelerated Partial Breast Irradiation or Whole Breast Irradiation Using 3-Dimensional Conformal External Beam Radiation Therapy

Purpose

To compare rates of acute and late skin toxicities and cosmetic outcomes after accelerated partial breast irradiation (APBI) or whole breast irradiation (WBI) using 3-dimensional conformal external beam radiation therapy in women with breast cancer after breast conservation surgery (BCS).

Methods and Materials

Women >35 years of age with invasive or noninvasive breast cancer ≤4 cm treated by BCS were randomized to 3D-CRT APBI (34 Gy/10 fractions/5 days) or WBI (40 Gy/16 fractions/3 weeks ± boost irradiation). The primary outcome was ipsilateral breast tumor recurrence. Important secondary outcomes were skin toxicities using Radiation Therapy Oncology Group scores, Late Effects Normal Tissue Task Force and Subjective, Objective, Management, Analytic scales, and adverse cosmetic outcome. This interim analysis focuses on the secondary endpoints of radiation toxicities and cosmesis. Patient and tumor characteristics and rates of adverse cosmetic outcomes and skin toxicities were compared using Fisher exact tests. All statistical tests were 2 sided, with P < .05 considered statistically significant.

Results

Between June 2011 and December 2015, 133 women with breast cancer were randomized to 3D-CRT APBI or WBI. Patient and tumor characteristics were balanced between the 2 arms. Median follow-up was 60 months (range, 12-93 months). Grade 4 late toxicity was not seen in either of the treatment arms, and grade 3 toxicity was very low for each endpoint assessed in both the groups. The rates of grade ≥2 acute dermatitis were 8% and 15%, respectively, for APBI and WBI (P = .18). Rates of grade ≥1 late radiation toxicities were higher in the WBI arm compared with the APBI arm for breast shrinkage (P = .008), pigmentation (P = .028), fibrosis (P = .040), induration (P = .048), and edema (P = .33). Adverse cosmesis at last follow-up was significantly higher in patients treated with WBI: 33% compared with 6% with APBI (P < .001).

Conclusions

In women with breast cancer after BCS, APBI was associated with better cosmetic outcome and fewer late radiation toxicities than WBI.