Abstract
Our purpose was to evaluate cosmetic changes after 5-fraction adjuvant stereotactic partial breast irradiation (S-PBI). 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. 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). 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.
Highlights
Breast conservation surgery with whole breast irradiation (WBI) for early stage breast cancer results in similar survival outcomes to mastectomy[1,2,3] and is typically favored in eligible women
In 2013, interest in 3-dimensional conformal radiation therapy (3D-CRT) for accelerated partial breast irradiation (APBI) diminished with the publication of the interim cosmetic findings of the Randomized trial of Accelerated Partial Breast Irradiation (RAPID) trial, which demonstrated an approximate doubling of adverse cosmesis in the APBI arm compared with WBI, as assessed by trained nurses and by patients and physician panels.[14]
On post hoc analysis of variance, larger ipsilateral breast, clinical target volume (CTV), and planning target volume (PTV) volumes were associated with the 37.5 Gy cohort
Summary
Breast conservation surgery with whole breast irradiation (WBI) for early stage breast cancer results in similar survival outcomes to mastectomy[1,2,3] and is typically favored in eligible women. External beam techniques for APBI, including 3D-CRT and IMRT, are favored by some over interstitial or intracavitary approaches, as they are noninvasive, not requiring catheter insertion, and are less affected by operator experience in procedural skills. In 2013, interest in 3D-CRT for APBI diminished with the publication of the interim cosmetic findings of the Randomized trial of Accelerated Partial Breast Irradiation (RAPID) trial, which demonstrated an approximate doubling of adverse cosmesis in the APBI arm compared with WBI, as assessed by trained nurses and by patients and physician panels.[14] Subsequent publications of smaller trials using external beam approaches for APBI reported mixed findings.[18,19,20] Most recently at American Society for Radiation Oncology 2019, the cosmetic outcomes for National Surgical Adjuvant Breast and Bowel Project (NSABP) B39Radiation Therapy Oncology Group (RTOG) 0413 were reported, demonstrating a lack of patient-reported detriment in cosmesis when comparing APBI (73% 3D-CRT) to WBI but with a discordant physician-reported and panelreported worsening of cosmesis in patients who received chemotherapy.[21] The lack of a patient-reported worsening in cosmesis with NSABP B39-RTOG 0413 was promising. The worse cosmetic outcomes noted in many external beam APBI approaches, including from the RAPID trial, suggest that external beam approaches could be further optimized to improve cosmesis without compromising tumor control
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