Improving the Therapeutic Ratio Among Older Women With Early Stage Breast Cancer by Reevaluating Adjuvant Radiation Therapy and Hormone Therapy

Long-Term Outcomes of Radiation Monotherapy Versus Combined Radiation Monotherapy + Hormone Therapy in Low-Risk Early-Stage Breast Cancer Patients 70 Years or Older After Breast-Conserving Surgery

PURPOSE

Standard therapy for breast cancer after breast-conserving surgery is radiation therapy (RT) plus hormone therapy (HT). For patients with a low-risk of recurrence, there is an interest in deescalating therapy.

METHODS AND MATERIALS

A retrospective study was carried out for patients treated at the Swedish Cancer Institute from 2000 to 2015, aged 70 years or older, with pT1N0 or pT1NX estrogen receptor-positive and ERBB2-negative unifocal breast cancer without positive surgical margins, high nuclear grade, or lymphovascular invasion.

RESULTS

Patient numbers were sufficient to carry out analyses for RT + HT (n = 307) and RT alone (n = 148). The median follow-up was 9.6 years. There were no statistically significant differences in adjusted overall survival (OS), disease-specific death, progression-free survival (PFS), distant recurrence, and second primary cancers with RT monotherapy compared with RT + HT. Cumulative rates of all of these outcomes were <5%, even at 15 years of follow-up, regardless of treatment, greatly outweighed by the incidence of death from other causes in this elderly population. In matched analysis, we calculated a hazard ratio of 1.12 (95% CI, 0.82-1.53) for RT versus RT + HT for OS and a hazard ratio of 1.12 (95% CI, 0.82-1.53) for RT versus RT + HT for PFS.

CONCLUSIONS

Our data suggest that elderly, low-risk breast cancer patients have similarly high OS and PFS with low rates of local recurrence, distant recurrence, and death from breast cancer with much higher rates of death from competing causes, whether treated with RT or HT + RT. These patients are likely to die of other causes without disease recurrence, regardless of which of these treatments is used. Thus, they may benefit from the administration of more modern forms of breast irradiation without the need for adjuvant systemic hormone therapy. A detailed analysis of which clinical, pathologic, genomic, and comorbidity variables are needed to select these patients.

Dose Deintensified 3-Day Photon, Proton, or Brachytherapy: A Nonrandomized Controlled Partial Breast Irradiation Trial

PURPOSE

The optimal approach for partial breast irradiation (PBI) is unknown. We investigated a novel de-intensified 3-fraction PBI regimen for photons, protons, and brachytherapy.

METHODS AND MATERIALS

A multicenter nonrandomized controlled trial with the primary outcome of adverse cosmesis at 3 years versus before PBI. Eligibility criteria were age ≥50 years treated with breast-conserving surgery for node-negative estrogen receptor-positive (ER+) invasive breast cancer or any ductal carcinoma in situ (DCIS) measuring ≤2.5 cm. Photon and proton PBI were prescribed 21.9 Gy (relative biological effectiveness) and brachytherapy 21 Gy in 3 fractions. Radiation therapy technique and adjuvant endocrine therapy were selected at physician and patient discretion.

RESULTS

Between June 17, 2015, and July 13, 2017, 161 eligible patients were treated with photons (56), protons (49), or brachytherapy (56). Median patient age was 66.8 years. One hundred twenty-six (78.3%) had invasive breast cancer (all ER+) and 35 (21.7%) had DCIS (88.6% ER+). Fifty-four percent of patients with invasive breast cancer and 25.8% of patients with ER+ DCIS initiated and adhered to the prescribed endocrine therapy. The proportion of patients with adverse cosmesis (by trained nurse assessment) was 14.5% at baseline and 2.3% at 3 years (difference, -12.2%; 95% CI, -100% to -6.4%). Adverse cosmesis at the last follow-up, with a median follow-up of 5 years, was 5.7% by nurse assessment, 5.6% by panel assessment of digital photographs, and 5.2% by patient self-report. There were no observed clinically meaningful changes in other patient-reported outcomes, and just 2 grade 2 or higher adverse events, both grade 2, in the brachytherapy cohort. Five-year local recurrence-free survival and progression-free survival were 98.0% and 95.5%, respectively. There were no local recurrences among 60 patients with invasive breast cancer and Ki67 ≤13.25%.

CONCLUSIONS

Deintensified 3-day PBI provided favorable disease control, tolerability, and cosmetic outcomes, meeting the prespecified criteria for acceptability. This approach is an attractive option for patients with small node-negative ER+ breast cancer and DCIS.