Meta-analyses of randomized trials for breast conserving surgery has shown reduction in local failure and equates into a survival advantage favoring whole breast radiation (Van de Steene J).
Whole breast irradiation after breast conserving surgery remains the standard of care for early breast cancer.
Standard whole breast irradiation is typically delivered over 3-6 weeks in a once/day manner five days a week.
Most common schedule for whole breast irradiation after breast conserving radiation with 45 to 50 Gy deliverd over 5 weeks with 1.8 to 2.0 Gy daily treatment fractions, given 5 days a week.
The Standardization of Breast Radiotherapy Trials (START) suggest that instead of 50 Gy in 25 fractions that 40 Gy in 15 fractions for three weeks should be the standard of care.
Many radiation centers an additional boost to the lumpectomy site with an additional 10-16 Gy in 5-8 daily fractions.
NSABP B06 evaluated 1851 women with stage I or II invasive breast cancer <4cm randomized to mastectomy alone, lumpectomy alone, or lumpectomy followed by postoperative whole breast irradiation: After 20 years of follow-up cumulative incidence of recurrent tumor in the ipsilateral breast was 14.3% in women who underwent lumpectomy and breast irradiation compared with 39.2% in those who underwent lumpectomy alone, but no difference among the three groups with respect of disease free survival, distant disease free survival and overall survival (Fisher ER).
Meta-analysis of randomized trials evaluating breast conserving surgery with or without postoperative radiation therapy showed addition of whole breast irradiation improved survival in most populations.
Recent studies in node negative patients suggest that total doses of whole breast irradiation of 40 Gy in 15 fractions indicate local recurrence rates of 3.5-15% with good cosmetic results (Olivotto IA, Shekkey W).
In a 20 year follow-up of patients with stage I and stage II breast cancer who underwent breast conserving surgery and whole breast irradiation and who were randomized to 16 Gy boost compared to those with no boost:the radiation boost group had no improvement on long-term overall survival, but did improve local control, with the largest absolute benefit in young patients (EORTC).
In the above study a 16 Gy boost increased the risk of moderate to severe fibrosis, and the extra radiation dose could be avoided in most patients older than 60 years.
In the above study ipsilateral breast tumor recurrence was the first treatment failure in 13% in the no boost group versus 9% in the boost group, and the 20 year cumulative incidence of ipsilateral breast tumor recurrence was 16.4% in the no boost group versus 12% in the boost group.
Whole breast irradiation is associated with potential acute and chronic toxicities to include dermatitis, soft tissue fibrosis, rib fractures, hyperpigmentation, volume loss of the treated breast, increased risk of cardiac disease in patients with left-sided breast cancer.
In a retrospective study in older women with invasive BC treated with lumpectomy followed by RT: brachytherapy was associated with higher risk for subsequent mastectomy with a five-year cumulative incidence of 3.95 percent compared with 2.18% in patients who received WBI (Smith G et al).
In the above study brachytherapy was associated with high risk for infectious and noninfectious postoperative complications 27.5% versus 16.9% and was associated with a higher risk for complications within five years of radiation 24.9% versus 18.8% for WBI.
In the above study overall survival was similar.
AMAROS trial of women with early sentinel lymph node positive breast cancer comparing axillary radiation to axillary lymph node dissection: rates of axillary recurrence 1% vs 0.5% after 5 years, with no differences in 5 year disease free or overall survival (Rutgers EJ et al).
In the above study axillary resection associated with more lymphedema than axillary radiotherapy.
Hypofractionated WBI is of shorter duration treatment than conventional WBI.
Hypofractionated WBI has fewer but higher dose fractions than WBI and is generally delivered over three weeks.
Hypofractionation study revealed in a randomized trial of whole breast irradiation comparing 42.5 Gy in 16 fractions with 50 GY in 24 fractions reported equivalent efficacy and toxicity (Whelan TJ et al).
The above study showed it was noninferiority in terms of local regional tumor relapse and the lower dose was superior in terms of percentage of patients free of adverse events.
Hypofractionated breast radiation WBI increases convenience, reduces treatment burden, and lowers healthcare costs with offering similar control of the cancer and cosmesis compared to conventional WBI.
Hypofractionated WBI is associated with fewer short-term side effects and lower rates of fatigue than standard treatment WBI.
Only 20% of the eligible patients in the United States receive hypofractionated WBI instead of conventional fractionated WBI.
Randomized clinical trial’s show that hypofractionated WBI is equivalent to conventional fractionated WBI for patients 50 years or older who have pathologic stage T1-T2 N0 breast cancer and have not received systemic chemotherapy.
In an M.D. Anderson Cancer Center study patients 40 years and older with ductal carcinoma in situ or early invasive breast cancer pathologically Tis, T1, T2, and N0, N1mi, or N1a treated with breast conservative surgery and negative surgical margins: patients were randomly assigned conventional fractionated WBI 50 GY and 25 fractions followed by tumor bed boost of 10-14 Gy in 5 to 7 fractions or hypo fractionated WBI of 42.5 6Gy in 16 fractions followed by a tumor boost of 10-12.5 GU in 4-5 fractions-six months after completing radiation therapy the patients who received hypofractionated WBI treatment had better physical well-being, less fatigue scores and oncologic outcomes were similar.