Partial-Breast Irradiation - Current Situation with Evidence

Abstract

The implementation of breast-conserving surgery in the management of early breast cancer is one of the most important successes of the modern treatments in the field. Numerous randomized clinical trials initiated more than 30 years ago have reported 20-year durable results documenting that survival is equivalent to mastectomy when the breast is conserved by removal of the index cancer with wide excision followed by whole-breast radiotherapy (1-4). Nearly simultaneously with the initial trials studying breast conservation instead of mastectomy, investigators began to study alternative approaches that could achieve comparable cancer outcomes while reducing the burden of care imposed by the 4-6 weeks of daily radiotherapy delivery post lumpectomy. Administration of radiation to the breast tissue that is adjacent to the surgical cavity, i.e., partial-breast irradiation is one of the treatment alternatives studied. The first trials in this approach were initiated nearly as early as breast-conserving surgery trials. Multiple influences have since contributed to the development and success of accelerated partial-breast irradiation and made it one of many effective approaches for radiotherapy following lumpectomy in selected early-stage breast cancer patients. In this editorial, we decided to touch on the historical advances of partial-breast irradiation. The rationale of alternatives to whole-breast irradiationSince the 1980s, it has been well-recognized that breast-conserving therapy is a safe alternative to mastectomy for selected early-stage breast cancer patients. In those trials and similar trials searching for relapse patterns after breast-conserving surgery, it was reported that the majority of the local relapses (87-90%) were in or around the primary tumor foci (5-10). The local recurrences outside the primary foci were less than 1% in the group of patients who were treated with whole-breast irradiation and around 1.5-3.5% in the group of patients who were observed after surgery. In any case, those numbers were fewer than the number of recurrences around the primary foci in the group of patients who were observed after surgery (4.1-22%). Historical advances in partial-breast irradiationThe initial trials comparing partial-breast irradiation with whole-breast irradiation were done using external beam radiotherapy techniques. The first trial came from England (Christie Hospital) where the increased number of patients for whole-breast irradiation due to breast-conserving surgery became troublesome. This trial was initiated as early as the trials comparing mastectomy with breast-conserving surgery and was comparing partial-breast irradiation performed with electrons with whole-breast irradiation after breast-conserving surgery with no intervention to axilla (11). The in-breast recurrence rates in the first 37 months of this trial were 8% vs 4%; these rates were reported to be 19.6% vs 11% after 7 years of follow-up. The majority of the patients experiencing a local failure were the ones with invasive lobular histol...