Comparing accelerated partial-breast irradiation and whole-breast irradiation in patients with early breast cancer.

This trial was carried out to assess the long-term results of external-beam accelerated partial-breast irradiation (APBI) intensity-modulated radiation therapy (IMRT) compared to whole-breast irradiation (WBI) in early-stage breast cancer (BC). The authors found that the 10-year recurrence of breast tumors was similar between the 2 methods, with less toxicity with external APBI.

BC remains one of the most common forms of cancer found in women. Standard care for BC remains chemotherapy, surgical removal of tumors, and radiation therapy. Breast-conserving treatment (BCS) is the preferred treatment option for most early-stage BCs. This is where the tumor is removed from the breast while the remaining breast tissue is left. BCS in combination with radiation therapy usually has a good outcome in terms of survival and the quality of life in patients. 

WBI has previously been used as a conventional radiation therapy. This commonly involves delivering 25 sessions of radiation over the whole breast. Recently, APBI has been suggested as an alternative treatment approach for patients with early BC. This involves delivering a lower dose of radiation in 5 sessions over 5 consecutive days only in the area where the tumor was. This is thought to shorten treatment times and reduce the rates of side effects. The long-term safety and effectiveness of APBI compared to conventional WBI in women with early BC remain under investigation.

There were 520 patients with early BC in this study. All patients had received BCS. 260 patients were assigned to WBI. 260 patients were assigned to APBI. The average follow-up of patients was 10.7 years. 

The 10-year recurrence rate of the breast tumor was 2.5% in the WBI group and 3.7% in the APBI group. The overall survival rate at 10 years was 91.9% in both groups. The percentages of patients who were still alive at 10 years following a diagnosis with BC was 96.7% in the WBI group and 97.8% in the APBI group. 

The APBI group showed a lower rate of mild side effects (19.1%) compared to the WBI group (28.8%) soon after treatment. Longer after treatment, side effects were reported by 4.5% of the APBI group compared to 27.3% of the WBI group. A significantly higher number of patients reported poor esthetic outcomes following WBI (14.6%) compared to APBI (0.8%).

The authors found that external APBI and WBI had similar recurrence rates, while APBI was associated with improved toxicity profiles in the long-term.