Recent advancements in therapeutic strategies for breast cancer have opened the door to more personalized and less invasive treatment options. Notably, the concept of irradiating only the surgical bed, known as Partial Breast Irradiation (PBI), has gained traction. Well-aligned with this innovative approach is the 5-Year update of the HYPAB (Hypofractionated Whole Breast Irradiation versus Accelerated Partial Breast Irradiation) Trial, presenting results that could shift the paradigm in postoperative breast cancer care. This article delves into the details of the trial, offering insights and implications for the future of breast cancer treatment.


Breast cancer remains a leading cause of cancer-related morbidity among women worldwide, prompting continuous research and improvement in treatment modalities. One particular area of interest is postoperative radiation therapy, a critical component of breast-conserving treatment. The HYPAB Trial, first conceptualized in 2014, sought to examine whether Accelerated Partial Breast Irradiation (APBI) could stand as a viable alternative to the more traditional Hypofractionated Whole Breast Irradiation (WBI), with an emphasis on toxicity, cosmesis, and treatment efficacy.

The HYPAB Trial: An Overview

Institutionalized at the IRCCS Humanitas Research Hospital, Milan, the HYPAB was a randomized trial that recruited 172 postmenopausal women with early-stage breast cancer following conservative surgery. From 2015 to 2018, participants were assigned to either adjuvant WBI delivering 40.5 Gy over 15 fractions with a simultaneous boost to 48 Gy to the tumor bed or APBI administering 30 Gy across 5 fractions. Both treatments employed the advanced Volumetric Modulated Arc Therapy-Rapid Arc (VMAT-RA) technique.

Methods and Measurements

Upon enrollment and post-surgery, clinical evaluation of the patients transcended from their first visit, consistently through the radiotherapy schedule, and persistently over the follow-up period. The primary endpoints were to evaluate the incidence of late skin toxicities and the aesthetic outcome post-treatment using the Harvard Scale for Breast Cosmesis.

Results: Safety, Efficacy, and Quality of Life

The publication date of January 2024 marked the disclosure of the 5-year follow-up data. Out of the initial 172, 161 patients remained eligible for analysis, with a median follow-up of 67 months. Findings showed that late skin toxicities, primarily G1 fibrosis and oedema, occurred more frequently in the WBI group, with no reports of G3 toxicities. Only 6 cases were reported with poor cosmesis. Impressively, 147 patients were disease-free at their last follow-up, and there were no disease-related deaths.

Discussion: Striking a Balance

These long-term results from the HYPAB Trial affirm the safety and efficacy of APBI for selected early-stage breast cancer patients. A noticeable reduction in late toxicity rates underlines the potential benefits of APBI, although it accompanies a marginal increase in local relapse rates. The compelling evidence from HYPAB could significantly influence the broader application of APBI, aligning with the modern push for de-escalation in cancer therapy.

Implications for Future Research and Practice

Based on these results, further scrutiny into APBI is warranted to clarify its positioning as a standard treatment avenue. Upcoming trials are anticipated to refine patient selection criteria and to further analyze the long-term outcomes, such as survival rates and quality of life assessments.


The HYPAB Trial’s 5-year update offers conclusive evidence of APBI’s viability as an alternate radiation therapy in postmenopausal women with early-stage breast cancer. By demonstrating a favorable toxicological profile and maintaining high cosmetic standards, APBI presents as an integral component in the future of breast cancer treatment, emphasizing patient-specific care and improved quality of life.


1. Lo Faro, L. L., et al. (2024). Adjuvant Hypofractionated Whole Breast Irradiation (WBI) vs. Accelerated Partial Breast Irradiation (APBI) in Postmenopausal Women with Early Stage Breast Cancer: 5Years Update of the HYPAB Trial. Clinical Breast Cancer.
DOI: 10.1016/j.clbc.2023.12.012

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4. Polgár, C., et al. (2017). Patient selection for accelerated partial-breast irradiation (APBI) after breast-conserving surgery: Recommendations of the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO) breast cancer working group based on clinical evidence (2009). Radiotherapy and Oncology, 94(3), 264-273.

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1. Accelerated Partial Breast Irradiation
2. Postmenopausal Breast Cancer Treatment
3. Hypofractionated Whole Breast Irradiation
4. Breast Cancer Radiotherapy Advances
5. HYPAB Trial Outcomes

Conflict of Interest
The authors have disclosed no conflict of interest concerning this study.

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