title: Concurrent or Sequential Hormonal and Radiation Therapy in Breast Cancer: A Literature Review.
abstract: OBJECTIVE
  Adjuvant hormonal therapy is frequently used in the treatment of women with estrogen receptor (ER)/progesterone receptor (PR) positive breast cancer. When radiotherapy is given, hormone therapy may be delivered in a concurrent or sequential manner. Hormonal blockade with tamoxifen or aromatase inhibitors is thought to arrest hormonally dependent cancer cells in the early G1 phase of the cell cycle. This has been theorized to reduce the efficacy of radiation, which is known to be more effective in cells that are actively dividing. Therefore, there has been a reluctance by many to treat with concurrent hormonal and radiation therapy.
  
  
  METHODS
  We performed a search of the Medline database that led to the identification of 39 studies. Abstract and full-text review of these studies led to the identification of seven English non-review studies in peer-reviewed literature between 1995 and 2015 that addressed the question of timing of radiation and hormonal therapy. Outcome measures were captured from each of the studies.
  
  
  RESULTS
  No difference in survival or local-regional recurrence was identified between concurrent versus sequential treatment. Furthermore, no difference in cosmetic outcome or adverse effects was noted for either approach. However, when comparing radiation alone or radiation and hormonal therapy, there was an increased risk of breast and lung fibrosis with combined treatment.
  
  
  CONCLUSIONS
  Hormone therapy, concurrent or sequential, with radiation results in comparable disease-related outcomes, including survival and recurrence. However, given the theoretical reduction in efficacy and increased rates of fibrosis with concurrent use, it is reasonable to support the use of sequential therapy.
authors.affiliation: Department of Pathology, Schulich School of Medicine & Dentistry, Western University, London, Ontario, CA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Cecchini
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, CA; Schulich School of Medicine & Dentistry, Western University, London, Ontario, CA.
authors.forename: Edward
authors.initials: E
authors.lastname: Yu
authors.affiliation: Department of Medical Oncology, London Regional Cancer Program, London, Ontario, CA; Schulich School of Medicine & Dentistry, Western University, London, Ontario, CA.
authors.forename: Kylea
authors.initials: K
authors.lastname: Potvin
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, CA; Schulich School of Medicine & Dentistry, Western University, London, Ontario, CA.
authors.forename: David
authors.initials: D
authors.lastname: D'souza
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, CA; Schulich School of Medicine & Dentistry, Western University, London, Ontario, CA.
authors.forename: Michael
authors.initials: M
authors.lastname: Lock
keywords: aromatase inhibitor; breast cancer; breast fibrosis; lung fibrosis; radiation therapy; tamoxifen; timing of therapy