Evolution of radiotherapy techniques in breast conservation treatment

John Boyages1,2, Lesley Baker2. Gland Surg 2018;7(6):576-595

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Evolution of radiotherapy techniques in breast conservation treatment

John Boyages1,2, Lesley Baker2.  Gland Surg 2018;7(6):576-595

Radiation therapy (RT) is an important component of breast cancer treatment that reduces local recurrence and improves survival after breast conservation. Breast conservation rates have increased significantly since the late 1980s and techniques have improved with greater awareness of the impact of radiation on the heart. An overview of randomized controlled trials of breast conservation using standard whole breast irradiation, whole breast hypofractionation, accelerated partial breast irradiation (APBI) and intraoperative radiation are reviewed. Selection criteria for breast conservation and the utility of adding a boost dose to the primary tumor site are reviewed. Modern dose constraints are documented and 10 different radiation techniques from the 1980s through to modern volumetric modulated arc therapy (VMAT) are compared for a patient where the breast and internal mammary nodes are treated. A radiation boost reduces the risk of a recurrence for most, but not all patients. Short courses of RT over 3–4 weeks are generally as effective as longer courses. Short-term follow-up of trials of APBI show promise for selected good prognosis subgroups. The role of intraoperative radiation remains controversial. In the last 30 years, there have been significant advances in radiation techniques. Modern radiotherapy equipment and techniques will reduce complications and improve survival rates.

Main findings

  • This paper reviews the evolution of radiotherapy for breast cancer.
  • When whole breast radiation is required, it should be given with the minimum delay possible (usually 3–4 weeks), particularly for patients not receiving chemotherapy. Assuming a 10-year risk of breast cancer recurrence of 6%, it is estimated that the absolute risk is increased by a further 0.5% for every month treatment is delayed.
  • There is a danger with modern voluming that potential under-dosing can occur of the primary tumour bed compared to older techniques.
  • It is insufficient simply to “boost the scar”, because, with modern oncoplastic techniques, the scar often has no relationship to the actual primary tumour site where the risk of recurrence is highest.
  • With accelerated whole breast irradiation (AWBI) hypofractionation involves a shorter or accelerated radiation course with higher daily doses for the same biological effect. AWBI saves the patient time and money and reduces pressure on public radiotherapy units.
  • 15 fractions over 3 weeks. Shorter schedules were not worse for local recurrence or survival compared to the control group (4.7%, P=0.01), except for high-grade tumours (15.6% 10-year local recurrence).
  • In practice, standard fractionation appears to be better for larger-breasted women for whom increased breast oedema can be a problem.
  • The Australian and US guidelines only recommend hypofractionated treatment for patients 50 years or older who have node-negative tumours up to 5cm, have had no chemotherapy and where breast size and treatment technique minimises dose variation across the volume and the Australian guidelines advise caution when recommending this approach to other patients.
  • The use of accelerated partial breast irradiation is not yet entirely clear, largely because of the still relatively short follow-up in these studies. However, it is an option for older patients with small, unicentric good prognosis tumours with negative margins.
  • For intraoperative radiotherapy, it is unclear of its use. Five-year overall survival was not significantly different between the two groups (intraoperative compared with the whole breast) and approached 97%. There were significantly fewer skin side effects in women in the intraoperative radiotherapy group than in the external radiotherapy group.
  • Treatment of the internal mammary chain requires being careful of the heart. There have been significant advances in radiotherapy technology, with sophisticated imaging integrated into planning systems using techniques that protect the heart with shielding or deep inspiration breath holding.