Hypofractionation is the preferred means of giving whole breast irradiation to women with invasive breast cancer, according to updated guidance from the American Society for Radiation Oncology.

A dose of 4,000 cGy given in 15 fractions or 4,250 cGy in 16 fractions is recommended, with or without inclusion of the low axilla, and regardless of a variety of factors such as tumor grade, prior chemotherapy, and patient age.

“Previously, accelerated treatment was recommended only for certain patients, including older patients and those with less advanced disease,” Benjamin Smith, MD , one of the cochairs of the guideline task force, said in an ASTRO news release .

Dr. Smith, of the University of Texas MD Anderson Cancer Center, Houston, added that recent long-term ­data from several large trials “strongly support the safety and efficacy of accelerated treatment for most breast cancer patients.”

Treatment decisions and plans still need to be individualized, but the updated ASTRO guidance notes that whole breast irradiation (WBI) can be offered to most women with invasive breast cancer independent of breast size and whether or not the cancer is in the left or right breast, provided that homogeneous dosing can be achieved. Hormone receptor, HER2 status, and postsurgical margin status also appear not to matter.

Historically, conventional fractionation (CF) with or without a tumor bed boost was used for WBI, Dr. Smith and associates wrote in the guidelines, which were published online in Practical Radiation Oncology . This consisted of daily doses of 180-200 cGy for a total dose of 4,500-5,000 cGy.

“Recognizing the limitations of CF for convenience and cost, randomized trials in the 1990s and 2000s investigated if moderate hypofractionation [HF], defined as daily doses of 265-330 cGy, could yield oncologic and functional/cosmetic outcomes similar to CF-WBI,” they said.

Initial results of these trials “supported the safety and effectiveness of HF-WBI” and were then used to form ASTRO’s 2011 guideline on dose fractionation for WBI. With longer term data from these trials now available, it was time to review the evidence again. A systematic literature review was thus conducted to identify all relevant studies published during 2009-2016, and 100 articles met the task force criteria and were used to create the updated guideline.

Aside from the delivery and dosing of WBI, other key recommendations look at the use of a radiation boost to the tumor bed, and preferred techniques for treatment planning.

With regards to a radiation boost, this needs to be considered on an individual basis but can be independent of any previous WBI. A radiation boost is recommended if patients have any grade invasive cancer and are aged 50 years or younger, have a high-grade tumor and are aged 51-70 years, or if there is a positive margin following surgery. A radiation boost also is recommended in women with ductal carcinoma in situ if they are aged 50 years or younger, have a high-grade tumor, and positive or close postsurgical margins.

As for treatment planning, 3-dimensional conformal treatment planning with a “field-in-field” technique is recommended as the initial approach. This is to minimize the volume of breast tissue that receives more than 105% of the radiation dose. The guideline also covers optimal patient positioning and how to avoid nearby tissues and organs, such as the heart, lungs and contralateral breast.

ASTRO hopes that the updated guideline will increase the use of hypofractionation, which has been reportedly low in recent years, with as few as 35% of eligible patients received hypofractionation in one study ( JAMA. 2014;312[23]:2542-50 ).

“We hope that this guideline encourages providers to counsel their patients on options including hypofractionation,” said Reshma Jagsi, MD, DPhil , professor of radiation oncology at the University of Michigan, Ann Arbor, who cochaired the guideline task force with Dr. Smith.

“Hypofractionated radiation therapy offers patients a more convenient and lower cost option for their treatment without compromising the likelihood that their cancer will return or increasing their risk of side effects,” Dr. Jagsi noted. Furthermore, “a shorter course of radiation equates to more time with family, less time away from work and lower treatment costs.”

SOURCE: Smith BD et al. Pract Radiat Oncol. 2018 March 12. doi: 10.1016/j.prro.2018.01.012.