Partial Breast Radiation Good for Early Breast Cancer

The NSABP B 39 / RTOG 0413 a 10-year randomized trial could not definitively conclude that partial breast irradiation (PBI) is equivalent to whole breast irradiation (WBI) in controlling local in-breast tumor recurrence, but the absolute difference between the two treatments was very small, suggesting it could be a useful option in some women.

In the effort to improve the quality of life of patients, Frank Vicini, MD, of William Beaumont Hospital in Royal Oak, Michigan, studied whether corn to it would be possible to reduce the treatment time for women undergoing radiation:

• While WBI can mean 5 to 6 weeks of treatment, a PBI approach could bring that down toward 5 to 6 days.

Vicini presented results of a trial comparing PBI and WBI in 4,216 women with ductal carcinoma in situ, or invasive N0 or N1 breast cancer, at the San Antonio Breast Cancer Symposium (SABCS), held December 4 to 8 (abstract GS4-04).

• The WBI patients received 50 Gy at 2.0 Gy/fraction or 50.4 Gy at 1.8 Gy/fraction to the whole breast, followed by an additional boost of at least 60 Gy

• The PBI patients received 10 treatments on 5 days totaling 34 Gy in 3.4-Gy fractions of interstitial brachytherapy or MammoSite balloon catheter, or 38.5 Gy in 3.85-Gy fractions using 3D conformal external beam therapy.

In total, there were 161 ipsilateral breast tumor recurrence (IBTR) events, including 90 events with PBI and 71 with WBI, for a hazard ratio (HR) of 1.22 (90% CI, 0.94–1.58).

• The trial design required that the upper bound of the 90% CI to be under 1.5, meaning the study failed to meet its primary endpoint.

  • However, the absolute difference in 10-year cumulative incidence of IBTR between the two therapies was only 0.7% (4.6% vs 3.9%).

• Similarly, the recurrence-free interval slightly favored the WBI group:

  • The 10-year recurrence-free survival rate was 93.4% with WBI and 91.8% with PBI, for an HR of 1.33 (95% CI, 1.04–1.69; P = .02).

  • The 10-year distant disease–free rate was 97.1% with WBI and 96.7% with PBI, for an HR of 1.31 (95% CI, 0.91–1.91; P = .15).

  • Overall survival was also similar, with 10-year rates for WBI and PBI of 91.3% and 90.6%, respectively, and an HR of 1.10 (95% CI, 0.90–1.35; P = .35).

Though the study did fail to meet its primary endpoint, Vicini said the absolute differences mean PBI should not be ruled out:

• Because the differences relative to both IBTR and recurrence-free interval were small, PBI may be an acceptable alternative to WBI for a proportion of women who undergo breast-conserving surgery.

 

Rodrigo Arrangoiz MS, MD, FACS a surgical oncologist and is a member of Sociedad Quirúrgica S.C at the America British Cowdray Medical Center in Mexico City:

• He is an expert in the management of breast cancer.

  • If you have any questions about PBI please fill free to ask him.

Training:

• General surgery:

• Michigan State University:

• 2004 al 2010

• Surgical Oncology / Head and Neck Surgery / Endocrine Surgery:

• Fox Chase Cancer Center (Filadelfia):

• 2010 al 2012

• Masters in Science (Clinical research for health professionals):

• Drexel University (Filadelfia):

• 2010 al 2012

• Surgical Oncology / Head and Neck Surgery / Endocrine Surgery:

• IFHNOS / Memorial Sloan Kettering Cancer Center:

• 2014 al 2016