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To boost or not to boost?

The standard technique is to radiate the whole breast (from side to side with tangential fields) and the give an extra dose to the site of the tumor (referred to as a boost or booster dose.)

If the tumor was small and the surgical margins were clear, it may not be necessary to include the boost field in everyone (particularly in older women, with small tumors and no DCIS.) By and large most studies show that a boost lower the long term risk of a local relapse (go here).

A recent study (Bartelink; NEJM 2001;345:1378) is noted below. Other studies show the greatest benefit from a boost is in the younger women (go here).

see summary table here

Breast Recurrent Rates at 5 Years
Variable No Boost Radiation Boost Radiation Given
Age    
< 40 y 19.5% 10.2%
41 - 50y 9.5% 5.8%
51 - 60y 4.2% 3.4%
>60y 4% 2.5%
Menopausal status    
Premenopausal 10.3% 6.8%
Postmenopausal 4.6% 2.8%
Tumor stage    
T1 5.9% 4.0%
T2 7.8% 4.5%
DCIS    
absent 5.4% 3.5%
present 9.3% 5.6%


Recurrence Rates after Treatment of Breast Cancer with Standard Radiotherapy with or without Additional Radiation
Harry Bartelink,NEJM 2001;345:1378
After lumpectomy and axillary dissection, patients with stage I or II breast cancer received 50 Gy of radiation to the whole breast in 2-Gy fractions over a five-week period. Patients with a microscopically complete excision were randomly assigned to receive either no further local treatment (2657 patients) or an additional localized dose of 16 Gy, usually given in eight fractions by means of an external electron beam (2661 patients).

Results During a median follow-up period of 5.1 years, local recurrences were observed in 182 of the 2657 patients in the standard-treatment group and 109 of the 2661 patients in the additional-radiation group. The five-year actuarial rates of local recurrence were 7.3 percent (95 percent confidence interval, 6.8 to 7.6 percent) and 4.3 percent (95 percent confidence interval, 3.8 to 4.7 percent), respectively (P<0.001), yielding a hazard ratio for local recurrence of 0.59 (99 percent confidence interval, 0.43 to 0.81) associated with an additional dose. Patients 40 years old or younger benefited most; at five years, their rate of local recurrence was 19.5 percent with standard treatment and 10.2 percent with additional radiation (hazard ratio, 0.46 [99 percent confidence interval, 0.23 to 0.89]; P=0.002). At five years in the age group 41 to 50 years old, no differences were found in rates of metastasis or overall survival (which were 87 and 91 percent, respectively). Overall, 47 percent of the local recurrences occurred in the primary tumor bed, 9 percent in the scar, and 29 percent outside the area of the original tumor, and 27 percent were diffuse throughout the breast

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