2656 - Smoking History and Breast Shrinkage Following Breast Conserving Treatment and Radiation Therapy

Smoking History and Breast Shrinkage Following Breast Conserving Treatment and Radiation Therapy

Purpose/Objective(s):

 Cosmetic outcomes of breast-conserving treatment (BCT) and radiation therapy (RT) are important for survivorship.  One important factor is breast volume loss.  Smoking during RT has been associated with increased risk of toxicity, but it is unknown whether smoking history affects volume loss. It was hypothesized that smoking would be associated with increased volume loss, via increased susceptibility to radiation toxicity. This study aimed to explore any associations.

Materials/Methods:

Breast volume changes were calculated for 112 patients (113 breasts) following T1 tumor lumpectomies.  From preoperative baseline to seven years post-radiation, volumes were calculated from mammograms using π/3* height*radius².  Mann-Whitney U-Tests compared volume changes at each time point between patients actively smoking (n=1) or with a smoking history (n=29), and patients who never smoked (n=83).  Multivariate analysis assessed volume change as a function of patient age, pack-years smoked, diabetes, radiation dosage, fractions, technique, boost dose, whole/partial breast RT, treatment length, chemotherapy (hormonal/cytotoxic), baseline breast volume, and months since treatment.

Results:

Smoking group average age was 62.6 (SD=6.8) years, median pack-years smoked was 5 (IQR=19.9), median RT dose was 4272 cGy (IQR=749) over 16 (IQR=4.8) fractions for median duration 3.2 (IQR=1.0) weeks. N=24 (80%) received endocrine therapy.  Non-smoking group average age was 57.6 (SD=8.8) years, median RT dose was 5005 cGy (IQR=749) over 20 (IQR=4) fractions for median duration 3.6 (IQR=1.3) weeks. N=64 (77.1%) received endocrine therapy.  Treatment details are summarized in Table 1.  

Patients with a smoking history experienced significantly greater volume loss during the first two years after treatment. By year one, 26.5% of baseline breast volume was lost compared to 13.4% among non-smoking patients (p=0.02).  By year two, smoking group volume loss was 23.9%, compared to 16.3% for non-smoking patients (p=0.04).  Larger baseline breast volume and increased pack-years smoked were significant predictors of increased volume loss during years one, two and three (p<0.05). For year three a diabetes diagnosis was also significant (p=0.03).

Conclusion:

Findings suggest prior smoking may contribute to increased breast shrinkage within the first two years following BCT/RT.  Increased pack-years and larger baseline breast volume may predict greater volume loss.  Anticipating these changes is important for patient education and planning future interventions.