Dosimetric Inhomogeneity Predicts for Long-Term Breast Pain Following Breast-Conserving Therapy

Abstract

The objective of this cross-sectional questionnaire study was to characterize long-term breast pain in patients undergoing breast conserving surgery and radiation (BCT) and to identify predictors of this pain. We identified 355 eligible patients with Tis-T2, N0, M0 breast cancer who underwent BCT in 2007-2011, without recurrent disease. Patients with invasive disease were required to have a negative sentinel lymph node biopsy with ≤5 nodes removed. Patients who received radiation therapy (RT) with a separate nodal field, high tangents, partial breast plan, or prone positioning and those who received chemotherapy were excluded. A questionnaire with 10 items derived from the Late Effects Normal Tissue Task Force (LENT)-Subjective, Objective, Management, Analytic (SOMA) scale detailing the severity, frequency, duration, and impact of pain or discomfort in the treated breast over the previous 2 weeks was mailed to all eligible women. A logistic regression model was built to identify predictors of long-term breast pain based on survey results and patient, disease, and treatment data. Questionnaire response rate was 80% (N = 285). Median time from RT was 50.3 months. A total of 135 patients (47%) reported pain in the treated breast; 19 (14%) had pain constantly or at least daily, and 15 (11%) had intense pain. Pain interfered with daily activities in 11 patients (8%), with 6 (4%) taking analgesics for this pain. Fourteen (10%) reported that the pain affected their quality of life. Ninety-three (69%) noted their pain had been present for at least 1 year. Sixty-eight (50%) reported that the pain was not changing with time, while 16 (12%) stated that the pain was getting worse. On univariable analysis, volume of breast tissue treated to ≥105% of the prescribed dose (OR = 1.001 per cc, 95% CI = 1.000-1.002; p = 0.045), volume of breast tissue treated to ≥110% of the prescribed dose (OR = 1.009 per cc, 95% CI = 1.002-1.016; p = 0.012) and hormone therapy (OR = 1.98, 95% CI = 1.13-3.48; p = 0.02) predicted for long-term breast pain. There was no impact of hypofractionation (n = 41). On multivariable analysis, volume ≥110% (OR = 1.01 per cc, 95% CI = 1.003-1.017; p = 0.007), shorter time since treatment (OR = 0.98, 95% CI = 0.96-0.997; p = 0.03) and hormone therapy (OR = 1.91, 95% CI = 1.08-3.40; p = 0.03) were independent predictors of pain. Volume ≥105% was not included in the multivariable model with volume >110% due to a high degree of collinearity, but was also independently associated with breast pain in a model with time since treatment and hormone therapy. Long-term breast pain was common after BCT. While nearly half of patients had pain, most considered it tolerable. Dosimetric inhomogeneity independently predicted for pain and should be minimized to the greatest extent possible.