Characterization of Chest Wall Toxicity During Long-term Follow Up After Thoracic Stereotactic Body Radiation Therapy.

PURPOSE: Chest wall (CW) pain and rib fractures are frequently diagnosed after stereotactic body radiation therapy (SBRT) for malignant lung tumors. We hypothesize that multiple risk factors, including bone mineral density (BMD), are associated with CW toxicity, and that CW pain and rib fractures often evolve into chronic clinical problems. METHODS AND MATERIALS: A total of 118 lung tumors treated with SBRT in 100 patients with a minimum follow-up period of 2 years were retrospectively analyzed. The incidence, clinical course, and related demographic, clinical, and dosimetric factors of CW pain and rib fractures were analyzed. In addition, BMD was assessed, and the radiographic appearance of radiation-induced rib fractures and their healing process were characterized. RESULTS: The median follow-up was 49 months (range, 24-106 months). CW pain developed in 33 of 118 treatments (28%) after, on average, 12.5 months (range, 0-50 months), and was more common in women (P = .04). The mean duration of CW pain was 25 months (range, 2-63 months), and 36% of patients never had resolution of CW pain. A total of 34 of 118 treatments (29%) resulted in rib fractures at a mean time of 22 months (range, 3-46 months); rib fractures were more common in women, African Americans, upper/middle lobe tumors, and patients with lower BMD (P < .05). The mean duration of rib fractures was 25 months (range, 5-41 months), and only 16 rib fractures (47%) healed. Shorter CW planning target volume distance resulted in a higher risk for both rib fractures and CW pain (P = .01). Sixty-seven percent of fractures developed surrounding soft tissue fibrosis, and 62% (21 of 34 fractures) heterotopic ossification. Diabetes, body mass index, and steroid use were not associated with CW pain or rib fracture. CONCLUSIONS: Several factors were associated with a higher risk of SBRT-related CW toxicity. Optimal CW sparing (eg, volumetric modulated arc therapy, lower dose per fraction) should be considered in this patient group without compromising tumor control. SBRT-induced rib fractures commonly heal abnormally and result in potential chronic CW pain.

Updated feasibility and reproducibility results of multi-institutional study of noninvasive breast tumor bed boost.

PURPOSE: To report updated feasibility and reproducibility results for high-dose-rate noninvasive breast brachytherapy (NIBB) for tumor bed boost with whole breast radiation therapy (WBRT) in the setting of expanded patient and treatment facility number. METHODS AND MATERIALS: Fifteen independent community-based and academic centers reported 518 early-stage breast cancer patients from July 2007 to February 2015 on a privacy-encrypted online data registry. All patients' treatment included lumpectomy followed by combination of WBRT and NIBB. NIBB was completed with commercially available (AccuBoost, Billerica, MA) mammography-based system using high-dose-rate 192Ir emissions along orthogonal axes. Harvard scale was used to grade cosmesis. RESULTS: Total patient cohort had median followup of 12 months (1-75 months) with subset of 268 having available cosmesis. Greater than 2- and 3-year followup was 29% and 14%, respectively. Entire cohort had 97.4% excellent/good (E/G) breast cosmesis and freedom from recurrence of 97.6% at the final followup. WBRT timing with respect to NIBB delivery demonstrated no statistically significant difference in E/G cosmesis. Achieved E/G cosmesis rate was also not statistically significant (χ2p-value = 0.86) between academic and community institutions with 97.8% vs. 96.6%. CONCLUSIONS: NIBB represents an alternative method for delivery of breast tumor cavity boost that has shown feasibility in a diverse group of both academic and community-based practices with reproducible early cosmesis and tumor control results. Recommendations are updated noting ideal timing of boost delivery likely to be before or early during WBRT given equal cosmesis and less documented treatment discomfort.