A Contura Catheter Offers Dosimetric Advantages over a MammoSite Catheter that Increase the Applicability of Accelerated Partial Breast Irradiation

Abstract

St. Mary's Duluth Clinic Health System, Duluth, MNPurpose/Objective(s): Small vessel damage and fibrotic changes are thought to occur following radiotherapy. Decreased blood flow and decreased oxygenation may result from radiotherapy and contribute to long-term toxicity. We sought to test the hypothesis that normal tissue becomes hypoxic following radiotherapy. Materials/Methods: Transcutaneous oxygen sensing electrode probe was used to determine breast tissue oxygen levels in irradiated and non-irradiated breast tissue one year after breast conserving therapy for early stage breast cancer. Oxygenation was measured at the lumpectomy site and a distant site in the irradiated breast for each subject. Oxygenation levels were also determined at corresponding locations in the non-irradiated (control) breast. Radiation Therapy Oncology Group toxicity criteria were used to assess skin and subcutaneous tissue damage. Measurements from twenty subjects were analyzed. Oxygenation levels were compared using a t-test for equality of means. Results: Transcutaneous measures of tissue oxygenation one year following breast radiotherapy were lower in irradiated versus control tissue. Subjects without diabetes had an average oxygenation level of 64.8 +/-19.9 mmHg in the irradiated breast at the non-lumpectomy site and an average of 72.3 +/-18.1 mmHg (p=0.014) at the corresponding location in the control breast. One subject had developed clinical grade 2 cutaneous changes one year after treatment, all others showed grade one changes. The subject with grade 2 toxicity had oxygenation levels of 74.5 and 58.8 in the control and irradiated breasts, respectively. Patients with diabetes (n = 4) showed a different oxygenation pattern, with lower oxygenation levels in control tissue and no decrease in the irradiated breast.Conclusions: Radiotherapy appears to decrease breast tissue oxygenation in non-diabetic patients one year after treatment. Transcutaneous oxygenation measurements may provide a useful tool to assess and quantify normal tissue injury following radiotherapy.Purpose/Objective(s): 3D-CRT is the most widely and available form of APBI used in the United States; it provides improved dose homogeneity compared to other APBI techniques, theoretically leading to improved cosmetic outcomes. However, the target volumes in 3D-CRT are highly dependent on the volume of the seroma after surgery and the optimal timing of APBI with respect to surgery has yet to be determined. S210I.