Radiotherapy of MRI-detected involved internal mammary lymph nodes in breast cancer.

BACKGROUND: The internal mammary (IM) lymph node chain, along with the axillary nodal basin, is a first-echelon breast lymphatic draining site. A growing body of evidence supports irradiation of this region in node-positive breast cancer. This study evaluated the effectiveness of radiotherapy in treating magnetic resonance imaging (MRI)-detected abnormal IM lymph nodes in newly-diagnosed non-metastatic breast cancer. METHODS: A structured query was performed on an electronic institutional database to identify women with radiographic evidence of abnormal IM node(s) on breast MRI from 2005 to 2013. Manual review narrowed inclusion to patients with a primary diagnosis of non-metastatic breast cancer with abnormal IM node(s) based on pathologic size criteria and/or abnormal enhancement. RESULTS: Of the 7070 women who underwent pre-treatment MRI, 19 (0.3%) were identified on imaging to have a total of 25 abnormal pre-treatment IM lymph nodes, of which 96% were located in the first two intercostal spaces and 4% in the third space. A majority of the primary tumors were high-grade (94.7%) and hormone-receptor negative (73.7%), while 47.4% overexpressed HER-2/neu receptor. Axillary nodal disease was present in 89.5% of patients, while one patient had supraclavicular involvement. At a median follow-up of 38 months, 31.6% of patients had developed metastatic disease and 21.1% had died from their disease. Of the patients who received IM coverage, none had progressive disease within the IM lymph node chain. CONCLUSIONS: Radiologic evidence of pre-treatment abnormal IM chain lymph nodes was associated with advanced stage, high grade, and negative estrogen receptor status. The majority of positive lymph nodes were located within the first two intercostal spaces, while none were below the third. Radiation of the IM chain in combination with modern systemic therapy was effective in achieving locoregional control without surgical resection in this cohort of patients.

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity.

PURPOSE: To improve tumor dose conformity and homogeneity for COMS plaque brachytherapy by investigating the dosimetric effects of varying component source ring radionuclides and source strengths. MATERIAL AND METHODS: The MCNP5 Monte Carlo (MC) radiation transport code was used to simulate plaque heterogeneity-corrected dose distributions for individually-activated source rings of 14, 16 and 18 mm diameter COMS plaques, populated with (103)Pd, (125)I and (131)Cs sources. Ellipsoidal tumors were contoured for each plaque size and MATLAB programming was developed to generate tumor dose distributions for all possible ring weighting and radionuclide permutations for a given plaque size and source strength resolution, assuming a 75 Gy apical prescription dose. These dose distributions were analyzed for conformity and homogeneity and compared to reference dose distributions from uniformly-loaded (125)I plaques. The most conformal and homogeneous dose distributions were reproduced within a reference eye environment to assess organ-at-risk (OAR) doses in the Pinnacle(3) treatment planning system (TPS). The gamma-index analysis method was used to quantitatively compare MC and TPS-generated dose distributions. RESULTS: Concentrating > 97% of the total source strength in a single or pair of central (103)Pd seeds produced the most conformal dose distributions, with tumor basal doses a factor of 2-3 higher and OAR doses a factor of 2-3 lower than those of corresponding uniformly-loaded (125)I plaques. Concentrating 82-86% of the total source strength in peripherally-loaded (131)Cs seeds produced the most homogeneous dose distributions, with tumor basal doses 17-25% lower and OAR doses typically 20% higher than those of corresponding uniformly-loaded (125)I plaques. Gamma-index analysis found > 99% agreement between MC and TPS dose distributions. CONCLUSIONS: A method was developed to select intra-plaque ring radionuclide compositions and source strengths to deliver more conformal and homogeneous tumor dose distributions than uniformly-loaded (125)I plaques. This method may support coordinated investigations of an appropriate clinical target for eye plaque brachytherapy.