Accelerated partial-breast irradiation using intensity-modulated proton radiotherapy: do uncertainties outweigh potential benefits?

OBJECTIVE: Passive scattering proton beam (PSPB) radiotherapy for accelerated partial-breast irradiation (APBI) provides superior dosimetry for APBI three-dimensional conformal photon radiotherapy (3DCRT). Here we examine the potential incremental benefit of intensity-modulated proton radiotherapy (IMPT) for APBI and compare its dosimetry with PSPB and 3DCRT. METHODS: Two theoretical IMPT plans, TANGENT_PAIR and TANGENT_ENFACE, were created for 11 patients previously treated with 3DCRT APBI and were compared with PSPB and 3DCRT plans for the same CT data sets. The impact of range, motion and set-up uncertainties as well as scanned spot mismatching between fields of IMPT plans was evaluated. RESULTS: IMPT plans for APBI were significantly better regarding breast skin sparing (p<0.005) and other normal tissue sparing than 3DCRT plans (p<0.01) with comparable target coverage (p=ns). IMPT plans were statistically better than PSPB plans regarding breast skin (p<0.002) and non-target breast (p<0.007) in higher dose regions but worse or comparable in lower dose regions. IMPT plans using TANGENT_ENFACE were superior to that using TANGENT_PAIR in terms of target coverage (p<0.003) and normal tissue sparing (p<0.05) in low-dose regions. IMPT uncertainties were demonstrated for multiple causes. Qualitative comparison of dose-volume histogram confidence intervals for IMPT suggests that numeric gains may be offset by IMPT uncertainties. CONCLUSION: Using current clinical dosimetry, PSPB provides excellent dosimetry compared with 3DCRT with fewer uncertainties compared with IMPT. ADVANCES IN KNOWLEDGE: As currently delivered in the clinic, PSPB planning for APBI provides as good or better dosimetry than IMPT with less uncertainty.

Neovascularization in mucinous ductal carcinoma in situ suggests an alternative pathway for invasion.

AIMS: Ductal carcinoma in situ (DCIS) associated with invasive mucinous carcinoma (IMC) has not been well characterized. The aim was to characterize mucinous DCIS (mDCIS) of the breast and to describe, to our knowledge for the first time, neovascularization in mucin. METHODS AND RESULTS: The pathology reports and slides were reviewed from 44 patients treated between 2003 and 2006 at The University of Texas M. D. Anderson Cancer Center, whose diagnosis fulfilled the criteria of IMC or DCIS with mucin production. The patients, all female, had a mean age of 62 years. DCIS was present in 93% of cases and the predominant histological types were solid, cribriform and micropapillary. The DCIS was grade 1 in 12 of 41 cases (29.3%), grade 2 in 25 of 41 cases (61%) and grade 3 in four of 41 cases (9.8%). Mucin was seen in the lumen of the ducts involved by DCIS in 88% of cases, mucin and vessels in 63.4% of cases and neither mucin nor vessels in 12.2%. The DCIS was vascular endothelial growth factor-positive, platelet-derived growth factor receptor-beta-positive and CDX-2-negative (100%). Occasional luminal cells within the DCIS were immunopositive for CD68. CONCLUSIONS: A significant number of mDCIS showed neovascularization in intraluminal mucin. When identified on core needle biopsy, the presence of vascularized mucin should not be used alone to discriminate between invasive and in situ carcinoma. A hypothesis proposed for the source of recruitment of vessels in the mucin is that mucin can promote neovascularization and that tumour cells invade not into the adjacent fibroconnective tissue, but rather into the mucinous, richly vascularized stroma that they have induced. Alternatively, it is possible that both cells and their secretory product invade together. To our knowledge, this is the first study to characterize neovascularization within the mucinous component of DCIS associated with and without IMC.

Expression of ERalpha and ERbeta in lobular carcinoma in situ.

AIMS: Oestrogen is a modulator of cell growth and differentiation in the breast. It mediates most of its function through members of the oestrogen receptor (ER) family, ERalpha and ERbeta. Lobular carcinoma in situ (LCIS) is a known risk factor for the development of breast cancer; however, the use of tamoxifen for prevention is based upon data for ER+ (ERalpha) LCIS associated with invasion, but limited data exist on the use of tamoxifen in cases of ER+ (ERalpha) LCIS occurring in the absence of invasive carcinoma. The aim of this study was to examine ER expression in LCIS to determine the relationship of ERalpha to ERbeta and, thereby, to determine whether it is of clinical value to measure ERbeta along with ERalpha. METHODS AND RESULTS: Core biopsy specimens from 50 patients were examined retrospectively. Histology was reviewed and histological parameters were assessed. Formalin-fixed paraffin-embedded tissue was available for E-cadherin, ERalpha and ERbeta immunohistochemistry. The degree of ERalpha and ERbeta nuclear reactivity was quantified. The patients' mean age was 55 years. The mean follow-up duration was 48 months. All 50 cases of LCIS were E-cadherin-negative. All cases were ERalpha+ and ERbeta+. The staining intensity of ERbeta was strong and included staining of periductal stromal cells. The median percentage of cells immunoreactive for ERalpha was 75% and for ERbeta 70% (range 10% weak positive to 100% strong positive). There was a statistically significant relationship between ERbeta staining intensity and incidence of ipsilateral breast cancer (P = 0.010). CONCLUSIONS: The presence and intensity of both stromal and glandular ERbeta immunoreactivity suggest that the action of oestrogen on LCIS is on both stromal and glandular cells. Future studies are needed to determine whether the presence of ERbeta in LCIS could be targeted to influence the treatment of this disease and perhaps alter its natural history.

A custom three-dimensional electron bolus technique for optimization of postmastectomy irradiation.

PURPOSE: Postmastectomy irradiation (PMI) is a technically complex treatment requiring consideration of the primary tumor location, possible risk of internal mammary node involvement, varying chest wall thicknesses secondary to surgical defects or body habitus, and risk of damaging normal underlying structures. In this report, we describe the application of a customized three-dimensional (3D) electron bolus technique for delivering PMI. METHODS AND MATERIALS: A customized electron bolus was designed using a 3D planning system. Computed tomography (CT) images of each patient were obtained in treatment position and the volume to be treated was identified. The distal surface of the wax bolus matched the skin surface, and the proximal surface was designed to conform to the 90% isodose surface to the distal surface of the planning target volume (PTV). Dose was calculated with a pencil-beam algorithm correcting for patient heterogeneity. The bolus was then fabricated from modeling wax using a computer-controlled milling device. To aid in quality assurance, CT images with the bolus in place were generated and the dose distribution was computed using these images. RESULTS: This technique optimized the dose distribution while minimizing irradiation of normal tissues. The use of a single anterior field eliminated field junction sites. Two patients who benefited from this option are described: one with altered chest wall geometry (congenital pectus excavatum), and one with recurrent disease in the medial chest wall and internal mammary chain (IMC) area. CONCLUSION: The use of custom 3D electron bolus for PMI is an effective method for optimizing dose delivery. The radiation dose distribution is highly conformal, dose heterogeneity is reduced compared to standard techniques in certain suboptimal settings, and excellent immediate outcome is obtained.

Relationship of sentinel and axillary level I-II lymph nodes to tangential fields used in breast irradiation.

PURPOSE: To evaluate the volume of nodal irradiation associated with breast-conserving therapy, we defined the anatomic relationship of sentinel lymph nodes and axillary level I and II lymph nodes in patients receiving tangential breast irradiation. METHODS AND MATERIALS: A retrospective analysis of 65 simulation fields in women with breast cancer treated with sentinel lymph node surgery and 39 women in whom radiopaque clips demarcated the extent of axillary lymph node dissection was performed. We measured the relationship of the surgical clips to the anatomic landmarks and calculated the percentage of prescribed dose delivered to the sentinel lymph node region. RESULTS: A cranial field edge 2.0 cm below the humeral head the sentinel lymph node region was included or at the field edge in 95% of the cases and the entire extent of axillary I and II dissection in 43% of the axillary dissection cases. In the remaining 57%, this field border encompassed an average of 80% of cranial/caudal extent of axillary level I and II dissection. In 98.5% of the cases, all sentinel lymph nodes were anterior to the deep field edge and 71% were anterior to the chest wall-interface, whereas 61% of the axillary dissection cohort had extension deep to the chest wall-lung interface. If the deep field edge had been set 2 cm below the chest wall-lung interface, the entire axillary dissection would have been included in 82% of the cases, and the entire sentinel lymph node would have been covered with a 0.5-cm margin. The median dose to the sentinel lymph node region was 98% of the prescribed dose. CONCLUSIONS: By extending the cranial border to 2 cm below the humeral head and 2 cm deep to the chest wall-lung interface, the radiotherapy fields used to treat the breast can include the sentinel lymph node region and most of axillary levels I and II.

Cloning and characterization of the catalase gene of Neisseria gonorrhoeae: use of the gonococcus as a host organism for recombinant DNA.

The structural gene for the catalase of Neisseria gonorrhoeae was cloned into a Kat- strain of that organism by using a recombinant vector derived from one of the beta-lactamase-specifying plasmids found in that organism. The kat gene was then successfully subcloned into both pUC8 and pGB2, transformed into Escherichia coli, and shown to complement the E. coli katE mutants UM2 and UMRl. The gene was subsequently mutagenized and returned to the gonococcus to generate a Kat- strain that was phenotypically identical to the strain originally used to clone the gene. The sequence of the gene and the derived amino acid sequence showed that the gonococcal kat gene closely resembles the hktE gene of Haemophilus influenzae. The sequence of the promoter region of the gonococcal kat gene is unusual and may explain the extremely high, loosely regulated expression of the gene.

Characterization of a catalase-deficient strain of Neisseria gonorrhoeae: evidence for the significance of catalase in the biology of N. gonorrhoeae.

We obtained a catalase-deficient (Kat-) strain of Neisseria gonorrhoeae isolated from a patient who had been unsuccessfully treated with penicillin. Quantitative enzyme assays and electrophoresis of cell extracts on native polyacrylamide gels subsequently stained for catalase and peroxidase activities failed to detect both enzymes. The strain exhibited no growth anomalies or unusual requirements when grown under ordinary laboratory conditions. However, the Kat- strain proved extremely sensitive to exogenous hydrogen peroxide, and analysis of the bacterial DNA after such exposure showed extensive single-strand breakage in both chromosomal and plasmid DNAs. Partial characterization of the gonococcal catalase from a Kat+ laboratory strain revealed that the enzyme had the physical and chemical properties of both catalase and peroxidase.

Characterization of concatemeric plasmids of Neisseria gonorrhoeae.

Three strains of Neisseria gonorrhoeae carried novel plasmids of 7.8 megadaltons (mdal) molecular mass in addition to plasmids previously observed in this organism. The presence of the 7.8-mdal plasmids was not accompanied by any distinguishable phenotype in the strain possessing them. Analysis of plasmid DNA with restriction endonucleases showed that these plasmids were composed of three directly repeated copies of a 2.6-mdal cryptic plasmid frequently found in N. gonorrhoeae. In addition, the 7.8-mdal plasmids exhibited characteristics common to the 2.6-mdal plasmid, structural lability and sites resistant to cleavage with HpaII. The concatemeric forms of the cryptic plasmid appear to be stable in these strains and do not undergo internal recombination to produce the 2.6-mdal monomer, nor were higher concatemers detected.

Simple, transparent medium for study of legionellae.

A simple medium containing yeast extract, phosphate, and hemin as major components has been formulated for the study of legionellae. The medium supports the growth of a wide range of clinical and environmental isolates, with plating efficiencies comparable to those of charcoal-yeast extract agar. In addition, it does not contain activated charcoal or other components which may be associated with adverse reactions in humans. The medium is buffered and transparent; therefore, it would be suitable for genetic studies, production of biological reagents such as antigens and skin tests for human use, and antibiotic susceptibility assays.

Interference by Neisseria gonorrhoeae growth by other bacterial species.

Growth of Neisseria gonorrhoeae from clinical specimens has been enhanced by the use of selective media that inhibit the simultaneous growth of other microorganisms. One explanation for this enhancement could be that certain other bacteria inhibit gonococcal growth. This hypothesis was examined by testing 167 bacterial isolates for in vitro gonococcal inhibition; 34.1% of the isolates failed to inhibit the gonococcus, but 12.0% produced weak inhibition and 53.9% strongly inhibited N. gonorrhoeae. The pattern of in vitro gonococcal inhibition was consistently the same for all the individual isolates within some species, but individual isolates within other bacterial species varied in their ability to inhibit the gonococcus. Consistently strong in vitro N. gonorrhoeae inhibitors were Citrobacter diversus, Enterobacter cloacae, Serratia marcescens, and Pseudomonas. The in vivo significance of gonococcal interference was demonstrated in the subcutaneous chamber model of N. gonorrhoeae infection.

Lymphocyte transformation in repeated gonococcal urethritis.

In an attempt to ascertain whether cell-mediated hypersensitivity develops in the course of a naturally acquired gonorrhea infection, lymphocytes from men with gonococcal urethritis were cultured in vitro with a gonococcal antigen. The lymphocyte response was quantitated by a radioactive assay of deoxyribonucleic acid synthesis. Lymphocytes from subjects without gonorrhea were cultured in a similar manner to determine the specificity of the reaction. The recurrent nature of many gonococcal infections allowed a concurrent evaluation of whether the intensity of the in vitro lymphocyte response is related to the history of previous exposure to the antigen concerned. This study revealed a significantly greater lymphocyte response to the gonococcal antigen in those with gonorrhea infections than in the nongonorrhea subjects (P < 0.01). The intensity and timing of the response were also consistent with specific lymphocyte stimulation.