Do Patient-reported Outcome Measures Agree with Clinical and Photographic Assessments of Normal Tissue Effects after Breast Radiotherapy? The Experience of the Standardisation of Breast Radiotherapy (START) Trials in Early Breast Cancer

AIMS

In radiotherapy trials, normal tissue effects (NTE) are important end points and it is pertinent to ask whether patient-reported outcome measures (PROMs) could replace clinical and/or photographic assessments. Data from the Standardisation of Breast Radiotherapy (START) trials are examined.

MATERIALS AND METHODS

NTEs in the treated breast were recorded by (i) annual clinical assessments, (ii) photographs at 2 and 5 years, (iii) PROMs at 6 months, 1, 2 and 5 years after radiotherapy. Hazard ratios for the radiotherapy schedules were compared. Measures of agreement of assessments at 2 and 5 years tested concordance.

RESULTS

PROMs were available at 2 and/or 5 years for 1939 women, of whom 1870 had clinical and 1444 had photographic assessments. All methods were sensitive to the dose difference between schedules. Patients reported a higher prevalence for all NTE end points than clinicians or photographs (P < 0.001 for most NTEs). Concordance was generally poor; weighted kappa at 2 years ranged from 0.05 (telangiectasia) to 0.21 (shrinkage and oedema). The percentage agreement was lowest between PROMs and photographic assessments of change in breast appearance (38%).

CONCLUSIONS

All three methods produced similar conclusions for the comparison of trial schedules, despite low concordance between the methods on an individual patient basis. Careful consideration should be given to the different contributions of the measures of NTE in future radiotherapy trials.

Abstract P3-06-09: Test of association between Ki67 index of early breast cancer and local relapse after adjuvant hypofractionated radiotherapy

Introduction: There is a strong inverse association between the proliferation indices of early- and late-responding normal tissues and their sensitivity to radiotherapy fraction size. The aim of this study is to test for association between Ki67 index and the fractionation sensitivity of breast cancer. The hypothesis is that tumours with high Ki67 indices are relatively insensitive to fraction size and be over-represented in tumours relapsing after hypofractionated, radiotherapy.

Methods: Between 1986 and 2003, the START pilot and START A trials tested 2 test dose levels of a 13-fraction regimen (3.0 or 3.3 Gy & 3.0 or 3.2 Gy fractions, respectively) in 5 weeks against 25 fractions of 2.0 Gy following primary surgery for early breast cancer. Primary tumour blocks of patients with local tumour relapse were collected for immunohistochemistry (IHC) for Ki67 (manual counting in whole sections), HER2, ER & PR (Allred quick scores in tissue sections). Ki67 was assumed to be log normally distributed with a standard deviation of 0.5–0.9. Assuming evaluable blocks for 240 patients, a standardised detectable difference of 0.45 (90%+ power, 5% significance level) corresponded to a detectable difference in geometric means of 5–10%.

Results: From a total of 3646 patients entered into the START pilot and START A trials, 261 local tumour relapses were recorded at a median follow up of 8.4 years (range 0.9–17.5) and 7.2 (range 0.7–11.9) years respectively. Blocks from 213 patients were recovered, of which 176 were evaluable by IHC. There was no significant difference in proliferation between tumours relapsing after conventional and hypofractionated radiotherapy, with mean Ki67 scores of 7.63 (95%CI: 5.06–11.5) and 5.33 (95CI%: 3.86–7.35), respectively. Mean Ki67 scores in 48 primary triple negative tumours (TNT) that relapsed locally were 15.74 (95%CI: 8.53–29.06) after conventional and 7.52 (95%CI: 3.51–16.1) after hypofractionated radiotherapy, but TNT were equally represented (28%) in both groups.

Conclusion: An association between proliferative indices and fractionation sensitivity in breast tumours has not been demonstrated. If confirmed, it suggests that genetic and epigenetic features unrelated to proliferation are sources of inter-tumour variation in fractionation sensitivity.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-06-09.

The UK national study of magnetic resonance imaging as a method of screening for breast cancer (MARIBS)

The UK national study of magnetic resonance imaging as a method of screening for breast cancer (MARIBS) is in progress. The study design, accrual to date, and related research projects are described. Revised accrual rates and expected recruitment are given. 15 cancers have been detected to date, from a total of 1236 screening measurements. This event rate and the tumour grades reported are compared with recent reports from other studies in women at high risk of breast cancer.

Salmonella enterica serovar typhimurium surA mutants are attenuated and effective live oral vaccines

A previously described attenuated TnphoA mutant (BRD441) of Salmonella enterica serovar Typhimurium C5 (I. Miller, D. Maskell, C. Hormaeche, K. Johnson, D. Pickard, and G. Dougan, Infect. Immun. 57:2758-2763, 1989) was characterized, and the transposon was shown to be inserted in surA, a gene which encodes a peptidylprolyl-cis, trans-isomerase. A defined surA deletion mutation was introduced into S. enterica serovar Typhimurium C5 and the mutant strain, named S. enterica serovar Typhimurium BRD1115, was extensively characterized both in vitro and in vivo. S. enterica serovar Typhimurium BRD1115 was found to be defective in the ability to adhere to and invade eukaryotic cells. Furthermore, S. enterica serovar Typhimurium BRD1115 was attenuated by at least 3 log units when administered orally or intravenously to BALB/c mice. Complementation of the mutation with a plasmid carrying the intact surA gene almost completely restored the virulence of BRD1115. In addition, S. enterica serovar Typhimurium BRD1115 demonstrated potential as a vaccine candidate, since mice immunized with BRD1115 were protected against subsequent challenge with S. enterica serovar Typhimurium C5. S. enterica serovar Typhimurium BRD1115 also showed potential as a vehicle for the effective delivery of heterologous antigens, such as the nontoxic, protective fragment C domain of tetanus toxin, to the murine immune system.

Expression of the mouse c-abl type IV proto-oncogene product in the insect cell baculovirus system

The cellular gene c-abl is the normal homologue of the transforming gene (v-abl) within the genome of the Abelson leukaemia virus. The cDNA sequence coding for the cellular form of the murine abl gene (c-abl type IV) has been inserted into the baculovirus transfer vector, pAc36C, so that the c-abl gene is under the control of the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). Spodoptera frugiperda cells infected with the recombinant transfer vector in the presence of wild type AcNPV DNA yielded recombinant, polyhedrin negative virus that expressed moderate levels of the c-Abl protein (representing approx. 0.5-1% of the stained cellular proteins as determined by densitometric scanning). The insect derived c-Abl protein was compared to the P210-BCR/ABL protein from K562 cells, a cell line derived from a patient with chronic myelogenous leukaemia. Antibodies raised against synthetic peptides based on c-abl encoded peptides react with the insect derived c-Abl. In addition, the baculovirus derived c-Abl protein has a tyrosine kinase activity as demonstrated by phosphorylation of a synthetic polypeptide and also by autophosphorylation. Phosphoamino acid analysis of immunoprecipitated, autophosphorylated baculovirus derived c-Abl protein indicates that the majority of label incorporated is on the tyrosine residues. Immunofluorescence microscopy has been used to show that the majority of the c-Abl protein expressed in cells infected with recombinant virus is located in the nuclear and plasma membranes.

Functional properties of human thyroid hormone receptor beta 1 overexpressed using baculovirus

We have overexpressed the human beta 1 thyroid hormone receptor in insect cells using a recombinant baculovirus to a level of 5-10% of total cellular protein. The recombinant protein migrates as a 50 kDa band by SDS-PAGE and Western blot analysis. The expressed receptor binds to L-T3 with a Kd of 1.3 +/- 0.4 x 10(-10) M and to thyroid hormone analogues with an affinity hierarchy of TRIAC greater than L-T3 greater than L-T4 greater than rT3. Gel retardation assays show highly specific receptor binding to a TRE which is modified by the presence of ligand and avidin-biotin complex DNA analysis shows a Kd of 6.2 +/- 2.0 x 10(-10) M for this interaction. These results indicate high level expression of hTR beta with authentic hormone and DNA binding properties.

Characterization of recombinant human Kirsten-ras (4B) p21 produced at high levels in Escherichia coli and insect baculovirus expression systems

Kirsten-ras is the oncogene most frequently activated in human tumors. Studies of its biological function have been limited by the nonavailability of significant amounts of the major protein product, Kirsten-ras (4B) p21. When expressed in Escherichia coli K12, the recombinant protein was rapidly cleaved upon cell lysis in the lysine-rich C terminus region, probably by the ompT protease. However, soluble full-length protein was obtained when the Kirsten-ras gene was expressed in an E. coli strain lacking the ompT gene, and also in a baculovirus/insect cell expression system. Additionally, the baculovirus/insect cell system produced about half of the Kirsten-ras protein in a membrane-associated form, which was post-translationally modified by polyisoprenylation and carboxyl-methylation. A C-terminally truncated form (residues 1-166) was also expressed at high levels in E. coli for x-ray crystallographic studies. The kinetics of GDP release and of GTP hydrolysis of the purified proteins are similar to those of the corresponding Harvey-ras proteins, though there are small differences in the relative affinities for GDP and GTP. Biological activity of full-length Kirsten Val-12 p21 was demonstrated by microinjection into Swiss 3T3 cells, resulting in morphological transformation, with a lower potency than that of Harvey Val-12 protein.

The Ha-ras protein, p21, is modified by a derivative of mevalonate and methyl-esterified when expressed in the insect/baculovirus system

Using the insect/baculovirus expression system, we demonstrate the incorporation of [3H]mevalonate and [3H]methyl groups into recombinant c-Ha-ras protein (p21). Unlike the post-translational palmitoylation of p21 expressed in this system, the modification by mevalonate is not removed by hydroxylamine suggesting the absence of a thioester linkage. It is highly likely that the insect expression system recognizes the C-terminal CAAX Motif in p21, incorporates the mevalonate into the recently described polyisoprenylation modification and carboxyl-methylates the protein.

Expression and characterization of the Ha-ras p21 protein produced at high levels in the insect/baculovirus system

Normal and mutated cDNAs of Ha-ras have each been cloned into a standard (pAc373) and a novel (p36C) baculovirus transfer vector and introduced via homologous recombination into the genome of Autographa californica nuclear polyhedrosis virus immediately downstream of the polyhedrin promoter. Spodoptera frugiperda cells infected with recombinant virus containing the normal Ha-ras gene express very high levels of ras p21 protein (approximately 20% of total cell protein), whereas the mutant protein was expressed at considerably lower levels. Molecular analysis showed that this was most likely due to a post-transcriptional event. The expression vector p36C produced considerably higher levels of recombinant p21 compared to the more commonly used pAc373. The majority of the normal ras p21 protein is soluble, cytoplasmic, and appears to be nonacylated. However, about 10% of the p21 associates with the membrane fraction of infected cells and migrates as a slightly faster band on gels. Furthermore, this band is sensitive to hydroxylamine treatment and shows specific incorporation of [3H]palmitate, strongly suggesting that it is the palmitoylated form of p21, which is the biologically active form of the protein. Both the soluble and membrane-associated p21 have been purified to homogeneity under nondenaturing conditions, the latter in the presence of detergents. The isolation of native palmitoylated p21 has not been reported previously. The difference in hydrophobicity between these two proteins has been demonstrated by Triton X-114 partitioning. The use of the insect/baculovirus expression system to express relatively high levels (20 mg/liter) of palmitoylated p21 should aid experiments to resolve the structural and functional properties of this molecule.