KRAS and BRAF mutations in anal carcinoma.

The EGF receptor (EGFR) is expressed in most cases of anal carcinomas. Anecdotal benefit from EGFR-targeted therapy has been reported in anal cancer and a negative correlation with Kirsten Ras (KRAS) mutation status has been proposed. The purpose of this retrospective study was to investigate the frequency and the prognostic value of KRAS and BRAF mutations in a large cohort of patients with anal cancer. One hundred and ninety-three patients with T1-4N0-3M0-1 anal carcinoma were included in the study. Patients were treated with curative (92%) or palliative intent (8%) between January 2000 and January 2010. KRAS mutations were detected using Therascreen(®)KRAS real-time PCR assay (Qiagen) and V600E or V600D/K BRAF mutations were uncovered using Pyrosequencing. The frequency of KRAS and BRAF mutations was low; KRAS mutations were detected in 1.6% and BRAF mutations in 4.7% of the biopsies. No impact of KRAS or BRAF status on survival was found. In conclusion, both KRAS and BRAF mutations are rare in anal cancer. The low frequency of KRAS mutations support protocols exploring EGFR-targeted therapy in patients with metastatic anal cancer, while treatment with BRAF inhibitors might be relevant for only a very few patients.

Human papillomavirus genotyping and p16 expression as prognostic factors for patients with American Joint Committee on Cancer stages I to III carcinoma of the anal canal.

PURPOSE: Carcinomas of the anal canal are strongly associated with the human papillomavirus (HPV). Expression of p16 is used as a surrogate marker of HPV infection. In a retrospective study, we evaluated HPV genotyping and p16 expression as prognostic markers of overall survival (OS) and disease-specific survival (DSS) in patients diagnosed with American Joint Committee on Cancer (AJCC) stages I to III carcinoma of the anal canal. PATIENTS AND METHODS: HPV genotyping polymerase chain reaction (high-risk subtypes 16, 18, 31, 33, 45, 52, and 58) and immunohistochemical expression of p16 were analyzed by using paraffin-embedded tumor biopsies from 143 anal carcinomas. The patients were treated with combined chemoradiotherapy or radiotherapy alone. RESULTS: HPV16 was detected in 81.0% of the tumors, followed by HPV33 (5.1%), HPV18 (2.2%), and HPV58 (0.7%). p16 positivity was found in 92.9% of the tumors. In univariable survival analysis, HPV positivity was significantly correlated with improved OS (74% v 52%; P=.036) and DSS (84% v 52%; P=.002), and p16 positivity was significantly correlated with improved OS (76% v 30%; P<.001) and DSS (85% v 30%; P<.001). In multivariable COX analysis that included HPV status, p16 status, sex, T stage, N stage, and treatment, p16 positivity remained an independent prognostic factor for OS (hazard ratio [HR], 0.07; 95% CI, 0.01 to 0.61; P=.016) and DSS (HR, 0.07; 95% CI, 0.01 to 0.53; P=.011). CONCLUSION: p16 positivity is an independent prognostic factor for OS and DSS in patients with AJCC stages I to III carcinoma of the anal canal.

Variability in prostate and seminal vesicle delineations defined on magnetic resonance images, a multi-observer, -center and -sequence study.

BACKGROUND: The use of magnetic resonance (MR) imaging as a part of preparation for radiotherapy is increasing. For delineation of the prostate several publications have shown decreased delineation variability using MR compared to computed tomography (CT). The purpose of the present work was to investigate the intra- and inter-physician delineation variability for prostate and seminal vesicles, and to investigate the influence of different MR sequence settings used clinically at the five centers participating in the study. METHODS: MR series from five centers, each providing five patients, were used. Two physicians from each center delineated the prostate and the seminal vesicles on each of the 25 image sets. The variability between the delineations was analyzed with respect to overall, intra- and inter-physician variability, and dependence between variability and origin of the MR images, i.e. the MR sequence used to acquire the data. RESULTS: The intra-physician variability in different directions was between 1.3 - 1.9 mm and 3 - 4 mm for the prostate and seminal vesicles respectively (1 std). The inter-physician variability for different directions were between 0.7 - 1.7 mm and approximately equal for the prostate and seminal vesicles. Large differences in variability were observed for individual patients, and also for individual imaging sequences used at the different centers. There was however no indication of decreased variability with higher field strength. CONCLUSION: The overall delineation variability is larger for the seminal vesicles compared to the prostate, due to a larger intra-physician variability. The imaging sequence appears to have a large influence on the variability, even for different variants of the T2-weighted spin-echo based sequences, which were used by all centers in the study.

Dosimetric and geometric evaluation of an open low-field magnetic resonance simulator for radiotherapy treatment planning of brain tumours.

BACKGROUND AND PURPOSE: Magnetic resonance (MR) imaging is superior to computed tomography (CT) in radiotherapy of brain tumours. In this study an open low-field MR-simulator is evaluated in order to eliminate the cost of and time spent on additional CT scanning. MATERIALS AND METHODS: Eleven patients with brain tumours are both CT and MR scanned and the defined tumour volumes are compared. Image distortions and dose calculations based on CT density correction, MR unit density and MR bulk density, bone segmentation are performed. Monte Carlo simulations using 4 and 8 MV beams on homogeneous and bone segmented mediums are performed. RESULTS: Mean MR and CT tumour volumes of approximately the same size (V MR =55+/-34 cm3 and V CT =51+/-32 cm3) are observed, but for individual patients, small intersection volumes are observed. The MR images show negligible distortion within radial distances below 12 cm (<1.5 mm). On unit density mediums, dose errors above 2% are observed in low dose areas. Monte Carlo simulations with 4 MV photons show large deviations in dose (>2%) just behind the skull if bone is not segmented. CONCLUSIONS: It is feasible to use an MR-simulator for radiotherapy planning of brain tumours if bone is segmented or a careful choice of beam energy (>4 MV) is selected.