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Biomedical subjects

M Larochelle

Publications and source records attributed to M Larochelle.

9 recordsLinked to original sources
PubMed2001

The impact of skin washing with water and soap during breast irradiation: a randomized study.

BACKGROUND: The effect of washing the irradiated skin during radiotherapy for breast cancer is uncertain. The purpose of this study was to evaluate the impact of washing the breast skin with water and soap during radiotherapy on the intensity of acute skin toxicity. MATERIALS AND METHODS: Ninety-nine patients treated for breast cancer were prospectively randomized prior to receiving radiotherapy to the breast into two groups: (1), no washing was allowed during radiotherapy (49 patients); and (2), washing was allowed with water and soap (50 patients). Acute toxicity was recorded according to the Radiation Therapy Oncology Group (RTOG) acute skin toxicity scale for each patient every week during radiotherapy and 1 month after the end of radiotherapy. Symptoms related to skin toxicity were scored by visual analogue scales at the same time intervals. Other data collected included sociodemographic data, characteristics related to the tumor and previous treatments, radiation technique, necessity for a second simulation due to loss of skin marks and treatment interruptions. RESULTS: In the non-washing group, the following maximum acute toxicity scores were observed: grade 0, 2%; grade 1, 41%; grade 2, 57%; grades 3 and 4, 0%. For the washing group, the scores were: grade 0, 0%; grade 1, 64%; grade 2, 34%; grade 3, 2%; and grade 4, 0%. Moist desquamation was seen in 33% of non-washing patients, but in only 14% of washing patients. The median scores of pain, itching and burning of the treated skin were higher in the non-washing group, although this was not statistically significant. In a multivariate analysis using logistic regression, acute skin toxicity was associated with the patient's weight, concomitant radiochemotherapy and hot spots on dosimetry, and there was a trend toward more acute skin toxicity in the non-washing group. CONCLUSION: Washing the irradiated skin during the course of radiotherapy for breast cancer is not associated with increased skin toxicity and should not be discouraged.

Acute Disease↗
PubMed2001

H2A.Z is required for global chromatin integrity and for recruitment of RNA polymerase II under specific conditions.

Evolutionarily conserved variant histone H2A.Z has been recently shown to regulate gene transcription in Saccharomyces cerevisiae. Here we show that loss of H2A.Z in this organism negatively affects the induction of GAL genes. Importantly, fusion of the H2A.Z C-terminal region to S phase H2A without its corresponding C-terminal region can mediate the variant histone's specialized function in GAL1-10 gene induction, and it restores the slow-growth phenotype of cells with a deletion of HTZ1. Furthermore, we show that the C-terminal region of H2A.Z can interact with some components of the transcriptional apparatus. In cells lacking H2A.Z, recruitment of RNA polymerase II and TATA-binding protein to the GAL1-10 promoters is significantly diminished under inducing conditions. Unexpectedly, we also find that H2A.Z is required to globally maintain chromatin integrity under GAL gene-inducing conditions. We hypothesize that H2A.Z can positively regulate gene transcription, at least in part, by modulating interactions with RNA polymerase II-associated factors at certain genes under specific cell growth conditions.

Amino Acid Sequence↗
PubMed2000

A variable speed translating couch technique for total body irradiation.

We have developed a variable speed translating patient couch system for the delivery of total body irradiation (TBI). For a whole body Rando-type phantom, dose variation at mid-plane relative to the prescription point (navel) can be as high as 15% (neck or legs) with a constant velocity. By taking into account variations in body thickness, the intensity modulation radiation therapy, resulting from variable velocities, effectively delivers a uniform dose distribution at mid plane. The couch control user interface, technical aspects and dose planning optimization procedure for determining velocity distribution are described.

Biophysical Phenomena↗
PubMed1999

Local failure is responsible for the decrease in survival for patients with breast cancer treated with conservative surgery and postoperative radiotherapy.

PURPOSE: The aim of the present study was to evaluate the role of local failure (LF) in the survival of patients treated with lumpectomy and postoperative radiotherapy and to investigate whether LF is not only a marker for distant metastasis (DM) but also a cause. METHODS: Charts of patients treated with breast conservative surgery between 1969 and 1991 were reviewed retrospectively. There were 2,030 patients available for analysis. The median duration of follow-up was 6 years. A Cox regression multivariate analysis was performed using LF as a time-dependent covariate. RESULTS: Local control (LC) was 87% at 10 years. Local failure led to poorer survival at 10 years than local control (55% v 75%, P < .00). In a Cox model, local failure was a powerful predictor of mortality. The relative risk associated with LF was 3.6 for mortality and 5.1 for DM (P < .00). In patients with LF, the rate of DM peaked at 5 to 6 years, whereas it peaked at 2 years for patients with LC. The mean time between surgery and DM was 1,050 days for patients without LF and 1,650 days for patients with LF (P < .00). CONCLUSION: Our results show that local failure is associated with an increase in mortality. The difference in the time distribution of distant metastasis for LF and LC could imply distinct mechanisms of dissemination. Local failure should be considered not only as a marker of occult circulating distant metastases but also as a source for new distant metastases and subsequent mortality.

Actuarial Analysis↗
PubMed1996

The role of palliative thoracic radiotherapy in non-small cell lung cancer.

Non-small cell lung cancer is the most common cause of cancer death in both males and females. Despite this high incidence and mortality, comparatively little research has addressed the palliative treatment of thoracic symptoms. Until recently, information regarding the indications and effectiveness of radiation in this setting was obtained from retrospective reviews of single institutional experiences. More recently, three major randomized trials from the UK Medical Research Council (1991, 1992, 1994) have addressed the use of external beam radiation in randomized comparisons of different dose and fractionation strategies for patients with non-small cell lung cancer and symptoms due to intra-thoracic tumor. These studies show that shorter fractionation schemes provide equivalent palliation and essentially equivalent survival in the patient groups studied. Moreover, they provide estimates of the probability of successful palliation of common symptoms, and estimates of the toxicity of each regimen. A panel of oncologists with expertise in radiation oncology, medical oncology and epidemiology discussed the above trial results and a literature review. The panel concluded that radiation was indicated in the palliation of hemoptysis, chest pain, dysphagia, and dyspnea, and that the results of the MRC studies provided reasonable estimations of the efficacy and toxicity of radiation in this setting. These studies show that symptoms are more often than not improved with palliative radiotherapy (symptom improvement rates ranged from about 50 to 85%) and that palliation lasted for a substantial portion of the patients' remaining survival. The panel could not reach uniform consensus on the appropriate fractionation for radiation given with palliative intent. The panel agreed that favourable patients with stage IIIB NSCLC should be offered combined modality therapy with the intent of prolonging survival, and that patient preferences regarding the risks and benefits of this therapy should be considered. Further study was recommended, namely, a randomized trial evaluating five fractions of radiation vs a single fraction, using patient-based evaluation of palliation. The panel also recommended phase II development of a combined chemotherapy and low-dose radiation protocol appropriate for future study.

Carcinoma, Non-Small-Cell Lung↗
PubMed1995

The radiosensitivity of uveal melanoma cells and the cell survival curve.

BACKGROUND: No study of the radiosensitivity of uveal melanoma cells and their survival curve has been published. The purpose of this study was to investigate the sensitivity to different single radiation doses of SP6.5, a human uveal melanoma cell line. METHODS: Cells were irradiated with cobalt-60 at doses from 0 to 1200 cGy. Radiosensitivity was measured by three methods: soft-agar bilayer assay, tritiated thymidine incorporation, and bromodeoxyuridine (BrdU) incorporation. RESULTS: The soft-agar bilayer assay, by assessing the colony-forming units, showed that the D1 value was 470 cGy, the Dq value was 400 cGy, and the n value exceeded 10, thus indicating a broad, shoulder and relative radioresistance. The doubling time as estimated by [3H]thymidine incorporation was unaffected at doses below 600 cGy, another indication of radioresistance. BrdU incorporation revealed no significant increase between 0 and 1000 cGy, indicating that the cell cycle was not interrupted. CONCLUSION: Cell survival, doubling time, and cell phases are parameters of growth kinetics, and the results suggest that SP6.5 is radioresistant and virtually unaffected by single radiation doses lower than 600 cGy. Our data parallel published data for cutaneous melanomas.

Aged↗
PubMed1995

The role of electronic portal imaging in tangential breast irradiation: a prospective study.

Side effects due to irradiation of normal tissues and local failure can be associated with deviations in the patient positioning in radiation therapy. In particular, tangential breast irradiation may include normal lung tissue or even a small portion of the heart in the field. A prospective study was performed to assess the precision and the reproducibility of the tangential breast irradiation technique with the help of on-line electronic portal imaging devices (EPID). The influence of respiration on the treatment set-up was evaluated. Also, a comparison was made with simulation films to study the degree of concordance with the intended treatment. Twenty patients with early breast cancer receiving post-operative radiotherapy were entered in the study. Geometrical parameters were measured from daily on-line portal images taken for approximately 17 fractions of each tangential fields. Multiple images were also acquired (six per field) for six fractions for all patients, yielding a total of 2120 images including the simulator films. Random and systematic errors were obtained. Variations of the parameters between various fractions and within the same fraction were about 3 mm (1 SD) or less. Variation between simulation and treatment set-up was 4.3 mm or less. Large maximum deviations, reaching 22.9 mm, were observed in rare cases. This confirms the need to implement daily verification procedures and to correct deviations in the treatment set-up. The study has shown that EPID can help reaching a high accuracy in patient treatment.

Breast Neoplasms↗