Biomedical subjects

P Aletti

Publications and source records attributed to P Aletti.

At least 19 recordsLinked to original sources

PubMed2006

[The French preliminary experience of the use of a seed-projector for exclusive iodine 125 prostate brachytherapy: feasibility and acute toxicity].

PURPOSE: To analyse a new technique for prostate brachytherapy with permanent Iodine implants characterized by the use of a seed projector after a 3D dosimetric peroperative treatment planning (FIRST technique). PATIENTS AND METHOD: 395 patients have been treated in France with this technique in six radiotherapy centres between November 2002 and December 2005 for a localized prostate cancer. RESULTS: Thirteen patients (3.3%) developped a urinary retention, and respectively 7.8 and 26.5% an acute RTOG grade 3 and 2 toxicity. The 6-weeks IPSS score was equal or lower to 15 in 73% with a 11 median IPSS value. A failure of the loading with the seed-projector, leading to a manual loading of the seeds, occurred in 9 patients (2.3%) in two centres, directly related to the loading procedure with the seed-projector in 5 cases. The median duration of the procedure was reduced by 30 minutes for the patients treated in 2005. CONCLUSIONS: This multicenter study establishes the feasibility of the routine use of a seed projector for permanent iodine 125 prostate implants with an initial tolerance similar to the best results published for other implants techniques.

Brachytherapy↗

PubMed2006

Esophageal cancer: determination of internal target volume for conformal radiotherapy.

BACKGROUND AND PURPOSE: To evaluate esophageal tumor and OAR movement during the respiratory cycle in order to obtain optimal values for ITV and PRV. To correlate tumor motion with chest wall displacement - information of value in the free-breathing gating system. MATERIAL AND METHOD: Inclusion criteria were: histologically proven squamous-cell carcinoma (SCC) or adenocarcinoma at stage T3 - T4 NX or TX N1 M0 according to the UICC 1997 classification. Two spiral scans were performed with breath-hold respiration under spirometric control: one at end expiration (EBH) and the other at end inspiration (IBH). Displacements between exhalation and inhalation were calculated according to ICRU report 42 recommendations. For the correlation study, CT-scan acquisition was performed at the isocenter over a 20 - 40 s period. After Fourier Transform, frequency spectra for amplitude and phase of tumor and chest wall motions were performed for each patient. RESULTS: Cumulative distribution of CTV motion in absolute values showed that 95% of data ranged from 0 to 1 cm. Cumulative distribution of GTV motion in absolute values showed that 95% of data ranged from 0 to 0.8 cm. The correlation study demonstrated no specific relationship between respiratory and esophageal motions. CONCLUSION: The ITV margin for 3D conformal radiotherapy in esophageal cancer was 1 cm when 95% of motions were taken into account in this clinical study involving eight patients. Before using a free-breathing gating system, the correlation between external markers and target displacement during irradiation must be established for each patient.

Adenocarcinoma↗

PubMed2004

[Intensity-modulated radiation therapy for head and neck cancers with bilateral irradiation of the neck : preliminary results].

PURPOSE: To report preliminary results of a prospective study of intensity-modulated radiotherapy (IMRT) for head and neck squamous cell carcinoma (HNC) with bilateral irradiation of the neck. PATIENTS AND METHODS: At the Alexis Vautrin Cancer Center, 23 patients have been treated with IMRT for HNC since January 2002-August 2003. The first 10 patients with a minimum follow-up of 3 months were analyzed. All tumors were oropharyngeal. There were four females and six males, with a mean age of 50 years (range 39-66). Stages were I-II in eight and III-IV in two. CTV1 was microscopic disease and N0 neck (prescribed dose : 50 Gy) and CTV2 was macroscopic disease and the volume at risk (prescribed dose: 66-70 Gy). PTV were CTV + 5 mm. Patient's immobilization consisted of a five-point head neck shoulder thermoplastic mask. Set-up verifications were done by semi-automatically matching portal images and digitized reconstructed radiographs. IMRT used dynamic multileaf collimation. Five patients (group A) received 50 Gy IMRT (two post-operative and three with a brachytherapy boost with a mean dose: 27.5 Gy), and five patients (group B) received 66-70 Gy IMRT (four post-operative). Acute and late normal tissue effects were graded according to the RTOG-EORTC radiation morbidity scoring criteria. RESULTS: With a median follow-up of 7.4 months (range 3-18.5), no patient died or had loco-regional relapse. The displacements were <4 mm in 98% cases. CTV1 and 2 received 95% of the prescribed dose in 100% of the volume. On average the mean dose to the contralateral parotid was 25.5 Gy for group A vs. 31 Gy for group B (P = 0.09). Mean doses <26 Gy were obtained in three of five patients in group A vs. zero of five patients in group B (P = 0.04). Acute skin toxicities were grade 1 in five patients, grade 2 in four and grade 3 in one. Acute mucositis cases were grade 1 in three patients, grade 2 in five and localized grade 3 in two. At 3 months, 50% of the patients had a grade 0-1 late xerostomia. CONCLUSION: The 26 Gy dose limit constraint to the contralateral parotid was easier to satisfy when IMRT was prescribed at a maximum dose of 50 Gy. Acute toxicity is low. The displacements in the mask indicate that it is possible to define the PTV as CTV + 4 mm. This reduction should decrease the mean dose to the parotids. At 3 months, a 50% rate of grade 0-1 late xerostomia encourages the hope of a very low rate at 2 years.

Adult↗

PubMed2004

[Recommendations for a head and neck IMRT quality assurance protocol].

Head and neck tumors represent very interesting targets for IMRT techniques because of the complex shape of the structures and the organs at risk close by. The use of this kind of techniques requires a quality assurance protocol. The physicists of the GORTEC group shared their experience to define some recommendations in order to draw up a QA protocol. The dosimetric verification of the treatment plans (in terms of absolute and relative dose), the control of the reproducibility of the patient positioning and the use of a record and verify system to control the different parameters form the main parts of these recommendations. Each chapter comprises a description of the different methods, recommendations concerning the equipment, the adopted tolerances, the frequency of controls. At the end of each chapter, a table summarizes the main actions to carry out. These recommendations will allow to harmonize our practices whatever the softwares and the accelerator that are being used. They will simplify the task of the teams that wish to implement IMRT for head and neck tumors.

Clinical Protocols↗

PubMed2004

[Conformal radiotherapy by modulation of intensity].

External beam radiation therapy has changed dramatically during the past decade. Intensity Modulated Radiotherapy (IMRT) represents one of the most important technical advances. IMRT allows dose escalation with potential improvement in local control and less toxicity to normal tissues. It's also a radical change in practice for the physicist but particularly for the radiation oncologist. In this article, we have been described the physical and technical principles of IMRT. Indications are reviewed and aiming to summarize the published data. At last, importance of rigorous and reproducible quality assurance procedures should be emphasized and reminded. The potential clinical applications of IMRT are broad and continue to expand but enthusiasm for IMRT does not have to mask reality. Undesired or even potentially dangerous results may occur and no clinical data are currently available to support its use. More long term data and prospective controlled trials are required to confirm the clinical benefits of IMRT.

Breast Neoplasms↗

PubMed2004

[Preliminary results of the assessment of intensity modulated radiotherapy (IMRT) for prostatic and head and neck tumors (STIC 2001)].

INTRODUCTION: Between May 2002 and May 2004, eight French comprehensive cancer centres did a prospective nonrandomized study including 200 patients, 100 with cancer of the prostate and 100 with head and neck cancers. Half of each patient group was treated by IMRT and the others by RTC 3D. This clinical study was associated with an economic study and a physics study. We report here the first results. PATIENTS AND METHODS: For the clinical study, the analysis of the data of the first 88 patients irradiated for a prostatic cancer shows that 39 received RTC and 49 IMRT with a mean dose of 78 Gy at the ICRU point at 2 Gy per fraction. For H&N tumours, the preliminary analysis was done on the 87 first patients with a mean follow-up of 11.5 months (2 to 25 months) and a median of 8.4 months for the IMRT groups and 13.2 months for the RTC group. The economic study was done on the first 157 patients included during the first 18 months: 71 treated by RTC (35 for H&N and 36 for prostate) and 86 treated by IMRT (38 for H&N and 48 for prostate). The assessment of the direct costs was realized by a micro-costing technique. The physical study compared dose distributions for both techniques and has created quality control recommendations. RESULTS: Clinical studies of the acute reactions do not show any difference between groups, but we want to point out the short follow-up and the relatively high dose delivered to cancers of the prostate. The physics study demonstrates that IMRT is technically feasible in good clinical conditions with high quality assurance, a good reproducibility and precision. Dosimetric data show that IMRT could certainly spare organs at risk more than RTC for H&N tumours. The direct costs of "routine" treatments for H&N tumours were 4922 euros for IMRT versus 1899 euros for RTC and for the prostatic cancers 4911 euros for IMRT versus 2357 for RTC.

Adolescent↗

PubMed2003

[Quality assurance program for intensity-modulated radiotherapy (IMRT) treatments of head and neck carcinomas].

A new technique such as intensity-modulated radiotherapy needs a quality assurance program. A French cooperative group joined to define a common program for the use of this technique in the case of head and neck carcinomas. Specific controls are necessary and even mandatory, for example: leaves position, speed of the leaves and the linearity of the dose with the monitor unit number. Measurements in homogeneous phantoms will validate calculated treatment plans. Absolute and relative measurements need ionisation chambers and films. Measurements for each beam, gantry at 0 degrees, are basic measurements. If those are impossible due to the treatment planning software, they can be performed with the treatment angles, films of course positioned perpendicularly to the beam axis. A consensus must be established between members to reduce the frequency and the number of measurements. Nevertheless, it currently seems mandatory to maintain measurements for each beam. Moreover, incidents that happen during this kind of treatment have to be recorded and new verifications will have to be realised then. This program is a unique possibility to match the application of a new technique whatever the type of equipment.

Algorithms↗

PubMed2003

[High dose rate brachytherapy: a potentially curative treatment for small invasive T1N0 endobronchial carcinoma and carcinoma in situ].

INTRODUCTION: High dose rate brachytherapy (HDR-BT) is an option for treatment of small invasive endobronchial carcinoma and carcinoma in situ. This retrospective study describes the results of 33 consecutive patients treated with curative intent and followed up for more than one year. METHODS: Between July 1994 and October 1999, 35 tumours were treated with HDR-BT alone using a standard protocol delivering 6 fractions of 5 Gy delivered across 1cm from the catheters over 3 to 6 weeks. In 31 patients, surgical treatment was ruled out because of histology (in situ carcinoma), history of pneumonectomy or significant co-morbidity. Two patients were treated for positive resection margins following pneumonectomy. All the tumours were Tis or T1 N0. RESULTS: The locations of tumours were: trachea - 2, main bronchus - 5, lobar - 20, and segmental - 8. Only one catheter was needed in 15 cases, 2 in 13 cases, 3 in 6 cases and 4 in 1 case. The median follow-up was 17 months (range, 5-53 months). The recurrence-free rate was 94.3% at 2 months and 86.2% at 6 months after the treatment. 15 patients (45.5%) developed local recurrence at a median time of 9 months. Three patients developed metastases. The 1-year and 2-year overall survival rate were 71.4% and 53.8% respectively and specific survival rates were 69.4% and 59%. One patient developed an acute pneumothorax, and late complications included 6 infections and 12 bronchial stenoses. There were no episodes of haemoptysis nor lethal complications. CONCLUSIONS: With strict selection criteria, HDR-BT can be a curative treatment for early invasive or in situ endobronchial carcinoma without serious toxicity. It is therefore a good alternative treatment with curative intent for inoperable patients.

Adult↗

PubMed2002

[Conformal radiotherapy in prostate cancer: for whom and how?].

External radiotherapy is one of the modalities used to cure localized prostate carcinoma. Most of localized prostate carcinomas, specially those of the intermediate prognostic group, may benefit from escalated dose above 70 Gy at least as regard biochemical and clinical relapse free survival. 3D-CRT allows a reduction of the dose received by organs at risk and an increase of prostate dose over 70 Gy. It is on the way to become a standard. Intensity modulated radiation therapy increases dose homogeneity and reduces rectal dose. These methods necessitate rigorous procedures in reproducibility, delineation of volumes, dosimetry, daily treatment. They need also technological and human means. It is clear that localized prostate cancer is a good example for evaluation of these new radiotherapy modalities.

Adenocarcinoma↗

PubMed2000

Dose escalation with 3D-CRT in prostate cancer: French study of dose escalation with conformal 3D radiotherapy in prostate cancer-preliminary results.

PURPOSE: To evaluate the feasibility of dose escalation in a multi-institutional study in prostate cancer patients. METHODS AND MATERIALS: Between October 1995 and October 1998, 164 patients with localized adenocarcinoma of the prostate were treated with 3-dimensional conformal radiotherapy at one of five French institutions. The dose of radiation was escalated from 66 to 80 Gy (ICRU point). The maximum dose to the rectal wall was limited to 75 Gy. RESULTS: Results were compared in two groups, one (group 1) receiving the standard dose (n = 46 patients; 66 to 70 Gy) and the other (group 2) receiving the escalated dose (n = 118 patients; 74 to 80 Gy). There was no difference in the characteristics of patients between the two groups. The mean follow-up time was 32 months in group 1 and 17.5 months in group 2. No statistical difference between the two groups was observed in the incidence of late gastrointestinal and urinary toxicities. The probability of achieving a posttreatment prostate-specific antigen nadir of </=1 ng/mL in the 120 patients who did not receive neoadjuvant androgen-deprivation therapy was significantly higher in the dose-escalation group and was directly related to the dose of radiation given. CONCLUSION: This multi-institutional study demonstrated the feasibility of escalating the dose of radiation to 80 Gy in prostate cancer patients.

Adenocarcinoma↗

PubMed1999

Preprocessing of control portal images for patient setup verification during the treatments in external radiotherapy.

The main problem in processing the control portal images is their poor quality. We have developed a way of improving the image quality to allow a segmentation stage. Three items were studied for this purpose the background gradient of intensity correction, the noise reduction, and the image restoration. The background was corrected by subtracting a smoothed version of the image from the original. We tested 15 noise reduction methods. The most appropriate for control portal images was found to be the truncated average. Finally, four restoration techniques were compared. The maximum a posteriori (MAP) algorithm was the most efficient. The algorithms were tested over a wide range of conditions (image quality). They produced a great improvement in anatomic detail for all the imaging systems, energies, and anatomical zones tested. For example, the signal-to-noise ratio of a SRI-100 pelvis image, acquired with 4 monitor units (MU) at 10 MV (very low quality image), increased from 0.97 to 42.84 after preprocessing. We found that the improvement in image quality facilitated or even enabled segmentation of the control portal images. The percentage of segments belonging to a structure increased from 30% to 65% in the example cited. The preprocessing of control portal images is the first step in checking the patient setup.

Algorithms↗

PubMed1999

Control portal images enhancement.

The general aim of our study is the patient setup verification using control portal images during the treatments. The main problem of the control portal images processing is their poor quality. We investigated a way of improving the image quality in order to allow a segmentation stage. Four items were studied for this purpose: the presence of distortion, the background gradient of intensity correction, the noise reduction, and the image restoration. The absence of significant distortion was checked with a grid pattern phantom. The background correction was performed by the subtraction from the original image of a smoothed version of this image. We tested 14 noise reduction methods. The most appropriate for our images is the truncated average. Four restoration techniques were compared. The Maximum a Posteriori algorithm is the most efficient. For all the imaging systems, the energies, and the anatomical zones tested an important improvement in anatomic detail was apparent. For example, the SNR of a SRI-100 pelvis image (4 monitor units at 10 MV), went up from 0.97 to 20.06 after enhancement. The image quality improvement will facilitate or enable the segmentation of the control portal images. It is the first step in the patient setup verification.

Humans↗

PubMed1998

A semi-empirical method for calculating the effect of air gap space on output factors on electron beam dose distributions.

BACKGROUND: A simple approach to calculate the effect of air gap on output factors on electron beam dose distribution is presented. METHODS: The method accounts for variations of pencil beam parameters using a model developed by Bruinvis et al. [4,5]. The evaluation of this method is based on measurements of the output factors at various distances between the final collimating device and the phantom surface. RESULTS: Comparison of calculations and measurements of output factors for various cone sizes and 0, 2 and 4 cm air gaps show agreement to within approximately 1.5% for electron energies of 6-13.5 MeV and field sizes of 5.3-10 cm in diameter. CONCLUSION: The accuracy of this semi-empirical method can be considered clinically acceptable and reduces the amount of experimental work needed.

Air↗

PubMed1997

Complications following definitive irradiation for cancers of the oral cavity and the oropharynx (in a series of 1134 patients).

PURPOSE: To study the rate and severity of complications in a series of 1134 patients treated by definitive irradiation for tumors of the oral cavity (772 cases) or the oropharynx (361 cases). METHODS AND MATERIALS: Patients were staged as 29.5% T1, 42% T2, 26% T3, 2.5% T4-Tx, and 74.5% N0 tumors. We treated 364 patients with brachytherapy only (192Ir) for the primary lesion. External irradiation and brachytherapy were combined for 770 patients. RESULTS: The results included local control and survival. Out of 1134 patients, 330 had 376 complications. Grade 1 complications occurred in 20% of the patients, Grade 2 in 9%; Grade 3 in 4%; and Grade 4 in 0.2%. Of the Grade 1 complications, 78% were soft tissue and only 24% were bone complications. For the more severe grades (2, 3, and 4), there were 56 soft tissue complications and 90 bone complications out of 1340 patients. The statistical analysis included tumor-related factors and treatment-related factors. For the first two factors, only tumor location was significant. The treatment-related factors significant for complications were studied in univariate and multivariate study. This multivariate study confirmed that for soft tissue complications dose rate and volume treated were important (p < 0.001). It also confirmed that for bone complications, total dose > 80 Gy, dose rate > 0.7 Gy/h, and the absence of leaded protection of the mandible were all important factors. CONCLUSION: This statistical study should allow future reduction of severe complications (Grades 2, 3, 4), if treatment factors inducing them can be taken into account. This is not always possible for very large tumors.

Analysis of Variance↗

PubMed1997

Conservative treatment by irradiation of epidermoid cancers of the anal canal: prognostic factors of tumoral control and complications.

UNLABELLED: We analyzed in a retrospective series of patients treated by conservative irradiation for an epidermoid cancer of the anal canal (ECAC) the prognostic factors of locoregional control (LRC), survival, late severe complications (LSC), and sphincter conservation (SC). METHODS AND MATERIALS: From 1976 until 1994, 118 patients presenting with an ECAC were conservatively treated (mean age, 65 years). According to the 1987 International Union Against Cancer (TNM) classification, they were: 19 T1, 70 T2, 22 T3, 7 T4, 94 N0, and 24 N1-3. The treatment started with external beam irradiation (EBI) (36 Gy in 3 weeks or 45 Gy in 5 weeks). Concomitant chemotherapy (5-fluorouracil and mitomycin C) was delivered to 31 patients. Two months later, a boost of 20 Gy was delivered by interstitial 192Ir brachytherapy to 101 patients and EBI in 5. Twelve other patients had an abdominoperineal resection (APR). The mean follow-up was 6 years. RESULTS: At 5 years the overall survival was 60%, and specific survival (SS) was 75%; it was 94% for T1, 79% for T2, 53% for T3, and 19% for T4. In multivariate analysis, tumor size (> or = 4 cm), node involvement, and no response to the EBI were factors of poor prognosis for SS. Thirty-two locoregional recurrences occurred of which 21 were local recurrences in the 106 patients treated by a conservative schedule. Only tumor size and response to the EBI were prognostic factors on multivariate analysis for local and LRC. A total of 17 patients presented with LSC (Grade 3, 16 patients; and Grade 4, 1 patient), which was treated by APR in 4 patients and colostomy in 11 (of which 7 were definitive). The only significant prognostic factor for LSC in the multivariate analysis was the total extrapolated response dose of irradiation. The definitive rate of SC after conservative treatment in cured patients was 100% for T1, 82% for T2, 58% for T3, and 100% for T4. Since 1989, improvements of the technique have allowed reduction of the LSC in maintaining the same local control. CONCLUSION: The results of this series are similar to those of the literature. The confirmation of pretherapeutic prognostic factors related to response to the treatment should allow us to adapt the therapeutic intensity for each case to obtain better tumor control, with as few sequelae as possible, to yield a better rate of SC.

Adult↗

PubMed1997

[Optimization of dose distribution of radiation in cancers of the cavum: association of an expert-system and a mathematical algorithm].

Optimization of radiation therapy in nasopharyngeal carcinoma is particularly complex due to both the proximity of at risk organs and the high dose that has to be delivered. To obtain an optimal dose distribution, a knowledge-based optimization technique has been designed that associates an expert-system, named CAVCAV, with numeric optimization (gradient projection method). Based on clinical and physical criteria, CAVCAV determines the geometric characteristics of the radiation fields (beam direction, location and shape of the shielding blocks) for the three stages of radiation therapy of nasopharyngeal carcinomas. Stage 2-treatment fields proposed by CAVCAV, though not perfectly adapted to the patient, are mathematically (beam weights, beam directions, isocenter position) and geometrically (adaptation of fields and shape of blocks by virtual simulation) optimized.

Algorithms↗

PubMed1996

[Recent progress in radiotherapy].

UNLABELLED: Radiation therapy has considerably evolved in 1 century. After the revolution due to cobalt in the beginning of the sixties, we are now entering the 2nd revolution in three fields in external radiotherapy. METHODOLOGY: the development of quality assurance programmes gives the guarantee that the treatment is done as it is prescribed. Technology: recent developments allow conformal radiation therapy which permits to increase the dose without increasing side effects. Biology: the implementation of predictive assays will permit to choose the best modality of treatment for each patient. In brachytherapy, the use of high dose rate radioactive sources increases indications in locations not yet accessible. Pulse dose rate brachytherapy increases radio-protection and will make optimization possible in complex volumes. In the future, indications of curative radiotherapy will probably increase in regard to earlier diagnosis of many cancers and to increase of efficacy of general treatments on metastatic disease.

Brachytherapy↗

PubMed1996

Role of interstitial brachytherapy in oral and oropharyngeal carcinoma: reflection of a series of 1344 patients treated at the time of initial presentation.

Our study focuses on a series of 1344 cases of carcinoma of the oral cavity and oropharynx treated between 1973 and 1992. Brachytherapy was always performed with iridium 192, either alone or in combination with external-beam irradiation or with surgery for the treatment of the primary tumor. For the oral cavity, we studied 565 cases of mobile tongue. The local control and overall survival rates, respectively, at 5 years are as follows: for T1, 92% and 70%; for T2, 62% and 42%; and for T3, 50% and 29%. For the subgroup T1T2NO, there was a better prognosis for treatment by brachytherapy of the primary lesion alone (p < 0.0001). Two hundred seven cases of floor-of-mouth carcinoma have been reported. The T3T4 patients were not considered surgical candidates. The local control and overall survival rates, respectively, at 5 years are as follows: for T1, 97% and 71%; for T2 72% and 42%; and for T3, 51% and 35%. Ninety-seven patients were treated by postoperative brachytherapy. These were patients for whom the margins after surgery were positive or narrow. A technique termed the modified bridge is described for lesions located in the mandible. Carcinomas of the buccal mucosa are rare in our country; only 42 cases were treated in this comparison of two techniques, and the overall survival rate was 48%. Epidermoid carcinomas of the oropharynx have nearly always been treated by a combination of external-beam irradiation and brachytherapy because of the bilateral node risk. Seventy-two patients with epidermoid cancers of the base of the tongue had an overall survival rate of 44%. The tonsil, soft palate, and pillars benefited from the use of the loop technique of brachytherapy combined with external-beam irradiation. Three hundred sixty-one patients were treated. Among these patients were two groups with different prognoses. Patients with tonsil, soft palate, and posterior pillar carcinomas had a local control rate of 84% and an overall survival rate of 57%. Conversely, the anterior pillar and the pharyngoglossal sulcus have a local control rate of only 65% and an overall survival rate of 38%. Statistical analysis revealed the prognostic factors for local control. The complications were classified into four grades: minor (20%), moderate (9%), major (4%), or inducing death (0.2%). The bone complications of grade 2 or 3 are more frequent for the floor of the mouth than for other locations.

Brachytherapy↗