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1.
Article de Anglais | MEDLINE | ID: mdl-39224831

RÉSUMÉ

Background and aims: Proton therapy (PRT) for Head Neck Cancer (HNC), in view of the Bragg peak, spares critical structures like oral mucosa better than IMRT. In PRT, mouth-bites, besides immobilising and separating mucosal surfaces, may also negate the end-of-range effect. We retrospectively analysed the details and dosimetric impact of mouth-bites in PRT for HNC. Materials and methods: The data of consecutive HNC patients treated with IMPT from May 2020 to August 2022 were studied retrospectively. Details of the mouth-bite used, compliance and resultant mucosal separation were noted. Further analysis, restricted to previously unirradiated patients, comprised volumetric dosimetric data pertaining to the mouth-bite and distal mucosal surfaces. High LET zones, corresponding to 6-12 keV/micron, for mouth-bite doses above 30 Gy, were recalculated from existing plans. Results: A mouth-bite was used in 69 of 80 consecutively treated patients, ranging from 8 to 42 mm in thickness, and 12 to 52 mm in the resultant mucosal sparing. In 42 patients in whom the mouth-bite V 32 Gy was > 0, median Dmean, absolute V32, V39, V50 and V60 GyE (Gray Equivalent) of the mouth bite was 35.65 GyE (Range: 2.65 - 60 GyE), 10 cc (Range: 0.1 - 32 cc), 7.6 cc (Range: 0.1 - 30.8 cc), 5.7 cc (Range: 0.2 - 29.2 cc) and 1.45 cc (Range: 0.2 - 18.1 cc) respectively, all significantly more than the spared adjacent mucosal surface. In absence of a mouth-bite, the spared mucosa would have at least partially received the high dose received by the mouth-bite. High LET zones were noted in 12 of 48 mouth-bites. Conclusion: In PRT for HNC, mouth-bites play a vital role in improving the sparing of mucosa outside the target.

2.
Cancer Treat Res Commun ; 36: 100721, 2023.
Article de Anglais | MEDLINE | ID: mdl-37301126

RÉSUMÉ

OBJECTIVE: Volumetric modulated arc therapy (VMAT) is a useful treatment technique that can reduce treatment time while producing improved dose distribution to target structures. The main aim of the study is to evaluate the outcome of oropharyngeal cancer patients treated with VMAT, sequential (SEQ) versus simultaneous integrated boost (SIB) technique in terms of survival and failures and to assess late radiation toxicities with their dosimetric parameters. MATERIAL AND METHODS: Total 54 patients of histologically proved oropharyngeal cancer patients treated by definitive radiotherapy using VMAT technique in January 2019 to December 2020 were followed up and evaluated in terms of survival, patterns of failure and late radiation toxicities by RTOG toxicity criteria. RESULTS: After a median follow up of 12 months, overall survival (OS) and disease free survival (DFS) were 64.8% and 48.1% respectively. In terms of patterns of failure, 44.4% showed local recurrence, 7.4% as regional relapse and 3.7% showed distant metastasis. While comparing sequential versus SIB, no significant difference was found in OS (64.9% vs. 59.8%, p = 0.689), DFS (52.8% vs. 35.3%, p = 0.266), local control (LC) (58.3% vs. 47.1%, p = 0.437) and regional control (RC) (94.3% vs. 88.2%, p = 0.151) respectively. Among late radiation toxicities, the most common were xerostomia (42.2% for SEQ and 24.2% for SIB group), dysphagia (33.3% for SEQ and 15.1% for SIB group) and hoarseness of voice (15.1% for SEQ and 12.1% for SIB group). CONCLUSION: SIB technique proved better than SEQ technique in terms of pattern of failure or late toxicity, but no significant difference can be reported.


Sujet(s)
Carcinomes , Tumeurs de l'oropharynx , Radiothérapie conformationnelle avec modulation d'intensité , Humains , Radiothérapie conformationnelle avec modulation d'intensité/effets indésirables , Radiothérapie conformationnelle avec modulation d'intensité/méthodes , Planification de radiothérapie assistée par ordinateur/méthodes , Récidive tumorale locale , Tumeurs de l'oropharynx/radiothérapie
3.
Rep Pract Oncol Radiother ; 27(4): 624-633, 2022.
Article de Anglais | MEDLINE | ID: mdl-36196415

RÉSUMÉ

Background: The purpose of this study was to evaluate dosimetric and radiobiological difference between volumetric modulated arc therapy (VMAT) and 3-dimensional conformal radiotherapy (3DCRT) in organ at risk (OAR) lumbosacral plexus (LSP) in cervical cancer patients. Materials and methods: 30 patients of cervical cancer who were treated using 3DCRT or VMAT along with chemotherapy followed by brachytherapy were enrolled. LSP was delineated retrospectively. Dosimetric and radiobiological difference was evaluated. Patients were followed for radiation induced lumbosacral plexopathy (RILSP). Results: Median follow-up was 12 months (3-16 months). 53.3% of patients were treated by 3DCRT and 46.7% by VMAT. The mean (±SD) LSP volume: 119.03 ± 15 cm3. The mean volume percentages (%) of the LSP: V5, V10, V20, V30, V40, V50, V55, and V60 were 100%, 99.8%, 99.2%, 94.3%, 84.03%, 59.7%, 0%, 0%, respectively. All patients received doses to the LSP in excess of 50 Gy, one patient received 55 Gy. A statistically significant difference was observed in the median value of V20, V30, V40, V50, D50, P2, P4, P7, P8, P9, and P10 across two different techniques of radiotherapy - VMAT and 3DCRT. None of the patients presented with RILSP. NTCP value was less in VMAT plans compared to 3DCRT, which is also statistically significant. Conclusion: RILSP is a rare and often refractory complication of pelvic radiotherapy. Advance radiotherapy technique with proper OAR delineation and constraint can prevent the occurrence of RILSP. VMAT has potential benefits for the probability of dose reduction in LSP. Further studies are required focusing on dose distribution in LSP-OAR and radiotherapy modality.

4.
Radiat Oncol J ; 38(2): 138-147, 2020 Jun.
Article de Anglais | MEDLINE | ID: mdl-33012157

RÉSUMÉ

PURPOSE: To evaluate the dosimetric variations in patients of head and neck cancer treated with definitive or adjuvant radiotherapy using optimized non-coplanar (ncVMAT) beams with coplanar (cVMAT) beams using volumetric arc therapy. MATERIALS AND METHODS: Twenty-two patients of head and neck cancer that had received radiotherapy using VMAT in our department were retrospectively analyzed. Each of the patients was planned using coplanar and non-coplanar orientations using an optimized couch angle and fluences. We analyzed the Conformity Index (CIRTOG), Dose Homogeneity Index (DHI), Heterogeneity Index (HIRTOG), low dose volume, target and organs-at-risk coverage in both the plans without changing planning optimization parameters. RESULTS: The prescription dose ranged from 60 Gy to 70 Gy. Using ncVMAT, CIRTOG, DHI and HIRTOG, and tumor coverage (ID95%) had improved, low dose spillage volume in the body V5Gy was increased and V10Gy was reduced. Integral dose and intensity-modulated radiation therapy factor had increased in ncVMAT. In the case of non-coplanar beam arrangements, maximum dose (Dmax) of right and left humeral head were reduced significantly whereas apex of the right and left lung mean dose were increased. CONCLUSION: The use of ncVMAT produced better target coverage and sparing of the shoulder and soft tissue of the neck as well as the critical organ compared with the cVMAT in patients of head and neck malignancy.

5.
Gulf J Oncolog ; 1(34): 58-64, 2020 Sep.
Article de Anglais | MEDLINE | ID: mdl-33431364

RÉSUMÉ

OBJECTIVE: Adjuvant radiotherapy is required for most post MRM breast cancer patients. Aim of treatment is to target radiation to region of interest while sparing Organs at Risk (OARs). Attempts are being made to decrease dose to OARs without compromising target coverage by evolving radiation techniques. In this study, a comparison of traditional 3DCRT plans is done with semi-automated complex VMAT plans for dose received by OARs namely Contralateral Breast (CLB), Ipsilateral lung (I/LL), and Contralateral Lung (C/LL). MATERIALS AND METHODS: It was planned for 30 post MRM breast cancer patients for chest wall, ipsilateral axilla and supraclavicular lymph node. The PTV dose was 42.5 Gy in 16 fractions, 2.66 Gy/fraction, 5 days a week. For each patient traditional 3DCRT and semi-automated complex VMAT plans (conventional + tangential VMAT plans) were prepared and evaluated by radiation oncologists. RESULTS: Dose evaluation of CLB shows higher Dmax for 3DCRT plans, while, Dmean was lower for the 3DCRT plan. Difference between D2 was not significant. V2.5 was significantly less in 3DCRT, while, difference between V5 and V10 were not significant. For C/LL Dmean, V2.5, V5, and V10 were higher for the VMAT plan. For I/LL Dmean, V5 and V10 were higher, while V20 and V30 were lower for VMAT plans. DISCUSSION AND CONCLUSION: The VMAT technique described here is a useful treatment option available for difficult planning situations. OARs stated above had a mixed result showing VMAT plans to be inferior at lower dose metrics, while, superior at higher dose metrics.


Sujet(s)
Tumeurs du sein/radiothérapie , Hypofractionnement de dose/normes , Planification de radiothérapie assistée par ordinateur/méthodes , Radiothérapie adjuvante/méthodes , Radiothérapie conformationnelle avec modulation d'intensité/méthodes , Femelle , Humains
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