ABSTRACT
PURPOSE: Radiotherapy for breast cancer includes different techniques and methods. The purpose of this study is to compare dosimetric calculations using TG-43 dose formalism and Varian Acuros™ BV (GBBS) dose calculation algorithm for interstitial implant of breast using metal catheters in high-dose-rate (HDR) brachytherapy, using (192)Ir. MATERIAL AND METHODS: Twenty patients who were considered for breast conservative surgery (BCS), underwent lumpectomy and axillary dissection. These patients received perioperative interstitial HDR brachytherapy as upfront boost using rigid metal implants. Whole breast irradiation was delivered TG-43 after a gap of two weeks. Standard brachytherapy dose calculation was done by dosimetry. This does not take into account tissue heterogeneity, attenuation and scatter in the metal applicator, and effects of patient boundary. Acuros™ BV is a Grid Based Boltzmann Solver code (GBBS), which takes into consideration all the above, was used to compute dosimetry and the two systems were compared. RESULTS: Comparison of GBBS and TG-43 formalism on interstitial metal catheters shows difference in dose prescribed to CTV and other OARs. While the estimated dose to CTV was only marginally different with the two systems, there is a significant difference in estimated doses of starting from 4 to 53% in the mean value of all parameters analyzed. CONCLUSIONS: TG-43 algorithm seems to significantly overestimate the dose to various volumes of interest; GBBS based dose calculation algorithm has impact on CTV, heart, ipsilateral lung, heart, contralateral breast, skin, and ribs of the ipsilateral breast side; the prescription changes occurred due to effect of metal catheters, inhomogeneities, and scatter conditions.
ABSTRACT
PURPOSE: Brachytherapy in the oral cavity is an important alternative to conventional treatment, and provides a high localized dose and short overall treatment time. A rapid fall of dose beyond radioactive source makes it possible for increased tumour control and sparing surrounding tissue, while short overall treatment duration reduces risk of tumour repopulation. Moulds are fabricated to hold the catheters in position as closely as possible to tumour surface to provide adequate dose coverage of tumour volume and increase distance to other normal surrounding structures. Image based planning and dose optimisation help in better defining target volume and dose coverage. MATERIAL AND METHODS: A retrospective analysis of patients of early squamous cell carcinomas of lip and buccal mucosa from September 2011 to June 2014 to study response to mould brachytherapy. Double plane moulds were prepared for all lip cancer cases and single plane for buccal mucosa cases. Patients are being followed up till disease recurrence. In this study evaluation was done of the technique used, planning details, response to therapy, and reactions encountered. RESULTS: Nine patients treated by mould therapy were reviewed; seven cases were of lip and two of buccal mucosal cancers. Dose delivered ranged from 12.5-48 Gy in fraction sizes of 2.5-3.5 Gy. Equivalent dose in 2 Gy fractions (EQD2) ranged from 18-64 Gy. Maximum dose to organs at risk (OAR) was 91% of prescribed dose. Local mucositis was only reaction in all cases, which resolved in 3-6 weeks. Median follow-up was 19 months. Eight out of nine patients are in remission at a minimum of 7 months (1 case, rest over 14 months) post therapy and only patient had nodal recurrence at 18 months. CONCLUSIONS: Mould therapy is an effective treatment method for selected early and superficial squamous cell carcinomas of the oral cavity, although indications are limited.
ABSTRACT
PURPOSE: Tamoxifen is used in the treatment of breast cancer to prevent recurrences. It is converted to its active metabolite endoxifen by CYP2D6 enzyme. This study was conducted to evaluate the influence of CYP2D6 genetic polymorphisms on the recurrence of breast cancer in patients receiving treatment with tamoxifen as an adjuvant hormonal therapy. METHODS: Breast cancer patients (n = 141) on adjuvant tamoxifen and not on any concomitant CYP2D6 inhibitors were recruited for the study. Patient characteristics and treatment history were obtained. Five milliliters of venous blood was collected for genotyping CYP2D6 alleles *1, *2, *4, *5 and *10. CYP2D6 activity score was calculated to determine the phenotype based on genotype. The activity scores were compared between patients with recurrence and patients with no recurrence of breast cancer. RESULTS: Of the 141 patients recruited for the study, genotyping was done for 132 of them. CYP2D6 activity score ≤0.5 is associated with a statistically significant increased risk of recurrence (OR-12.37; 95 % CI-3.23, 47.33; p < 0.001) and shorter recurrence free survival (52.68 ± 10.58 months (mean ± SEM); p < 0.001) as was shown in Kaplan-Meir survival estimates, when compared to activity score ≥1. The hazard ratio for activity score ≤0.5 is 7.29 (p < 0.001) when compared to activity score ≥1. Analysis of known estrogen receptor positive patients also showed statistically significant increased risk of recurrence and shorter recurrence free survival in patients with CYP2D6 activity score ≤0.5. The Cox proportional hazard ratio was found to be 7.15 (p = 0.006) for activity score ≤0.5. CONCLUSION: Reduced CYP2D6 activity is associated with poor treatment outcomes, in terms of increased risk of recurrence and shorter recurrence free survival, in breast cancer patients on adjuvant tamoxifen therapy.