PubMed · 7303129
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U Schulz. 1981. [Optimized interstitial afterloading therapy].. https://pubmed.ncbi.nlm.nih.gov/7303129/
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PURPOSE: Traditionally, transperineal prostate brachytherapy has been heavily operator dependent. To overcome this limitation, a treatment planning method was developed for intraoperative planning, guidance, and evaluation. In this setting, reliability, speed, and ease of understanding are primary considerations. This planning method has been implemented for ultrasound guided implants of the prostate, but can be extended for use in other body sites. METHODS AND MATERIALS: The length and cross-section of the target (prostate) and location of urethra and rectum are determined intraoperatively from live ultrasound imaging. The planning program then automatically generates a "reference plan" containing needle locations, dwell times, and the resulting isodose distribution. As needles are placed, this information is corrected to account for any deviation of needle placement or movement of the prostate. Once all needles are in place, the normalization is adjusted to reconcile remaining hot-spots with coverage of the target volume. Optimization is performed in three separate stages. Each stage works to enhance only a subset of the implant parameters. (a) Pattern Optimization attempts to find the most appropriate placement for the needles or catheters. It is based on the transverse contour of the target volume. Needles are placed uniformly around the perimeter, and interior needle positions are determined from the cross-sectional area and shape. Critical structures such as the urethra are explicitly avoided. This step provides the overall framework for the implant, and is not generally repeated. (b) Relative Dwell Time Optimization selects relative dwell times that will give the best uniformity of dose. It works by setting the relative dwell time in each source position inversely proportional to the dose delivered to that point by the other source positions. It is used in the reference plan, and is repeated as each needle is inserted. This provides dosimetric feedback to the physician, who can judge the effect of deviations from the reference plan. (c) Relative Volume Optimization is an interactive method for fine tuning the normalization based upon volume analysis. The volume analysis is presented in tabular and graphical form, both being updated rapidly as the normalization is adjusted. The information is formatted to help the operator judge coverage and uniformity. Special functions are provided that allow the operator to "jump" to special normalization values based on several indices of uniformity or uniformity/coverage. RESULTS: This system overcomes some conventional brachytherapy limitations. Rather than depend on the operator's intuitive judgement of where the needles should be placed, a global plan is generated and validated with full dose calculations. Immediate feedback is provided concerning the adequacy of placement and avoidance of critical structures. This information is provided in terms of actual tissue doses to the target volume and critical structures using point doses, isodose distributions, and volume analysis. Since the new method was introduced in January 1994, 33 implants have been performed. The needle placement method has been reliable in the clinic, with different doctors producing similar results on subsequent fractions for the same patient. CONCLUSION: The method of decomposing the optimization problem into several simple steps is capable of rapidly, consistently, and reliably designing conformal treatment plans of high uniformity. Operator dependence has been significantly reduced. We are adapting the method for other anatomic sites.
PURPOSE/OBJECTIVE: We tried to reduce the number of local recurrences after surgery and external beam irradiation (EBI) in carcinoma of the oral cavity, when margins were positive or close. MATERIAL AND METHODS: From 1980 to 1992, we treated 97 cases of carcinomas of the oral cavity by postoperative brachytherapy. Surgery was combined with EBI+brachytherapy in 51 cases and with brachytherapy alone in 46 cases. We treated 29 T1, 34 T2, 30 T3T4 and four Tx (73% were N0 at first examination and 23% had positive nodes). The type of surgery is analysed. Brachytherapy was performed in one or two planes along the surgical scar. If the mandibular rim was resected, especially when the tongue or the remaining floor were sutured to the internal face of the inferior lip or to the buccal mucosa, the bridge technique was used. To decrease the dose to the inferior part of the mandible, the bridge was modified thanks to experimental dosimetry. RESULTS: At 5 years, the local control (LC) is 89%, the locoregional control (LRC) 82%, the specific survival (SS) 74% and the overall survival (OS) 67%. COMPLICATIONS: We noted 19% of grade 1 (minor), 12% of grade 2 (moderate) and 6% of grade 3 (major) complications. CONCLUSION: Compared with the results of the literature, we think that postoperative brachytherapy can improve classical radiosurgical results in selected cases with a risk of local recurrence.
PURPOSE: Our aim was to study the results and the complications of this series of 207 patients treated from 1976 to 1992 and to compare them with the results of the literature. MATERIAL AND METHODS: The treatment consisted of a combination of external beam irradiation (EBI) (to the tumor and the node areas) and complementary brachytherapy to the primary tumor in 105 cases. In 102 cases, brachytherapy only was delivered to the tumor with or without neck dissection of the node areas. The brachytherapy was performed mostly with the hairpin technique in the beginning (in 61 cases) and subsequently the plastic tube technique with iridium wires. The dosimetry followed the Paris system rules. There were 41% T1, 48% T2, 8% T3, 2% T4 and 1% Tx with 83% N0, 12% N1, 3% N2, 2% N3. Ninety-one percent of patients were male and 9% were female. RESULTS: The local control at 5 years is 97, 72 and 51%, respectively, for T1, T2, T3. The specific survival (without the patients dead of intercurrent disease or second cancer) was 88, 47 and 36%, and the overall survival at 5 years was 71, 42 and 35%. Of note, approximately one third of patients died of intercurrent disease or second cancers (70 patients = 34%). Significant factors that can influence the results are: for local control, the size of the lesion T1/T2/T3 (p < 0.0001); for the locoregional control, the absence of node involvement. The following factors are not significant: age and sex (age significant for survival). The significant treatment factors are the safety margin (p < 0.0003), brachytherapy only on T for T2N0 (p = 0.01). A total duration of treatment of less than 50 days is also significant. The spacing and the total dose (higher dose for large tumors) were not found to be significant. The complications were classified into four grades: grade 1, 17% (median healing, 2 months for soft tissue complications and 5 months for bone complications); grade 2, 12%; grade 3, 6% (frequently requiring surgical resection); grade 4, 0.5% (death, one case). In this series, for the complications, the dose rate, the spacing and the total dose were found not to be significant. CONCLUSION: Carcinomas of the floor of mouth treated by exclusive irradiation have a rather good prognosis and the number of grade 2 and 3 complications remains acceptable. Exclusive brachytherapy is preferable to the combination of EBI plus brachytherapy for T1T2N0.