Pulsed Dose Rate Brachytherapy Research Articles

926P - Impact of Demographic Characteristics, Staging Methods and Treatment in a European Locally Advanced Cervical Cancer (Lacc) Population

ABSTRACT Aim: FIGO defines Cervical Cancer staging but in developed countries Pelvic MRI, PET/CT and surgical staging (SxS) are widely used. LACC standard of care is chemoradiotherapy (CTRT). Besides FIGO stage and Lymph nodes (LN) status, other prognostic factors (PF) are trying to be identified. Methods: Between May 2008 and November 2013, 148 consecutive LACC patients (pts) treated homogenously with CTRT from 2 Spanish academic Institutions were collected. Demographic, social, clinical characteristics and staging methods were analyzed and correlated with clinical outcomes. Results: Median age at diagnosis was 51.8 years (23-82.5) and PS 0-1(98%). Sixty-five percent had not followed screening program, 55% had a postmenopausal status, 58% never smokers. Median time from first symptom to diagnosis was 2.9 months (0- 58.3). Squamous cell 79.1%; G3 36.3%; High risk HPV 91.8%. FIGO Stage: IB2 8.8%; IIA 10.8%; IIB 48%; IIIB 17.6%; IVA 4.1% . MRI, PET/CT or both were performed in 95.3%, 51.7%, and 48.6% respectively. Clinical and MRI Stage correlation was: IB2 30.8%; IIB 76.1%; IIIB 19.2% and IVA 83.3%. Para-Aortic (PA) LN were studied by PET/CT, SxS and both in 51.7%, 50.7% and 33.1% respectively. In the combined group, negative PA LN were: 91.8% by PET/CT and 87.8% by SxS, showing a PET/CT specificity of 93%. All pts received Pelvic EBRT (median 45Gy) through 3D (81.8%) and IMRT (18.2%) concurrent with 6 weekly cisplatin (1-7). PA field and parametrial boost was added in 23% and 53.4% respectively. PDR Brachytherapy was delivered in 79.1%. Planned treatment was completed in 74.3%; median duration 8.5 weeks (3.8-18.8). Median follow-up was 22.4 months (2.3-61.2). RFS and OS at 2 years: 71.4%; 95%IC (63.4%-79%) and 80.7%; 95%IC (73.6%-88%) respectively. In univariate analysis OS main PF was FIGO Stage: IB2 92,3%, IIA 87.5%, IIB 81.7%, IIIB 65.4%, IVA 66.7%. Smoking does not impact in OS; oral anticonception and pre-menopausal status showed a trend to worse OS. Conclusions: CTRT is still an insufficient treatment in LACC. FIGO Staging might be improved adding imaging tests. PA Lymph nodes diagnostic method is still matter of controversy; our PET/CT data are according to literature. Neither social nor demographic characteristics were identified as PF. Disclosure: All authors have declared no conflicts of interest.

Treatment Outcome of Patients With Advanced Cervical Carcinoma After Concurrent Chemotherapy and External Beam Radiation Therapy Plus High-Dose-Rate (HDR) Brachytherapy

Purpose/Objective(s): Radiochemotherapy for cervical cancer may have a high risk of acuteand late side effects, and hence be considered too toxic for many elderly patients. The purpose was to evaluate treatment-, side effects and survival after radiotherapy (RT) alone, for patients age 80+. Materials/Methods: Consecutive cervical cancer patients, age 80+, treated between January 1, 2000 and December 31, 2011, receiving curative intended RT were included. Patient characteristics, toxicities and survival data were retrieved from our in-department patient database and retrospectively evaluated. Patients received external RT either 46 Gy in 23 fractions (4 pelvic field conformal RT or Volumetric Modulated Arc Therapy (Rapid Arc)) or 64 Gy in 32 fractions (5-field intensity modulated RT (IMRT)) depending on the presence of lymph nodes metastases. Patients were also planned for PDR brachytherapy either intracavitary 17.5 Gy x 2 to point A or interstitial 30 Gy. Results: Twenty-five patients were included. The median age was 82(range 80-88) and the histology of the primary tumors was: Squamous cell carcinoma (64%), Adenocarcinoma (16%), Undifferentiated (4%), Rare types (8%), and Unknown (8%). Primary FIGO stages were: IIA (4%), IIB (56%), IIIA (4%), IIIB (32%), and IVA (4%). Two patients experienced acute side effects of RTOG grade 3 to bladder and vagina respectively. Other two experienced late side effect grade 4 due to vesicoand/or recto-vaginal fistulas. Six patients had had a relapse of their disease (31% actuarial (C.I. 10-52%)). Conclusions: With a relapse rate of 31% and little severe toxicity, our results show that using RT without Cisplatin to 80+ years old cervical cancer patients is safe and provides a good disease control. Author Disclosure: H. Hansen: None. C. Hogdall: None. S. Engelholm: None.

Curiethérapie de débit de dose pulsé dans les cancers du col utérin : pourquoi, comment ?

The end of the production of 192 iridium wires terminates low dose rate brachytherapy and requires to move towards pulsed-dose rate or high-dose rate brachytherapy. In the case of gynecological cancers, technical alternatives exist, and many teams have already taken the step of pulsed-dose rate for scientific reasons. Using a projector source is indeed a prerequisite for 3D brachytherapy, which gradually installs as a standard treatment in the treatment of cervical cancers. For other centers, this change implies beyond investments in equipment and training, organizational consequences to ensure quality.

A case-control study of patients with squamous cell carcinoma of the oral cavity and oropharynx treated with pulsed-dose-rate brachytherapy.

Pulsed-dose-rate (PDR) brachytherapy is thought to mimic the radiobiological benefits of continuous low-dose-rate (cLDR) delivery but is safer for medical personnel. We set out to evaluate the outcomes of this technique in patients with head and neck squamous cell carcinoma. A total of 36 consecutive patients treated with PDR brachytherapy were randomly matched to 72 cLDR controls according to T-stage, tumor site, and management strategy. Local recurrence and late complications were compared between the two groups. Baseline characteristics were similar in both groups. Oral cavity cancers predominated at 81%, and 89% had T1/T2 tumors. Seventy-five percent of patients underwent surgery before radiation treatment. Median followup was 59 and 30months for cLDR and PDR patients, respectively. Three-year actuarial local recurrence-free survival was 97% and 94% for cLDR and PDR patients, respectively (p=0.77). Three-year cumulative risk of Grade ≥2 complications was 45% and 32% for cLDR and PDR patients, respectively (p=0.2). For cLDR, a dose rate exceeding 68cGy/h resulted in more complications (RR 5.3, p<0.05). Similarly, PDR patients receiving ≥75cGy/pulse were at higher risk. PDR brachytherapy in head and neck squamous cell carcinoma yields comparable results to cLDR treatment. Dose rate was correlated with the risk of late complications, regardless of technique.

Adaptive error detection for HDR/PDR brachytherapy: guidance for decision making during real-time in vivo point dosimetry.

This study presents an adaptive error detection algorithm (AEDA) for real-time in vivo point dosimetry during high dose rate (HDR) or pulsed dose rate (PDR) brachytherapy (BT) where the error identification, in contrast to existing approaches, does not depend on an a priori reconstruction of the dosimeter position. Instead, the treatment is judged based on dose rate comparisons between measurements and calculations of the most viable dosimeter position provided by the AEDA in a data driven approach. As a result, the AEDA compensates for false error cases related to systematic effects of the dosimeter position reconstruction. Given its nearly exclusive dependence on stable dosimeter positioning, the AEDA allows for a substantially simplified and time efficient real-time in vivo BT dosimetry implementation. In the event of a measured potential treatment error, the AEDA proposes the most viable dosimeter position out of alternatives to the original reconstruction by means of a data driven matching procedure between dose rate distributions. If measured dose rates do not differ significantly from the most viable alternative, the initial error indication may be attributed to a mispositioned or misreconstructed dosimeter (false error). However, if the error declaration persists, no viable dosimeter position can be found to explain the error, hence the discrepancy is more likely to originate from a misplaced or misreconstructed source applicator or from erroneously connected source guide tubes (true error). The AEDA applied on two in vivo dosimetry implementations for pulsed dose rate BT demonstrated that the AEDA correctly described effects responsible for initial error indications. The AEDA was able to correctly identify the major part of all permutations of simulated guide tube swap errors and simulated shifts of individual needles from the original reconstruction. Unidentified errors corresponded to scenarios where the dosimeter position was sufficiently symmetric with respect to error and no-error source position constellations. The AEDA was able to correctly identify all false errors represented by mispositioned dosimeters contrary to an error detection algorithm relying on the original reconstruction. The study demonstrates that the AEDA error identification during HDR/PDR BT relies on a stable dosimeter position rather than on an accurate dosimeter reconstruction, and the AEDA's capacity to distinguish between true and false error scenarios. The study further shows that the AEDA can offer guidance in decision making in the event of potential errors detected with real-time in vivo point dosimetry.

Volumetric evaluation of an alternative bladder point in brachytherapy for locally advanced cervical cancer

To evaluate an alternative dose point, so-called ALG (for Alain Gerbaulet), for the bladder in comparison to the International Commission on Radiation Units and Measurements (ICRU) point and D2cm(3) (minimal dose to maximally exposed 2 cm(3)) in a large cohort of patients with locally advanced cervical cancer treated with external beam radiotherapy followed by image-guided pulsed dose rate brachytherapy. For each patient, the ALG point was constructed 1.5 cm above the ICRU bladder, parallel to the tandem (coronal and sagittal planes). The dosimetric data from 162 patients were reviewed. Average doses to ALG and bladder points were 19.40 Gy ± 7.93 and 17.14 ± 8.70, respectively (p=0.01). The 2 cm(3) bladder dose averaged 24.40 ± 6.77 Gy. Ratios between D2cm(3) and dose points were 1.37 ± 0.46 and 1.68 ± 0.74 (p<0.001) for ALG and ICRU points, respectively. Both dose points appeared correlated with D2cm(3) (p<0.001) with coefficients of determination (R(2)) of 0.331 and 0.399 respectively. The estimated dose to the ICRU point of the rectum was 12.77 ± 4.21 and 15.76 ± 5.94 for D2cm(3) (p<0.0001). Both values were significantly correlated (p<0.0001, R(2) = 0.485). The ALG point underestimates the D2cm(3), but its mean on a large cohort is closer to D2cm(3) than the dose to ICRU point. However, it shows great variability between cases and the weak strength of its correlation to D2cm(3) indicates that it is not a good surrogate for individual volumetric evaluation of the dose D2cm(3).

Re-irradiation with interstitial pulsed-dose-rate brachytherapy for unresectable recurrent head and neck carcinoma

To assess the long-term results of protocol-based interstitial pulsed-dose-rate (PDR) brachytherapy combined with simultaneous chemotherapy in selected patients with recurrent head and neck tumors not amenable to salvage surgery. A total of 51 patients with recurrent head and neck cancer were treated with interstitial PDR brachytherapy. Forty patients (78%) had salvage brachytherapy alone using a median total dose of 60Gy. Salvage brachytherapy in combination with external beam therapy was performed in 11 patients (22%) using a median total dose of DREF=27Gy. Simultaneously with the PDR brachytherapy, a concomitant chemotherapy was administered in 35/51 (69%) of patients. The analysis was performed after a median followup of 58 months. Local control rates calculated according to Kaplan-Meier after 2 and 5 years were 71% and 57%, respectively. Comparing results of salvage PDR brachytherapy with or without simultaneous chemotherapy, the 5-year local recurrence-free survival rates were 78.9% vs. 38.5% (p=0.01), respectively. No other patient or treatment-related parameters had a significant influence on treatment results. A total of 9/51 (17.7%) and 6/51 (11.8%) patients developed soft-tissue necrosis or bone necrosis, respectively, but only 2% of patients required surgical treatment. PDR interstitial brachytherapy with pulse doses between 0.4 and 0.7Gy/h/24h with simultaneous chemotherapy is an effective and safe option for curative therapy in selected patients with head and neck cancer in previously irradiated areas, which are not suitable for salvage surgery.

External Beam Radiation Therapy Versus Image Guided High-Dose-Rate Endorectal Brachytherapy in the Management of Rectal Cancer: A Retrospective Study

brachytherapy is an effective treatment for anal cancer and is often used in Europe as exclusive or boost treatment. The purpose of this study was to retrospectively assess the clinical outcome of patients undergoing brachytherapy as sole treatment or in combination with external beam radiation therapy and to search clinical predictive factors of toxicity and efficacy. Materials/Methods: From June 2000 to June 2010, 89 patients with anal canal carcinoma were treated in the 3 institutions of the GOCO (Occitan Catalan Oncologic Group) (39 patients in Montpellier, 31 in Toulouse and 19 in Barcelona). Data was retrospectively collected. Survival analyses were performed with the Kaplan-Meier method. The log rank test was used to find predictive factors of efficacy ant toxicity. Results: Brachytherapy was given as a boost in 94% of the patients. Tumor staging reported was T1 Z 19 patients (21%), T2 Z 63 patients (71%), T3 Z 5 patients (6%), and T4 Z 2 patients (2%). Tumor size was less than 3 cm in 52% of the patients. Lymph node status was N0 in 74 patients (83%), N1 in 10 patients (11%) and N2 in 5 patients (6%). Concomitant chemotherapy was associated with external beam radiation therapy in 51% of the cases. Pulsed dose rate brachytherapy was used in 73% of the cases (low dose rate in 27%). The median brachytherapy dose was 20 Gy. The median total radiation therapy dose was 64.6 Gy. 95.5% of patients had a complete clinical response at 3 months. Acute grade 3 or 4 toxicity occurred in 25% of the patients and was significantly correlated with the use of concomitant chemotherapy (p Z 0.003). The median follow-up was 4.6 years. Late grade 3 or 4 toxicity was observed in 9% of the patients but no clinical factor was correlated. The overall survival was 96, 91and 78%, respectively, at 3, 5 and 7 years. Local relapse free survival (LRFS) was 90, 84 and 80%, respectively, at 3, 5 and 7 years. LRFS was significantly correlated with the use of concomitant chemotherapy (p Z 0.016), especially in tumors less than 3 cm in size (1 local relapse with concomitant chemotherapy Vs 7 local relapse without, p Z 0.043). Conclusions: Interstitial brachytherapy is an effective and safe treatment which permits to deliver high dose to the tumor while limiting the risk of induced toxicity. Concomitant chemotherapy during the first part of external radiation therapy induces more acute toxicity but is an important factor for local control, even in tumors less than 3 cm, and despite the high dose of radiation delivered. Author Disclosure: O. Riou: None. F. Castan: None. F. Picaud: None. C. Llacer Moscardo: None. C. Gutierrez: None. J. Dubois: None. M. Cambray: None. D. Azria: None. F. Ferrer: None. M. Delannes: None.

Vaginal Sparing Using a Mold in Anal Cancer Female Patients Treated With Intensity Modulated Radiation Therapy: A Dosimetric Feasibility Study

days was delivered (3 pts received 15 Gy in 3 fractions) after post-implant CT-scan planning. Dose-volume adaptation was manually achieved using graphical optimization. Dosimetric data and clinical outcome were retrospectively analyzed. Due to short follow-up, patients treated in 2013 (4 pts) were excluded from the clinical outcome analysis. Toxicities were graded using the CTC v4.0. Results: Dosimetric data are reported in Table. Median follow-up was 25.4 months (range, 1.5-81.6 months). Male/female ratio was 0.59 with a median age of 63 years (range, 34-84 years). Median dose of EBRT was 45 Gy (range, 43.20-52 Gy), median overall treatment time was 63 days (range, 5-249 days). Two-year actuarial survival rates were 84% (SE 8%) for local relapse free survival, 94% (SE 5%) for colostomy-free survival, 76% (SE 10%) for metastatic free survival. The 2.5-years actuarial overall survival rate was 92% (SE 7%). Acute toxicities following HDB (<2 months) were frequent but not severe: urinary (37% of grade 1 [G1], no G2, G3 or G4), anal (40.7% G1), cutaneous (3.7% G1). Late toxicities were: G1 (48.1%) and G2 (22.2%), 1 patient presented G3 toxicity with anal canal necrosis. Three patients (11.1%) underwent a colostomy including 1 pt with sphincter amputation. Conclusions: HDB for anal canal carcinoma represents a feasible technique compared to low or pulsed-dose rate brachytherapy. This technique remains an excellent approach to precisely boost the tumor in reducing the overall treatment time while high-dose rate is more and more used in the frame of brachytherapy. Author Disclosure: A. Falk: None. A. Claren: None. K. Benezery: None. A. Leysalle: None. J. Feuillade: None. M. Chand: None. E. Francois: None. J. Hannoun-Levi: None.

The implementation of a PDR 3D-guided gynaecological brachytherapy service in a UK centre

AbstractBackgroundDue to the discontinuation of the widely used low-dose rate (LDR) Caesium afterloader units, many centres in the past 10 years have moved from LDR Selectron treatments to Iridium 192 afterloaders. While the majority of UK centres have opted for high-dose rate (HDR) units, the Christie have invested in two pulsed dose rate (PDR) afterloaders alongside a move to full 3D-planned gynaecological brachytherapy.PurposeTo share the experience and learning curve involved in the implementation of a 3D-guided PDR brachytherapy service.MethodsThe specific logistical and practical challenges of implementing a PDR service are discussed alongside the more general challenges of implementing 3D-guided magnetic resonance (MR) based brachytherapy. A multidisciplinary approach was undertaken to streamline the patient pathway and give all disciplines a forum to discuss service improvements and resolve problems.ConclusionsThe lessons learned throughout this experience can inform the decisions of departments that may wish to implement a PDR service or indeed a 3D image-guided HDR brachytherapy service in the future. The focus on the utilisation of lean principles to the patient pathway, improved multidisciplinary working and enhancing service efficiency is of interest to all centres.

Biphasic and monophasic repair: comparative implications for biologically equivalent dose calculations in pulsed dose rate brachytherapy of cervical carcinoma

To consider the implications of the use of biphasic rather than monophasic repair in calculations of biologically-equivalent doses for pulsed-dose-rate brachytherapy of cervix carcinoma. Calculations are presented of pulsed-dose-rate (PDR) doses equivalent to former low-dose-rate (LDR) doses, using biphasic vs monophasic repair kinetics, both for cervical carcinoma and for the organ at risk (OAR), namely the rectum. The linear-quadratic modelling calculations included effects due to varying the dose per PDR cycle, the dose reduction factor for the OAR compared with Point A, the repair kinetics and the source strength. When using the recommended 1 Gy per hourly PDR cycle, different LDR-equivalent PDR rectal doses were calculated depending on the choice of monophasic or biphasic repair kinetics pertaining to the rodent central nervous and skin systems. These differences virtually disappeared when the dose per hourly cycle was increased to 1.7 Gy. This made the LDR-equivalent PDR doses more robust and independent of the choice of repair kinetics and α/β ratios as a consequence of the described concept of extended equivalence. The use of biphasic and monophasic repair kinetics for optimised modelling of the effects on the OAR in PDR brachytherapy suggests that an optimised PDR protocol with the dose per hourly cycle nearest to 1.7 Gy could be used. Hence, the durations of the new PDR treatments would be similar to those of the former LDR treatments and not longer as currently prescribed. Modelling calculations indicate that equivalent PDR protocols can be developed which are less dependent on the different α/β ratios and monophasic/biphasic kinetics usually attributed to normal and tumour tissues for treatment of cervical carcinoma.

Pulsed-dose-rate brachytherapy for uterine cervix carcinoma: 10 years of experience with 226 patients at a single institution

To analyze the long-term results of pulsed-dose-rate (PDR) brachytherapy (BT) in cervical carcinoma patients treated at a single institution. All patients with histopathologically proven Stages IB-IVA cervical carcinoma, treated at our institution with PDR intracavitary BT between April 1996 and November 2007, were included in this retrospective analysis. All patients underwent primary pelvic radiotherapy (45Gy) with concomitant chemotherapy from 1999 and PDR intracavitary BT (16Gy to the clinical target volume), followed by hysterectomy in 124 patients. Two hundred twenty-six patients received radiochemotherapy and BT. With a median followup of 81.7months, the 5-year overall survival, disease-free survival, and local control (LC) were 67%, 65%, and 80%, respectively; seventy-seven relapses were observed including 38 local recurrences. Multivariate analysis showed earlier FIGO (International Federation of Gynecology and Obstetrics) stage and absence of nodal involvement to be associated with better overall and disease-free survivals. Use of three-dimensional image-guided BT planning and absence of nodal involvement were associated with better LC in the multivariate analysis. Late Grade ≥3 toxicity was experienced by 22 patients (9.7%), consisting of gastrointestinal toxicity for 6 patients, urinary tract for 10 patients, lymphatics for 3 patients, and vaginal toxicity for 3 patients. This study demonstrates excellent LC rates with few late side effects with PDR BT for cervix carcinoma, similar to those reported in the literature with historical standard low-dose-rate BT.

Protocol-based image-guided salvage brachytherapy

To assess the overall clinical outcome of protocol-based image-guided salvage pulsed-dose-rate brachytherapy for locally recurrent prostate cancer after radiotherapy failure particularly regarding feasibility and side effects. Eighteen consecutive patients with locally recurrent prostate cancer (median age, 69 years) were treated during 2005-2011 with interstitial PDR brachytherapy (PDR-BT) as salvage brachytherapy after radiotherapy failure. The treatment schedule was PDR-BT two times with 30 Gy (pulse dose 0.6 Gy/h, 24 h per day) corresponding to a total dose of 60 Gy. Dose volume adaptation was performed with the aim of optimal coverage of the whole prostate (V100 > 95 %) simultaneously respecting the protocol-based dose volume constraints for the urethra (D0.1 cc < 130 %) and the rectum (D2 cc < 50-60 %) taking into account the previous radiation therapy. Local relapse after radiotherapy (external beam irradiation, brachytherapy with J-125 seeds or combination) was confirmed mostly via choline-PET and increased PSA levels. The primary endpoint was treatment-related late toxicities--particularly proctitis, anal incontinence, cystitis, urinary incontinence, urinary frequency/urgency, and urinary retention according to the Common Toxicity Criteria. The secondary endpoint was PSA-recurrence-free survival. We registered urinary toxicities only. Grade 2 and grade 3 toxicities were observed in up to 11.1 % (2/18) and 16.7 % (3/18) of patients, respectively. The most frequent late-event grade 3 toxicity was urinary retention in 17 % (3/18) of patients. No late gastrointestinal side effects occurred. The biochemical PSA-recurrence-free survival probability at 3 years was 57.1 %. The overall survival at 3 years was 88.9 %; 22 % (4/18) of patients developed metastases. The median follow-up time for all patients after salvage BT was 21 months (range, 8-77 months). Salvage PDR-brachytherapy of the prostate following local failure after radiation therapy is a treatment option with a low rate of genitourinary side effects and no late gastrointestinal side effects. The treatment efficacy in the first 3 years is promising.

Determination of air‐kerma strength for the 192Ir GammaMed iX pulsed‐dose‐rate brachytherapy source

Pulsed-dose-rate (PDR) brachytherapy was originally proposed to combine the therapeutic advantages of high-dose-rate (HDR) and low-dose-rate brachytherapy. Though uncommon in the United States, several facilities employ pulsed-dose-rate brachytherapy in Europe and Canada. Currently, there is no air-kerma strength standard for PDR brachytherapy (192)Ir sources traceable to the National Institute of Standards and Technology. Discrepancies in clinical measurements of the air-kerma strength of the PDR brachytherapy sources using HDR source-calibrated well chambers warrant further investigation. In this research, the air-kerma strength for an (192)Ir PDR brachytherapy source was compared with the University of Wisconsin Accredited Dosimetry Calibration Laboratory transfer standard well chambers, the seven-distance technique [B. E. Rasmussen et al., "The air-kerma strength standard for 192Ir HDR sources," Med. Phys. 38, 6721-6729 (2011)], and the manufacturer's stated value. Radiochromic film and Monte Carlo techniques were also employed for comparison to the results of the measurements. While the measurements using the seven-distance technique were within + 0.44% from the manufacturer's determination, there was a + 3.10% difference between the transfer standard well chamber measurements and the manufacturer's stated value. Results showed that the PDR brachytherapy source has geometric and thus radiological qualities that exhibit behaviors similar to a point source model in contrast to a conventional line source model. The resulting effect of the pointlike characteristics of the PDR brachytherapy source likely account for the differences observed between well chamber and in-air measurements.

Measurement verification of dose distributions in pulsed-dose rate brachytherapy in breast cancer

AimThe aim of the study was to verify the dose distribution optimisation method in pulsed brachytherapy. BackgroundThe pulsed-dose rate brachytherapy is a very important method of breast tumour treatment using a standard brachytheraphy equipment. The appropriate dose distribution round an implant is an important issue in treatment planning. Advanced computer systems of treatment planning are equipped with algorithms optimising dose distribution. Materials and methodsThe wax-paraffin phantom was constructed and seven applicators were placed within it. Two treatment plans (non-optimised, optimised) were prepared. The reference points were located at a distance of 5mm from the applicators’ axis. Thermoluminescent detectors were placed in the phantom at suitable 35 chosen reference points. ResultsThe dosimetry verification was carried out in 35 reference points for the plans before and after optimisation. Percentage difference for the plan without optimisation ranged from −8.5% to 1.4% and after optimisation from −8.3% to 0.01%. In 16 reference points, the calculated percentage difference was negative (from −8.5% to 1.3% for the plan without optimisation and from −8.3% to 0.8% for the optimised plan). In the remaining 19 points percentage difference was from 9.1% to 1.4% for the plan without optimisation and from 7.5% to 0.01% for the optimised plan.No statistically significant differences were found between calculated doses and doses measured at reference points in both dose distribution non-optimised treatment plans and optimised treatment plans. ConclusionsNo statistically significant differences were found in dose values at reference points between doses calculated by the treatment planning system and those measured by TLDs. This proves the consistency between the measurements and the calculations.

Case 6: Large Cervical Cancer Stage IIIB with Pathological Pelvic Nodes Treated with IMRT, Concomitant Chemotherapy, and MRI-Based Intracavitary and Interstitial Tandem/Ring Pulsed Dose Rate Brachytherapy with Needles

Case 6: Large Cervical Cancer Stage IIIB with Pathological Pelvic Nodes Treated with IMRT, Concomitant Chemotherapy, and MRI-Based Intracavitary and Interstitial Tandem/Ring Pulsed Dose Rate Brachytherapy with Needles

Radiobiologie de la curiethérapie

Low-dose rate brachytherapy has some radiobiological advantages compared to external beam radiotherapy: subletal damages repair during irradiation leading to a relative protection of healthy tissues; no tumor cell repopulation, cell cycle redistribution and a low oxygen enhancement ratio. High dose rate and pulsed dose rate modalities allow an optimization of dose distribution by varying the dwell times over the different dwell positions. Because of the use of afterloaders, they also offer a better radioprotection of the staff. High dose rate and pulsed dose rate treatments seem to offer the same results as low-dose rate brachytherapy, particularly in cervix carcinoma. For high dose rate brachytherapy, schedules must be designed according to the linear-quadratic model. In pulsed dose rate brachytherapy, pulse dose and time intervals must also be derived from the linear-quadratic model, but half-time repair must be taken into account.

Curiethérapie du canal anal

Low dose-rate brachytherapy as a boost after concomitant chemoradiation therapy is a standard of care for locally advanced anal carcinoma, providing a rigorous selection taking into account the initial staging and tumor response to external beam radiotherapy. Local control is likely to be superior when the boost is performed with brachytherapy than with external beam radiotherapy. The several steps of the brachytherapy procedure are described. The standard treatment scheme is a concomitant chemoradiation therapy, including 45Gy (1,8Gy×5) pelvic external beam radiotherapy and two courses of 5-fluorouracil and mitomycin-C, followed by a 15Gy brachytherapy boost with a gap limited to 2 to 3weeks. Higher irradiation dose for the most advanced cases has not yet demonstrated a therapeutic gain in terms of colostomy free survival. Exclusive brachytherapy for in-situ carcinoma or invasive carcinoma less than 10mm is not recommended due to a high risk of local recurrence. Pulsed dose rate brachytherapy is an alternative to low dose rate brachytherapy (iridium wires) providing the respect of the recommended dose rate (0.5 to 1Gy/hour). High dose rate brachytherapy is still under evaluation.

Case 6: Large Cervical Cancer Stage IIIB with Pathological Pelvic Nodes Treated with IMRT, Concomitant Chemotherapy, and MRI-Based Intracavitary and Interstitial Tandem/Ring Pulsed Dose Rate Brachytherapy with Needles

Case 6: Large Cervical Cancer Stage IIIB with Pathological Pelvic Nodes Treated with IMRT, Concomitant Chemotherapy, and MRI-Based Intracavitary and Interstitial Tandem/Ring Pulsed Dose Rate Brachytherapy with Needles

Case 3: Large Cervical Cancer Stage IIA2, No Nodes, Treated with 3D Conformal EBRT, with Concomitant Chemotherapy, and MRI-Based Intracavitary Tandem/Ovoid PDR Brachytherapy.

Case 3: Large Cervical Cancer Stage IIA2, No Nodes, Treated with 3D Conformal EBRT, with Concomitant Chemotherapy, and MRI-Based Intracavitary Tandem/Ovoid PDR Brachytherapy.