Stephan Kreppner

Radiation exposure of the heart, lung and skin by radiation therapy for breast cancer: A dosimetric comparison between partial breast irradiation using multicatheter brachytherapy and whole breast teletherapy

BACKGROUND AND PURPOSE Accelerated partial breast irradiation by means of multicatheter brachytherapy shows great promise in the modern treatment of early breast cancer combining high efficacy in preventing tumour recurrence with low levels of toxicity. The present work attempts a dosimetric comparison between this treatment modality and conventional whole breast external beam radiotherapy by looking at differences in risk organ exposure to radiation. PATIENTS AND METHODS The planning CT data sets of 16 consecutive patients with left-sided breast cancer who received external beam radiotherapy to the whole breast followed by a boost to the tumour bed using multicatheter interstitial brachytherapy after breast conserving surgery were used to create two independent physical treatment plans - one for an external radiotherapy, one for sole partial breast brachytherapy in each case assuming a total reference dose of 50Gy for each patient. Dose-volume parameters D(0.1cc), D(0.5cc), D(1cc,)D(2cc), D(5cc,)D(10cc), D(25cc), D(50cc), V(100), V(90), V(50), V(10), V(5) for the ipsilateral lung, the heart and the adjacent skin were calculated and compared between the two treatment modalities. RESULTS All organs at risk showed a substantially lower radiation exposure in the brachytherapy plan. This was most pronounced for the heart with values differing by a factor of four. Although somewhat less marked this was also true for the ipsilateral lung and the adjacent skin with exposure ratios of three and two, respectively. CONCLUSIONS With the use of multicatheter interstitial brachytherapy substantial reductions in the radiation exposure of risk organs can be achieved in comparison to whole breast external beam radiotherapy. These are likely to translate into profound clinical benefits.

Interstitial pulsed-dose-rate brachytherapy for head and neck cancer--Single-institution long-term results of 385 patients.

PURPOSE To assess the long-term results of protocol-based pulsed-dose-rate (PDR) interstitial brachytherapy (iBT) in 385 patients with head and neck cancer who underwent PDR-iBT preferably after minimal, nonmutilating surgery. METHODS AND MATERIALS From 1997 to 2009, a total of 385 patients received protocol-based PDR-iBT for head and neck cancer. Brachytherapy was preceded by surgery in most of our patients (326/385, 84.7%). Altogether, 246 of 385 patients (63.9%) received iBT alone and 135 of 385 patients (36.1%) in combination with external beam radiation therapy. The analysis was done after a median followup of 63 months. RESULTS The 5-, 10-, and 15-year local relapse-free survival rates according to Kaplan-Meier test for all analyzed patients were 85.8%, 83.1%, and 80.2%, respectively. The 5-, 10-, and 15-year overall survival and disease-free survival rates were 68.9%, 52.2%, and 44.1%, and 81.3%, 79.3%, and 76.3%, respectively. For N0-/N1- vs. N2-patients, we observed significantly different 5-year local recurrence-free survival rates with values of 92.3% and 73.7%, respectively (p=0.007). No other patient or treatment-related parameters had a significant influence on treatment results. Serious late side effects, such as soft tissue or bone necrosis, were observed in 39 of 385 patients (10.2%) and 18 of 385 patients (4.9%), respectively. CONCLUSIONS The PDR-iBT with 0.4-0.7Gy each hour, 24h per day for patients with head and neck cancer is a proven, effective, and safe treatment method with excellent long-term data.

Electromagnetic tracking (EMT) technology for improved treatment quality assurance in interstitial brachytherapy

Abstract Electromagnetic Tracking (EMT) is a novel technique for error detection and quality assurance (QA) in interstitial high dose rate brachytherapy (HDR‐iBT). The purpose of this study is to provide a concept for data acquisition developed as part of a clinical evaluation study on the use of EMT during interstitial treatment of breast cancer patients. The stability, accuracy, and precision of EMT‐determined dwell positions were quantified. Dwell position reconstruction based on EMT was investigated on CT table, HDR table and PDR bed to examine the influence on precision and accuracy in a typical clinical workflow. All investigations were performed using a precise PMMA phantom. The track of catheters inserted in that phantom was measured by manually inserting a 5 degree of freedom (DoF) sensor while recording the position of three 6DoF fiducial sensors on the phantom surface to correct motion influences. From the corrected data, dwell positions were reconstructed along the catheters track. The accuracy of the EMT‐determined dwell positions was quantified by the residual distances to reference dwell positions after using a rigid registration. Precision and accuracy were investigated for different phantom‐table and sensor‐field generator (FG) distances. The measured precision of the EMT‐determined dwell positions was ≤ 0.28 mm (95th percentile). Stability tests showed a drift of 0.03 mm in the first 20 min of use. Sudden shaking of the FG or (large) metallic objects close to the FG degrade the precision. The accuracy with respect to the reference dwell positions was on all clinical tables < 1 mm at 200 mm FG distance and 120 mm phantom‐table distance. Phantom measurements showed that EMT‐determined localization of dwell positions in HDR‐iBT is stable, precise, and sufficiently accurate for clinical assessment. The presented method may be viable for clinical applications in HDR‐iBT, like implant definition, error detection or quantification of uncertainties. Further clinical investigations are needed.

Long-Term Results of a Prospective Dose Escalation Phase-II Trial: Interstitial Pulsed-Dose-Rate Brachytherapy as Boost for Prostate Cancer

Purpose: We reviewed our ten-year single institution experience with pulsed dose rate brachytherapy by dose escalation Phase-II study in patients with intermediateand high-risk prostate cancer (according the definition by d’Amico). Materials andMethods:We treated a total of 130 patients for intermediate and high risk prostate cancer between 2000 and 2007 using PDRbrachytherapy as a boost after conformal external beam radiation therapy to 45-50 Gy. Boost brachytherapy doses ranged from 25 to 35 Gy e 33 pts. received 25 Gy (total dose 70 Gy), 63 pts. 30 Gy (total dose 75-80 Gy) and 34 pts. 35 Gy,(total dose 85 Gy) given in one session (dose per pulse was 0.60 -0.70 Gy delivered for 24 h per day, night and day, with a time interval of 1 h between two pulses, total time 48-50 hours). PSArecurrence-free survival according to Kaplan-Meier was calculated and changes in American Urological Association symptom scores and also acute and chronic toxicities according Common Toxicity Criteria scale were assessed. Results: At the time of analysis with a median followup of 66 months local control according to the Phoenix definition was achieved by 88% of patients e only 16/130 patients (12,3%) developed a biochemical relapse. A strong correlation between frequency of a local control according to the Phoenix definition and the brachytherapy dose has been documented: At time of analysis 82%, 86% and 97% of our patients were disease-free for boost doses in values of 25 Gy, 30 Gy and 35 Gy, respectively. The side effects of therapy were negligible: There were 18 cases (14%) of grade 1/2 rectal proctitis, one case (0.8%) grade 3 proctitis, 18 cases (14%) of grade 1/2 cystitis, no cases (0%) with dysuria grade 3. No patient had new onset incontinence or a bulbourethral stricture requiring dilation. Conclusions: Image-guided conformal PDR-brachytherapy as boost after external beam radiation therapy is a very effective treatment option with very lowmorbidity by patientswith intermediate or high risk prostate cancer.