Silvia Johansson

Hypofractionated Proton Boost Combined with External Beam Radiotherapy for Treatment of Localized Prostate Cancer

Proton boost of 20 Gy in daily 5 Gy fractions followed by external beam radiotherapy (EBRT) of 50 Gy in daily 2 Gy fractions were given to 278 patients with prostate cancer with T1b to T4N0M0 disease. Fifty-three percent of the patients received neoadjuvant androgen deprivation therapy (N-ADT). The medium followup was 57 months. The 5-year PSA progression-free survival was 100%, 95%, and 74% for low-, intermediate-, and high-risk patients, respectively. The toxicity evaluation was supported by a patient-reported questionnaire before every consultant visit. Cumulative probability and actuarial prevalence of genitourinary (GU) and gastrointestinal (GI) toxicities are presented according to the RTOG classification. N-ADT did not influence curability. Mild pretreatment GU-symptoms were found to be a strong predictive factor for GU-toxicity attributable to treatment. The actuarial prevalence declined over 3 to 5 years for both GU and GI toxicities, indicating slow resolution of epithelial damage to the genitourinary and gastrointestinal tract. Bladder toxicities rather than gastrointestinal toxicities seem to be dose limiting. More than 5-year followup is necessary to reveal any sign of true progressive late side effects of the given treatment. Hypofractionated proton-boost combined with EBRT is associated with excellent curability of localized PC and acceptable frequencies of treatment toxicity.

How much will linked deformable registrations decrease the quality of multi-atlas segmentation fusions?

Background and purposeMulti-atlas segmentation can yield better results than single atlas segmentation, but practical applications are limited by long calculation times for deformable registration. To shorten the calculation time pre-calculated registrations of atlases could be linked via a single atlas registered in runtime to the current patient. The primary purpose of this work is to investigate and quantify segmentation quality changes introduced by such linked registrations. We also determine the optimal parameters for fusing linked multi-atlas labels using probabilistic weighted fusion.Material and methodsComputed tomography images of 10 head and neck cancer patients were used as atlases, with parotid glands, submandibular glands, the mandible and lymph node levels II-IV segmented by an experienced radiation oncologist following published consensus guidelines. The change in segmentation quality scored by Dice similarity coefficient (DSC) for linking free-form deformable registrations, modeled by B-splines, was investigated for both single- and multi-atlas label fusion by using a leave-one-out approach.ResultsThe median decrease of the DSC was in the range 2.8% to 8.4% compared to direct registrations for all structures while reducing the computer calculation time to that of a single deformable registration. Linking several registrations showed a DSC decrease almost linear to the number of links, suggesting that extrapolation to zero links provides an observer independent measure of the inherent precision with which the segmentation guidelines can be applied.ConclusionsLinking pre-made registrations of multiple atlases via a runtime registration of a single atlas provides a feasible method for reducing computation time in multi-atlas registration.

Assessment of Whether Patients' Knowledge, Satisfaction, and Experience Regarding Their 18F-Fluoride PET/CT Examination Affects Image Quality.

The aim of this study was to investigate patients’ previous knowledge, satisfaction, and experience regarding an 18F-fluoride PET/CT examination and to explore whether any discomfort or pain during the examination was associated with reduced image quality. A further aim was to explore whether patients’ health-related quality of life (HRQoL) was associated with their satisfaction and experience regarding the examination. Methods: Between November 2011 and April 2013, 50 consecutive patients with a histopathologic diagnosis of prostate cancer who were scheduled for 18F-fluoride PET/CT were asked to participate in the study. A questionnaire was used to collect information on the patients’ previous knowledge and experience regarding the examination. Image quality was assessed according to an arbitrary scale. The European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (QLQ-C30) and the prostate cancer–specific module (QLQ-PR25) were used to assess HRQoL. Results: Forty-six patients (96%) completed the questionnaire. Twenty-six percent did not at all know what a 18F-fluoride PET/CT examination was. Most (52%–70%) were satisfied to a very high degree with the care provided by the nursing staff but were less satisfied with the information given before the examination. Image quality was similar between patients who were exhausted or claustrophobic during the examination and those who were not. No correlations between HRQoL and the patients’ experience regarding 18F-fluoride PET/CT were found. Conclusion: Most patients were satisfied with the care provided by the nursing staff, but there is still room for improvement, especially regarding the information provided before the examination. A long examination time may be strenuous for the patient, but there was no difference in image quality between patients who felt discomfort or pain during the examination and those who did not.

Dose painting of prostate cancer based on Gleason score correlations with apparent diffusion coefficients

Abstract Background: Gleason scores for prostate cancer correlates with an increased recurrence risk after radiotherapy (RT). Furthermore, higher Gleason scores correlates with decreasing apparent diffusion coefficient (ADC) data from diffusion weighted MRI (DWI-MRI). Based on these observations, we present a formalism for dose painting prescriptions of prostate volumes based on ADC images mapped to Gleason score driven dose-responses. Methods: The Gleason score driven dose-responses were derived from a learning data set consisting of pre-RT biopsy data and post-RT outcomes for 122 patients treated with a homogeneous dose to the prostate. For a test data set of 18 prostate cancer patients with pre-RT ADC images, we mapped the ADC data to the Gleason driven dose-responses by using probability distributions constructed from published Gleason score correlations with ADC data. We used the Gleason driven dose-responses to optimize dose painting prescriptions that maximize the tumor control probability (TCP) with equal average dose as for the learning sets homogeneous treatment dose. Results: The dose painting prescriptions increased the estimated TCP compared to the homogeneous dose by 0–51% for the learning set and by 4–30% for the test set. The potential for individual TCP gains with dose painting correlated with increasing Gleason score spread and larger prostate volumes. The TCP gains were also found to be larger for patients with a low expected TCP for the homogeneous dose prescription. Conclusions: We have from retrospective treatment data demonstrated a formalism that yield ADC driven dose painting prescriptions for prostate volumes that potentially can yield significant TCP increases without increasing dose burdens as compared to a homogeneous treatment dose. This motivates further development of the approach to consider more accurate ADC to Gleason mappings, issues with delivery robustness of heterogeneous dose distributions, and patient selection criteria for design of clinical trials.

Kidney dosimetry during 177Lu-DOTATATE therapy in patients with neuroendocrine tumors: aspects on calculation and tolerance

Abstract Background: Fractionated therapy with 177Lu-DOTATATE has been reported to be an effective treatment for patients with metastasized neuroendocrine tumors. To optimize the treatment, absorbed doses to risk organs are calculated for the individual patient. For each organ, absorbed dose due to activity in the organ itself (self-dose) and that originating from other organs (cross-dose) are calculated from serial measurements to obtain the activity distribution following treatment. The main aim of the present work were to calculate the cross-dose contribution to the total absorbed kidney dose. Methods: Five hundred patients with neuroendocrine tumors undergoing therapy with 177Lu-DOTATATE were included. Scintigraphic planar whole body images and single photon emission computed tomography/computed tomography (SPECT/CT) over the abdomen were acquired at 1, 4 and 7 days after treatment. Kidney self-dose was calculated based on radioactivity distribution obtained from SPECT/CT. Cross-dose to kidneys was estimated using organ-based analysis of planar whole body images and cross-fire dose factors from Olinda/EXM 1.1. Results: Cross-dose to kidneys in the majority of patients were less than 2% and almost all cross-doses were less than 10%. Cross-dose exceeded 10% only in rare cases of patients with high tumor burden and low absorbed doses to kidneys. Conclusions: The absorbed dose from 177Lu-octreotate to solid organs due to cross-fire is generally low and can usually be neglected.

PD-0525: Analysis of recurrence probability versus pre-treatment FDG-PET SUV for RT patients with HNSCC for dose painting

Results: The maximum doses (in EQD2) for different critical organs in the H&N case are presented in Table 1, along with doses calculated without deformable registration or compensation for biological dose effects. For medulla, deformable EQD2 values are approximately 10% less than for the rigid raw sum; for other organs the difference varies from 0 to 8%. Conclusions: Considerations of dose to organs at risk may be a limiting factor for treatment planning of secondary malignancies at the same site. This work has shown a complete framework to examine re-treatment planning accounting for different patient positions, dose sizes and fractionation schemes of new and previous treatments. This accurate summed EQD2 distribution is helpful in seeing which dose tolerances are reached, and where the treatment plan could be modified further.