Evaluation of the clinical value of automatic online dose restoration for adaptive proton therapy of head and neck cancer

INTRODUCTION

Intensity modulated proton therapy (IMPT) is highly sensitive to anatomical variations which can cause inadequate target coverage during treatment. This study compares not-adapted (NA) robust plans to two adaptive IMPT methods - a fully-offline adaptive (FOA) and a simplified automatic online adaptive strategy (dose restoration (DR)) to determine the benefit of DR, in head and neck cancer (HNC).

MATERIAL/METHODS

Robustly optimized clinical IMPT doses in planning-CTs (pCTs) were available for a cohort of 10 HNC patients. During robust re-optimization, DR used isodose contours, generated from the clinical dose on pCTs, and patient specific objectives to reproduce the clinical dose in every repeated-CT(rCT). For each rCT(n=50), NA, DR and FOA plans were robustly evaluated.

RESULTS

An improvement in DVH-metrics and robustness was seen for DR and FOA plans compared to NA plans. For NA plans, 74%(37/50) of rCTs did not fulfill the CTV coverage criteria (D98%>95%Dprescription). DR improved target coverage, target homogeneity and variability on critical risk organs such as the spinal cord. After DR, 52%(26/50) of rCTs met all clinical goals. Because of large anatomical changes and/or inaccurate patient repositioning, 48%(24/50) of rCTs still needed full offline adaptation to ensure an optimal treatment since dose restoration was not able to re-establish the initial plan quality.

CONCLUSION

Robust optimization together with fully-automatized DR avoided offline adaptation in 52% of the cases. Implementation of dose restoration in clinical routine could ensure treatment plan optimality while saving valuable human and material resources to radiotherapy departments.

Myocardial functional and structural abnormalities after adjuvant radiotherapy for breast cancer. Relation to cardiac radiation exposure

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): The Funds Pierre Masure, Alphonse and Marie Walckiers & De Winter-Vermant, by King Baudouin Foundation

Background

Radiation therapy (RXT) is a keystone in breast cancer (BC) treatment which allows to reduce risk of local recurrence and cancer related mortality. Yet these benefits may be offset by increases in cardiovascular mortality due to late radiation induced cardiotoxicity. Indeed, prior works in patients exposed to high cardiac radiation dose demonstrated development of diffuse and focal myocardial fibrosis by cMR. However, whether such effects may also occur after contemporary BC-RXT with lower cardiac dose exposure, has not yet been evaluated.

Purpose

To evaluate the long-term cardiac safety of contemporary RXT for BC, we sought to estimate the prevalence of cardiac functional and structural focal and myocardial abnormalities in BC survivors treated by RXT 10 years earlier, in direct relation to measured local radiation dose exposure.

Methods

In a prospective cross-sectional study, we studied 27 women (mean age 62 ± 7 years) treated with adjuvant RXT but without chemotherapy for a first left (n= 12) or right sided (n= 15) BC between 2009 and 2011, which had no history of coronary artery or cardiac disease and compared them to 20 age matched (64 ± 10 years) healthy female controls (without history of BC or RXT). All subjects underwent 3T cMR to measure LV volumes, function, global longitudinal (GLS), circumferential (GRS) and radial strains (GRS) as well as extracellular volume (ECV) and late gadolinium enhancement (LGE). Functional and structural abnormalities in women with BC were compared to healthy controls. We also compared abnormalities among patients with left vs right BC and related them to mean heart radiation dose measured at the time of RXT (Figure).

Results

Mean cardiac radiation exposure in BC survivors was 1.87 ± 1.7 Gy (range 0-7.9 Gy). Exposure was significantly (p < 0.001) higher in left (3.3 ± 0.66 Gy) than in right (0.84 ± 0.65 Gy) sided BC. Indexed LV mass was slightly lower in BC patients than in controls (46 ± 6 vs 51 ± 9 g/m2, p = 0.03), whereas indexed end-diastolic (66 ± 11 vs 66 ± 12 ml/m2, p = NS) and end-systolic volumes (25 ± 8 vs 24 ± 7 ml/m2, p = NS) were similar. Also, LV ejection fraction (63 ± 6 vs 64 ± 6, p = NS), GLS (-14.7 ± 1.9 vs -15.5 ± 1.8, p = NS), GCS (-20.0 ± 3.6 vs -19.3 ± 5.9, p = NS) and GRS (40.9 ± 10.7 vs 37.0 ± 9.0, p = NS) were not statistically different in BC survivors than in controls. No patient presented LGE, and ECV was similar in BC patients exposed to RXT (28.3 ± 2.8) than in controls (29.3 ± 2.4, p = 0.58). Also, no differences in ECV between left and right sided BC and no statistical correlation between ECV and mean heart dose (r = 0.01, p = NS) was observed.

Conclusions

In this preliminary work, patients with BC treated by adjuvant RXT 10 years ago, presented no significant structural or functional abnormalities in relation to cardiac dose exposure nor in comparison to healthy controls. This suggests that current RXT protocols for BC are safe without long-term functional or morphological cardiac side effects.

Impact of machine log-files uncertainties on the quality assurance of proton pencil beam scanning treatment delivery

Irradiation log-files store useful information about the plan delivery, and together with independent Monte Carlo dose engine calculations can be used to reduce the time needed for patient-specific quality assurance (PSQA). Nonetheless, machine log-files carry an uncertainty associated to the measurement of the spot position and intensity that can influence the correct evaluation of the quality of the treatment delivery. This work addresses the problem of the inclusion of these uncertainties for the final verification of the treatment delivery. Dedicated measurements performed in an IBA Proteus Plus gantry with a pencil beam scanning (PBS) dedicated nozzle have been carried out to build a 'room-dependent' model of the spot position uncertainties. The model has been obtained through interpolation of the look-up tables describing the systematic and random uncertainties, and it has been tested for a clinical case of a brain cancer patient irradiated in a dry-run. The delivered dose has been compared with the planned dose with the inclusion of the errors obtained applying the model. Our results suggest that the accuracy of the treatment delivery is higher than the spot position uncertainties obtained from the log-file records. The comparison in terms of DVHs shows that the log-reconstructed dose is compatible with the planned dose within the 95% confidence interval obtained applying our model. The initial mean dose difference between the calculated dose to the patient based on the plan and recorded data is around 1%. The difference is essentially due to the log-file uncertainties and it can be removed with a correct treatment of these errors. In conclusion our new PSQA protocol allows for a fast verification of the dose delivered after every treatment fraction through the use of machine log-files and an independent Monte Carlo dose engine. Moreover, the inclusion of log-file uncertainties in the dose calculation allows for a correct evaluation of the quality of the treatment plan delivery.

Solitary extramedullary plasmocytoma of the thyroid: a case report and histological approach to plasma cells infiltrate in the thyroid gland

BACKGROUND

Solitary extramedullary plasmacytoma (SEP) is a rare malignant neoplasm arising from plasma cells. SEP mostly occurs in the upper respiratory tract. Thyroid gland is rarely affected (<78 cases).

METHODS/RESULTS

We describe the case of a 78-year-old woman presenting a rapidly enlarging palpable thyroid mass. Neck computed tomography scan showed enlargement of both thyroid lobes. Laboratory tests were normal, including serum protein level with no monoclonal gamma globulin peak. Cytology was suspicious for lymphoma. Biopsy showed an infiltrating neoplasm composed of atypical tumor cells with abundant cytoplasm and eccentric nuclei. These revealed diffuse immunoreactivity for CD138 and predominant staining for immunoglobulin kappa light chains. Clinical workup for multiple myeloma was negative.

CONCLUSIONS

SEP should be considered in the differential diagnosis of a rapidly enlarging thyroid nodule and be distinguished from involvement of thyroid in multiple myeloma, mucosa-associated lymphoid tissue lymphoma, plasma cell granuloma and medullary carcinoma. Clinical correlation and immunohistochemistry are crucial in avoiding pitfalls.

Implementation of hypoxia PET imaging in radiation therapy planning

Hypoxia has historically been relevant to radiation oncology as it relates to radioresistance, poor response to therapy and unfavorable patient's outcome in many solid tumors. In that regard, the recent advances in imaging, computation and radiation delivery techniques have been offering new perspectives to prescribe and deliver radiation dose in accordance with the spatial distribution of hypoxia mapped with molecular or functional imaging modalities, i.e., the so-called dose painting (DP). At first glance, the concept of dose painting appears promising and let foresee likely improvement in tumor local control at an acceptable clinical cost. However, adapting radiotherapy planning and delivery according to hypoxia imaging implicitly assumes: 1) that the imaging variable actually correlates with a local biological property associated with individual therapy outcome; 2) that the spatial distribution of the imaging parameter can be adequately converted into dose; and 3) that an irradiation device can actually deliver such a heterogeneous dose in fractionated RT treatments. In that regard, many uncertainties and difficulties remain at each step of the DP process, mainly related to the limitations of the current imaging techniques and the treatment fractionation. This paper will thus review the state of the art of DP with a specific focus on hypoxia, going from cancer biology to adaptive dose delivery. It will address the technological challenges and the clinical validation, which are both essential to translate an intuitively appealing concept into a clinically meaningful practice.

[Potential place of FDG-PET for the GTV delineation in head and neck and lung cancers]

The recent progresses performed in imaging, computational and technological fields bring new opportunities to achieve high precision radiation dose delivery. However, IMRT requires a particular attention at the target delineation step to avoid inadequate dosage to TVs/OARs. In this context, the biological information provided by PET might advantageously complete CT-Scan to refine the target delineation in HNSCC and lung cancer. Integrating PET into the treatment planning however requires the use and validation of accurate and reproducible segmentation methods, which adequately integrate the PET image properties such as the blur effect and the high level of noise. In this context, we developed specific tools, i.e. edge-preserving filters for denoising and deconvolution algorithms for deblurring that allowed the detection of gradient intensity peaks. Our gradient-based method has been validated on phantom and patient materials, and proved to be more accurate than threshold-based approaches. With this tool in hand, we demonstrated that the use of FDG-PET resulted in smaller TVs than the CT-based TVs, on both pre- and per-treatment images, and significantly improved the dose distributions to the TVs/OARs. This opens avenues for dose escalation strategies that might potentially improve the tumor local control.

Determination of tumour hypoxia with [18F]EF3 in patients with head and neck tumours: a phase I study to assess the tracer pharmacokinetics, biodistribution and metabolism

PURPOSE

The aim of this study was to assess the pharmacokinetics, biodistribution and metabolism of [(18)F]EF3, a labelled 2-nitroimidazole hypoxia marker, in ten patients with head and neck cancer.

METHODS

[(18)F]EF3 was administered intravenously (group 1, n=5, mean dose+/-SD: 324+/-108 MBq; group 2, n=5, mean dose+/-SD: 1,134+/-138 MBq) to patients (nine male, one female). Blood and urine samples and whole-body PET scans were obtained from 20 s to 4-6 h. Radioactivity was determined in several regions of interest.

RESULTS

No serious adverse event was reported. [(18)F]EF3 concentration in blood exhibited a bi-exponential decline. [(18)F]EF3 was mainly eliminated in the urine. By 7 h 40 min after injection, 53+/-14% of the injected dose was collected in the urine. There was no significant difference between the low- and high-dose groups. A progressive accumulation occurred also in the colon, indicating a hepatobiliary excretion. Except in organs involved in the elimination of [(18)F]EF3, the tumour-to-organ ratio remained close to or below unity in muscle, lungs, heart and brain at various times after injection. In one patient, tumour hypoxia was observed with a tumour-to-blood ratio ranging from 1.4 to 1.9. Last, [(18)F]EF3 remained very stable after injection, with percentage of native tracer above 87% in the serum and 84% in the urine.

CONCLUSION

Administration of [(18)F]EF3 in head and neck cancer patients is feasible and safe. Uptake and retention in tumour was observed, indicating the presence of hypoxia.