RadShap: An Explanation Tool for Highlighting the Contributions of Multiple Regions of Interest to the Prediction of Radiomic Models.

Explaining the decisions made by a radiomic model is of significant interest, as it can provide valuable insights into the information learned by complex models and foster trust in well-performing ones, thereby facilitating their clinical adoption. Promising radiomic approaches that aggregate information from multiple regions within an image currently lack suitable explanation tools that could identify the regions that most significantly influence their decisions. Here we present a model- and modality-agnostic tool (RadShap, https://github.com/ncaptier/radshap), based on Shapley values, that explains the predictions of multiregion radiomic models by highlighting the contribution of each individual region. Methods: The explanation tool leverages Shapley values to distribute the aggregative radiomic model's output among all the regions of interest of an image, highlighting their individual contribution. RadShap was validated using a retrospective cohort of 130 patients with advanced non-small cell lung cancer undergoing first-line immunotherapy. Their baseline PET scans were used to build 1,000 synthetic tasks to evaluate the degree of alignment between the tool's explanations and our data generation process. RadShap's potential was then illustrated through 2 real case studies by aggregating information from all segmented tumors: the prediction of the progression-free survival of the non-small cell lung cancer patients and the classification of the histologic tumor subtype. Results: RadShap demonstrated strong alignment with the ground truth, with a median frequency of 94% for consistently explained predictions in the synthetic tasks. In both real-case studies, the aggregative models yielded superior performance to the single-lesion models (average [±SD] time-dependent area under the receiver operating characteristic curve was 0.66 ± 0.02 for the aggregative survival model vs. 0.55 ± 0.04 for the primary tumor survival model). The tool's explanations provided relevant insights into the behavior of the aggregative models, highlighting that for the classification of the histologic subtype, the aggregative model used information beyond the biopsy site to correctly classify patients who were initially misclassified by a model focusing only on the biopsied tumor. Conclusion: RadShap aligned with ground truth explanations and provided valuable insights into radiomic models' behaviors. It is implemented as a user-friendly Python package with documentation and tutorials, facilitating its smooth integration into radiomic pipelines.

Promising Candidate Prognostic Biomarkers in [18F]FDG PET Images: Evaluation in Independent Cohorts of Non-Small Cell Lung Cancer Patients.

The normalized distances from the hot spot of radiotracer uptake (SUVmax) to the tumor centroid (NHOC) and to the tumor perimeter (NHOP) have recently been suggested as novel PET features reflecting tumor aggressiveness. These biomarkers characterizing the shift of SUVmax toward the lesion edge during tumor progression have been shown to be prognostic factors in breast and non-small cell lung cancer (NSCLC) patients. We assessed the impact of imaging parameters on NHOC and NHOP, their complementarity to conventional PET features, and their prognostic value for advanced-NSCLC patients. Methods: This retrospective study investigated baseline [18F]FDG PET scans: cohort 1 included 99 NSCLC patients with no treatment-related inclusion criteria (robustness study); cohort 2 included 244 NSCLC patients (survival analysis) treated with targeted therapy (93), immunotherapy (63), or immunochemotherapy (88). Although 98% of patients had metastases, radiomic features including SUVs were extracted from the primary tumor only. NHOCs and NHOPs were computed using 2 approaches: the normalized distance from the localization of SUVmax or SUVpeak to the tumor centroid or perimeter. Bland-Altman analyses were performed to investigate the impact of both spatial resolution (comparing PET images with and without gaussian postfiltering) and image sampling (comparing 2 voxel sizes) on feature values. The correlation of NHOCs and NHOPs with other features was studied using Spearman correlation coefficients (r). The ability of NHOCs and NHOPs to predict overall survival (OS) was estimated using the Kaplan-Meier method. Results: In cohort 1, NHOC and NHOP features were more robust to image filtering and to resampling than were SUVs. The correlations were weak between NHOCs and NHOPs (r ≤ 0.45) and between NHOCs or NHOPs and any other radiomic features (r ≤ 0.60). In cohort 2, the patients with short OS demonstrated higher NHOCs and lower NHOPs than those with long OS. NHOCs significantly distinguished 2 survival profiles in patients treated with immunotherapy (log-rank test, P < 0.01), whereas NHOPs stratified patients regarding OS in the targeted therapy (P = 0.02) and immunotherapy (P < 0.01) subcohorts. Conclusion: Our findings suggest that even in advanced NSCLC patients, NHOC and NHOP features pertaining to the primary tumor have prognostic potential. Moreover, these features appeared to be robust with respect to imaging protocol parameters and complementary to other radiomic features and are now available in LIFEx software to be independently tested by others.

EANM procedural recommendations for managing the paediatric patient in diagnostic nuclear medicine.

PURPOSE: The manuscript aims to characterize the principles of best practice in performing nuclear medicine procedures in paediatric patients. The paper describes all necessary technical skills that should be developed by the healthcare professionals to ensure the best possible care in paediatric patients, as it is particularly challenging due to psychological and physical conditions of children. METHODS: We performed a comprehensive literature review to establish the most relevant elements of nuclear medicine studies in paediatric patients. We focused the attention to the technical aspects of the study, such as patient preparation, imaging protocols, and immobilization techniques, that adhere to best practice principles. Furthermore, we considered the psychological elements of working with children, including comforting and distraction strategies. RESULTS: The extensive literature review combined with practical conclusions and recommendations presented and explained by the authors summarizes the most important principles of the care for paediatric patient in the nuclear medicine field. CONCLUSION: Nuclear medicine applied to the paediatric patient is a very special and challenging area, requiring proper education and experience in order to be performed at the highest level and with the maximum safety for the child.

Cytidine analogs are synthetic lethal with base excision repair default due to MBD4 deficiency.

Inactivating mutations of MBD4 have been reported in subsets of various tumors. A deficiency of this DNA glycosylase, recognizing specifically T:G mismatch resulting from the deamination of methyl-cytosine, results in a hypermutated phenotype due to the accumulation of CpG>TpG transitions. Here, we hypothesize that the difference in DNA metabolism consecutive to MBD4 deficiency may result in specific cytotoxicities in MBD4-deficient tumor cells in a synthetic lethality fashion. After a large-scale drug repurposing screen, we show in two isogenic MBD4 knock-out cell models that the inactivation of MBD4 sensitizes cancer cells to cytidine analogs. We further confirm the exquisite activity of gemcitabine in an MBD4-deficient co-clinical model as (i) it completely prevented the development of an MBD4-deficient uveal melanoma patient-derived xenograft and (ii) treatment in the corresponding patient resulted in an exceptional tumor response. These data suggest that patients harboring MBD4-deficient tumors may be treated efficiently by cytidine analogs.

Surgical or medical strategy for locally-advanced, stage IIIA/B-N2 non-small cell lung cancer: Reproducibility of decision-making at a multidisciplinary tumor board.

BACKGROUND: Stage IIIA/B-N2 is a very heterogeneous group of patients and accounts for one third of NSCLC at diagnosis. The best treatment strategy is established at a Multidisciplinary Tumor Board (MTB): surgical resection with neoadjuvant or adjuvant therapy versus definitive chemoradiation with immune checkpoint inhibitors consolidation. Despite the crucial role of MTBs in this complex setting, limited data is available regarding its performances and the reproducibility of the decision-making. METHODS: Using a large cohort of IIIA/B-N2 NSCLC patients, we described patient's characteristics and treatment strategies established at the initial MTB: with a "surgical strategy" group, for potentially resectable disease, and a "medical strategy" group for non-resectable patients. A third group consisted of patients who were not eligible for surgery after neoadjuvant treatment and switched from the surgical to the medical strategy. We randomly selected 30 cases (10 in each of the 3 groups) for a blinded re-discussion at a fictive MTB and analyzed the reproducibility and factors associated with treatment decision. RESULTS: Ninety-seven IIIA/B-N2 NSCLC patients were enrolled between June 2017 and December 2019. The initial MTB opted for a medical or a surgical strategy in 44% and 56% of patients respectively. We identified histology, tumor size and localization, extent of lymph node involvement and the presence of bulky mediastinal nodes as key decision-making factors. Thirteen patients were not eligible for surgical resection after neoadjuvant therapy and switched for a medical strategy. Overall concordance between the initial decision and the re-discussion was 70%. The kappa correlation coefficient was 0.43. Concordance was higher for patients with limited mediastinal node invasion. Survival did not appear to be impacted by conflicting decisions. CONCLUSIONS: Reproducibility of treatment decision-making for stage IIIA/B-N2 NSCLC patients at a MTB is moderate but does not impact survival.

A Rare Cause of SCC Antigen Elevation: Inverted Sinonasal Papilloma.

ABSTRACT: We report the case of a 68-year-old woman who underwent 18F-FDG PET/CT for squamous cell carcinoma antigen (SCC Ag) elevation in the follow-up of a uterine cervical cancer. The examination showed an FDG-avid mass of the left nasal cavity with left maxillary sinusitis and no other site of abnormal FDG uptake. Surgical resection of the nasal polyp was performed, and pathological examination of the specimen revealed an inverted sinonasal papilloma. SCC Ag returned to normal after surgery. Inverted sinonasal papilloma is a rare cause of SCC Ag elevation, which can be depicted by 18F-FDG PET/CT.

Pembrolizumab Plus Chemotherapy in Metastatic Thymic Carcinoma: A Case Report.

Metastatic thymic carcinomas have a poor prognosis. Pembrolizumab, an anti-PD-1 antibody, has recently been evaluated for patients with metastatic thymic carcinomas progressing after at least one line of platinum-based chemotherapy. The antitumor activity of immunotherapy appears to be promising for these patients and pembrolizumab in monotherapy is actually a treatment option in second metastatic line. To the best of our knowledge, we report the first case of a patient treated for metastatic thymic adenocarcinoma with a combination of chemotherapy-immunotherapy. The patient is a 46-year-old man with metastatic thymic adenocarcinoma treated in third metastatic line with a combination of pembrolizumab plus platinum-based chemotherapy with a very good metabolic tumor response. He had a progression-free survival of 7.9 months and did not experience any severe side effects related to pembrolizumab. The association of immunotherapy and chemotherapy, as in non-small cell and small cell lung cancers, could be of interest for future therapeutic trials evaluating the survival of patients with metastatic thymic carcinoma.

A Case of Sarcoidosis After Lymphoma.

We report the case of a 62-year-old woman with previous history of stage III Hodgkin lymphoma. Routine follow-up CT scan revealed 2 years after end of treatment the appearance of mediastinal nodes, suspected of lymphoma recurrence. An F-FDG PET/CT was performed showing hypermetabolic mediastinal lymph nodes with diffuse symmetric osteomedullar hypermetabolism of pelvis and scapulae. In the hypothesis of either recurrence or multisystemic inflammatory disorder, bone marrow and lymph node biopsies were performed, revealing the presence of noncaseating epithelioid cell granulomas, leading to the diagnosis of multisystemic sarcoidosis. This case illustrates the sarcoidosis-lymphoma syndrome.

18F-Choline PET/CT Imaging for Intracranial Hemangiopericytoma Recurrence.

We report the case of a 50-year-old man, with previous history of grade 3 intracranial hemangiopericytoma with initial complete surgical resection, addressed for local recurrence. Surgical revision performed 18 months after initial surgery allowed only partial resection, leaving residual disease along the optic nerve. Complementary radiotherapy with proton was decided. F-FDG PET/CT and F-choline PET/CT were both performed for treatment planning. F-FDG PET showed no uptake of the residual tumor, whereas F-choline depicted highly metabolic residual disease uptake with excellent delineation of local recurrence. F-choline PET/CT appears as a useful PET tracer for hemagiopericytoma imaging.

Gallbladder Metastasis From Conjunctival Melanoma.

Malignant conjunctival melanoma is a rare tumor. A 46-year-old woman with a history of locally recurrent left conjunctival melanoma was followed by F-FDG PET/CT. Four years after the local recurrence treated by orbital exenteration, the follow-up PET/CT scan showed an incidental intense FDG uptake mass infiltrating the gallbladder associated with a low uptake of an infracentimetric pulmonary nodule. The patient was completely asymptomatic with no sign of local recurrence. Laparoscopic cholecystectomy was performed, and histopathologic findings were consistent with gallbladder metastasis of melanoma. After almost 2 years of immunotherapy, the patient is still in complete response.

Primary and Secondary Breast Angiosarcoma: FDG PET/CT Series.

Breast angiosarcoma is a rare and aggressive tumor. The role of F-FDG PET/CT in breast angiosarcoma is poorly known. We report a series of 13 lesions in 11 patients with histologically proven primary or secondary breast angiosarcoma who underwent FDG PET/CT at the initial assessment in our institution. All breast lesions showed FDG avidity. Visually and statistically, we observed a significant difference of SUVmax uptake foci between primary and secondary breast angiosarcoma (Wilcoxon test P < 0.0046) and a significantly poorer prognosis for high SUVmax than those with low SUVmax (P = 0.049) regardless of primary or secondary origins.

Rhabdomyosarcoma Revealed by a Breast Metastasis.

A 38-year-old woman was referred for staging of an alveolar rhabdomyosarcoma revealed by a breast metastasis with unknown primary. Whole-body F-FDG PET/CT localized the primary tumor as an asymptomatic soft tissue lesion of the right foot with a significant uptake. PET/CT detected hepatic and pancreatic metastases and also showed a multifocal bone marrow involvement, which was not detected by the contrast-enhanced CT. These results led to a significant change in treatment management as the patient received local radiotherapy of the primitive lesion and polychemotherapy.

PET/CT imaging in management of concomitant Hodgkin lymphoma and tuberculosis - a problem solver tool.

Infectious lymph nodes mimicking lymphoma is challenging for accurate staging. Although 18F-FDG is a nonspecific tracer accumulating not only in tumor cells but also in inflammatory tissues, the metabolic features and uptake kinetics give valuable information: 18F-FDG PET/CT appears as a useful problem solver tool in ambiguous situation.