Markerless liver online adaptive stereotactic radiotherapy: feasibility analysisCervantes

Objective. Radio-opaque markers are recommended for image-guided radiotherapy in liver stereotactic ablative radiotherapy (SABR), but their implantation is invasive. We evaluate in thisin-silicostudy the feasibility of cone-beam computed tomography-guided stereotactic online-adaptive radiotherapy (CBCT-STAR) to propagate the target volumes without implanting radio-opaque markers and assess its consequence on the margin that should be used in that context.Approach. An emulator of a CBCT-STAR-dedicated treatment planning system was used to generate plans for 32 liver SABR patients. Three target volume propagation strategies were compared, analysing the volume difference between the GTVPropagatedand the GTVConventional, the vector lengths between their centres of mass (lCoM), and the 95th percentile of the Hausdorff distance between these two volumes (HD95). These propagation strategies were: (1) structure-guided deformable registration with deformable GTV propagation; (2) rigid registration with rigid GTV propagation; and (3) image-guided deformable registration with rigid GTV propagation. Adaptive margin calculation integrated propagation errors, while interfraction position errors were removed. Scheduled plans (PlanNon-adaptive) and daily-adapted plans (PlanAdaptive) were compared for each treatment fraction.Main results.The image-guided deformable registration with rigid GTV propagation was the best propagation strategy regarding tolCoM(mean: 4.3 +/- 2.1 mm), HD95 (mean 4.8 +/- 3.2 mm) and volume preservation between GTVPropagatedand GTVConventional. This resulted in a planning target volume (PTV) margin increase (+69.1% in volume on average). Online adaptation (PlanAdaptive) reduced the violation rate of the most important dose constraints ('priority 1 constraints', 4.2 versus 0.9%, respectively;p< 0.001) and even improved target volume coverage compared to non-adaptive plans (PlanNon-adaptive).Significance. Markerless CBCT-STAR for liver tumours is feasible using Image-guided deformable registration with rigid GTV propagation. Despite the cost in terms of PTV volumes, daily adaptation reduces constraints violation and restores target volumes coverage.

Regression of a melanoma brain metastasis that had appeared after immune checkpoint inhibitor discontinuation: a hypothesis-generating case

We present the case of a 50-year-old woman previously treated with nivolumab-ipilimumab combination therapy for a metastatic melanoma. Despite premature discontinuation of these immune checkpoint inhibitors (ICIs) after 2 cycles due to severe immune-related hepatitis, the patient achieved a complete response. Nine months later, brain magnetic resonance imaging (MRI) showed progression of a single cerebral lesion, and the patient was referred for stereotactic radiosurgery. Unexpectedly, the brain MRI acquired one month later as part of radiosurgery planning showed a spontaneous regression of this lesion, allowing for radiosurgery cancellation. Follow-up imaging showed a sustained response, although the patient did not receive any other oncological treatment. We discuss here the potential immune mechanisms involved in this unusual course and the importance of better understanding the behaviour of tumours in the era of ICIs.

Cone-beam computed tomography-guided online-adaptive radiotherapy for inoperable right colon cancer: First in human

We report the case of a medically inoperable patient with localised colon cancer. Due to symptomatic bleeding, definitive radiotherapy (5 daily fractions of 5 Gy) has been performed using cone-beam computed tomography-based online-adaptive radiotherapy (ART). Online-ART enables compensation of interfraction motion of abdominal organs by performing daily delineation of organs at risk (OARs) and target volumes. Daily treatment replanning maximised target volume coverage while lowering the dose to OARs. Intrafraction variation of the tumour was still significant and had to be incorporated in the planning target volume margin computation. After the treatment, the patient did not develop any acute radiotherapy-induced adverse events and had no further rectal bleeding either at the end of the radiotherapy or at oncological follow-up 4 months later. Online-ART for colon cancer is feasible and is a valuable alternative when surgery is not an option.

Implications of the Organ-Specific Immune Environment for Immune Priming Effect of Radiotherapy in Metastatic Setting

With the development of immune checkpoint inhibitors (ICIs), the tumour immune microenvironment (TIME) has been increasingly considered to improve cancer management. The TIME of metastatic lesions is strongly influenced by the underlying immune contexture of the organ in which they are located. The metastatic location itself appears to be an important prognostic factor in predicting outcomes after ICI treatment in cancer patients. Patients with liver metastases are less likely to respond to ICIs than patients with metastases in other organs, likely due to variations in the metastatic TIME. Combining additional treatment modalities is an option to overcome this resistance. Radiotherapy (RT) and ICIs have been investigated together as an option to treat various metastatic cancers. RT can induce a local and systemic immune reaction, which can promote the patient's response to ICIs. Here, we review the differential impact of the TIME according to metastatic location. We also explore how RT-induced TIME modifications could be modulated to improve outcomes of RT-ICI combinations.

Dose mimicking based strategies for online adaptive proton therapy of head and neck cancer

OBJECTIVE

To compare a not adapted (NA) robust planning strategy with three fully automated online adaptive proton therapy (OAPT) workflows based on the same optimization method: dose mimicking (DM). The added clinical value and limitations of the OAPT methods are investigated for head and neck cancer (HNC) patients.&#xD;&#xD;&#xD;Approach: The three OAPT strategies aimed at compensating for inter-fractional anatomical changes by mimiking different dose distributions on corrected cone beam CT images (corrCBCTs). Order by complexity, the OAPTs were: (1) online adaptive dose restoration (OADR) where the approved clinical dose on the planning-CT (pCT) was mimicked, (2) online adaptation using DM of the deformed clinical dose from the pCT to corrCBCTs (OADEF), and (3) online adaptation applying DM to a predicted dose on corrCBCTs (OAML). Adaptation was only applied in fractions where the target coverage criteria were not met (D98% < 95% of the prescribed dose). For 10 HNC patients, the accumulated dose distributions over the 35 fractions were calculated for NA, OADR, OADEF, and OAML.&#xD;&#xD;Main results: Higher target coverage was observed for all OAPT strategies compared to no adaptation. OADEF and OAML outperformed both NA and OADR and were comparable in terms of target coverage to initial clinical plans. However, only OAML provided comparable NTCP values to those from the clinical dose without statistically significant differences. When the NA initial plan was evaluated on corrCBCTs, 51% of fractions needed adaptation. The adaptation rate decreased significantly to 25% when the last adapted plan with OADR was selected for delivery, to 16% with OADEF, and to 21% with OAML. The reduction was even greater when the best plan among previously generated adapted plans (instead of the last one) was selected.&#xD;&#xD;Significance: The implemented OAPT strategies provided superior target coverage compared to no adaptation, higher OAR sparing, and fewer required adaptations.

Radiation therapy-induced left vocal cord paralysis following lung stereotactic body radiation therapy: A case report and review of the literature

We report the case of a 50-year old women with an oncological history of metastatic breast carcinoma who underwent lung stereotactic body radiation therapy (SBRT) of 60Gy in 8 fractions for a left upper lobe metastatic lesion. Seven months later, she complains about hoarseness and weakness of voice. Tumoral relapse and other frequent etiologies were excluded. The diagnosis of radiation induced left recurrent laryngeal nerve paralysis causing left vocal cord paralysis (VCP) was made. The symptomatology did not improve till the disease progression and death of the patient 29 months after SBRT. VCP after lung SBRT is a rare adverse event that has not yet been well described in the medical literature.

c-MET as a Potential Resistance Mechanism to Everolimus in Breast Cancer: From a Case Report to Patient Cohort Analysis

BACKGROUND

We describe in a patient with breast cancer the change in c-MET expression during everolimus treatment, opening a better understanding of the resistance to everolimus and a role for cabozantinib.

OBJECTIVE

The objective of this study was to evaluate c-MET as a potential predictive biomarker for everolimus efficacy in breast cancer.

METHODS

We first selected a patient with breast cancer with a long-lasting response to everolimus and retrospectively profiled biopsies that were taken before everolimus initiation (Biopsy 1) and at progression on everolimus (Biopsy 2) using amplicon sequencing and immunohistochemistry. We then retrospectively evaluated c-MET expression in a cohort of patients with breast cancer treated with everolimus.

RESULTS

While not expressed in Biopsy 1, c-MET was highly expressed in Biopsy 2, suggesting a role for c-MET in breast cancer progression. Cabozantinib resulted in a rapid radiological response in this patient. Twenty-nine patients were included (12 c-MET-positive and 17 c-MET-negative patients) in the second part of the study. Baseline c-MET expression was associated with higher tumor grade, higher frequency of visceral metastases, and lower endocrine sensitivity. The c-MET-positive patients presented with a shorter progression-free survival (6.1 vs 10.5 months, respectively; p = 0.002) and a lower response rate (0% vs 12%) to everolimus, compared with c-MET-negative patients.

CONCLUSIONS

c-MET could play a role in the resistance to everolimus and its inhibition should be evaluated in breast cancer.

Impact of the gut microbiome on immune checkpoint inhibitor efficacy-a systematic review

Background

Immune checkpoint inhibitors (icis) are increasingly being used in clinical practice, improving outcomes for cancer patients. Preclinical models showed significant interaction between the gut microbiome (gm) and response to icis. However, that interaction remains unclear in clinical practice.

Methods

We performed a systematic review in medline to determine■ whether antibiotics affect ici efficacy,■ whether baseline gm composition and ici efficacy show any correlations,■ whether baseline gm composition and emergence of immune-related adverse events (iraes) show any correlations, and■ whether gm manipulation can alleviate the iraes.Included publications had to be written in English or French and had to describe a quantifiable link between gm composition or its modification and the response to icis or the occurrence of iraes, or both.

Results

Of 1451 articles published before December 2018, 13 publications met the inclusion criteria. Five full-text articles and two abstracts highlighted a negative effect of antibiotics on ici efficacy. The composition of the gm was associated with ici efficacy in five full-text articles and one abstract, and with iraes in two full-text articles. In 2 cases, fecal microbiota transplantation was reported to reduce immune colitis.

Conclusions

If possible, antibiotics should be avoided before ici treatment because of their negative effect on ici anticancer efficacy. No specific commensal bacterium was associated with ici efficacy, but an intact gm with high bacterial diversity and a good ratio of "responder-associated" bacteria to "non-responder-associated" bacteria seem to be correlated with better patient outcomes. Fecal microbiota transplantation is a promising technique for reducing ici-associated colitis.

Isolated adrenocorticotropic hormone (ACTH) deficiency and Guillain-Barré syndrome occurring in a patient treated with nivolumab

The increased use of immune checkpoint inhibitors (ICIs) has led to the observation of a variety of immune-related adverse events (irAEs). These irAEs occur usually within the first months after ICIs onset and can involve theorically all organs. We describe two rare irAEs occurring in a 70-year-old caucasian man who was treated with nivolumab for an advanced urothelial cancer of the left kidney. He developed an isolated adrenocorticotropic hormone deficiency that was diagnosed at week 19 and a neurological complication that appeared at week 79 and initially confounded with a lumbar spinal stenosis. Diagnosis of Guillain-Barré syndrome was finally confirmed with the complete resolution of symptoms after 5 days of intravenous immunoglobulin and corticosteroids. We highlight the importance of quickly recognising these potential life-threatening irAEs such as cortisol insufficiency and neurologic adverse events whose initially presentation could be non-specific.

Mechanism of action of K channel openers on skeletal muscle KATP channels. Interactions with nucleotides and protons

The molecular mechanisms underlying the actions of K channel openers (KCOs) on KATP channels were studied with the patch clamp technique in excised inside-out patches from frog skeletal muscle fibers. Benzopyran KCOs (levcromakalim and SR 47063) opened channels partially blocked by ATP, ADP, or ATP gamma s, with and without Mg2+, but they had no effects in the absence of internal nucleotides, even after channel activity had significantly declined because of rundown. The effects of KCOs could therefore be attributed solely to a competitive interaction between KCOs and nucleotides, as confirmed by observations that ATP decreased the apparent affinity for KCOs and that, conversely, KCOs decreased ATP or ADP sensitivity. Protons antagonized the action of the non-benzopyran KCOs, pinacidil and aprikalim, by enhancing their dissociation rate. This effect resembled the effect of acidification on benzopyran KCOs (Forestier, C., Y. Depresle, and M. Vivaudou. FEBS Lett. 325:276-280, 1993), suggesting that, in spite of their structural diversity, KCOs could act through the same binding sites. Detailed analysis of the inhibitory effects of protons on channel activity induced by levcromakalim or SR 47063 revealed that, in the presence of 100 microM ATP, this effect developed steeply between pH 7 and 6 and was half maximal at pH 6.6. These results are in quantitative agreement with an allosteric model of the KATP channel possessing four protonation sites, two nucleotidic sites accessible preferentially to Mg(2+)-free nucleotides, and one benzopyran KCO site. The structural implications of this model are discussed.

Sequence and transcript analysis of the nitrogenase structural gene operon (nifHDK) of Rhodobacter capsulatus: evidence for intramolecular processing of nifHDK mRNA

Northern blot analysis of RNA prepared from cells of Rhodobacter capsulatus derepressed for nitrogenase (N2ase) synthesis, using a 6.0-kb DNA probe containing the entire nifHDK operon, revealed the presence of at least six hybridizing species of the estimated sizes, 4.4, 3.5, 2.7, 1.3, 0.9 and 0.38 kb. No hybridization was detected with RNA prepared from cells grown in the presence of an excess of NH4+, which represses N2ase synthesis. Hybridization with gene-specific probes revealed that the 4.4-kb species hybridized with all three probes, and presumably corresponded to the full-length nifHDK transcript, whereas the 3.5-kb species hybridized with nifD and nifK only, and the 2.7-kb transcript hybridized with nifH and nifD. The 1.3 and 0.9-kb species hybridized with all three probes, but appeared to hybridize most strongly with nifH. In contrast, the 0.38-kb species hybridized with none of the gene-specific probes, and was also detected in RNA from cells of strain RcM1, which contains a chromosomal deletion of the nifHDK operon. This species probably corresponds to the transcript of a gene, named fdxD, which was found to be located just upstream from the nifHDK operon. Nucleotide (nt) sequencing of the nifH-D and nifD-K intergenic regions revealed the presence of inverted repeat (IR) sequences potentially capable of forming stable stem-loop structures in mRNA. Primer extension analysis of the nifDK-homologous species showed that the 5' end was located one or two nt downstream from the IR sequence between nifH and nifD, suggesting that the putative stem-loop structure may be a target for intramolecular processing of the nifHDK mRNA.

Site-directed mutagenesis of the target arginine for ADP-ribosylation of nitrogenase component II in Rhodobacter capsulatus

The role of the conserved residue arginine-102 in the functioning and the regulation of the nitrogenase component II protein in Rhodobacter capsulatus has been studied by site-directed mutagenesis. The arginine at position 102 was replaced by thirteen different amino acids, and the effect of these substitutions on diazotrophic growth, in vivo and in vitro nitrogenase activity, and ADP-ribosylation of the component II protein was tested. The results show that although arginine is the optimal amino acid at this position, it is not essential for activity. However, the mutant proteins were not modified by ADP-ribosylation, either in the dark or after addition of NH4+, consistent with the specificity of the post-translational regulatory mechanism for the Arg-102. Indirect evidence suggest that this residue may be involved in interaction with the in vivo low-potential electron donor.

Posttranslational regulation of nitrogenase in Rhodobacter capsulatus: existence of two independent regulatory effects of ammonium

In the photosynthetic bacterium Rhodobacter capsulatus, nitrogenase activity is regulated by ADP-ribosylation of component II in response to the addition of ammonium to cultures or to the removal of light. The ammonium stimulus results in a fast and almost complete inhibition of the in vivo acetylene reduction activity, termed switch-off, which is reversed after the ammonium is exhausted. In the present study of the response of cells to ammonium, ADP-ribosylation of component II occurred but could not account for the extent and timing of the inhibition of activity. The presence of an additional response was confirmed with strains expressing mutant component II proteins; although these proteins are not a substrate for ADP-ribosylation, the strains continued to exhibit a switch-off response to ammonium. This second regulatory response of nitrogenase to ammonium was found to be synchronous with ADP-ribosylation and was responsible for the bulk of the observed effects on nitrogenase activity. In comparison, ADP-ribosylation in R. capsulatus was found to be relatively slow and incomplete but responded independently to both known stimuli, darkness and ammonium. Based on the in vitro nitrogenase activity of both the wild type and strains whose component II proteins cannot be ADP-ribosylated, it seems likely that the second response blocks either the ATP or the electron supply to nitrogenase.