Association of Cardiac Dose with Cardiac Events and Survival for Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) Treated with Concurrent Chemoradiotherapy (cCRT) in the Era of Immune Checkpoint Inhibitor (ICI) Consolidation

PURPOSE/OBJECTIVE(S)

To assess the association of cardiac dose with post-cCRT cardiac events and survival among patients (pts) with LA-NSCLC after adoption of ICI consolidation, modern radiotherapy (RT) techniques, and data-driven cardiac constraints.

MATERIALS/METHODS

This single-institution, multi-site retrospective study included 335 pts with LA-NSCLC treated with definitive cCRT (60-70 Gy) from October 2017 to December 2021. Pts were evaluated for ICI consolidation. Cardiac dose constraints included heart volume receiving ≥50 Gy (V50) <25% and mean heart dose (MHD) <20 Gy. Heart, left anterior descending artery (LAD), and left ventricle were autocontoured, manually reviewed, and edited. 21 dosimetric parameters (mean dose, max dose, and min dose to the hottest x% volume [Dx%(Gy); x from 5-95 in 5% intervals]) for each were extracted, as well as LAD V15. Baseline cardiovascular disease (bCVD) was defined as heart failure (HF), coronary artery disease, peripheral vascular disease, or cerebrovascular disease. Primary endpoint was post-cCRT major adverse cardiac events (MACE), defined as acute coronary syndrome, HF hospitalization/urgent visit, coronary revascularization, or cardiac death. Secondary endpoints were grade ≥3 cardiac events (CTCAE v5.0), overall survival (OS), cancer specific mortality (CSM), and other cause mortality (OCM). Competing risk regression was used for MACE and grade ≥3 cardiac events, and Cox regression for OS, CSM, and OCM.

RESULTS

Median age was 68 years, 139 (41%) had bCVD, and 225 (67%) received consolidation ICI. Proton therapy was used in 117 (35%), intensity-modulated RT in 199 (59%), and 3D conformal RT in 19 (6%). Median MHD was 8.7 Gy (IQR 4.6-14.4) and median LAD V15 1.4% (IQR 0-22). Median follow-up was 39.5 months. 35 MACE events occurred; 1- and 2-year cumulative incidence (CI) were 4.2% and 9.5%. No cardiac dosimetric parameter associated with MACE after adjusting for bCVD and age (e.g., MHD sHR 0.98/Gy, 95% CI 0.93-1.03, p = 0.43) or within the following 3 subgroups: no bCVD, photon therapy, and ICI consolidation. 87 grade ≥3 cardiac events occurred; 1- and 2- year CI were 12.6% and 20.4%. Heart dose was not associated with grade ≥3 cardiac events after adjusting for bCVD, ECOG, and BMI (e.g., MHD sHR 1.00/Gy, 95% CI 0.97-1.03, p = 0.85) or within the 3 aforesaid subgroups. 183 OS events occurred, including 125 CSM and 58 OCM events. Multiple cardiac dosimetric parameters associated with worse OS on multivariable analysis (e.g., LAD V15 HR 1.01/%, 95% CI 1.00-1.02, p = 0.003), driven by associations with CSM (LAD V15 HR 1.02/%, p<0.001) but not OCM (LAD V15 HR 1.00/%, p = 0.73). Median OS was worse for LAD V15 ≥10% (22.2 vs 35.1 months, p = 0.004).

CONCLUSION

Among pts with LA-NSCLC treated with cCRT after adoption of ICI consolidation, modern RT techniques, and cardiac constraints, post-cCRT cardiac events were common but showed no association with cardiac dose. Cardiac dose associated with OS, driven by an association with CSM and not OCM, which may not reflect cardiac toxicity.

Proton Beam Therapy (PBT) Versus Intensity-Modulated Radiotherapy (IMRT) for Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) in the Era of Immune Checkpoint Inhibitor (ICI) Consolidation: A Retrospective Cohort Study

PURPOSE/OBJECTIVE(S)

Patients (pts) with LA-NSCLC treated with concurrent chemoradiation (cCRT) and ICI consolidation are at high risk for treatment-related toxicities and subsequent hospitalization. We hypothesized that PBT is associated with a reduction in acute unplanned hospitalizations as compared to IMRT in the era of ICI consolidation.

MATERIALS/METHODS

This single institution, multi-site retrospective study included consecutive pts with LA-NSCLC treated with definitive cCRT with either PBT or IMRT from October 2017 to December 2021. Pts were evaluated for consolidative ICI. Primary endpoint was unplanned treatment-related hospitalization within 90 days of first radiation (RT) treatment. Secondary endpoints included grade 3+ pneumonitis, grade 3+ esophagitis, PFS and OS. Logistic regression was used to assess associations with 90-day hospitalization. Competing risk regression was used for grade 3+ pneumonitis and esophagitis, and Cox regression for PFS and OS.

RESULTS

A total of 316 pts were included: 117 (37%) received PBT and 199 (63%) IMRT. Median age was 68.5 yrs; median RT dose 66.6 Gy (IQR 65.9-70.0). PBT group was older (median 71.1 vs 67.2 yrs, p<0.005) and had a higher Charlson comorbidity index (CCI) (median 4 vs 3, p = 0.02). There was no significant difference in ECOG, smoking pack-years, T stage, N stage, target volume size, or receipt of ICI consolidation (66.7% vs 68.3%, p = 0.76). PBT group had lower mean heart dose (5.9 vs 10.8 Gy, p<0.001), LAD V15 (0 vs 6 %, p = 0.001), mean lung dose (14.7 vs 15.7 Gy, p <0.008) and effective dose to immune circulating cells (median 3.7 vs 4.9 Gy, p<0.001) but not mean esophagus dose. PBT was associated with fewer unplanned 90-day hospitalizations (23.9% vs 34.7%); which persisted on multivariable analysis (OR 0.52, 95% CI 0.30-0.90, p = 0.02) after adjusting for CCI, smoking pack-years, T4 tumors and target volume. Reasons for hospitalization in PBT and IMRT groups included progression (1.7% vs 1.5%), definite/probable toxicity from cCRT (11.1% vs 18.6%), possible toxicity from cCRT (7.7% vs 12.6%) or unrelated to cCRT (3.4% vs 2.0%). There was no significant difference between PBT or IMRT groups in G3+ pneumonitis (1-year 6.0% vs 9.1%, p = 0.49), G3+ esophagitis (1-year 6.0% vs 6.5%, p = 0.71), PFS (median 14.4 vs 15.1 months, p = 0.69), or OS (median 34.2 vs 29.4 months, p = 0.41).

CONCLUSION

Among pts with LA-NSCLC treated with cCRT in the era of ICI consolidation, PBT was associated with fewer acute unplanned hospitalizations compared to IMRT. There was no difference in G3+ pneumonitis, G3+ esophagitis, PFS or OS.

Patterns of Failure, Volume of Disease Progression, and Subsequent Ablative Management in Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC) Treated with Definitive Chemoradiation and Consolidation Immune Checkpoint Inhibitors (ICI)

PURPOSE/OBJECTIVE(S)

For patients (pts) with LA-NSCLC treated with chemoradiation and consolidation ICI (CRT+ICI), the patterns of failure (POF) and volume of disease progression (PD) are not well characterized. The primary objective of this study was to classify POFs, the frequency of low volume relapse (LVR), and identify pts eligible for further ablative therapy.

MATERIALS/METHODS

We retrospectively identified pts with unresectable stage III NSCLC treated with CRT+ICI between October 2017 and December 2021 at a single institution. Site of first failure was classified as locoregional (LRF), distant (DF), or synchronous LRF + DF. Any LRF was subclassified as in field (IFF; PD within 90% isodose line), marginal (MF; within 50% isodose line) or out of field (OOF; outside of 50% isodose line). LVR was defined as < 3 discrete sites of PD in any number or location of organs. Pts with distant LVR were considered to have oligometastatic relapse. Ablative candidates were defined as pts with < 3 discrete sites of PD amenable to further RT or surgery. Cumulative incidence of PD was calculated with death as a competing risk. Progression free survival (PFS) and overall survival (OS) were calculated from the end of RT and assessed via Kaplan Meier. Multivariable Cox modeling was used to assess correlation of pt characteristics and time-to-event outcomes. Logistic regression was used to predict variables associated with LVR.

RESULTS

A total of 229 pts received CRT+ICI. Median follow up was 39 months and 119 pts experienced PD. Median PFS and OS were 18.4 and 34.5 months, respectively. Of pts with PD, 71 (60%) had DF, 28 (24%) had LRF+DF, and 20 (17%) had LRF. Of pts with any LRF, 28 (57%) had IFF, 10 (21%) had MF, and 10 (21%) had OOF. Estimated 1-year cumulative incidence of LRF, DF, and LRF+DF were 9.3% (95% CI 4.5-16), 39% (95% CI 31-48), and 19% (95% CI 12-27), respectively. A total of 63 (53%) pts had LVR. In pts with LVR, 19 (30%) had isolated thoracic relapse and 44 (69%) had oligometastatic relapse. Most oligometastatic disease was intracranial (22 metastases, 44%). Pts with LVR had a longer median OS vs pts with high volume relapse (37.4 vs 15.2 months, p<0.001). At time of PD, 56 (47%) pts were candidates for further ablative therapies. Subsequent anticancer therapies were local therapy alone (35%), local and systemic therapy (16%), systemic therapy alone (36%), or no therapy (13%). On multivariable analysis, LVR (HR 0.39; 95% CI 0.21-0.73, p = 0.003) and longer receipt of ICI (HR 0.96; 95% CI 0.95-0.98; p<0.001) were associated with improved survival while squamous histology (HR 2.26; 95% CI 1.18-4.32; p = 0.039) was associated with worse survival. Longer receipt of ICI was the only variable predictive for the development of LVR (OR 1.03; 95% CI 1.01-1.05; p = 0.004).

CONCLUSION

This is the largest real-world series reporting POF after CRT+ICI for stage III NSCLC. Approximately half of pts experience LVR and are candidates for further ablative therapy. Further data are needed to define optimal treatment strategies for pts with LVR after CRT+ICI.

Pneumonitis after Palliative Thoracic Radiotherapy +/- Immunotherapy: A Retrospective Propensity-Matched Cohort Study

PURPOSE/OBJECTIVE(S)

Patients (pts) with advanced lung cancer often receive combined palliative thoracic radiotherapy (RT) and immune checkpoint inhibitors (ICI). There are limited data assessing the toxicities of combined ICI-RT in this setting. We sought to compare the rates of clinically significant pneumonitis among pts with lung cancer receiving palliative thoracic RT with or without recent or concomitant ICI. We hypothesized there would be a higher rate of grade 2+ pneumonitis among RT pts who received recent or concomitant ICI compared to those who did not.

MATERIALS/METHODS

We retrospectively identified consecutive pts with advanced/recurrent lung cancer from a tertiary academic center who received palliative thoracic RT with recent (defined as within 95 days of RT start) or concomitant ICI (ICI-RT group) between January 2014 and February 2020. Pts were propensity matched in a 1:1 manner (by age, sex, ECOG, RT modality, and RT dose) to lung cancer pts who received palliative thoracic RT without any history of ICI receipt (RT-only group). The presence and grade (CTCAE v5.0) of pneumonitis were independently assessed by two investigators. The primary endpoint was grade 2+ pneumonitis, estimated using the cumulative incidence function and compared between the ICI-RT and RT-only groups using Gray's test. The secondary endpoint was overall survival, estimated using the Kaplan-Meier method and compared between groups using the log-rank test.

RESULTS

A total of 146 pts were included in the study (73 in each group). There were no statistically significant differences between the ICI-RT and RT-only groups with respect to age (median 67.7 vs. 67.6, p = 0.97), sex (52% vs. 52% female, p = 1.00), pre-treatment ECOG 0-1 (74% vs 75%, p = 0.85), or biologically effective dose greater than 45 (48% vs. 48%, p = 1.00). The most common RT regimens were 30 Gy in 10 fractions (33 pts, 23%) and 20 Gy in 5 fractions (18 patients, 12%). A plurality of cases utilized 3DCRT (67 pts, 46%). In the ICI-RT group, the median time from last dose of ICI to the start of palliative RT was 16 days; three pts in this group-initiated ICI while receiving RT treatment. The most common ICI was pembrolizumab (36 pts, 49%). A total of eleven grade 2+ pneumonitis events (nine grade 2 and two grade 3 events) were observed. The ICI-RT group had a higher cumulative incidence of grade 2+ pneumonitis compared with the RT-only group (1-year rate, 12.3% vs. 2.7%, p = 0.029); grade 3 pneumonitis occurred in 1/73 (1.4%) in each group. There was no difference in overall survival between groups (median 239 vs. 218 days, p = 0.76).

CONCLUSION

In pts with advanced lung cancer treated with palliative thoracic RT, recent or concomitant ICI use was associated with a higher cumulative incidence of grade 2+ pneumonitis. However, the incidence of grade 3+ pneumonitis was low (1.4%) regardless of ICI receipt.

Acute hematological effects of solar particle event proton radiation in the porcine model

Acute radiation sickness (ARS) is expected to occur in astronauts during large solar particle events (SPEs). One parameter associated with ARS is the hematopoietic syndrome, which can result from decreased numbers of circulating blood cells in those exposed to radiation. The peripheral blood cells are critical for an adequate immune response, and low blood cell counts can result in an increased susceptibility to infection. In this study, Yucatan minipigs were exposed to proton radiation within a range of skin dose levels expected for an SPE (estimated from previous SPEs). The proton-radiation exposure resulted in significant decreases in total white blood cell count (WBC) within 1 day of exposure, 60% below baseline control value or preirradiation values. At the lowest level of the blood cell counts, lymphocytes, neutrophils, monocytes and eosinophils were decreased up to 89.5%, 60.4%, 73.2% and 75.5%, respectively, from the preirradiation values. Monocytes and lymphocytes were decreased by an average of 70% (compared to preirradiation values) as early as 4 h after radiation exposure. Skin doses greater than 5 Gy resulted in decreased blood cell counts up to 90 days after exposure. The results reported here are similar to studies of ARS using the nonhuman primate model, supporting the use of the Yucatan minipig as an alternative. In addition, the high prevalence of hematologic abnormalities resulting from exposure to acute, whole-body SPE-like proton radiation warrants the development of appropriate countermeasures to prevent or treat ARS occurring in astronauts during space travel.

Intraperitoneal photodynamic therapy

Peritoneal carcinomatosis and sarcomatosis are generally incurable problems for which there are few good treatment options. Intraperitoneal PDT is potentially an ideal therapy for peritoneal carcinomatosis because of its relatively superficial treatment effect. A Phase II trial of IP PDT with the first generation photosensitizer, Photofrin, demonstrates that this treatment approach is tolerable clinically but is associated with substantial toxicity suggesting a narrow therapeutic index. Remarkably, responses were observed in heavily pre-treated patients suggesting clinical activity. Correlative studies of photosensitizer uptake in human tumour and normal tissues show little tumour selectivity. This lack of photosensitizer selectivity for tumour in combination with tumour hypoxia (as opposed to oxic normal tissues) is likely a major reason for the narrow therapeutic index of intraperitoneal PDT. However, the advent of novel and potentially molecularly targeted photosensitizers, combined with enhancement of PDT cancer cell cytotoxicity through inhibition of growth factor signaling should greatly improve the therapeutic index of intraperitoneal PDT. In addition, other approaches, including the use of nanotechnology, may allow the administration of fractionated PDT which may also improve the therapeutic index of this treatment. The clinical implementation of these technologies may allow for highly effective and well tolerated treatment of intraperitoneal carcinomatosis with PDT.

CD45 negatively regulates monocytic cell differentiation by inhibiting phorbol 12-myristate 13-acetate-dependent activation and tyrosine phosphorylation of protein kinase Cdelta

The protein-tyrosine phosphatase CD45 is expressed on all monocytic cells, but its function in these cells is not well defined. Here we report that CD45 negatively regulates monocyte differentiation by inhibiting phorbol 12-myristate 13-acetate (PMA)-dependent activation of protein kinase C (PKC) delta. We found that antisense reduction of CD45 in U937 monocytic cells (CD45as cells) increased by 100% the ability of PMA to enlarge cell size, increase cell cytoplasmic process width and length, and induce surface expression of CD11b. In addition, reduction in CD45 expression caused the duration of peak PMA-induced MEK and extracellular signal-regulated kinase (ERK) 1/2 activity to increase from 5 min to 30 min while leading to a 4-fold increase in PMA-dependent PKCdelta activation. Importantly, PMA-dependent tyrosine phosphorylation of PKCdelta was also increased 4-fold in CD45as cells. Finally, inhibitors of MEK (PD98059) and PKCdelta (rottlerin) completely blocked PMA-induced monocytic cell differentiation. Taken together, these data indicate that CD45 inhibits PMA-dependent PKCdelta activation by impeding PMA-dependent PKCdelta tyrosine phosphorylation. Furthermore, this blunting of PKCdelta activation leads to an inhibition of PKCdelta-dependent activation of ERK1/2 and ERK1/2-dependent monocyte differentiation. These findings suggest that CD45 is a critical regulator of monocytic cell development.

JAK1-dependent phosphorylation of insulin receptor substrate-1 (IRS-1) is inhibited by IRS-1 serine phosphorylation

Serine phosphorylation of insulin receptor substrate-1 (IRS-1) reduces its ability to act as an insulin receptor substrate and inhibits insulin receptor signal transduction. Here, we report that serine phosphorylation of IRS-1 induced by either okadaic acid (OA) or chronic insulin stimulation prevents interferon-alpha (IFN-alpha)-dependent IRS-1 tyrosine phosphorylation and IFN-alpha-dependent IRS-1/phosphatidylinositol 3'-kinase (PI3K) association. In addition, we demonstrate that serine phosphorylation of IRS-1 renders it a poorer substrate for JAK1 (Janus kinase-1). We found that treatment of U266 cells with OA induced serine phosphorylation of IRS-1 and completely blocked IFN-alpha-dependent tyrosine phosphorylation of IRS-1 and IFN-alpha-dependent IRS-1/PI3K association. Additionally, IRS-1 from OA-treated cells could not be phosphorylated in vitro by IFN-alpha-activated JAK1. Chronic treatment of U266 cells with insulin led to a 50% reduction in IFN-alpha-dependent tyrosine phosphorylation of IRS-1 and IRS-1/PI3K association. More importantly, serine-phosphorylated IRS-1-(511-722) could not be phosphorylated in vitro by IFN-alpha-activated JAK1. Taken together, these data indicate that serine phosphorylation of IRS-1 prevents its subsequent tyrosine phosphorylation by JAK1 and suggest that IRS-1 serine phosphorylation may play a counter-regulatory role in pathways outside the insulin signaling system.

Insulin activates caspase-3 by a phosphatidylinositol 3'-kinase-dependent pathway

Activation of the caspase proteases by c-Jun N-terminal kinase 1 (JNK1) has been proposed as a mechanism of apoptotic cell death. Here we report that insulin activates caspase-3 by a pathway requiring phosphatidylinositol 3'-kinase (PI3-kinase). JNK1 assays demonstrated that insulin treatment of myeloma cells induced 3-fold activation of JNK1. Inhibition of PI3-kinase with wortmannin and LY294002 blocked insulin-dependent activation of JNK1. Caspase assays demonstrated that insulin increased caspase-3 activity 3-fold and that inhibition of PI3-kinase blocked this effect. Cell death was doubled by insulin and was due to a 3-fold increase in apoptosis of cells in the G1/G0 phase of the cell cycle. Inhibition of PI3-kinase completely blocked this effect. Finally, inhibition of caspase-3 with benzyloxycarbonyl-Asp-2,6-dichlorobenzoyloxymethylketone blocked cell death due to insulin. Taken together, these findings indicate that insulin activates caspase-3 by a PI3-kinase-dependent pathway resulting in increased apoptosis and cell death.

Phosphatidylinositol 3'-kinase associates with an insulin receptor substrate-1 serine kinase distinct from its intrinsic serine kinase

Serine phosphorylation of insulin receptor substrate-1 (IRS-1) has been proposed as a counter-regulatory mechanism in insulin and cytokine signalling. Here we report that IRS-1 is phosphorylated by a wortmannin insensitive phosphatidylinositol 3'-kinase (PI 3-kinase)-associated serine kinase (PAS kinase) distinct from PI 3-kinase serine kinase. We found that PI 3-kinase immune complexes contain 5-fold more wortmannin-insensitive serine kinase activity than SH2-containing protein tyrosine phosphatase-2 (SHP2) and IRS-1 immune complexes. Affinity chromatography of cell lysates with a glutathione S-transferase fusion protein for the p85 subunit of PI 3-kinase showed that PAS kinase associated with the p85 subunit of PI 3-kinase. This interaction required unoccupied SH2 domain(s) but did not require the PI 3-kinase p110 subunit binding domain. In terms of function, PAS kinase phosphorylated IRS-1 and, after insulin stimulation, PAS kinase phosphorylated IRS-1 in PI 3-kinase-IRS-1 complexes. Phosphopeptide mapping showed that insulin-dependent in vivo sites of IRS-1 serine phosphorylation were comparable to those of PAS kinase phosphorylated IRS-1. More importantly, PAS kinase-dependent phosphorylation of IRS-1 reduced by 4-fold the ability of IRS-1 to act as an insulin receptor substrate. Taken together, these findings indicate that: (a) PAS kinase is distinct from the intrinsic serine kinase activity of PI 3-kinase, (b) PAS kinase associates with the p85 subunit of PI 3-kinase through SH2 domain interactions, and (c) PAS kinase is an IRS-1 serine kinase that can reduce the ability of IRS-1 to serve as an insulin receptor substrate.

Phosphatidylinositol 3'-kinase is associated with a serine kinase that is activated by okadaic acid

Okadaic acid (OA) is a potent inhibitor of PP1 and PP2A serine/threonine phosphatases and an inhibitor of phosphatidylinositol 3'-kinase (PI 3-kinase) recruitment/ activation. Here we report that PI 3-kinase associates with a serine kinase activated by OA. Whole cell phosphorylation studies showed that PI 3-kinase associates with a wortmannin insensitive 76 kDa serine phosphoprotein (pp76) distinct from the p85 subunit of PI 3-kinase. Serine kinase assays demonstrated that pp76 phosphorylation was dependent upon a wortmannin insensitive serine kinase contained within PI 3-kinase/pp76 complexes and that this kinase had different cation requirements than PI 3-kinase serine kinase. Treatment of whole cells with OA lead to a wortmannin-independent 7.6-fold increase in pp76 serine phosphorylation and to a 7-fold rise in pp76 kinase activity. Together, these findings indicate that pp76 is a PI 3-kinase associated phosphoprotein and suggest that pp76 may be a novel PI 3-kinase associated serine kinase that is activated by OA.

Site-specific phosphorylation of the human immunodeficiency virus type-1 Rev protein accelerates formation of an efficient RNA-binding conformation

Phosphorylation is important in the regulation of many cellular processes, yet the precise role of protein phosphorylation for many RNA-binding protein substrates remains obscure. In this report, we demonstrate that phosphorylation of a recombinant human immunodeficiency virus type-1 Rev protein promotes rapid formation of an efficient RNA-binding state. The apparent dissociation constant for ligand binding is enhanced 7-fold for the protein following phosphorylation; however, phosphate addition leads to a 1. 6-fold decrease in RNA ligand-protein complex stability. RNA ligand binding stimulates slow formation of an equally competent binding state for the unphosphorylated protein, indicating that the addition of phosphate or ligand binding promotes a similar conformational change in Rev. Phosphorylation directly alters the conformation of Rev, as revealed by modification experiments that monitor the solvent accessibility of cysteines in the protein. These biochemical properties are attributed to the addition of phosphate at one of two serine residues (Ser-54 or Ser-56) that lie within the multimerization domain adjacent to the RNA-binding helix. Glutaraldehyde-mediated cross-linking experiments revealed that phosphorylation of Rev does not affect Rev multimerization activity. The Rev protein from the less pathogenic HIV-2 isolate lacks this phosphorylation site in the amino acid sequence; thus, the described biochemical properties of the phosphorylated protein may contribute to Rev activity and possibly to HIV-1 virulence during natural infection.