Nonconventional patterns of benefit of solid tumors treated with PD-(L)1 inhibitors: a systematic review

A review on lymphocyte radiosensitivity and its impact on radiotherapy

It is well known that radiation therapy causes lymphopenia in patients and that this is correlated with a negative outcome. The mechanism is not well understood because radiation can have both immunostimulatory and immunosuppressive effects. How tumor dose conformation, dose fractionation, and selective lymph node irradiation in radiation therapy does affect lymphopenia and immune response is an active area of research. In addition, understanding the impact of radiation on the immune system is important for the design and interpretation of clinical trials combining radiation with immune checkpoint inhibitors, both in terms of radiation dose and treatment schedules. Although only a few percent of the total lymphocyte population are circulating, it has been speculated that their increased radiosensitivity may contribute to, or even be the primary cause of, lymphopenia. This review summarizes published data on lymphocyte radiosensitivity based on human, small animal, and in vitro studies. The data indicate differences in radiosensitivity among lymphocyte subpopulations that affect their relative contribution and thus the dynamics of the immune response. In general, B cells appear to be more radiosensitive than T cells and NK cells appear to be the most resistant. However, the reported dose-response data suggest that in the context of lymphopenia in patients, aspects other than cell death must also be considered. Not only absolute lymphocyte counts, but also lymphocyte diversity and activity are likely to be affected by radiation. Taken together, the reviewed data suggest that it is unlikely that radiation-induced cell death in lymphocytes is the sole factor in radiation-induced lymphopenia.

The Optimal Second-Line Systemic Treatment Model for Recurrent and/or Metastatic Head and Neck Squamous Cell Carcinoma: A Bayesian Network Meta-Analysis

Background

The optimal second-line systemic treatment model for recurrent and/or metastatic head and neck squamous cell carcinoma (R/M HNSCC) remains controversial. A Bayesian network meta-analysis (NMA) was performed to address this issue with regard to efficacy and toxicity.

Methods

By searching MEDLINE (via PubMed), Embase, the Cochrane Central Register of Controlled Trials and Web of Science, we extracted eligible studies. Efficacy, represented as overall survival (OS) and progression-free survival (PFS), and overall toxicity, represented as ≥ grade 3 severe acute events (sAE), were assessed to compare the following 7 treatment models through an NMA: standard-of-care therapy (SoC), single targeted therapy different from SoC (ST), double targeted therapy (DT), targeted therapy combined with chemotherapy (T+C), single immune checkpoint inhibitor therapy (SI), double immune checkpoint inhibitor therapy (DI) and single chemotherapy different from SoC (SC). Rank probabilities according to the values of the surface under the cumulative ranking curve (SUCRA) were separately determined for efficacy and toxicity.

Results

In total, 5285 patients from 24 eligible studies were ultimately screened, with 5184, 4532 and 4026 involved in the NMA of OS, PFS and sAE, respectively. All qualifying studies were absent from first-line immune checkpoint inhibitor therapy. In terms of OS, SI was superior to the other treatments, followed by DI, ST, T+C, SoC, DT and SC. Other than SI and SC, all treatments tended to be consistent, with hazard ratios (HRs) close to 1 between groups. For PFS, ST ranked first, while DT ranked last. For the toxicity profiles, compared with the other models, SI resulted in the lowest incidences of sAE, with statistical significance over SoC (odds ratio [OR] 0.31, 95% credible interval [CrI] 0.11 to 0.90), ST (OR 0.23, 95% CrI 0.06 to 0.86) and DT (OR 0.11, 95% CrI 0.02 to 0.53), while DT was the worst. When the SUCRA values of OS and sAE were combined, a cluster plot illustrated the superiority of SI, which demonstrated the best OS and tolerability toward sAE.

Conclusion

For R/M HNSCC patients without immune checkpoint inhibitors in the first-line setting, SI may serve as the optimal second-line systemic treatment model, demonstrating the best OS and least sAE.

Exploration of modified progression-free survival as a novel surrogate endpoint for overall survival in immuno-oncology trials

BACKGROUND

Progression-free survival (PFS) exhibits suboptimal performance as the surrogate endpoint for overall survival (OS) in trials studying immune checkpoint inhibitors (ICIs). Here we propose a novel surrogate endpoint, modified PFS (mPFS), which omits the events of disease progression (but not deaths) within 3 months after randomization.

METHODS

PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials were searched for randomized trials studying ICIs in advanced solid tumors with available PFS and OS data up to May 2020. Individual patient-level data (IPD) for PFS and OS were reconstructed for eligible trials. A simulation-based algorithm was used to match the reconstructed, disconnected PFS and OS IPD, and 1000 independent simulated datasets of matched PFS-OS IPD were generated for each trial. mPFS durations and statuses were then measured for each of the matched PFS-OS IPD. Trial-level correlation between Cox HRs for PFS or mPFS and HRs for OS was assessed using Pearson correlation coefficient (rp) weighted by trial size; patient-level correlation between PFS or mPFS and OS was assessed using Spearman's rank correlation coefficient (rs). Findings were further validated using the original IPD from two randomized ICI trials.

RESULTS

Fifty-seven ICI trials totaling 29,429 participants were included. PFS HR showed moderate correlation with OS HR (rp=0.60), and PFS was moderately correlated with OS at the patient level (median rs=0.66; range, 0.65-0.68 among the 1000 simulations). In contrast, mPFS HR achieved stronger correlation with OS HR (median rp=0.81; range, 0.77-0.84), and mPFS was more strongly correlated with OS at the patient level (median rs=0.79; range, 0.78-0.80). The superiority of mPFS over PFS remained consistent in subgroup analyses by cancer type, therapeutic regimen, and treatment setting. In both trials with the original IPD where experimental treatment significantly improved OS, mPFS successfully captured such clinical benefits whereas PFS did not.

CONCLUSIONS

mPFS outperformed PFS as the surrogate endpoint for OS in ICI trials. mPFS is worthy of further investigation as a secondary endpoint in future ICI trials.

Immunotherapy in Neuroendocrine Neoplasms: Where Are We Now?

OPINION STATEMENT

Immune checkpoint inhibitors (ICIs) represent a breakthrough in the management of many hard-to-treat cancers over the past decade with demonstrable improvement in survival outcomes. We reviewed the state of the art of ICIs in neuroendocrine neoplasms (NENs). While ICIs have become part of the standard of care for the management of small cell lung cancer (SCLC), their role is still unclear in the management of extra-pulmonary (EP) poorly differentiated neuroendocrine carcinomas (NECs) as well as in the management of well-differentiated neuroendocrine tumors (NETs). Conflicting results derived from the various studies in NETs and EP NECs therefore for specific settings, such as the lung NETs, or therapeutic regimen, e.g., combo vs single agent, for ICIs benefit. Therefore, at the moment, no ICIs approach is justified for NETs and EP NECs in clinical practice. Future investigations should be designed with the aim to overcome the several limitations of the current trials, e.g., lacking of a central pathology review or heterogeneity of the cohorts, in order to reduce the risk of biases. Future trials combining ICIs with other biological agents are welcome. This review aims to provide a comprehensive overview of the biological rationale and evolving clinical applications of the use of ICIs in the management of NENs (both well-differentiated and poorly differentiated groups).

Comparison of the Immunotherapy Response Evaluation Criteria in Solid Tumours (iRECIST) with RECIST for capturing treatment response of patients with metastatic urothelial carcinoma treated with pembrolizumab

OBJECTIVE

To evaluate the clinical usefulness of Immunotherapy Response Evaluation Criteria in Solid Tumours (iRECIST) in patients with metastatic urothelial carcinoma (UC) treated with pembrolizumab. The iRECIST is designed to accurately capture the tumour response treated with immunotherapy.

PATIENTS AND METHODS

We conducted a multicentre retrospective study evaluating the clinical utility of iRECIST in 91 patients with metastatic UC treated with second-line pembrolizumab. The objective response (OR) and time to progression (TTP) in accordance with both iRECIST and RECIST version 1.1 were compared with overall survival (OS) and risk of all-cause mortality, and analysed using log-rank and multivariable Cox regression models, respectively. Predictive performance of the criteria was studied using Harrell's concordance index (c-index). The clinical usefulness of each criterion was compared using decision curve analysis.

RESULTS

Of 57 patients with progressive disease per RECIST, a considerable number of patients were reclassified to immune stable disease (six, 10.5%), immune partial response (two, 3.5%), and immune complete response (two, 3.5%) per iRECIST. Multivariable Cox regression models showed that both OR (hazard ratio [HR] 0.10, 95% confidence interval [CI] 0.03-0.35; P = 0.001) and TTP (HR 0.59, 95% CI 0.46-0.77; P < 0.001) per iRECIST were significantly associated with all-cause mortality. Furthermore, iRECIST had a significant, increased predictability of OS compared with RECIST (OR, c-index: 0.70, increase: 0.04, P = 0.046; TTP, c-index: 0.88, increase: 0.07, P = 0.039). On decision curve analysis, iRECIST presented better net benefit gains than did RECIST.

CONCLUSIONS

Compared with RECIST, iRECIST could more accurately predict OS of patients with metastatic UC treated with pembrolizumab. The iRECIST has the potential to be a new standard for tumour response evaluation of these patients.

Chemotherapy efficacy after first-line immunotherapy in 18 advanced melanoma patients

In BRAF wild type advanced melanoma, immune checkpoint blockers such as anti-PD1 (anti-programmed cell death 1) are usually continued beyond progression for a hypothetical rare further response. Chemotherapy as a second-line option is considered ineffective by many practitioners based on historical data. Continuing anti-PD1 beyond progression has a high health-economic impact and is not recommended by the FDA. This study aimed to describe the efficacy and survival of advanced melanoma patients who received second-line (or more) chemotherapy after immunotherapy failure.This was a retrospective single center study conducted in a French University Hospital during an 11-month period. All advanced melanoma patients treated with chemotherapy after immunotherapy failure were included.Eighteen patients were analyzed. Therapeutic response to chemotherapy was evaluable in 16 patients: partial response was achieved in 3/16 (19%), stable disease in 1/16 (6%) and progressive disease in 12/16 (75%). Median overall survival from chemotherapy start was 12 months. Median progression-free survival was 5.4 months. The 6-month overall survival rate was 81% and the 6-month progression-free survival rate was 40%.Although the disease control rate with chemotherapy was low (25%), survival data in our study are far superior to those previously published. This could be linked to a high proportion of patients treated with anti-PD1 just prior to chemotherapy, which may suggest a potential synergy between immunotherapy and chemotherapy.

Atypical patterns of responses in the era of immune checkpoint inhibitors in head and neck cancer

The discovery and implementation into everyday clinical practice of immune checkpoint inhibitors (ICIs) has marked a therapeutic renaissance in the treatment of advanced solid tumors. In head and neck cancer, nivolumab and pembrolizumab have both been approved for recurrent/metastatic disease based on robust clinical activity observed in landmark phase III clinical trials. Despite tremendous improvements in overall survival, patterns of response and progression to ICIs may be distinct from those traditionally described with classical chemotherapy or molecularly targeted therapies. In this context, pseudoprogression is observed in patients treated with ICIs that show response after a transient increase in tumor burden and hyperprogression is described as rapid radiological or clinical progression after immunotherapy. Most importantly, the assessment of radiological response in patients receiving ICIs needs to be differentiated. In this review, we aim to describe radiologic criteria for immune response evaluation and illustrate the newly reported concepts of atypical patterns of response to ICIs.

Patterns of Response and Progression to Immunotherapy

Patterns of response and progression to immunotherapy may differ from those observed with drugs such as chemotherapy and molecularly targeted agents. Specifically, some patients experience a response after progression that is retrospectively named pseudoprogression. This phenomenon of pseudoprogression, first reported in patients with melanoma who were treated with ipilimumab, has led to the development of immune-specific related response criteria, such as irRC (immune-related response criteria), irRECIST (immune-related RECIST), and iRECIST (immunotherapy RECIST) that allow continued treatment beyond progression. However, the rate of pseudoprogression has never exceeded 10% of patients across tumor types. Conversely, rapid progressions after immunotherapy, called hyperprogressions, were reported by three different teams in 9% to 29% of patients treated with immunotherapy. Because of the absence of control arms in these studies, it remains to be determined whether these rapid progressions reflect a detrimental effect of immunotherapy in these patients. Finally, preliminary data suggest that immunotherapy might also affect response to subsequent standard therapies. In total, given the rarity of pseudoprogressions across tumor types and the recent description of hyperprogressions, classic RECIST remains a reasonable and rational method to assess response to immunotherapy. Continuation of treatment beyond progression should be proposed only in carefully selected patients whose clinical conditions have improved and who have not experienced severe toxicities. Although there is an urgent need to identify predictive biomarkers of efficacy to immunotherapy, there is an equally urgent need to identify predictive factors of progression or possibly hyperprogression.

Surrogate end points for overall survival in trials of PD-(L)1 inhibitors for urinary cancers: a systematic review

Aim: Numerous trials for PD-(L)1 inhibitors in the management of advanced urinary cancers (urothelial carcinoma and renal cell carcinoma) were published recently. It is not known exactly what should be the optimal surrogate end point for overall survival (OS) in this context. Materials & methods: PubMed database and ASCO meeting library were searched till August 2017. Eligible studies included prospective clinical studies evaluating PD-(L)1 inhibitors for the management of advanced urothelial carcinoma or renal cell carcinoma. The review author extracted relevant data on the characteristics of participants and the outcomes of the different studies. In order to conduct a proper correlation analysis, normality testing using Shapiro-Wilk test was first used. Based on the result of the normality testing, either Pearson's product–moment correlation or Spearman's rank correlation was used. Results: Thirteen trials (nine urothelial carcinoma and four renal cell carcinoma trials) with 2792 participants were included. The correlation of overall response rate with median OS was very weak to weak (for urothelial carcinoma: r = -0.120, n = 9, p = 0.758; for renal cell carcinoma: r = -0.397, n = 6, p = 0.436). Likewise, the correlation of progression-free survival with median OS was very weak to weak (for urothelial carcinoma: r = -0.024, n = 8, p = 0.955; for renal cell carcinoma: r = 0.394, n = 6, p = 0.440). On the other hand, 1-year survival rate may be a better surrogate end point for median OS (for urothelial carcinoma: r = 0.806, n = 8, p = 0.016; for renal cell carcinoma: r = 0.941, n = 6, p = 0.005). Conclusion: RECIST-defined overall response rate and progression-free survival are not reliable surrogate end points for median OS in trials of PD-(L)1 inhibitor therapy for urinary cancers. The use of other surrogate end points (e.g., 1-year survival) in early phase studies may be considered.