Association of differential censoring with survival and suboptimal control arms among oncology clinical trials

Differential censoring (DC), referring to censoring imbalance between treatment arms, may bias the interpretation of survival outcomes in clinical trials. In 146 phase 3 oncology trials with statistically significant time-to-event surrogate primary endpoints (PEPs), we evaluated the association between DC in the surrogate PEP, control arm adequacy, and the subsequent statistical significance of OS results. Twenty-four (16%) trials exhibited DC favoring the control arm (ConDC), while 15 (10%) exhibited experimental arm DC (ExpDC). Positive OS was more common in ConDC trials (63%) than trials without DC (37%) or with ExpDC (47%; odds ratio [OR] 2.64, 95% CI 1.10-7.20; P=.04). ConDC trials more frequently used suboptimal control arms (46%) compared to 20% without DC and 13% with ExpDC (OR 3.60, 95% CI 1.29-10.0; P=.007). The presence of ConDC in trials with surrogate PEPs, especially in those with OS conversion, may indicate an inadequate control arm and should be examined and explained.

Factors Associated With Open Access Publishing Costs in Oncology Journals: Cross-sectional Observational Study

BACKGROUND

Open access (OA) publishing represents an exciting opportunity to facilitate the dissemination of scientific information to global audiences. However, OA publishing is often associated with significant article processing charges (APCs) for authors, which may thus serve as a barrier to publication.

OBJECTIVE

In this observational cohort study, we aimed to characterize the landscape of OA publishing in oncology and, further, identify characteristics of oncology journals that are predictive of APCs.

METHODS

We identified oncology journals using the SCImago Journal & Country Rank database. All journals with an OA publication option and APC data openly available were included. We searched journal websites and tabulated journal characteristics, including APC amount (in US dollars), OA model (hybrid vs full), 2-year impact factor (IF), H-index, number of citable documents, modality/treatment specific (if applicable), and continent of origin. All APCs were converted to US-dollar equivalents for final analyses. Selecting variables with significant associations in the univariable analysis, we generated a multiple regression model to identify journal characteristics independently associated with OA APC amount. An audit of a random 10% sample of the data was independently performed by 2 authors to ensure data accuracy, precision, and reproducibility.

RESULTS

Of 367 oncology journals screened, 251 met the final inclusion criteria. The median APC was US $2957 (IQR 1958-3450). The majority of journals (n=156, 62%) adopted the hybrid OA publication model and were based in Europe (n=119, 47%) or North America (n=87, 35%). The median (IQR) APC for all journals was US $2957 (1958-3540). Twenty-five (10%) journals had APCs greater than US $4000. There were 10 (4%) journals that offered OA publication with no publication charge. Univariable testing showed that journals with a greater number of citable documents (P<.001), higher 2-year IF (P<.001), higher H-index (P<.001), and those using the hybrid OA model (P<.001), or originating in Europe or North America (P<.001) tended to have higher APCs. In our multivariable model, the number of citable documents (β=US $367, SD US $133; P=.006), 2-year IF (US $1144, SD US $177; P<.001), hybrid OA publishing model (US $991, SD US $189; P<.001), and North American origin (US $838, SD US $186; P<.001) persisted as significant predictors of processing charges.

CONCLUSIONS

OA publication costs are greater in oncology journals that publish more citable articles, use the hybrid OA model, have a higher IF, and are based in North America or Europe. These findings may inform targeted action to help the oncology community fully appreciate the benefits of open science.

Incidence and impact of proportional hazards violations in phase 3 cancer clinical trials

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Background: Hazard ratio (HR)-based analyses used in oncology trials rely on the assumption of proportional hazards, i.e. a HR that is constant over time. Proportional hazards violations (PHVs) may lead to misinterpretation of trial results. Restricted mean survival time (RMST) is valid with non-proportional hazards and has received recent attention specifically for immunotherapy (IO) trials but has not been routinely adopted in oncology trial design as a whole. We aimed to comprehensively characterize the incidence and factors associated with PHVs among phase 3 oncology trials and assess RMST as an alternate measure of treatment effect in survival analysis. Methods: We used Clinicaltrials.gov to identify all superiority-design, 2-arm phase 3 cancer trials with time-dependent endpoints with published results through February 2020. We manually reconstructed patient-level data from published Kaplan-Meier (KM) curves, assessed PHVs with the Schoenfeld residual test (p <.05) and analyzed the RMST. To assess reconstruction accuracy, reported and reconstructed HRs were compared. Univariable logistic regression was used to assess the likelihood of PHVs by trial characteristic, with statistically significant factors (p <.05) included in a multivariable analysis. Concordance of RMST-based and HR-based analysis was established when both tests agreed as to the statistical significance of the comparison. Results: Of 342 KM comparisons eligible for reconstruction, 318 comparisons across 315 trials, enrolling 347,538 patients from 1989-2017, were accurately reconstructed and analyzed. PHVs were identified in 76/318 (23.9%) trials. There was no difference in likelihood of PHVs among IO vs non-IO trials (LR 2.31, 95% CI 0.30 – 17.85, P =.37), nor by disease site, year of trial initiation, or sample size. Few trials with PHVs (16/76) pre-specified a plan to account for non-proportional hazards in statistical design. Trials with an overall survival (OS) primary endpoint (PEP) were less likely to have PHVs than trials with a non-OS PEP (LR: 0.50, 95% CI 0.28 - 0.90, P =.02). Trials whose PEP was non-significant were more likely to have PHVs (LR 1.73, 95% CI 1.01 - 2.97, P =.047). No factor remained significantly associated with PHV in multivariable analysis. Overall, 291/318 (91.5%) KM comparisons were concordant. Among trials with PHVs, 5/76 were significant by RMST but not HR, and 5/76 were significant by HR but not RMST. Of these, 1 led to FDA drug approval, and 2 others are cited in NCCN guidelines. Conclusions: PHVs are common across all phase 3 cancer clinical trials. Attempts to account for PHVs in trial design are lacking despite the potential for trial misinterpretation in the event of non-proportional hazards. RMST-based analysis is broadly concordant with HR-based analysis and may aid in interpretation of trials with PHVs. Hence, we recommend that prospective trials include a priori a statistical plan to account for PHVs.

Factors associated with open access publishing costs in oncology journals

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Background: The open access (OA) publishing model represents an exciting opportunity to facilitate dissemination of scientific information to global audiences. In contrast to many traditional models, which require readers to pay subscription fees or rely upon institutional subscriptions for article access, the OA model grants free access to all consumers. However, OA publication is often associated with significant article processing charges (APCs) for authors, which may thus serve as a barrier to publication. In this investigation, we aimed to identify journal-level factors associated with OA publication costs in oncology journals. Methods: We identified oncology journals using the SCImago Journal & Country Rank database. All journals under the “Oncology” category that offer an OA publishing option with APC data openly available were included. For all journals, we searched journal websites and tabulated journal characteristics, including APC amount (USD), OA model (hybrid vs full), journal 2-year impact factor (IF), H-index, number of citable documents, primary treatment modality (surgery, radiation, medical, non-specific), treatment site (e.g. breast, etc), and continent of origin. Pearson correlation was used to evaluate univariate linear relationships between variables; for variables with significant correlation, we generated a multiple regression model to identify journal characteristics independently associated with OA APC amount. Results: Of 367 oncology journals screened, 266 met final inclusion criteria. The median APC was 2810 USD (range 0 – 5200). On univariate linear correlation regression testing, journals with the full OA model (p < 0.001), higher journal IF (p < 0.001), higher H-index (p < 0.001), greater number of published articles (p < 0.001), and those from North America or Europe (p < 0.001) tended to have higher OA publishing costs. When these co-variates were analyzed in a multiple regression model, only full OA status (p < 0.001), higher IF (p < 0.001), and North American or European origin (p < 0.001) persisted as independently associated with greater OA APC. Conclusions: Large APCs may serve as a barrier to OA publication and therefore create or exacerbate disparities among scientific investigators seeking to share their research. In this investigation, we find that OA publication costs are greater in oncology journals that utilize the hybrid OA model, have higher IF, and are based in North America or Europe. These findings may inform targeted action to help the oncology community fully appreciate the benefits of open science.

A phase I trial of the monoclonal antibody FG-3019 to connective tissue growth factor (CTGF) in locally advanced or metastatic pancreatic cancer

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Background: CTGF is highly expressed in pancreatic tumors and is thought to mediate local desmoplasia. FG-3019 is a fully human monoclonal antibody against CTGF. Studies using FG-3019 in murine xenograft models have shown reduced tumor growth and metastasis.

Methods: This open-label, dose escalation study assessed the safety and pharmacokinetics of FG-3019 (3, 10, 15, and 25 mg/kg q14D). FG-3019 was initiated on D1 to assess single-agent toxicity. Standard gemcitabine and erlotinib were added on D15. Chemotherapy-naive patients with locally advanced or metastatic adenocarcinoma were eligible. Seventeen subjects (median age 66 yrs) were enrolled: n=4, 3, and 10 at 3, 10, and 15 mg/kg respectively. Enrollment is ongoing in the 25 mg/kg cohort. Seven subjects were female; four were stage 3, and 13 were stage 4.

Results: No safety signals were detected with single-agent FG-3019. After beginning chemotherapy, four subjects experienced seven SAEs, which were deemed unrelated to FG-3019 including three deaths: sepsis, suicide, and disease progression. Nine subjects experienced grade 3 AEs, all of which were expected in patients with pancreatic cancer. There were no grade 4 hematologic abnormalities. AEs related to gemcitabine (hematologic, abnormal LFTs) and erlotinib (rash) occurred at a rate and severity consistent with the prescribing information (preliminary data). Steady-state Cmax (median 428, range 236-455 μg/mL), and T1/2 (median 6.6, range 6.3-6.7 days) at the 10 mg/kg dose level were comparable to PK data from subjects in non-oncological trials who received FG-3019 at the same dose level. One subject had a partial response by RECIST criteria for 9.7+ months. Another subject had a minor response for 7.7 months. Three of five subjects with PET scans at baseline and D15 experienced stable to reduced PET activity before starting chemotherapy. The median TTP across all cohorts was 3.7 months (95% CI 1.9-6.2), and the median OS was 9.4 months (95% CI 1.9-10.6).

Conclusions: FG-3019 is well tolerated and dose escalation continues. Reduced PET activity after treatment with single-agent FG-3019 may indicate a biological effect of the agent.

[Table: see text]

Evaluation of patterns of failure and subjective salivary function in patients treated with intensity modulated radiotherapy for head and neck squamous cell carcinomas

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Background: Conventional RT (CRT) for head and neck squamous cell carcinoma (HNSCC) is associated with severe late side effects which can worsen quality of life of surviving patients. Intensity-modulated radiotherapy (IMRT) allows the delivery of tumoricidal doses to the target volume while maintaining tolerable doses to critical organs. Several previous studies have demonstrated promising results for tumor control and disease free survival for HNSCC treated with IMRT. In this study, we correlated patterns of failure with target volume delineations in HNSCC treated with IMRT at our instittuion and evaluated subjective xerostomia outcomes after IMRT as compared to CRT. Material and Methods: Between 1/00 and 4/05, 69 patients with newly diagnosed non-metastatic HNSCC underwent curative parotid sparing IMRT at Stanford University. Sites included were oropharynx (39), oral cavity (8), larynx (8), hypopharynx (8) and unknown primary (6). Forty-six patients received definitive IMRT (66 Gy, 2.2 Gy/fraction), and 23 patients received post-operative IMRT (60.2 Gy, 2.15 Gy/fraction). Fifty-one patients also received concomitant chemotherapy. Post-treatment salivary gland function was evaluated by a validated xerostomia questionnaire (XQ) in 29 IMRT and 75 matched non-IMRT patients > 6 months after completing RT. Results: At a median follow-up of 17 months for living patients (range 6.5–60), 7 locoregional failures were observed, 5 in the gross target volume (GTV), 1 in the clinical target volume (CTV), and 1 at the junction of the IMRT and supraclavicular fields. The 2-year Kaplan Meier estimates of locoregional control and overall survival were 92% and 80% for definitive IMRT and 85% and 85% for post-op IMRT patients, respectively. The mean total XQ score was significantly better for IMRT than for non-IMRT patients (p = 0.006). Conclusions: The predominant pattern of failure in IMRT treated patients is in the GTV. Parotid sparing with IMRT resulted in decreased subjective xerostomia and may improve quality of life in irradiated HNSCC patients.

No significant financial relationships to disclose.

Radiation dose reduction in four‐dimensional computed tomography

Four-dimensional (4D) CT is useful in many clinical situations, where detailed abdominal and thoracic imaging is needed over the course of the respiratory cycle. However, it usually delivers a larger radiation dose than the standard three-dimensional (3D) CT, since multiple scans at each couch position are required in order to provide the temporal information. Our purpose in this work is to develop a method to perform 4D CT scans at relatively low current, hence reducing the radiation exposure of the patients. To deal with the increased statistical noise caused by the low current, we proposed a novel 4D penalized weighted least square (4D-PWLS) smoothing method, which can incorporate both spatial and phase information. The 4D images at different phases were registered to the same phase via a deformable model, thereby, a regularization term combining temporal and spatial neighbors can be designed for the 4D-PWLS objective function. The proposed method was tested with phantom experiments and a patient study, and superior noise suppression and resolution preservation were observed. A quantitative evaluation of the benefit of the proposed method to 4D radiotherapy and 4D PET/CT imaging are under investigation.