A Randomized, Phase III Trial to Evaluate Rucaparib Monotherapy as Maintenance Treatment in Patients With Newly Diagnosed Ovarian Cancer (ATHENA-MONO/GOG-3020/ENGOT-ov45).

PURPOSE: ATHENA (ClinicalTrials.gov identifier: NCT03522246) was designed to evaluate rucaparib first-line maintenance treatment in a broad patient population, including those without BRCA1 or BRCA2 (BRCA) mutations or other evidence of homologous recombination deficiency (HRD), or high-risk clinical characteristics such as residual disease. We report the results from the ATHENA-MONO comparison of rucaparib versus placebo. METHODS: Patients with stage III-IV high-grade ovarian cancer undergoing surgical cytoreduction (R0/complete resection permitted) and responding to first-line platinum-doublet chemotherapy were randomly assigned 4:1 to oral rucaparib 600 mg twice a day or placebo. Stratification factors were HRD test status, residual disease after chemotherapy, and timing of surgery. The primary end point of investigator-assessed progression-free survival was assessed in a step-down procedure, first in the HRD population (BRCA-mutant or BRCA wild-type/loss of heterozygosity high tumor), and then in the intent-to-treat population. RESULTS: As of March 23, 2022 (data cutoff), 427 and 111 patients were randomly assigned to rucaparib or placebo, respectively (HRD population: 185 v 49). Median progression-free survival (95% CI) was 28.7 months (23.0 to not reached) with rucaparib versus 11.3 months (9.1 to 22.1) with placebo in the HRD population (log-rank P = .0004; hazard ratio [HR], 0.47; 95% CI, 0.31 to 0.72); 20.2 months (15.2 to 24.7) versus 9.2 months (8.3 to 12.2) in the intent-to-treat population (log-rank P < .0001; HR, 0.52; 95% CI, 0.40 to 0.68); and 12.1 months (11.1 to 17.7) versus 9.1 months (4.0 to 12.2) in the HRD-negative population (HR, 0.65; 95% CI, 0.45 to 0.95). The most common grade ≥ 3 treatment-emergent adverse events were anemia (rucaparib, 28.7% v placebo, 0%) and neutropenia (14.6% v 0.9%). CONCLUSION: Rucaparib monotherapy is effective as first-line maintenance, conferring significant benefit versus placebo in patients with advanced ovarian cancer with and without HRD.

ATHENA (GOG-3020/ENGOT-ov45): a randomized, phase III trial to evaluate rucaparib as monotherapy (ATHENA-MONO) and rucaparib in combination with nivolumab (ATHENA-COMBO) as maintenance treatment following frontline platinum-based chemotherapy in ovarian cancer.

BACKGROUND: The optimal treatment strategy for women with newly diagnosed ovarian cancer has yet to be determined. Poly(ADP-ribose) polymerase (PARP) inhibitors have demonstrated substantial improvement in progression-free survival as monotherapy maintenance treatment in the frontline setting versus active surveillance. Furthermore, preclinical and early clinical studies have shown that PARP inhibitors and immune checkpoint inhibitors have synergistic antitumor activity and may provide an additional therapeutic option for patients in this population. PRIMARY OBJECTIVES: In women with newly diagnosed ovarian, fallopian tube, or peritoneal cancer, we wish to assess the efficacy of frontline maintenance treatment with the PARP inhibitor rucaparib versus placebo following response to platinum-based chemotherapy (ATHENA-MONO), and to assess the combination of rucaparib plus nivolumab (a programmed death receptor 1 (PD-1)-blocking monoclonal antibody) versus rucaparib alone (ATHENA-COMBO). STUDY HYPOTHESIS: (1) Maintenance therapy with rucaparib monotherapy may extend progression-free survival following standard treatment for ovarian cancer in the frontline setting. (2) The combination of nivolumab plus rucaparib may extend progression-free survival following standard treatment for ovarian cancer in the frontline setting compared with rucaparib alone. TRIAL DESIGN: ATHENA is an international, randomized, double-blind, phase III trial consisting of two independent comparisons (ATHENA-MONO and ATHENA-COMBO) in patients with newly diagnosed platinum-sensitive ovarian cancer. Patients are randomized 4:4:1:1 to the following: oral rucaparib+ intravenous nivolumab (arm A); oral rucaparib + intravenous placebo (arm B); oral placebo+ intravenous nivolumab (arm C); and oral placebo + intravenous placebo (arm D). The starting dose of rucaparib is 600 mg orally twice a day and nivolumab 480 mg intravenously every 4 weeks. ATHENA-MONO compares arm B with arm D to evaluate rucaparib monotherapy versus placebo, and ATHENA-COMBO evaluates arm A versus arm B to investigate the effects of rucaparib and nivolumab in combination versus rucaparib monotherapy. ATHENA-MONO and ATHENA-COMBO share a common treatment arm (arm B) but each comparison is independently powered. MAJOR INCLUSION/EXCLUSION CRITERIA: Patients ≥18 years of age with newly diagnosed advanced, high-grade epithelial ovarian, primary peritoneal, or fallopian tube cancer who have achieved a response after completion of cytoreductive surgery and initial platinum-based chemotherapy are enrolled. No other prior treatment for ovarian cancer, other than the frontline platinum regimen, is permitted. PRIMARY ENDPOINT: The primary endpoint is investigator-assessed progression-free survival by Response Evaluation Criteria in Solid Tumors v1.1. SAMPLE SIZE: Approximately 1000 patients have been enrolled and randomized. ESTIMATED DATES FOR COMPLETING ACCRUAL AND PRESENTING RESULTS: The trial completed accrual in 2020. While dependent on event rates, primary results of ATHENA-MONO are anticipated in early 2022 and results of ATHENA-COMBO are anticipated to mature at a later date. TRIAL REGISTRATION: This trial is registered at clinicaltrials.gov (NCT03522246).

Research biopsies in patients with gynecologic cancers: patient-reported outcomes, perceptions, and preferences.

BACKGROUND: Despite the growing integration of mandatory biopsies for correlative endpoints within oncology clinical trials, there are sparse data on patient-reported outcomes, perceptions, and preferences. OBJECTIVE: This study aimed to prospectively assess the impact of research biopsies on the quality of life in patients with gynecologic cancer, evaluate patient-reported outcomes, and determine factors associated with patients' willingness to undergo sequential biopsies. STUDY DESIGN: We conducted a prospective study in patients with gynecologic malignancies undergoing research biopsies between 2015 and 2019 at Princess Margaret Cancer Centre (ClinicalTrials.gov Identifier: NCT02334761). Here, we report the results of the paper-based surveys performed before and 1 week after biopsy. Although the questionnaires each assessed the impact of anxiety using a modified version of the Hospital Anxiety and Depression Scale, the postbiopsy questionnaire specifically assessed the likelihood of future biopsies, postbiopsy symptoms, complications, and perceptions. RESULTS: A total of 129 patients were enrolled, of which 91 (70.5%) completed at least 1 questionnaire. These patients had either ovarian (89%; 81 of 91) or endometrial cancer (11%; 10 of 91). Of all biopsies taken, 75% were from the abdomen or pelvis (67 of 89). There was 1 clinician-reported complication, a perihepatic hematoma (1%). Pain during the biopsy and physical discomfort were experienced by 60.3% (41 of 68) and 61.8% (42 of 68), respectively. Embarrassment and loss of dignity were experienced by 13.2% (9 of 68) and 11.8% (8 of 68), respectively. Although the mean Hospital Anxiety and Depression Scale score was in the normal range before and after biopsy, there was a significant decline in the total score after the biopsy (prebiopsy, 5.3 [standard deviation, 4.7] vs postbiopsy, 3.7 [standard deviation, 4.5]; P=.005); 84% of subjects (58 of 69) stated that they would definitely or likely consent to another biopsy. There was no impact on patients' willingness for future biopsies based on Eastern Cooperative Oncology Group status, biopsy site, age, number of cores, and pain during the biopsy; however, subjects who reported feeling physically uncomfortable (odds ratio, 0.14; P=.005), embarrassed (odds ratio, 0.03; P=.004) or experienced loss of dignity (odds ratio, 0.05; P=.01) during the biopsy and those who experienced flu-like symptoms (odds ratio, 0.2; P=.018) or felt feverish (odds ratio, 0.2; P=.035) 1 week after biopsy, were less likely to undergo a sequential biopsy. Similarly, those with higher Hospital Anxiety and Depression Scale scores before biopsy (odds ratio, 0.83; P=.008) and after biopsy (odds ratio, 0.8; P=.003) were less likely to consent for another biopsy. CONCLUSION: Research biopsies were generally well accepted. Most patients (83%) were willing to undergo serial biopsies if necessary. Addressing the potentially modifiable psychosocial aspects of the procedure may improve the experience with research biopsies for patients with gynecologic cancers.

Investigating strategies to improve clinical trial opportunities for patients with cancer in New Zealand-INSIGHT.

AIMS: Fewer than 5% of adult cancer patients participate in clinical trials, with multiple patient, clinician and institutional barriers identified. This study aimed to explore patient factors that impact access to cancer trials in New Zealand. METHODS: A questionnaire that included demographics and factors that might impact trial participation was circulated via nine district health boards (DHBs) and four cancer foundations to patients with a cancer diagnosis. RESULTS: Between July 2016 and August 2017, 691 patients responded, 62% female and 77% aged >50 years. Most patients (86%) would consider trial participation, which differed by income (p=0.0001) but not by age, tumour type or gender. Patients would consider attending another hospital (44%) or relocating (11%); 10% considered trials a last resort. Advantageous factors to participation included: benefiting others (92%), better treatment (82%), more scans and longer follow-up (47% and 51%). Disincentives included fear of randomisation (78%), treatment toxicities (71%), time and cost of more visits (40%) and unspecified future research (32%). CONCLUSION: Identified barriers to trial participation were similar in New Zealand to other developed countries. In this motivated cohort, patients are very interested in trial participation at any stage of their treatment and did not mind extra travel or tests.

Mechanisms of resistance to PARP inhibitors - an evolving challenge in oncology.

Poly-adenosine diphosphate ribose polymerase inhibitors (PARPi) lead to synthetic lethality when used in cancers harbouring a BRCA mutation or homologous recombination deficiency. There are now four PARPi approved by the Food and Drug Administration for therapeutic use is ovarian and breast cancer. In addition to this, there is data supporting its use in pancreatic adenocarcinoma and prostate cancer. However, development of resistance to PARPi limits the duration of response. Key mechanisms found to date include: (1) restoration of homologous recombination; (2) changes in PARP1; (3) suppression of non-homologous end joining; (4) replication fork protection; and (5) drug concentration. Gaining a better understanding of resistance mechanisms may guide combination therapies to overcome the resistance and improve the efficacy of PARPi. The purpose of this review is to describe the resistance mechanisms to PARPi and discuss their early detection.

A practical guide to understanding, using and including patient reported outcomes in clinical trials in ovarian cancer.

Health related quality of life (HRQOL) is a key priority for patients with ovarian cancer as there is significant morbidity associated with the disease and the treatment. It is therefore essential to include measures of HRQOL and patient reported outcomes (PROs) in all clinical trials and ideally report them in the initial manuscript. The results of these analyses help interpret the primary trial endpoints which are typically progression free survival and overall survival from the perspective of the patients, but can also assist with regulatory approval of new drugs and inform future patients regarding the potential benefits and downsides of the treatment as well as help support clinical recommendations. Including PROs in clinical trials allows patient-defined clinical benefits to be assessed in parallel to traditional survival outcomes to provide a more holistic overview and aid in the interpretation of the trial results. Given the importance of these instruments in clinical trials, greater effort is required to improve the appropriate inclusion, quality of analyses and reporting of PROs. It is also essential that all clinicians understand the intricacies of the selection, implementation and interpretation of these measures of HRQOL and PRO's and how important their contribution is to clinical trials as well as clinical practice. This review is a practical guide for clinicians to gain a better understanding of PROs and how they can be incorporated into ovarian cancer trials.

A Systematic Review of Health-Related Quality of Life Reporting in Ovarian Cancer Phase III Clinical Trials: Room to Improve.

BACKGROUND: Epithelial ovarian cancer (OC) remains a significant cause of morbidity and mortality for women worldwide. Patients may experience a multitude of disease- and treatment-related symptoms that can impact quality of life (QOL) and should be measured and reported in clinical trials. This systematic review investigated the adequacy of reporting of QOL in randomized phase III trials in OC in both the first-line and recurrent disease setting. MATERIALS AND METHODS: A systematic review of MEDLINE and EMBASE identified randomized clinical trials of systemic therapy in OC from 1980 to 2014. The adequacy of reporting QOL was evaluated with respect to adherence to established guidelines on reporting QOL in clinical trials and the recent recommendations on the inclusion of patient-reported outcomes in clinical trials from the Fifth Ovarian Cancer Consensus Conference. RESULTS: Of 3,247 abstracts, 35 studies, including 24,664 patients, met inclusion criteria. Twenty-two trials (63%) were in the first-line setting, with 13 (37%) in the recurrent setting. The inclusion of QOL assessments increased from 2% (1980s) to 62% (2010+). Quality of life was a co-primary endpoint in only one trial.Minimal clinically important differences in QOL were defined in eight trials (23%), with results included in the abstract in 37% and article in 86%. Compliance was reported in 26 trials (74%), with 13 trials (37%) reporting specifically how they dealt with missing data. Only seven trials reported the reasons for missing data (20%).Group results were published in 29 trials (83%), with 6 (17%) reporting individual patient results. Results were more commonly reported as a mean overall score (21 trials; 60%), with specific domain scores in only 9 trials (26%). No studies reported QOL beyond progression or included predefined context-specific endpoints based on objectives of treatment (i.e., palliation/cure/maintenance) and the patient population. Duration of benefit of palliative chemotherapy was reported in only one study. CONCLUSION: Inclusion and reporting of QOL as a trial endpoint has improved in phase III trials in OC, but there are still significant shortfalls that need to be addressed in future trials. IMPLICATIONS FOR PRACTICE: The impact of treatment on quality of life (QOL) is an important consideration in patients with ovarian cancer for whom treatment is often given with palliative intent. Both the disease and treatment impact a patient's QOL and require careful evaluation in clinical trials. Matching the QOL questions to the patient population of interest is critical. Similar rigor to that used to assess progression-based endpoints is essential to guide clinical decisions. This systematic review demonstrated that although the inclusion and reporting of QOL as a trial endpoint has improved in phase III trials there are still significant shortfalls that need to be addressed in future trials.

MicroRNA profiling of ovarian granulosa cell tumours reveals novel diagnostic and prognostic markers.

BACKGROUND: The aim of this study was to explore the clinical utility of microRNAs (miRNAs) as improved markers of ovarian granulosa cell tumours (GCTs) for cancer diagnosis and prognosis prediction. Current histopathological and genetic markers, such as the presence of a FOXL2 gene mutation to distinguish between the two major subtypes are not wholly accurate and as such novel biomarkers are warranted. METHODS: The miRNA expression profiles of five formalin-fixed, paraffin-embedded (FFPE) adult-GCTs and five juvenile-GCTs were assessed using Affymetrix miRNA 3.0 Arrays and compared for differential expression. Ten miRNAs were assessed in an additional 33 FFPE tumours and four normal granulosa cell samples by quantitative RT-PCR, and their expression correlated to clinical information. RESULTS: MicroRNA array found 37 miRNAs as differentially expressed between the two GCT subtypes (p < 0.05, fold change ≥2 and among these, miRs -138-5p, -184, -204-5p, -29c-3p, -328-3p and -501-3p were validated by RT-qPCR as differentially expressed between the two GCT subtypes (p < 0.05). In addition, the expression of miR-184 was predictive of tumour recurrence in adult-GCTs, specifically for patients diagnosed with stage I and II and stage I only disease (p < 0.001 and p < 0.05, respectively). CONCLUSIONS: This study is the first to report on global miRNA expression profiles of human ovarian GCTs using FFPE tumour samples. We have validated six miRNAs as novel markers for subtype classification in GCTs with low levels of miR-138-5p correlating with early tumour stage. Low miR-184 abundance was correlated with tumour recurrence in early stage adult-GCT patients as a candidate predictive biomarker. Further studies are now needed to confirm the clinical utility of these miRNAs as diagnostic and recurrence markers, and understand their possible roles in the pathogenesis of GCTs.

Resisting RECIST-Uniformity Versus Clinical Validity.

OBJECTIVES: The Response Evaluation Criteria in Solid Tumors (RECIST) International Working Group developed criteria for tumor response and progression to standardize radiological assessment in patients receiving chemotherapy in phase 2 trials. However, it is unclear whether the defined percentage change in tumor size and volume reflects true clinical benefit for the patient. The RECIST criteria were designed to improve objectivity in trials, but not to replace clinical decision making. The aim of this study was to understand clinicians' opinions about RECIST in current oncology practice. METHODS: Using Web-based questionnaires, we investigated attitudes to the use of RECIST at a large comprehensive cancer center and in an international group of gynecologic cancer specialists through the Gynecologic Cancer InterGroup. The results reported here relate to the survey focusing on gynecologic cancer. RESULTS: Sixty medical professionals from 13 countries responded to the survey. The majority of respondents worked at a tertiary or specialist cancer center (51; 86%). Overall, 66% of respondents felt RECIST increased trial objectivity and was a good measure of response. The majority of respondents (81%) reported that they infrequently challenged RECIST evaluation. Overall, 60% felt more than 10% of patients came off trial for clinical rather than radiological progression. In the context of a new small lesion, only 35% felt that should always be considered disease progression. The importance of both clinician and radiologist input was highlighted with nontarget progression. Nontarget progression and target progression were recognized as equally important for clinical decision making (72%). CONCLUSIONS: RECIST is a key criterion for endpoint assessment in clinical trials with its value recognized by clinicians. However, this survey also highlights the practical limitations of RECIST. Disconnect can be seen between the radiological result and the clinical picture-learning from these patients is critical. Continued efforts to improve metrics assessing patient benefit in trials remains a priority.

Stage I granulosa cell tumours: A management conundrum? Results of long-term follow up.

UNLABELLED: Optimal management of women with early stage granulosa cell tumours (GCT) presents a management conundrum - they have excellent prognosis but a third will relapse. Advances uncovering the molecular characteristics of GCT have not been matched by improvements in our understanding and treatment. METHODS: Stage I GCT patients referred to Auckland City Hospital (1955-2012) and Princess Margaret Cancer Centre (1992-2012) were identified. Baseline characteristics, histopathology and outcomes were recorded retrospectively. RESULTS: One hundred and sixty stage I GCT patients were identified with a median age of 49 years. Median follow-up was 7.0 years (range 0.1-44.2 years). Fifty-one patients (32%) relapsed with a median time to relapse (TTR) of 12.0 years (1.3-17.7 years) - 20 initial relapses occurred 10 years post-diagnosis. Higher relapse rates (43% vs. 24% p=0.02) and shorter TTR (10.2 vs. 16.2 years p=0.007) were seen with stage Ic versus stage Ia disease. Cyst rupture was associated with increased relapse (p=0.03). Surgery was the main therapeutic modality at relapse. Eighty six percent of patients received non-surgical management at least once post-relapse. Clinical benefit rate was 43% with chemotherapy, 61% with hormonal therapy and 86% with radiation. Five- and 10-year overall survival (OS) were 98.5 and 91.6%, respectively. Median OS was similar in patients with (24.3 years) and without relapse (22.3 years). CONCLUSION: Surgery remains fundamental at diagnosis and relapse. Caution should be exercised in recommending adjuvant chemotherapy at initial diagnosis given median OS was greater than 20 years even with relapse. Hormonal therapy at relapse appears encouraging but needs further assessment. Novel treatment strategies need exploration with international collaboration essential for this.

A phase II study of single-agent RO4929097, a gamma-secretase inhibitor of Notch signaling, in patients with recurrent platinum-resistant epithelial ovarian cancer: A study of the Princess Margaret, Chicago and California phase II consortia.

PURPOSE: A phase II study was performed to evaluate the efficacy and safety of single-agent RO4929097 (a gamma-secretase inhibitor) in patients with recurrent platinum-resistant ovarian cancer. EXPERIMENTAL DESIGN: Women with progressive platinum-resistant ovarian cancer treated with ≤2 chemotherapy regimens for recurrent disease were enrolled in this trial. Patients received oral RO4929097 at 20 mg once daily, 3 days on/4 days off each week in a three week cycle. The primary endpoint was progression-free survival (PFS) rate at the end of 4 cycles. Secondary objectives included assessment of the safety of RO4929097 and exploration of molecular correlates of outcome in archival tumor tissue and serum. RESULTS: Of 45 patients enrolled, 40 were evaluable for response. Thirty-seven (82%) patients had high-grade ovarian cancer. No objective responses were observed. Fifteen patients (33%) had stable disease as their best response, with a median duration of 3.1 months. The median PFS for the whole group was 1.3 months (1.2-2.5). Treatment was generally well tolerated with 10% of patients discontinuing treatment due to an adverse event. In high grade serous ovarian cancer patients, the median PFS trended higher when the expression of intracellular Notch (NICD) protein by immunohistochemistry was high versus low (3.3 versus 1.3 months, p=0.09). No clear relationship between circulating angiogenic factors and PFS was found despite a suggestion of an improved outcome with higher baseline VEGFA levels. CONCLUSIONS: RO4929097 has insufficient activity as a single-agent in platinum-resistant ovarian cancer to warrant further study as monotherapy. Future studies are needed to explore the potential for cohort enrichment using NICD expression.

Outcomes and endpoints in trials of cancer treatment: the past, present, and future.

Cancer treatment should allow patients to live better or longer lives, and ideally, both. Trial endpoints should show clinically meaningful improvements in patient survival or quality of life. Alternative endpoints such as progression-free survival, disease-free survival, and objective response rate have been used to identify benefit earlier, but their true validity as surrogate endpoints is controversial. In this Review we discuss the measurement, assessment, and benefits and limitations of trial endpoints in use for cancer treatment. Many stakeholders are affected, including regulatory agencies, industry partners, clinicians, and most importantly, patients. In an accompanying Review, reflections from individual stakeholders are incorporated into a discussion of what the future holds for clinical trial endpoints and design.

Outcomes and endpoints in cancer trials: bridging the divide.

Cancer is not one disease. Outcomes and endpoints in trials should incorporate the therapeutic modality and cancer type because these factors affect clinician and patient expectations. In this Review, we discuss how to: define the importance of endpoints; make endpoints understandable to patients; improve the use of patient-reported outcomes; advance endpoints to parallel changes in trial design and therapeutic interventions; and integrate these improvements into trials and practice. Endpoints need to reflect benefit to patients, and show that changes in tumour size either in absolute terms (response and progression) or relative to control (progression) are clinically relevant. Improvements in trial design should be accompanied by improvements in available endpoints. Stakeholders need to come together to determine the best approach for research that ensures accountability and optimises the use of available resources.

Estimation of expectedness: predictive accuracy of standard therapy outcomes in randomized phase 3 studies in epithelial ovarian cancer.

BACKGROUND: The anticipated clinical outcome of the standard/control arm is an important parameter in the design of randomized phase 3 (RP3) trials to properly calculate sample size, power, and study duration. Changing patterns of care or variation in the study population enrolled may lead to a deviation from the initially anticipated outcome. The authors hypothesized that recent changes in patterns of care in epithelial ovarian cancer (EOC) have led to challenges in correctly estimating the outcome of control groups. METHODS: A systematic review of the literature was conducted for RP3 trials of EOC published between January 2000 and December 2010. The expected outcome of the control arm as well as the actual outcome achieved by this cohort was collected and a ratio (actual-over-expected ratio) was calculated. The estimation of outcome was deemed accurate if the outcome of the control arm was between 0.75 to 1.25 times the anticipated outcome. RESULTS: A total of 35 trials were eligible for analysis. Fifteen trials had survival as the primary endpoint whereas 20 had a progression-based primary endpoint. In total, 12 of 15 trials with a survival-based endpoint significantly underestimated the outcome of the control arm, whereas only 4 of 20 trials with a progression-based endpoint did. Studies with a survival endpoint underestimated outcome more frequently than those with a progression endpoint (P<.001). CONCLUSIONS: Survival of the control arm has frequently been underestimated in recent EOC RP3 trials. This underestimation means that the initial statistical assumptions of these trials may have been inaccurate. Underestimating the outcome of the control arm may result in trials being underpowered to demonstrate the absolute benefit they were designed to show.

Review of high-dose intravenous vitamin C as an anticancer agent.

In the 1970s, Pauling and Cameron reported increased survival of patients with advanced cancer treated with high-dose intravenous (IV) vitamin C (L-ascorbate, ascorbic acid). These studies were criticized for their retrospective nature and lack of standardization of key prognostic factors including performance status. Subsequently, several well-designed randomized controlled trials failed to demonstrate a significant survival benefit, although these trials used high-dose oral vitamin C. Marked differences are now recognized in the pharmacokinetics of vitamin C with oral and IV administration, opening the issue of therapeutic efficacy to question. In vitro evidence suggests that vitamin C functions at low concentrations as an antioxidant but may have pro-oxidant activity at high concentrations. The mechanism of its pro-oxidant action is not fully understood, and both intra- and extracellular mechanisms that generate hydrogen peroxide have been proposed. It remains to be proven whether vitamin C-induced reactive oxygen species occur in vivo and, if so, whether this will translate to a clinical benefit. Current clinical evidence for a therapeutic effect of high-dose IV vitamin C is ambiguous, being based on case series. The interpretation and validation of these studies is hindered by limited correlation of plasma vitamin C concentrations with response. The methodology exists to determine if there is a role for high-dose IV vitamin C in the treatment of cancer, but the limited understanding of its pharmacodynamic properties makes this challenging. Currently, the use of high-dose IV vitamin C cannot be recommended outside of a clinical trial.