Influence of milk feeding levels and calf housing on subsequent performance of Holstein heifers

The purpose of this study was to investigate the effects of increased milk feeding levels or social housing during the preweaning stage of Holstein dairy heifers on subsequent weight gain, health, and reproductive parameters over time. A total of 210 heifers were grouped by calving date in groups of 10 and randomly assigned to one of 3 treatments: low-milk individual housing (LMI; 4 L of milk/d), high-milk individual housing (HMI; 8 L of milk/d), or low-milk social housing (LMS; 4 L of milk/d). Data collected included passive transfer status, disease events, weight gain at different time periods, age at first calving, calving intervals, and milk yield over the first 3 lactations. Passive transfer was successful in 189 calves, and, overall, disease events were low in this herd. The average daily gain for heifers in the HMI group (0.79 ± 0.05 kg/d) was significantly higher (F _{2, 9} = 4.76) during the preweaning treatment period compared with the other groups (LMI: 0.59 ± 0.05 kg/d; LMS: 0.68 ± 0.04 kg/d). Although treatment groups did not differ with respect to age at first calving, the LMS and HMI heifers calved (22 and 15 d, respectively) earlier than the LMI heifers. Milk yield over 3 lactations was similar among the treatment groups. This suggests that both nutrition and social dynamics can influence performance of preweaned calves. Further investigation is needed to understand the mechanisms driving increased weight gain in socially housed calves.

Enhanced Detection of Treatment Effects on Metastatic Colorectal Cancer with Volumetric CT Measurements for Tumor Burden Growth Rate Evaluation

PURPOSE

Mathematical models combined with new imaging technologies could improve clinical oncology studies. To improve detection of therapeutic effect in patients with cancer, we assessed volumetric measurement of target lesions to estimate the rates of exponential tumor growth and regression as treatment is administered.

EXPERIMENTAL DESIGN

Two completed phase III trials were studied (988 patients) of aflibercept or panitumumab added to standard chemotherapy for advanced colorectal cancer. Retrospectively, radiologists performed semiautomated measurements of all metastatic lesions on CT images. Using exponential growth modeling, tumor regression (d) and growth (g) rates were estimated for each patient's unidimensional and volumetric measurements.

RESULTS

Exponential growth modeling of volumetric measurements detected different empiric mechanisms of effect for each drug: panitumumab marginally augmented the decay rate [tumor half-life; d [IQR]: 36.5 days (56.3, 29.0)] of chemotherapy [d: 44.5 days (67.2, 32.1), two-sided Wilcoxon P = 0.016], whereas aflibercept more significantly slowed the growth rate [doubling time; g = 300.8 days (154.0, 572.3)] compared with chemotherapy alone [g = 155.9 days (82.2, 347.0), P ≤ 0.0001]. An association of g with overall survival (OS) was observed. Simulating clinical trials using volumetric or unidimensional tumor measurements, fewer patients were required to detect a treatment effect using a volumetric measurement-based strategy (32-60 patients) than for unidimensional measurement-based strategies (124-184 patients).

CONCLUSIONS

Combined tumor volume measurement and estimation of tumor regression and growth rate has potential to enhance assessment of treatment effects in clinical studies of colorectal cancer that would not be achieved with conventional, RECIST-based unidimensional measurements.

The rate of tumor growth, g, as a biomarker for overall survival (OS) in prostate cancer (PC) in clinical trials as well as in real-world data from the Veterans Administration Medical Centers (VAMCs)

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Background: Novel assessments of efficacy are needed to improve determination of treatment outcomes in clinical trials and in real-world settings. Methods: Cancer treatments usually lead to concurrent regression and growth of the drug-sensitive and drug-resistant fractions of a tumor, respectively. We have exploited novel methods of analysis that assess these two simultaneous processes and have estimated rates of tumor growth ( g) and regression ( d) in over 30,000 patients (pts) with diverse tumors. Results: In prostate cancer (PC) we have analyzed both clinical trial and real-world data from Veterans. Using clinical trial data from 6819 pts enrolled in 15 treatment arms we have established separately and by combining all the data that g correlates highly (p<0.0001) with overall survival (OS) – slower g associated with better OS. In PC, abiraterone (ABI) and docetaxel (DOC) are superior to placebo, prednisone and mitoxantrone. ABI (median g =0.0017) is superior to DOC ( g=0.0021) in first line (p=0.0013); and ABI in 2nd line ( g=0.0034) is inferior to ABI in 1st line ( g=0.0017; p<0.0001). Finally, using combined clinical trial data as a benchmark we could assess the efficacy of novel therapies in as few as 30-40 patients. Amongst 7457 Veterans, the median g on a taxane ( g=0.0022) was similar to that from clinical trials ( g=0.0012). Although only 258 Veterans received cabazitaxel (CAB), g values for CAB ( g=0.0018) and DOC ( g=0.0023) were indistinguishable (p=0.3) consistent with their identical mechanism of action. Finally, outcomes with DOC in African American (AA) ( g=0.00212) and Caucasian ( g=0.00205) Veterans were indistinguishable (p=0.9) and comparable across all VAMCs. Conclusions: The rate of tumor growth, g, is an excellent biomarker for OS both in clinical trials and in real-world settings. g allows comparisons between trials and for large trial data sets to be used as benchmarks of efficacy. Real-world outcomes in the VAMCs are similar to those in clinical trials. In the egalitarian VAMCs DOC efficacy in PC is comparable in AA and Caucasian Veterans -- indicating inferior outcomes reported in AAs are likely due to differential health care access, not differences in biology.

Role of radiomics to differentiate benign from malignant pheochromocytomas and paragangliomas on contrast enhanced CT scans

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Background: Radiomics features, which are quantitative features generated by computational analysis of routine clinical imaging like CT scans, have been shown to be associated with clinical outcomes and tumor’s behavior in some solid tumors. We compared the radiomic features of malignant and benign pheochromocytomas/paragangliomas (P/P). Methods: Through an IRB approved study at our institution, we identified 20 consecutive patients with P/P and with available contrast-enhanced abdominopelvic CT. A radiologist with experience in oncologic imaging identified and segmented tumors on every slice using a MatLab-based imaging platform. The entire tumor image then underwent computational analysis generating 1160 radiomics features reflecting tumor size, shape, density, textural heterogeneity, and margins. These radiomics features were compared between malignant and benign P/P using Wilcoxon-Rank sum test. Results: Of the twenty patients included in this analysis, there were 6 patients with malignant P/P and 14 patients with benign tumors. Patients had been followed for at least 5 and many for at least 10 years after resection of the tumor. At diagnosis, the mean age of patients with benign and malignant tumors were 51 and 45, respectively. A 60% majority of patients with benign tumors were females while a 77% majority of patients with malignant tumors were male. Benign P/P were significantly different from malignant ones in: tumor intensity textures (spatial correlation [p-value = 0.0010], Laws [p-value = 0.0064], LoG [p-value = 0.0087], and Gabor [p-value = 0.0325]), and tumor local surface shape (Shape Index SI7 [p-value = 0.0325]). Conclusions: This initial analysis sought to discern differences in these rare tumors that might be exploited clinically. The results show that compared to benign tumors, malignant P/P tend to have more heterogenous texture, irregular edges, and less rounded shape on contrast enhanced abdominal CT scan. However, because these radiomics phenotype properties are subtle, they cannot be made reliably in an objective fashion using human visual assessment and thus these radiomics features may have a role as a quantitative imaging biomarker in P/P to predict tumor behavior. The cohort is being expanded and data will be updated at the time of the presentation. With larger numbers, the contribution to the radiomics profile of a SDHx mutation will be explored in greater depth to understand the differential impact of SDHx loss and of evolution into a cancer to the radiomics profiles.

Neutral evolution of drug resistant colorectal cancer cell populations is independent of their KRAS status

Emergence of tumor resistance to an anti-cancer therapy directed against a putative target raises several questions including: (1) do mutations in the target/pathway confer resistance? (2) Are these mutations pre-existing? (3) What is the relative fitness of cells with/without the mutation? We addressed these questions in patients with metastatic colorectal cancer (mCRC). We conducted an exhaustive review of published data to establish a median doubling time for CRCs and stained a cohort of CRCs to document mitotic indices. We analyzed published data and our own data to calculate rates of growth (g) and regression (d, decay) of tumors in patients with CRC correlating these results with the detection of circulating MT-KRAS DNA. Additionally we estimated mathematically the caloric burden of such tumors using data on mitotic and apoptotic indices. We conclude outgrowth of cells harboring intrinsic or acquired MT-KRAS cannot explain resistance to anti-EGFR (epidermal growth factor receptor) antibodies. Rates of tumor growth with panitumumab are unaffected by presence/absence of MT-KRAS. While MT-KRAS cells may be resistant to anti-EGFR antibodies, WT-KRAS cells also rapidly bypass this blockade suggesting inherent resistance mechanisms are responsible and a neutral evolution model is most appropriate. Using the above clinical data on tumor doubling times and mitotic and apoptotic indices we estimated the caloric intake required to support tumor growth and suggest it may explain in part cancer-associated cachexia.

TARP vaccination is associated with slowing in PSA velocity and decreasing tumor growth rates in patients with Stage D0 prostate cancer

T-cell receptor alternate reading frame protein (TARP) is a 58-residue protein over-expressed in prostate and breast cancer. We investigated TARP peptide vaccination's impact on the rise in PSA (expressed as Slope Log(PSA) or PSA Doubling Time (PSADT)), validated tumor growth measures, and tumor growth rate in men with Stage D0 prostate cancer. HLA-A*0201 positive men were randomized to receive epitope-enhanced (29-37-9V) and wild-type (27-35) TARP peptides administered as a Montanide/GM-CSF peptide emulsion or as an autologous peptide-pulsed dendritic cell vaccine every 3 weeks for a total of five vaccinations with an optional 6th dose of vaccine at 36 weeks based on immune response or PSADT criteria with a booster dose of vaccine for all patients at 48 and 96 weeks. 41 patients enrolled with median on-study duration of 75 weeks at the time of this analysis. Seventy-two percent of patients reaching 24 weeks and 74% reaching 48 weeks had a decreased Slope Log(PSA) compared to their pre-vaccination baseline (p = 0.0012 and p = 0.0004 for comparison of overall changes in Slope Log(PSA), respectively). TARP vaccination also resulted in a 50% decrease in median tumor growth rate (g): pre-vaccine g = 0.0042/day, post-vaccine g = 0.0021/day (p = 0.003). 80% of subjects exhibited new vaccine-induced TARP-specific IFNγ ELISPOT responses but they did not correlate with decreases in Slope Log(PSA). Thus, vaccination with TARP peptides resulted in significant slowing in PSA velocity and reduction in tumor growth rate in a majority of patients with PSA biochemical recurrence.

Colorectal Cancer Survival Gains and Novel Treatment Regimens: A Systematic Review and Analysis

IMPORTANCE

The past 2 decades have witnessed progress in the management of metastatic colorectal cancer (mCRC) with more effective agents and better surgical, medical, and supportive care. While substantial progress has been made, much more must be achieved to prolong the lives of patients.

OBJECTIVE

To conduct a systematic review to ascertain what percentage of the life expectancy gain in locally advanced and mCRC over the past 2 decades is due to novel therapies vs improvements in supportive care or secular trends and to thus inform treatment development strategies.

EVIDENCE REVIEW

We searched Cochrane Controlled Trials Register, Medline, Embase, CancerLit, and Healthstar electronic databases for trials covering the period 1993 to 2015, scanned reference lists of articles, and searched recent conference abstracts. Ninety-six phase 3 trials and large (>50 patients) phase 2 trials in mCRC were examined. Outcomes evaluated in the experimental arms (EAs) and control arms (CAs) included overall response rate, stable disease, progression-free survival (PFS), and overall survival (OS).

FINDINGS

Over the period covered by the studies, the OS in EAs increased at a mean (95% CI) rate of 0.80 (0.67-0.93) mo/y. Importantly, OS in the CAs improved 0.63 (0.51-0.75) mo/y, reflecting in part the use of experimental regimens in subsequent studies. Chemotherapy contributed only partly to the gains in OS, given that (1) mean (95% CI) improvements in PFS were only 0.31 (0.22-0.39) mo/y in the EAs and 0.23 (0.15-0.31) mo/y in CAs; (2) gains in survival not directly attributable to the protocol were greater than gains in PFS (0.46 [0.36-0.57] mo/y in EAs and 0.39 [0.29-0.49] mo/y in CAs; and (3) effects on OS were much lower in second-line trials (median [interquartile range] response rates, 8.6% [0%-11.0%] in EAs and 7.5% [3.8%-12.8%] in CAs) compared with first-line trials (39.5% [24.0%-50.2%] for EAs and 29.4% [16.4%-39.4%] for CAs).

CONCLUSIONS AND RELEVANCE

The OS of patients with mCRC has improved gradually over the past 2 decades, with gains from chemotherapy occurring alongside gains from lead-time bias and improved locoregional approaches and supportive care. Gains from first-line therapies have been modest but consistent; however, gains from second-line therapies have been disappointing. We believe that future progress will be greater if emphasis is placed on enrolling patients in experimental trials to explore and develop alternative first-line regimens and better second-line therapies.

Phase II Clinical Trial of Ixabepilone in Metastatic Cervical Carcinoma

LESSONS LEARNED

Accrual to cervical cancer studies remains a puzzling challenge given the lack of options and the dismal prognosis of this disease. The majority of patients referred for a trial such as this have very advanced disease that is difficult to manage.The observation of 4 partial responses among the 41 patients indicates that ixabepilone has some activity but not sufficient for further development without greater understanding of mechanisms of sensitivity and resistance.

BACKGROUND

Ixabepilone is a microtubule-stabilizing agent approved for metastatic breast cancer. Preclinical data have shown that ixabepilone is active in taxane-sensitive and -resistant cells. Metastatic cervical carcinoma (mCC) has a poor prognosis and no established second-line therapies. This study assessed the efficacy and safety of ixabepilone in previously treated mCC.

METHODS

Patients with histologically confirmed mCC and at least one prior cisplatin-containing regimen were treated with ixabepilone [6 mg/m(2) per day for 5 days] every 21 days. The primary endpoint was progression-free survival (PFS) according to the Response Evaluation Criteria in Solid Tumors (RECIST). Secondary endpoints were response rate, rate of tumor growth, overall survival (OS), and safety. Levels of glu-terminated and acetylated tubulin, markers of microtubule stabilization, and surrogates for target engagement were assessed by Western blot.

RESULTS

In total, 41 patients were enrolled; 34 had tumors with primarily squamous histology. The median number of prior therapies was 2 (range 1-6). Four patients (9.7%) had a partial response. Median PFS in months was 2.3 for all, 3.84 for taxane-naïve, and 2.03 for taxane-pretreated patients (p = .13). Consistent with this, we found statistically similar (p = 1) rates of growth in taxane-naive patients (0.0035 per day) and taxane pretreated patients (0.0053 per day). Median OS was 5.84 months. G1/2 toxicities included vomiting (43%), sensory neuropathy (21%), and fatigue (60%). Bowel fistulas were observed in 7% of patients. Glu and acetylated tubulin were assessed in tumor samples from 11 patients during the first cycle of treatment. Although there was clear evidence of "target engagement" and microtubule stabilization in all tumors, a correlation between the extent of tubulin stabilization and response to therapy could not be demonstrated.

CONCLUSION

Ixabepilone was well tolerated but showed very modest activity in second- or later-line mCC and cannot be recommended as a therapy. Target engagement was demonstrated but was not correlated with responses, suggesting that other factors mediate drug sensitivity. New strategies are needed for refractory mCC.

Gefitinib and erlotinib in metastatic non-small cell lung cancer: a meta-analysis of toxicity and efficacy of randomized clinical trials

BACKGROUND

Tyrosine kinase inhibitors (TKIs) targeting the epidermal growth factor receptor (EGFR) have been evaluated in patients with metastatic and advanced non-small cell lung cancer (NSCLC). The U.S. Food and Drug Administration initially granted accelerated approval to gefitinib but subsequently rescinded the authorization. Erlotinib and afatinib are similar compounds approved for the treatment of metastatic NSCLC. The objective of this study was to compare the efficacy and toxicity of erlotinib, gefitinib, and afatinib in NSCLC.

METHODS

We tabulated efficacy variables including overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) and quantitated toxicities and rates of dose reductions and discontinuation. Summary odds ratios were calculated using random and fixed-effects models. An odds ratio was the summary measure used for pooling of studies.

RESULTS

We examined 28 studies including three randomized trials with afatinib. Clinical toxicities, including pruritus, rash, anorexia, diarrhea, nausea, fatigue, mucositis, paronychia, and anemia, were similar between erlotinib and gefitinib, although some statistical differences were observed. Afatinib treatment resulted in more diarrhea, rash, and paronychia compared with erlotinib and gefitinib. Regarding efficacy, similar outcomes were recorded for ORR, PFS, or OS in the total population and in specific subgroups of patients between erlotinib and gefitinib. All three TKIs demonstrated higher ORRs in first line in tumors harboring EGFR mutations.

CONCLUSION

Gefitinib has similar activity and toxicity compared with erlotinib and offers a valuable alternative to patients with NSCLC. Afatinib has similar efficacy compared with erlotinib and gefitinib in first-line treatment of tumors harboring EGFR mutations but may be associated with more toxicity, although further studies are needed. Gefitinib deserves consideration for U.S. marketing as a primary treatment for EGFR-mutant NSCLC.

Therapies with diverse mechanisms of action kill cells by a similar exponential process in advanced cancers

Successful cancer treatments are generally defined as those that decrease tumor quantity. In many cases, this decrease occurs exponentially, with deviations from a strict exponential being attributed to a growing fraction of drug-resistant cells. Deviations from an exponential decrease in tumor quantity can also be expected if drugs have a nonuniform spatial distribution inside the tumor, for example, because of interstitial pressure inside the tumor. Here, we examine theoretically different models of cell killing and analyze data from clinical trials based on these models. We show that the best description of clinical outcomes is by first-order kinetics with exponential decrease of tumor quantity. We analyzed the total tumor quantity in a diverse group of clinical trials with various cancers during the administration of different classes of anticancer agents and in all cases observed that the models that best fit the data describe the decrease of the sensitive tumor fraction exponentially. The exponential decrease suggests that all drug-sensitive cancer cells have a single rate-limiting step on the path to cell death. If there are intermediate steps in the path to cell death, they are not rate limiting in the observational time scale utilized in clinical trials--tumor restaging at 6- to 8-week intervals. On shorter time scales, there might be intermediate steps, but the rate-limiting step is the same. Our analysis, thus, points to a common pathway to cell death for cancer cells in patients. See all articles in this Cancer Research section, "Physics in Cancer Research."

Tyrosine kinase inhibitors directed against the vascular endothelial growth factor receptor (VEGFR) have distinct cutaneous toxicity profiles: a meta-analysis and review of the literature

PURPOSE

Inhibition of the vascular endothelial growth factor receptor (VEGFR) with tyrosine kinase inhibitors (TKIs) is associated with cutaneous adverse effects that increase patient morbidity. Our objective was to examine the skin toxicity profile of anti-VEGFR TKIs and determine the changing incidence in clinical trials.

METHODS

PubMed was queried for phase II or III trials of anti-VEGFR TKIs between 2000 and 2013 involving ≥50 patients. Adverse events were abstracted, with results presented in both fixed and random effects models. Odds ratios (OR) and 95 % confidence intervals (CIs) were estimated for studies with at least two arms.

RESULTS

Across 82 included studies, all grades rash (OR, 2.68; 95 % CI, 2.45-2.94), hand-foot skin reaction (HFSR) (OR, 2.70; 95 % CI, 2.43-3.00), and pruritus (OR, 1.25; 95 % CI, 1.12-1.39) were associated with anti-VEGFR TKIs. Vandetanib had the highest incidence of rash (41 %), while sorafenib was most commonly associated with HFSR (37 %) and pruritus (14 %). The incidence of HFSR from 2000 to 2013 showed an upward trend (r (2) = 0.042, p = 0.10) and in sunitinib therapy increased significantly (r (2) = 0.237, p = 0.04).

CONCLUSION

The incidence of HFSR, rash, and pruritus varies considerably by drug. Our data suggest a continued need to address skin toxicities and improve reporting strategies.

Abstract LB-106: Microtubule-targeting agents (MTAs) disrupt intracellular trafficking of DNA repair proteins and augment the toxicity of DNA damaging agents (DDAs)

MTAs have long been thought to cause cell death primarily by inducing mitotic arrest, a paradigm that applies to rapidly dividing cells in preclinical models. However, mitotic arrest cannot explain the activity of MTAs in much more slowly growing human cancers. In the latter, we have proposed interference with trafficking on interphase microtubules (MTs) as the principal mechanism of cytotoxicity. Satisfying this paradigm requires identification of the proteins whose trafficking on MTs, when disrupted, leads to cytotoxicity. MTAs in combination with DNA-damaging agents (DDAs) have emerged as preferred regimens for the treatment of ovarian, lung, some head and neck cancers, and many lymphomas. We proposed that by interfering with the trafficking of DNA repair proteins, MTAs could synergize with DDAs, augmenting their toxicity and enhancing cell death. To explore this hypothesis, we systematically investigated the effects of either paclitaxel or vincristine on treatment-induced DNA damage and on the distribution and biology of nine different proteins involved in DNA repair: ATM, ATR, DNA-PK, Rad50, Mre11, p95/NBS1, TP53, 53BP1 and p63. In several cell models including A549 cells and four Burkitt's lymphoma models (CA46, DG-75, Ramos and ST486) addition of vincristine increased cytoplasmic retention of the DNA repair proteins, thus excluding a greater fraction from the nucleus. The latter effect was observed only with MTAs and not with an inhibitor of Aurora kinase, despite similar cell cycle effects, confirming the cytoplasmic retention seen with MTAs is not due to alterations in the cell cycle. Increased cytoplasmic retention of DNA repair proteins following MT disruption suggests these proteins traffic on MTs and are vulnerable to MTAs, and this is supported by both confocal microscopy demonstrating co-localization of DNA repair proteins and α- or αβ-tubulin, as well as co-immunoprecipitation of these proteins with antibodies against the MT motor, dynein. In both A549 and MCF cells, the repair of DNA as measured by the level and persistence of γ-H2AX, was prolonged by the addition of paclitaxel to radiation. Moreover, when MCF7 or A549 cells were treated with either adriamycin or etoposide, γ-H2AX was induced to higher levels and for longer times when cells were treated with vincristine prior to and with the DDA and during DDA washout, when vincristine was present. In comparison, γ-H2AX decline was more rapid after DDA washout for cells treated only with the DDA. Together these data demonstrate that many DNA damage repair proteins travel on MTs and that the addition of MTAs promotes their sequestration in the cytoplasm. By interfering with the repair of DNA, cytoplasmic retention results in greater toxicity and likely explains why combinations of MTAs and DDAs have emerged as favored drug combinations for therapy of a diverse group of cancers.

Citation Format: Marianne S. Poruchynsky, Edina Komlodi-Pasztor, Julia Wilkerson, Shana Trostel, Mauricio Burroto-Pichun, Tito Fojo. Microtubule-targeting agents (MTAs) disrupt intracellular trafficking of DNA repair proteins and augment the toxicity of DNA damaging agents (DDAs). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-106. doi:10.1158/1538-7445.AM2014-LB-106

Continuing a cancer treatment despite tumor growth may be valuable: sunitinib in renal cell carcinoma as example

BACKGROUND

The US FDA and the EMA have approved seven agents for the treatment of renal cell carcinoma, primarily based on differences in progression-free survival (PFS). Because PFS is an arbitrary endpoint we hypothesized that an analysis would demonstrate the growth rate of tumors remained constant at the time of RECIST-defined disease progression.

METHODS

We previously estimated the growth (g) and regression (d) rates and the stability of g using data from the Phase III trial comparing sunitinib and interferon.

RESULTS

Sufficient data were available and rate constants statistically valid in 321 of 374 patients randomized to sunitinib. Median d was 0•0052 days(-1); in 53 patients no tumor growth was recorded. Median g was 0•00082 days(-1) and was stable for a median of 275 days on therapy, remaining stable beyond 300, 600 and 900 days in 122, 65 and 27 patients, respectively. A possible increase in g while receiving sunitinib could be discerned in only 18 of 321 patients. Given a median g of 0•00082 days(-1) the estimated median time to a second progression were sunitinib continued past RECIST-defined progression was 7.3 months. At 100, 200, and 300 days after starting therapy, an estimated 47%, 27%, and 13% of tumor remains sunitinib sensitive and could explain a RECIST-defined response to a new TKI.

CONCLUSION

Prolonged stability of g with sunitinib suggests continued sunitinib beyond RECIST-defined progression may provide a beneficial outcome. Randomized trials in patients whose disease has "progressed" on sunitinib are needed to test this hypothesis.

The VEGF inhibitor axitinib has limited effectiveness as a therapy for adrenocortical cancer

CONTEXT

Adrenocortical carcinoma (ACC) is a rare malignancy with a poor prognosis in need of more effective treatment options. Published evidence indicates many ACCs express the vascular endothelial growth factor receptor (VEGFR), suggesting inhibiting vascular endothelial growth factor signaling could potentially impact tumor growth.

OBJECTIVE

The objective of the study was to determine the antitumor efficacy of axitinib (AG-013736), a potent, selective inhibitor of VEGFR1, -2, and -3.

DESIGN

This was a phase II, open-label trial using a two-stage design.

PATIENTS

Thirteen patients with metastatic ACC previously treated with at least one chemotherapy regimen with or without mitotane participated in the study.

INTERVENTION

Starting axitinib dose was 5 mg orally twice daily. Dose escalations were permitted if the administered dose was tolerable.

RESULTS

Thirteen patients were enrolled. Dose escalation was possible in seven patients, but the majority could not tolerate a dose higher than the starting 5 mg, twice-daily dose for prolonged periods of time. All patients experienced known grade 1/2 toxicities, and 10 of 13 patients had at least one grade 3/4 adverse event. No patient tumor could be scored as a Response Evaluation Criteria in Solid Tumors response, although the growth rate on therapy compared with that prior to starting axitinib was reduced in 4 of the 13 patients. The median progression-free survival was 5.48 months, and the median overall survival was longer than 13.7 months.

CONCLUSION

Axitinib has limited effectiveness in ACC. Together with 48 patients previously reported who received either sorafenib or sunitinib, a total of 61 ACC patients have now been treated with a VEGFR tyrosine kinase inhibitor without an objective Response Evaluation Criteria in Solid Tumors response. Future trials in ACC should look to other targets for possible active agents.

Relationship of the emergence of KRAS mutations and resistance to panitumumab in second-line treatment of colorectal cancer (CRC)

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Background: Multiple analyses have concluded anti-EGFR antibodies are detrimental to a majority of patients (pts) whose CRCs harbor mutant KRAS. While panitumumab may benefit some pts with tumors harboring WT KRAS, in the majority the added benefit is small and transient. Recent studies have claimed emergence of KRAS mutations mediates acquired resistance to EGFR inhibitors. Methods: We analyzed published and unpublished data to assess this possibility, calculating growth and regression rate constants and estimating doubling times of CRC. Results: Amongst 24 pts with CRC whose tumors were initially KRAS WT, circulating mutant KRAS transcripts were detected in 9 treated in second line with panitumumab plus chemotherapy [Diaz et al, Nature 2012]. The growth rate of tumor in the 9 pts with circulating MT KRAS was 0.0019 days-1. This value is statistically indistinguishable [p = .2439] from the growth rate of 0.0021 days-1 calculated for tumors in 15 pts with no detectable circulating MT KRAS transcripts. Both values were also statistically indistinguishable [p = .3055 for MT KRAS; p = .7688 for WT KRAS] from the growth rate [0.002 days-1] of tumors in a cohort treated in second line with the same chemotherapy without an EGFR inhibitor. Similar results were observed when growth rates were calculated using CEA values [WT, 0.00087 days-1; MT, 0.0024 days-1; p = .1265] and similar regression rate constants were also calculated [WT, 0.0114 days-1; MT, 0.0117 days-1; p = .858]. Furthermore, in pts with detectable serum MT KRAS transcripts the growth rate remained constant even as MT KRAS transcripts appeared to increase. The growth rates allowed us to estimate tumor doubling times of 110 to 124 days in these pts receiving second line therapies, consistent with clinical data for disease progression in second line; and similar to the estimated doubling time of 116 days in the cohort that did not receive panitumumab. Conclusions: Resistance to panitumumab in tumors harboring WT KRAS cannot be explained by overgrowth of cells with MT KRAS. Other mechanisms must be sought to explain the limited efficacy of panitumumab. The data suggest such mechanism(s) are inherent and likely present in the majority of cells.

Continuation of sunitinib following RECIST progression on first-line sunitinib

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Background: In the last seven years the FDA and the EMA have approved seven agents for treatment of RCC. Five of these target the VEGF pathway. Methods: We conducted a detailed analysis of data from the sunitinib registration trial examining the growth and regression rate constants and the stability of the growth rate as measures of effectiveness and to understand development of resistance. Results: Sufficient data was available for the analysis of 350/374 patients enrolled. Statistically valid data was obtained in 321(91.7%). The median regression rate constant was 0.0048 days-1, and in 59 patients no evidence of growth was recorded while on study, only regression. The median growth rate was 0.00082 days-1 and this rate was stable a median of 267 days, remaining stable beyond 300 days in 172 patients, beyond 600 days in 95 patients, and beyond 900 days in 49 pts. A suggestion of a possible increase of the growth rate while sunitinib was administered could be discerned in only 15/321 pts. With a median growth rate 0.00082 days-1 the estimated time to progression were sunitinib discontinued and then re-started would have been a minimum of 7.3 months. Thus a meaningful outcome could be achieved provided continued sunitinib is tolerable. Finally with an estimated 47%, 27% and 13% of tumor still sensitive to sunitinib 100, 200 and 300 days after starting therapy, shrinkage with a new TKI in patients who discontinue sunitinib before day 300 for toxicity may not be a sign of non-cross resistance, but of residual sensitive tumor. Conclusions: Prolonged stability of the growth rate of RCC on sunitinib is consistent with intrinsic and not acquired resistance. Baring toxicity, continued sunitinib beyond RECIST criteria for progression may provide a beneficial outcome and can be considered a treatment alternative in selected patients. Randomized trials to assess the value of VEGF TKI’s in patients whose disease has “progressed” on sunitinib should consider including an arm that continues sunitinib to test this hypothesis.

Using a program that computes tumor decay (d) and regrowth (g) rates and the fraction (Φ) of tumor killed to assist in clinical trials and improve patient survival

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Background: Clinical trials collect much data on tumor quantity as therapy proceeds. From this data progression endpoints and response rates are reported and used to evaluate efficacy. But there is much information contained therein that allows us to understand mechanisms of drug action and how to best administer therapies. Methods: We have developed mathematical equations that enable extraction of the rates of tumor decay (d) and regrowth (g) and also the fraction (Φ) of tumor killed. Results: We have analyzed data from >3,000 cases of various tumor histologies including prostate, breast, renal, and medullary thyroid cancers as well as multiple myeloma (MM). These malignancies have been treated with “cytotoxic” and “targeted” therapeutics as well as vaccines. Across all treatment modalities, overall survival does not correlate with the rate of decay, d, but correlates strongly with the growth rate, g. In some drug/tumor combinations, Φ can also be extracted and its role in the drug’s action ascertained. Most therapies developed in metastatic cancers such as ixabepilone in breast cancer and sunitinib in renal cancer are “g therapies”. Such therapies reduce g, impact survival favorably and could further impact survival if administered beyond conventional endpoints for progression. In contrast, “Φ therapies”, such as bortezomib in MM and ATTP in prostate cancer kill a larger fraction of tumor and are proposed to be effective as adjuvant and neo-adjuvant treatments, with little benefit from extending treatment in the metastatic setting. Furthermore, the data suggest resistance in most is likely intrinsic since tumor growth rates on therapy do not change appreciably over time. Conclusions: We have developed an analytical method that characterizes a tumor’s response to a therapy and enables extraction of tumor decay (d) and regrowth (g) rates and the fraction (Φ) of tumor killed. Both g and Φ, but not d, determine the effectiveness of a therapy. Use of these parameters should allow for the conduct of smaller trials and may also help improve patient survival. A stand-alone computer program has been built, is available to the research community and will be demonstrated.

Abstract 5152: Estimating the fraction of a tumor that is killed by a drug

We analysed mathematically the progress of thousands of patients enrolled in clinical trials with diagnoses of prostate, renal cell, breast, and thyroid carcinomas and multiple myeloma, treated with cytotoxic and targeted drugs, tumor quantity being measured radiologically or by serum markers (see, e.g., Stein et al Clin Cancer Res. 2011,17, 907-17, for prostate cancer). Treatment often results in reduction of tumor quantity, with subsequent regrowth. In some regression does not occur; in others regrowth is not recorded. All these outcomes are described by a simple mathematical formula (see Eq. (1) below) that describes progress of treatment, yielding the rate of tumor decay, d, and rate of regrowth, g. When regrowth is not seen, g is indistinguishable from zero, as is d if tumor quantity fails to decrease. Parameter g is a surrogate measure of overall survival. Median g values can be used to compare the arms of a clinical trial.

In a minority of cases, increase in tumor quantity is delayed for an extended period of time before regrowth occurs, and the simple formula must be modified to include an additional parameter, Ø, the fraction of tumor killed by the drug, see Eq. (2). In a trial of 750 multiple myeloma (MM) patients treated with liposomal doxorubicin plus bortezomib (PLD + B) or bortezomib (B) alone, 114 cases were better fitted by Eq. (2) than by Eq. (1). For these, the median value of Ø was 0.99, meaning that 99% of the tumor was destroyed by drug, only 1% being left to regrow. Were this 1% of tumor to regrow at rate 0.0131 per day (the median for these 114 patients) it would return to the initial tumor quantity, expanding 100-fold, in ln(100)/0.0131 days or 11.5 months. The OS for these patients who died before the study closed was 12.7 (8.9 to 16) months, close to the predicted. If Ø is less than 0.85, and g is larger than 0.02 per day, the predictions of Eqs. 1 and 2 are similar. Slight scatter in the data will not allow a distinction to be made between the models, nor a definitive value of Ø estimated. Nevertheless, aggregating data from numerous patients enables Ø to be estimated for such a data set. Aggregating the data for the 388 MM patients for whom g and/or d but not Ø could be established, Ø was 0.84 for the PLD + B arm and 0.79 for B. To regrow to the initial tumor quantity requires 2.7 doublings for the PLD + B arm and 2.2 for B, a difference that would result in only a trivial increase in OS. However, the difference between the computed tumor growth rates, 0.0019 and 0.0037 for the PLD + B arm and B respectively, would be expected to lead to a noticeable increase in OS were treatment to continue beyond conventional endpoints.

Measuring the fraction of tumor killed by a drug, and the rate of growth recovery, can give insight into drug/tumor interactions and guide development of new therapies.

Equation 1: f(t) = exp (-d • t) + exp (g • t) -1, exp is the base of the natural logarithms, and f(t) the tumor measurement at time t, normalized to the tumor measurement at day 0;

Equation 2: f(t) = Ø • exp (-d • t) + (1-Ø) • exp (g • t)]

Citation Format: Wilfred D. Stein, Julia Wilkerson, Elisabet Manasanch, Sen H. Zhuang, Susan E. Bates, Tito Fojo. Estimating the fraction of a tumor that is killed by a drug. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5152. doi:10.1158/1538-7445.AM2013-5152

Hemorrhagic events in hepatocellular carcinoma patients treated with antiangiogenic therapies

The presence of cirrhosis increases the potential risk of hemorrhage for patients with hepatocellular carcinoma (HCC). We evaluated the relative risk for hemorrhage in patients with HCC treated with antiangiogenic agents. We performed a systematic review and meta-analysis of antiangiogenic studies in HCC from 1995 to 2011. For nonrandomized studies we compared bleeding risk with other HCC single-arm studies that did not include an antiangiogenic agent. To separate disease-specific factors we also performed a comparison analysis with renal cell cancer (RCC)) studies that evaluated sorafenib. Sorafenib was associated with increased bleeding risk compared to control for all grade bleeding events (odds ratio [OR] 1.77; 95% confidence interval [CI] 1.04, 3.0) but not grade 3-5 events in both HCC and RCC (OR 1.46; 95% CI 0.9, 2.36; P=0.45). When comparing the risk of bleeding in single-arm phase 2 studies evaluating antiangiogenic agents, this risk for all events (OR 4.34; 95% CI 2.16, 8.73) was increased compared to control.

CONCLUSION

This analysis of both randomized and nonrandomized studies evaluating an antiangiogenic agent in HCC showed that whereas the use of sorafenib was associated with an increased risk of bleeding in HCC, this was primarily for lower-grade events and similar in magnitude to the risk encountered in RCC.

Effect of PSA-tricom, a pox-viral vaccine in prostate cancer (PCa), on tumor growth rates within 80 days after initiation in nonmetastatic PCa

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Background: Our understanding of immunotherapies for prostate cancer (PSA-TRICOM, sipuleucel-T, ipilimumab) is incomplete in that such therapies have improved overall survival (OS) without changes in time to progression (TTP) in randomized trials. In an effort to better understand this discrepancy, we evaluated data from studies of PSA-TRICOM. A pox viral vaccine expressing PSA and 3 T-cell co-stimulatory molecules, PSA-TRICOM has demonstrated PSA-specific immune responses and evidence of clinical activity that supported initiation of a currently accruing Phase III trial. An analysis of NCI PCa trials (including a PSA-TRICOM trial) suggests that immune therapies may eventually slow the growth rate (GR) of tumors, leading to unaltered short term TTP, yet improved OS (Stein et al. Clin Can Res. 2011). Methods: PSA-TRICOM was administered to 50 hormone-naïve patients (pts.) with non-metastatic, castration naive PCa in a multi-center trial (ECOG 9802). Pts were treated every 4 weeks for 3 months, then every 12 weeks (preliminary data previously reported, DiPaola, RS et al. ASCO GU 2009). PSA values were used to calculate tumor GR within the first 100 days of treatment. (Pts were given no additional therapies during this time.) As previously described, a two-phase mathematical equation yielded concomitant PSA GR and regression rate constants.(Stein et. al., 2011) Results: See Table. Conclusions: These data suggest that PSA-TRICOM can alter GR significantly within 3 months. If confirmed in future trials, it could explain why vaccines have demonstrated improved OS without improved TTP. A slowing of the GR may not lead to substantial differences in short term TTP, but may enhance OS in the long term. This concept will be evaluated in an international Phase III trial of PSA-TRICOM in minimally symptomatic, metastatic castration-resistant PCa that is currently recruiting pts. Clinical trial information: NCT00108732. [Table: see text]

Sunitinib does not accelerate tumor growth in patients with metastatic renal cell carcinoma

Preclinical studies have suggested that sunitinib accelerates metastases in animals, ascribing this to inhibition of the vascular endothelial growth factor receptor or the tumor’s adaptation. To address whether sunitinib accelerates tumors in humans, we analyzed data from the pivotal randomized phase III trial comparing sunitinib and interferon alfa in patients with metastatic renal cell carcinoma. The evidence clearly shows that sunitinib was not harm- ful, did not accelerate tumor growth, and did not shorten survival. Specifically, neither longer sunitinib treatment nor a greater effect of sunitinib on tumors reduced survival. Sunitinib did reduce the tumor’s growth rate while administered, thereby improving survival, without appearing to alter tumor biology after discontinuation. Concerns arising from animal models do not apply to patients receiving sunitinib and likely will not apply to similar agents.

Histone deacetylase inhibitors induce CXCR4 mRNA but antagonize CXCR4 migration

The stromal cell-derived factor-1α SDF-1α (CXCL12)/CXCR4 axis has been linked to poor prognosis in some cancers. As histone deacetylase inhibitors (HDIs) exert antitumor effects by targeting proteins affecting cell migration, we sought to evaluate the effects of the HDIs apicidin, vorinostat, entinostat (MS-275) and romidepsin on the expression and function of CXCR4 in human cancer cell lines. After treatment with romidepsin, CXCR4 mRNA expression increased 12-fold in UOK121 renal cancer cells, 16-fold in H460 non-small cell cancer cells and 4-fold in SF295 glioma cells; treatment with other HDIs yielded similar effects. CXCR4 induction was not observed in MCF7 breast cancer cells or SW620 colon cancer cells. To evaluate the corresponding functional increase, the effect of CXCR4 ligand, CXCL12, on ERK1/2, STAT3 and c-SRC activation and cell migration was examined in UOK121, SF295 and H460 cells. Alone, the HDIs increased pERK1/2, while reducing pSTAT-3 and pSRC. Following CXCL12 exposure, pERK1/2 induction was maintained, but STAT3 and SRC phosphorylation was impaired. These findings resulted in reduced basal and CXCL12-mediated cell migration. In conclusion, HDIs upregulated CXCR4 mRNA expression but impaired CXCL12-dependent signaling cascades through STAT3 and c-SRC, suggesting a potential role for HDIs in delaying or preventing metastatic processes in solid tumors.

Two decades of therapy in metastatic colorectal cancer (mCRC): An analysis to discern the contribution and progress made by chemotherapy

e14064

Background: The past 20 years have seen progress in mCRC with more effective agents and better medical, surgical and supportive care. Methods: Systematic review of 101 phase III and large phase II trials in mCRC to quantify benefit over time with first-line and subsequent therapies. Outcomes in the experimental (EA) and control arms (CA) included progression-free survival (PFS), overall response rate (ORR), stable disease (SD), and overall survival (OS). Data were analyzed according to dates of publication and median enrollment. Results: Significant outcomes are reported; most had R2 values > 0.6. OS of EA improved 0.83 mos/yr. Importantly OS of CA improved 0.58 mos/yr likely reflecting subsequent use of experimental regimens in CA and improvement in mCRC care over time. Chemotherapy has contributed only partly to gains in OS since (1) only modest improvements of PFS (0.33 [EA] and 0.26 [CA] mos/yr) and we have shown OS gains are proportional to PFS gains indicating other factors are as or more important than chemotherapy; and (2) lack of OS improvement in 14 second/subsequent line trials. Furthermore, to assess the contribution of each drug/drug class to improvement in OS we performed linear regression with OS the dependent variable versus time publication. We found oxaliplatin, irinotecan and bevacizumab have contributed to progress; but not cetuximab/panitumumab likely explained by inclusion of pts with tumors harboring mutant ras in studies. Not surprisingly, capecitabine in place of 5-fluorouracil had no impact on progress made. As expected PFS correlates highly with OS, but importantly ORR had very high correlations with both PFS and OS. SD was an “adverse” outcome, OS decreasing as SD rates increase. Conclusions: OS of mCRC patients has improved gradually over the past two decades, with gains from chemotherapy and importantly gains from other factors, including lead-time bias, better loco-regional approaches and supportive care. Gains from first line therapies have been modest but consistent; gains from second line therapies have been disappointing. We believe future progress will be more fruitful if emphasis is given to improving second line therapies.

A method for assessing tumor response to therapy and more precisely guiding treatment decisions so as to improve survival

e13122

Background: The response of tumors to chemotherapy is monitored using imaging data or tumor markers and this quantitative data provides a rich source for an objective response assessment and treatment decisions. Responses are usually assessed as categorical variables based on percentage increase or decrease in tumor size. Methods: We have developed mathematical equations that describe efficacy as a continuous variable, enabling the extraction of the appropriate rate constants for tumor growth and regression (decay), designated g and d, respectively. Both are used to describe the rates of tumor growth and regression for the fraction of tumor that is growing despite treatment and the fraction dying as a result of therapy, respectively. Results: Using data from randomized phase III trials in kidney and breast cancer, multiple myeloma, and medullary thyroid carcinoma; as well as phase II trials in prostate cancer we have shown that: (1) values of g but not those of d are strongly correlated (negatively) with patient survival; (2) g can be discerned early in treatment, before growth is demonstrated clinically, providing an early efficacy measure; (3) g typically does not change over time, even over years, suggesting resistance is intrinsic and predictable and does not worsen over time; (4) effective therapies both increase d, and reduce g; and (5) in every cancer studied, the evidence suggests tumor growth reverts to its pre-treatment rate when chemotherapy is discontinued. Conclusions: The observation that g remains stable allows one to predict the most likely outcome of continued therapy. The evidence indicates that the increase in g occurring after treatment discontinuation is due to a resumption of a pre-treatment growth rate and not a change in biology. Our hypothesis is that if a favorable growth rate that slows tumor growth can be identified, survival might be improved if therapies that achieve this favorable growth rate are continued despite crossing conventional disease progression boundaries. We plan a prospective test of this model to provide a more informed decision and better survival outcome by maximizing the benefit obtained from approved therapies.

Difference between duration of treatment (DOT) and progression-free survival (PFS) as a marker of unbalanced censoring

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Background: In the conduct of randomized trials Kaplan and Meier envisioned rates of censoring as similar between arms, providing accurate assessment of clinical trial results. Censoring is used when patients withdraw consent, leave study due to toxicity, or reach data cut-off without disease progression or death. Censoring can lead to erroneous conclusions as it can be either beneficial or detrimental to the arm under study. Such censoring can also explain how a statistically valid difference in PFS “disappears” when overall survival (OS) is examined. We hypothesized that censoring, especially that due to toxicity, would lead to a discrepancy between DOT and PFS since two different patient populations would be scored. Methods: We reviewed all phase III randomized studies of drugs approved by FDA since 2005 for pts with metastatic solid tumors, looking for DOT and PFS. We used standard statistical analyses using SAS. Results: We identified 55 Phase III studies conducted with abiraterone, axitinib, bevacizumab, cabazitaxel, cetuximab, eribulin, erlotinib, everolimus, ipilimumab, ixabepilone, lapatinib, panitumumab, pazopanib, sorafenib, sunitinib, temsirolimus and vandetinib. DOT was not provided in 27%. Forty-four comparisons (88 arms) were included in the analysis. The median PFS, DOT, delta PFS (difference in PFS between experimental and control arms) and delta DOT were: 161, 126, 51 and 36 days, respectively. The slopes of PFS vs DOT and delta PFS vs delta DOT were 1.16 and 1.03, respectively close to the ideal of 1.0. Five trials fell above the 90% CI boundary with delta PFS/delta DOT of 3 to 36, including two everolimus studies (PNET and breast cancer) two sunitinb studies (RCC and PNET) and one bevacizumab study (E2100, breast cancer). Conclusions: PFS and DOT as well as delta PFS and delta DOT should be concordant. The most likely explanation for a discordance between these values is toxicity-driven censoring and its occurrence raises concerns regarding the degree of efficacy. A greater utilization of “Time to Treatment Failure”, an endpoint that includes toxicity in its definition would be valuable in oncology trials, particularly those with high levels of toxicities.

Abstract 765: Growth rates of tumors with numerous histologies remain constant while patients are on therapy

Tumor Growth Rates Remain Constant while Patients are on Therapy: Evidence that Continued Treatment does not Select for More Rapidly Growing Tumors Background: Increasingly, clinical investigators continue therapies with the hopes of improving survival. Where tumor growth is occurring, such a strategy will only succeed if the rate of tumor growth remains slow and unchanged while therapy continues. We tested this assumption using a large database of tumor measurements in patients on clinical trials. Results: We analyzed 2250 tumor growth curves from patients with advanced cancer and diagnoses of multiple myeloma, breast, renal, castration refractory prostate cancer (CRPC) or medullary thyroid carcinoma (MTC). Patients received various therapies: sunitinib, vandetanib, ixabepilone, capecitabine, bevacizumab, thalidomide, taxotere and interferon alpha. Measurements comprised serum markers (M-spike, PSA, CEA, calcitonin) and radiographic imaging. A simple computer-based model allowed extraction of statistically valid results for growth and decay rates (in over 85% of cases) and the fraction of surviving tumor in cases where marked responses occurred (up to 30% of MTC and CRPC). Analysis of the data obtained while patients were on therapy (including those still alive when the study closed and also those who died but survived long after therapy was discontinued) showed little evidence of an increase (0.3%) or a decrease (0.7%, most being MTC) in growth rate while they were treated, consistent with expansion of a pre-existing clone that is relatively resistant. Also in those MTC and CRPC cases where there was no detectable growth for a period of time, restoration of growth was consistent with expansion of a pre-existing, inherently-resistant clone, growing at a constant rate, rather than with emergence of a clone that has acquired resistance. In cases where therapy continued well beyond a year (median, 25%-75%: 498, 420-727 days) until just before death (interval duration median, 25% to 75%: 95, 63-129 days), there was neither evidence of acceleration nor the slowing that would be predicted by a Gompertz model. Many patients in whom therapy reduced the tumor growth rate to well below that of placebo, died sooner than expected. Modeling their survival data and their tumor growth rates suggested a return to the pre-therapy rate when treatment was discontinued. Conclusion: Data obtained on tumor growth rates for 2250 patients receiving therapy in clinical trials shows little evidence that tumor growth rates change while patients receive treatment. Analysis of the smaller sample of cases where death occurred within months after therapy ceased suggests that while growth rates remain constant while patients continue therapy, tumor growth returns to the pre-treatment rate when therapy is discontinued. These observations support a strategy of continuing therapy beyond the conventional criteria for discontinuation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 765. doi:1538-7445.AM2012-765

Analyzing the pivotal trial that compared sunitinib and IFN-α in renal cell carcinoma, using a method that assesses tumor regression and growth

PURPOSE

We applied a method that analyzes tumor response, quantifying the rates of tumor growth (g) and regression (d), using tumor measurements obtained while patients receive therapy. We used data from the phase III trial comparing sunitinib and IFN-α in metastatic renal cell carcinoma (mRCC) patients.

METHODS

The analysis used an equation that extracts d and g.

RESULTS

For sunitinib, overall survival (OS) was strongly correlated with log g (Rsq = 0.44, P < 0.0001); much less with log d (Rsq = 0.04; P = 0.0002). The median g of tumors in these patients (0.00082 per days; log g = -3.09) was about half that (P < 0.001) of tumors in patients receiving IFN-α (0.0015 per day; log g = -2.81). With IFN-α, the OS/log g correlation (Rsq = 0.14) was weaker. Values of g from measurements obtained by study investigators or central review were highly correlated (Rsq = 0.80). No advantage resulted in including data from central review in regressions. Furthermore, g can be estimated accurately four months before treatment discontinuation. Extrapolating g in a model that incorporates survival generates the hypothesis that g increased after discontinuation of sunitinib but did not accelerate.

CONCLUSIONS

In patients with mRCC, sunitinib reduced tumor growth rate, g, more than did IFN-α. Correlating g with OS confirms earlier analyses suggesting g may be an important clinical trial endpoint, to be explored prospectively and in individual patients.

Tumor regression and growth rates determined in two intramural NCI prostate cancer trials: The growth rate constant as an indicator of therapeutic efficacy

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Background: Like ATTP [bevacizumab + thalidomide + docetaxel + prednisone], ARTP [bevacizumab + lenalidomide + docetaxel + prednisone] is active in CRPC and in both the data suggest acquired resistance does not develop, supporting a strategy that continues therapy if tolerable. Discerning amongst new therapies in CRPC would be helped by novel assessment strategies that yield answers from smaller trials and allow comparisons across trials. We have validated a novel assessment method that quantifies tumor regression (d) and growth (g) rate constants using data obtained while pts are treated in a trial. We utilized this method to evaluate a phase II trial of ARTP in CRPC contrasting this with a previous study using thalidomide instead of lenalidomide (ATTP).

Methods: Using PSA values and a two-phase mathematical equation we determined d and g. A three-phase equation was used to determine resistant fractions.

Results: The median log g value with ARTP (-2.84) was statistically similar (p=0.204) to that observed with ATTP (-3.16). Both therapies had similar effects on log d (ARTP=-2.18; ATTP=-2.64; p=0.404). In a subset of pts with robust data both regimen are highly effective with only 3.01% and 5.46% of tumor resistant to ATTP and ARTP, respectively. In individual pt, statistically valid g and d values could be estimated after the fourth PSA value had been obtained, long before PSA increased - providing an early indicator of treatment failure. In most pts receiving prolonged treatment – as long as 700 d – the growth rate constant did not change, despite rising PSA values, indicating acquired resistance did not develop, and that if tolerable, therapy can be continued for longer periods of time.

Conclusions: The substitution of daily thalidomide with lenalidomide 14/21 days in ARTP resulted in a combination statistically as effective as ATTP. As with ATTP majority of pts experienced marked reductions in the tumor’s g, and surprisingly in most, there was no evidence of acquired resistance, g remaining unchanged over prolonged time periods. Given the tolerability of this combination, pts with marked reductions in g may benefit from prolonged ARTP therapy.

Twenty years of chemotherapy for colorectal cancer (CRC): Progress made, insights gleaned

596

Background: The past 20 years have seen progress in CRC therapy with more effective agents and better medical, surgical and supportive care.

Methods: We conducted a systematic review of 101 phase III and large phase II trials in CRC to quantify benefit over time with first-line and subsequent therapies. Outcomes examined in the experimental (EA) and control arms (CA) included progression-free survival (PFS), overall response rate (ORR), stable disease (SD), overall survival (OS) and post-treatment survival (PTS). Data were analyzed according to dates of publication and median enrollment.

Results: Significant outcomes are reported; most had R2 values > 0.6. OS of EA improved 0.83 mos/yr. Importantly the OS of CA improved 0.58 mos/yr likely reflecting use of experimental therapies in CA in subsequent studies and improvement in CRC care over time as suggested by: (1) modest improvements of PFS: 0.33 [EA] and 0.26 [CA] mos/yr; (2) PTS gains of 0.48 [EA] and 0.29 [CA] mos/yr, accounting for majority of OS gains; and (3) lack of OS improvement in 14 second/subsequent line trials. Using logistic regression to examine all drugs as class predictors of increasing OS, oxaliplatin [OX], bevacizumab [BEV], and irinotecan [IRI] were significant in the EA, but only OX and BEV were significant in the CA. Capecitabine [CAP] and cetuximab/panitumumab [CET/PAN] were not significant in EA or CA, with CAP odds ratio towards null and CET/PAN odds ratio away from null. The lack of IRI effect in CA concurs with observation that only IRI regimens had worse OS in CA compared with EA. The CET/PAN results likely reflect lack of efficacy/harm in patients with WT KRAS tumors. As expected PFS and PTS correlate highly with OS, but importantly ORR had very high correlations with both PFS and OS. SD emerged as an “adverse” outcome, OS decreasing as SD rates increase.

Conclusions: OS of CRC patients has improved gradually over past two decades, with gains from chemotherapy but also other factors, such as lead-time bias, more loco-regional approaches and improved supportive care. IRI performed better in EA than in CA. CET/PAN had negative effects in the entire population. In CRC, ORR correlates highly with OS, while SD portends a poor outcome.

Hazard ratios in cancer clinical trials--a primer

The increase and diversity of clinical trial data has resulted in a greater reliance on statistical analyses to discern value. Assessing differences between two similar survival curves can pose a challenge for those without formal training in statistical interpretation; therefore, there has been an increased reliance on hazard ratios often to the exclusion of more-traditional survival measures. However, because a hazard ratio lacks dimensions it can only inform the reader about the reliability and uniformity of the data. It does not provide practitioners with quantitative values they can use, nor does it provide information they can discuss with patients. Motivated by a non-scientific poll of oncologists in training and those with board certification that suggested only a limited understanding of the derivation of hazard ratios we undertook this presentation of hazard ratios: a measure of treatment efficacy that is increasingly used and often misused.

Determining the rate of tumor growth and decay in patients with metastatic breast cancer as an early efficacy endpoint: A study assessing ixabepilone efficacy

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Background: Early efficacy assessment in drug development should help find new cancer therapies. We have developed a novel method to analyze tumor response to therapy by quantifying the rate of tumor regression (d) and growth (g). We have shown g is slower when pts are on effective therapy and that g correlates with survival (Stein et al, Oncologist 2008). We utilized this method to evaluate a phase III trial of capecitabine (CAP) ± IXA in second line therapy (Tomas et al, JCO 2007) and a three-cohort phase II trial in second and subsequent lines of therapy in pts with MBC consisting of (1) Daily X 5 IXA given to taxane (TAX)-naïve patients (Denduluri et al, JCO 2007); (2) Daily X 5 IXA in pts previously treated with TAX (Low et al, JCO 2005); and (3) Daily X 3 IXA in pts previously treated with TAX (Denduluri et al, Invest New Drug 2007).

Methods: Using tumor measurements assessed by RECIST and a two-phase mathematical equation we determined d and g.

Results: In the phase III study g was superior to PFS identifying a significant difference between the arms very early—before the 200th pt had enrolled. In an individual patient the g values could be estimated as early as the 3rd evaluation, long before tumor growth was observed clinically. IXA + CAP in second line (g = 0.0018) was more effective than CAP (g = 0.0023) at reducing g, and more effective (p=0.0085) than single agent IXA in the Phase II study (g = 0.0027). Single agent IXA was comparably effective (p=0.814) in reducing the g of tumors previously exposed to a TAX (g = 0.0032) as in reducing the g of TAX-naïve tumors (g = 0.0035), consistent with its development as an agent active in TAX-refractory disease. Unlike differences in g, the d of single agent IXA (0.118) was comparable to that of IXA+CAP (0.0074) suggesting differences were primarily driven by effect on the growth of residual tumor.

Conclusions: Unlike PFS, an incremental measure of efficacy, g is a continuous variable and can more accurately assess differences between treatments. Because calculations of g are indifferent to assessment intervals, estimating a tumor’s g allows comparison of efficacy across trials.

Abstract 2620: Identification of cell context specific and pleiotropic effects of the histone deacetylase inhibitors romidepsin (depsipeptide) and vorinostat (SAHA)

Histone deacetylase inhibitors (HDIs) constitute a promising new class of anticancer agents that can induce growth arrest and apoptosis in malignant cells through histone decompaction and other, yet unknown mechanisms.

Although HDIs are effective in T-cell lymphomas, only occasional responses have been reported for solid tumors. To better understand these disparate effects, we have performed a systematic survey of 19 different cell lines representing various solid tumors with different molecular phenotypes. The cell lines were derived from breast (MCF-7, MCF-10A, SK-Br-3, MDA-MB-231), lung (A549, H460, EKVX, H146, H526), colon (HCT-116, HCT-116 p21-/-, S1, SW620), melanoma (MDA-MB-435, LOX IMVI, UACC-62), CNS (SF295), prostate (PC-3), and lymphoma (HUT-78), and their response to HDIs was studied at both the molecular and cellular level.

The effect of two different HDIs, romidepsin (depsipeptide) and vorinostat (SAHA), at several concentrations (3-fold serial dilutions of 0.1 – 30 nM depsipeptide, 0.1 – 30 uM vorinostat) and at different time points (8 – 24 – 48 – 72 – 96 h) were analyzed. The response parameters included cytotoxicity (MTT assay), flow cytometric analysis of cell cycle (propidium iodide), apoptosis (short exposure Annexin V), and mitotic arrest (TG3 staining). In addition, to enable high throughput screening of protein expression and modification (including histone acetylation, methylation, and phosphorylation), we took advantage of a newly developed, custom designed, reverse phase dot blot microarray containing 4992 spots per slide.

Multivariate analysis, including multiple regression and unsupervised hierarchical clustering of the data organized in heat-maps, revealed that the effects of HDIs are complex involving multiple proteins and pathways, and depend on the cellular context. In particular, cell cycle analysis revealed major differences in response to HDIs between cell lines, ranging from only minor changes in G1/S/G2/M distribution to profound G2 arrest (HCT-116 p21-/-) even at the lowest concentration (0.1 nM) of HDI. Such a nuanced picture was not observed with the standard MTT cytotoxicity assay, underscoring the value of cell cycle analysis in future drug-response studies. With a few notable exceptions, we observed good agreement between the Annexin V assay and the Sub-G0 population, both measures of apoptosis.

In conclusion, the two HDIs, romidepsin and vorinostat, have pleiotropic effects that are not confined to histone modification. The heterogeneous responses that we observe across different cell lines reflect the clinical situation with very variable outcome of HDI treatment. We believe that the mechanistic insights obtained in the current study will aid in the design of new and improved HDI treatment regimens, including combination therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2620. doi:10.1158/1538-7445.AM2011-2620

Mitosis is not a key target of microtubule agents in patient tumors

Mitosis-specific agents have, to date, not been clinically successful. By contrast, microtubule-targeting agents (MTAs) have a long record of success, usually attributed to the induction of mitotic arrest. Indeed, it was this success that led to the search for mitosis-specific inhibitors. We believe the clinical disappointment of mitosis-specific inhibitors stands as evidence that MTAs have been successful not only by interfering with mitosis but, more importantly, by disrupting essential interphase cellular mechanisms. In this Perspective we will review literature that supports a paradigm shift in how we think about one of our most widely used classes of chemotherapeutics-MTAs. We believe that the steady presence and constant physiological role of microtubules are responsible for the overall success of MTAs. While mitosis-specific inhibitors are effective on only a small fraction of the tumor mass (dividing cells), MTAs target tubulin, a protein that has crucial roles in both mitotic and non-mitotic cells.

25 EFFECT OF REPRODUCTIVE TRACT SIZE ON CONCEPTION RATES IN LACTATING DAIRY COWS UTILIZING A REPRODUCTIVE TRACT SCORING SYSTEM

Reproductive tract scoring (RTS) systems have been effective in evaluating fertility of heifers. A similar RTS system has not been reported in lactating dairy cows pertaining to conception rates following artificial insemination. Objectives of this study include development of a RTS system for lactating dairy cows and determining if RTS had an effect on artificial insemination (AI) success with various types of semen [conventional (CS), sexed (SS)]. During pre-breeding examinations (typically 30–60 DIM) by trained personnel, cows were assigned a RTS (1, 2, or 3) based on size and length of the cervix and uterine horns, but not including status of the ovaries. Tracts for RTS 1 were small, compact uterine horns resting within the pelvic cavity, RTS 2 were intermediate in size with uterine horns resting partially outside the pelvic cavity, and RTS 3 were large, deep tracts resting entirely outside the pelvis into the abdominal cavity. Additionally, cows were evaluated for RTS at a local abattoir before harvest, and tracts collected for volume and length measurements. Volume measurements were collected using Foley catheters and measuring water displaced in the uterine horns at a constant pressure. Length of the vagina, cervix, and uterine horns were measured using a flexible tape. Insemination data analysis was performed using mixed model analysis of variance in Glimmix SAS 9.2 (SAS Institute Inc., Cary, NC, USA). Insemination data included 613, 308, and 572 scores in first, second, and third+ lactation cows, respectively. First-lactation cows had 65.25% with RTS 1, 30.02% RTS 2, and 4.73% RTS 3. Second-lactation cows had 53.25% RTS 1, 39.29% RTS 2, and 7.47% RTS 3. Cows with 3+ lactations had 43.18% RTS 1, 43.88% RTS 2, and 12.94% RTS 3. Cows were artificially inseminated (n = 2401 inseminations) with either CS (n = 1981) or SS (n = 420). Conception rates for CS were 38.65%, 34.26%, and 24.41% for RTS 1, 2, and 3, respectively (P = 0.0154 for RTS 1 v. 3). Conception rates for CS (38.65%, RTS 1; 34.26%, RTS 2) were higher compared to SS (21.37%, RTS 1 (P = 0.0001); 20.72%, RTS 2 (P = 0.0186)). No differences were detected between CS (24.40%) and SS (22.35%) within RTS 3; however, observations were limited for SS inseminations with RTS 3. Preliminary data regarding total length (vagina, cervix, and uterine horns; RTS 1, 2, 3 = 103.1 cm, 114.9 cm, 134 cm, respectively) and volume (RTS 1, 2, 3 = 102 mL, 131 mL, 133.3 mL, respectively) suggest both increase as RTS increases but limited observations prevent conclusions at this time. Conception rates indicate smaller reproductive tracts have improved fertility in lactating dairy cows when using CS. Identification of larger reproductive tracts will allow for more economically efficient AI programs by utilising inexpensive, high fertility semen.

Abstract 2554: Copper transporter 2 (CTR2) is able to transport cisplatin and/or oxaliplatin in drug-resistant cell lines

The clinical use of platinum (Pt) agents is often compromised by the occurrence of drug resistance. Studies have shown reduced intracellular Pt accumulation in cells resistant to Pt drugs. Copper transporters have been reported to have a role in Pt influx and efflux. While the first member of this family, CTR1, has been shown to transport Pt, the role of the structurally similar CTR2 in Pt transport is unclear. The aim of this study was to assess the role of CTR2 in Pt based drug-transport using KB-3.1 cervical carcinoma cells and its cisplatin (KB-CP20) or oxaliplatin (KB-OX60) resistant subclones. In previous studies we reported that compared to parental cells the resistant cell lines have lower levels of intracellular Pt following cisplatin (CIS) or oxaliplatin (OX) exposure. We transfected parental KB-3.1 cells and its drug resistant sublines with CTR1, CTR2 or both transporters, and incubated cells with either CIS or OX. Intracellular Pt accumulation was not increased in any of the transfected parental KB-3.1 cells. In contrast, KB-CP20 cells transfected with CTR1, CTR2 or both trasnporters accumulated more CIS but not more OX compared to non-transfected KB-CP20 cells; while transfected KB-OX60 cells accumulated higher levels of both CIS and OX compared to non-transfected KB-OX 60 cells. In both resistant cell lines, the increased intracellular Pt observed after transtfection of the transporters was accompanied by increased DNA platination. Given the clinical utility of OX in colon carcinoma we next determined intracellular CIS and OX levels, the expression of proteins involved in copper transport (ATP7A, ATP7B, CTR1 and CTR2), and the IC50 for CIS and OX of six colon carcinoma cell lines. We found an inverse correlation between intracellular Pt levels and the IC50 of both drugs, and correlations between: (1) the IC50 of CIS and expression levels of CTR1, (2) intracellular CIS levels and expression levels of ATP7A, (3) expression levels of ATP7B and CTR2, and (4) OX accumulation and expression levels of ATP7A. In summary, we have shown CTR2 is able to transport Pt-containing drugs and increases intracellular Pt accumulation that is accompanied by greater DNA-platination. In unselected colon cancer cells, we have shown that the IC50 of a Pt based drug is determined by the intracellular accumulation of that drug, and to varying extent by the expression of copper transporters.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2554.

Value of stable disease (SD) in drug development of targeted therapies (TGT)

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It has been widely asserted that the efficacy of TGT cannot be assessed by traditional response measures since they are not expected to cause tumor shrinkage. Despite the lack of substantiating data, this idea has become conventional wisdom, often guiding clinical trial design. Aware the acceptance of SD as a measure of activity led to its being increasingly reported with traditional cytotoxic agents (CTX), we set about to methodically compare the occurrence of SD in phase II trials of TGT and CTX. We systematically catalogued response assessments in 147 phase II studies reported between 10/06 and 3/08 in 5 journals (Cancer, BJC, CCR, JCO, and Lancet Oncology). Eighty used CTX, 59 used TGT and 8 used both “classes” of agents. Thirty-eight properties including CR, PR, SD, PFS, and OS were recorded for each study. CTX and TGT studies were comparable with similar distribution of histologies and similar PFS and OS in these patients with refractory tumors. For CTX vs. TGT, the median numbers of pts/study was 47.1 vs. 51.9; median PFS, 5.55 vs. 4.54 mos; and median OS, 12.55 vs. 12.88 mos. SD was defined by duration in only 31% of studies, a median duration of 9.5 weeks. SD rates were nearly identical for the two therapy groups - 34.6% for CTX and 33.1% for TGT- and their distribution by histology was similar, suggesting properties other than therapy are responsible for SD. Correlations or lack thereof between %SD and PFS or OS were similar for both CTX and TGT. The overall response rate (CR + PR) was higher with CTX than with TGT (29.4% vs. 13.3%) and demonstrated a strong correlation (p<0.0001) of uncertain importance with PFS and OS for all therapies. Examination of 33 NSCLC studies (16 CTX/17 TGT) found similar results. We conclude that SD as currently defined and measured in not a property of TGT but of the phase II patient population and is similarly found with CTX. Responses are observed with TGT as with CTX, and this analysis suggests that even for TGT it is a measure of activity that should be sought. Assertions that SD is a particular characteristic of TGT should be replaced by definitions that seek clinically meaningful SD.

No significant financial relationships to disclose.