PIK3CA mutations in plasma circulating tumor DNA predict survival and treatment outcomes in patients with advanced cancers

Background

Oncogenic mutations in PIK3CA are prevalent in diverse cancers and can be targeted with inhibitors of the phosphoinositide-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway. Analysis of circulating tumor DNA (ctDNA) provides a minimally invasive approach to detect clinically actionable PIK3CA mutations.

Patients and methods

We analyzed PIK3CA hotspot mutation frequency by droplet digital PCR (QX 200; BioRad) using 16 ng of unamplified plasma-derived cell-free DNA from 68 patients with advanced solid tumors (breast cancer, n = 41; colorectal cancer, n = 13; other tumor types, n = 14). Results quantified as variant allele frequencies (VAFs) were compared with previous testing of archival tumor tissue and with patient outcomes.

Results

Of 68 patients, 58 (85%) had PIK3CA mutations in tumor tissue and 43 (74%) PIK3CA mutations in ctDNA with an overall concordance of 72% (49/68, κ = 0.38). In a subset analysis, which excluded samples from 26 patients known not to have disease progression at the time of sample collection, we found an overall concordance of 91% (38/42; κ = 0.74). PIK3CA-mutated ctDNA VAF of ≤8.5% (5% trimmed mean) showed a longer median survival compared with patients with a higher VAF (15.9 versus 9.4 months; 95% confidence interval 6.7-17.1 months; P = 0.014). Longitudinal analysis of ctDNA in 18 patients with serial plasma collections (range 2-22 time points, median 5) showed that those with a decrease in PIK3CA VAF had a longer time to treatment failure (TTF) compared with patients with an increase or no change (10.7 versus 2.6 months; P = 0.048).

Conclusions

Detection of PIK3CA mutations in ctDNA is concordant with testing of archival tumor tissue. Low quantity of PIK3CA-mutant ctDNA is associated with longer survival and a decrease in PIK3CA-mutant ctDNA on therapy is associated with longer TTF.

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Testing for PIK3CA mutations in ctDNA is concordant with testing of tumor tissue.

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High PIK3CA-mutant abundance in ctDNA was associated with shorter survival.

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Increasing PIK3CA-mutant abundance in serial blood samples was associated with shorter TTF.

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Longitudinal monitoring of PIK3CA-mutant ctDNA tracked with cancer clinical course.

Relative value of serum cytokines and clinical factors in predicting weight loss in advanced pancreatic cancer (PC)

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Background: The identification of PC patients at high risk for cachexia may allow for early intervention to prevent this outcome. Symptoms such as pain, nausea, and anorexia might predict weight loss. Likewise, inflammatory cytokines are also associated with cachexia. We evaluated the ability of each to predict weight loss in patients beginning treatment for PC.

Methods: We evaluated 44 newly diagnosed advanced or metastatic PC patients for baseline symptomatology via the M. D. Anderson Symptom Inventory (MDASI). This survey assesses symptom severity, such as nausea, vomiting, fatigue, pain, diarrhea, and constipation, on a 1-10 scale. Baseline serum levels of IL-1a, IL-1b, IGF-1, CXCL-12, CXCL-16, CRP, IL-6, IL-8, VEGF, CEA, and CA 19-9 were assessed. Logistic regression analysis was performed to determine the odds ratio (OR) and confidence interval (CI) for the association of different parameters with 10% weight loss at 60 days from treatment initiation. Student t-test was used to compare the mean values across different strata.

Results: A weight loss of >10% was observed in 15 patients (34%). Only the use of mild (but not strong) opioids was associated with weight loss; estimated OR = 6.2 (C.I. 1.2-31.9, p=.03). No association was observed for the MDASI parameters. Baseline levels of cytokines were available for 23 patients. We observed significant differences in the mean values of CXCL-16 (p=.05) and IL-6 (p=.045) in patients with weight loss as compared to those without weight loss. Moreover, serum level of erythropoietin may be negatively associated with weight loss (p=0.06).

Conclusions: Alterations in serum cytokine levels may correlate more strongly with cachexia than clinical symptoms and underscore the importance of cytokine analysis in identifying PC patients at high risk for cachexia.

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Retrospective evaluation of patients with colorectal cancer (CRC) and type II non-insulin-dependent diabetes (NIDDM)

507

Background: Patients with NIDDM have an increased risk of colorectal adenomas and CRC possibly mediated through the insulin growth factor receptor pathway. Metformin is associated with anticancer efficacy in preclinical models and a lower risk of cancer mortality in patients with NIDDM. We undertook to evaluate the difference in outcome in NIDDM patients with CRC based upon their medications taken for glycemic control.

Methods: We conducted an IRB-approved (DR09-0719) retrospective analysis of 4,758 patients seen at a single institution (University of Texas M. D. Anderson) with CRC between the years of 2005-2008, to determine the prevalence of NIDDM in this patient population, in addition to determining whether patient survival differs based upon their diabetic therapy.

Results: 425 out of 4,758 CRC patients (8.9%) were identified as having NIDDM. Gender, male:female 283:142 (67%, 33%), age, mean 62 years (range 31-91), stage I/II/III/IV 37:55:175:158 (8.7%, 12.9%, 41.2%, 37.2%). Overall survival (OS) for the 397 patients with follow-up data available, by univariable Kaplan Meier analysis, was 63.7 months (95% confidence interval (CI), 52.3-75.5). Patients with NIDDM and CRC treated with metformin as one of their diabetic medications had a survival of 76.9 months (95% CI, 61.4-102.4) as compared to 56.9 months in those patients not treated with metformin (95% CI, 44.8- 68.8), p = 0.048. By using a Cox regression model adjusted for age, sex, race, body mass index, and initial stage of disease we demonstrated that NIDDM patients treated with metformin had a 30% improvement in OS when compared to NIDDM patients treated with other diabetic agents. There was a non-statistically significant trend toward higher complete and minor pathologic response rate (≤ 10% residual tumor) in NIDDM patients with rectal cancer receiving chemoradiation who were treated with metformin when compared to those who were not (14/19, 74% vs. 9/19, 47%, p = 0.09).

Conclusions: In this analysis the use of metformin in NIDDM patients with CRC was associated with an improved overall survival. While these results are consistent with the findings in other solid tumors they will need to be validated in other colorectal cancer data sets.

No significant financial relationships to disclose.

Self-report of neuropathy from oxaliplatin-based regimens in the treatment of colorectal cancer: With or without bevacizumab

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Background: Neuropathy attributed to oxaliplatin-based chemotherapy is a dose limiting factor in the administration of chemotherapy. With premising clinical outomes, bevacizumab (BV) has been added with colorectal cancer (CRC) patients in first line and second- line therapy. Although toxicity been well documented, there is no evidence of the impact of adding BV to oxaliplatin-based chemotherapy on patient's neuropathy development during therapy.

Methods: The study enrolled 66 colorectal cancer patients naïve to oxaliplatin or to any microtubule stabilizing agents scheduled for oxaliplatin-based chemotherapy, 29 (44%) of whom also received BV. From first therapy cycle start date, patients rated symptoms weekly during chemotherapy via the M. D. Anderson Symptom Inventory (MDASI), and continued symptom assessment every two weeks for up to 48 weeks. Longitudinal symptom responses were analyzed by mixed-effect modeling which controlled for age, sex, staging, prior diabetes, and total cycles of chemotherapy received. All cases completed at least 2 cycles chemotherapy.

Results: A third of the sample was female; 24% were older than 65 years; 59% with stage IV disease. The five most severe symptoms were numbness, fatigue, sleep disturbance, drowsiness, and distress on MDASI symptom items. The severity of patient-reported numbness/tingling, rated on MDASI, increased overtime in following 48 weeks after started therapy (p < 0.0001). Oxaliplatin-based therapy plus BV, compared to no BV in the regimen, resulted a significant lower severity on numbness/tingling during the study period (estimate = -1.1325, p = 0.0005). Older patients reported more numbness/tingling. In contrast, pain severity remained low during the initial cycles of therapy, but significantly increased over time during therapy. Therapy with or without BV did not produce differences in pain development.

Conclusions: This prospective study suggests that adding BV to standard oxaliplitin-based therapy for CRC was associated with significantly reduced numbness/tingling development. This observation needs to be confirmed in larger studies. The mechanism(s) by which neuropathy could be attenuated by BV are unknown.

No significant financial relationships to disclose.

Gemcitabine, docetaxel, and capecitabine (GTX) in the treatment of metastatic pancreatic cancer (PC): A prospective phase II study

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Background: We have found that the combination of gemcitabine, docetaxel, and capecitabine (GTX), when administered in a specific sequence, will induce a p53 independent pathway of cell death through the MAP kinase pathway. The sequence overcomes drug resistance in PC cells in vitro. We have begun a prospective, phase II trial of GTX in patients with metastatic PC as first-line therapy. Methods: 23 patients with metastatic PC, ECOG 0–2 were enrolled at either Columbia or a community practice. Each cycle was administered over a 21 days. Capecitabine was administered at 750 mg/m2 twice daily for 14 days. Gemcitabine (750 mg/m2 over 75 minutes) and docetaxel (30 mg/m2) were administered on days 4 and 11. Responses were measured by CT (RECIST) and PET after every three cycles. A response by PET was defined as a 50% reduction in SUV while a CR was an absence of uptake. Results: Median age was 61, including 8 men and 15 women. Metastatic sites included liver (87%), abdomen (65%), and lung (17%). 70% of liver positive patients had at least five metastases. 22% had malignant ascites. 16 patients remain alive and 7 have progressive disease. Median survival has not yet been reached. Progression occurred at a median of 5.1 months. By CT, the response rate at metastatic sites was 39% (17% CR / 22% PR). Stable disease was observed in 48% at metastatic sites. PET showed a 53% response rate at metastatic sites. At the primary site, CT showed a 30% response rate including 17% complete responses. By PET criteria, there was a 31% response rate and a 26% CR rate at the primary site. In three patients, a PET response heralded a CT response by three cycles. In one patient, progressive disease on PET preceded progression on CT by two months. Toxicity: Grade 3 leukopenia and thrombocytopenia were 13% and 9%, respectively. There was no grade four hematologic toxicity. One patient experienced lung disease related to gemcitabine and withdrew from the study. A second patient experienced grade 4 mucositis, thrush, and sepsis which was presumed due to DPD deficiency. Grade 3–4 toxicities: HFS: 9%. There was no grade 3–4 diarrhea. Conclusions: GTX, elicits a promising response rate when used in metastatic P.C. PET detects a response and failure of chemotherapy earlier than CT scans.

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