Thanks, Carrie. Good afternoon and thank you for joining our first quarter 2021 earnings call. Everything we do at Guardant is motivated by our commitment to serve patients. In line with our patient first commitment, I will start off our call today with a patient story. Six years ago, a 64-year-old man was diagnosed with metastatic colorectal adenocarcinoma and went through numerous therapy regimens and surgeries. In the spring of 2020, his cancer recurred and his new oncologist ordered a Guardant360 test. A BRAF V600 E mutation was identified. It is estimated that this mutation occurs in approximately 8% to 10% of colorectal cancers. By identifying this actionable mutation, he was able to begin treatment with a combination of targeted therapies of encorafenib plus binimetinib only recently approved by the FDA. Fortunately, the patient responded to the subject therapy. But as we know, tumors are constantly evolving. After about six months, the patient was showing signs of progression. His oncologist ordered another Guardant360 test with our standard panel that includes tumor mutational burden, or TMB. The second Guardant360 test identified the patient's tumor as TMB high. A few months earlier, the FDA had approved pembrolizumab for patients with TMB high tumors of 10 mutations per megabase and above. So this finding opened up another therapeutic avenue for this patient. This story highlights how genomic profiling using Guardant360 can keep up with the evolution of a tumor and identify ongoing therapeutic options. Turning to our first quarter performance. We started the year strong, with revenue growing 17% to approximately $79 million. I am really proud of our team for their continued hard work this quarter, which translated to solid growth in our clinical business as well as progress across our product pipeline. As expected, we continue to see residual COVID impact at the beginning of the year, but over the course of the quarter as physician offices started to reopen, business improved further. Even with the persistent presence of COVID headwinds, clinical volume grew 21% to record levels of 18,390 tests. We continue to extend our position as the liquid biopsy leader for therapy selection and there is still a vast amount of greenfield opportunity ahead in this market. The underlying fundamentals of our clinical business are very strong, and we continue to see growth in both new physician adds and repeat orders. Even with the residual impact from COVID that we anticipate this year, we expect our clinical volume to grow more than 40% over 2020. We also made important progress on the reimbursement front. At the end of March, CMS confirmed that our Guardant360 CDx test meets the criteria for Advanced Diagnostic Laboratory Test or ADLT status, which is reserved for FDA approved tests as well as for innovative products that provide novel clinical information that cannot be obtained by any other method. With ADLT status, Guardant360 CDx will be reimbursed at a rate of $5,000 for all Medicare patients in line with our internal expectations. Now moving on to our recurrence monitoring opportunity with Guardant Reveal. We are very pleased with the tremendous enthusiasm we are hearing from oncologists since its launch in mid February. As a reminder, Reveal is the first blood-only liquid biopsy test for the detection of residual and recurrent disease. With a simple blood draw, the test improved disease management of early stage colorectal cancer patients by detecting ctDNA in blood after surgery to identify patients with a residual disease who may benefit most from adjuvant therapy, and by detecting recurrence months earlier than current standard of care. We believe Guardant Reveal is truly in a class of its own, with industry leading sensitivity and specificity and an average turnaround time of only seven days compared to other tests that require a tissue biopsy and have turnaround times of four to eight weeks. Much as we saw with the launch of Guardant360, a blood-only solution addresses the significant logistical challenges posed by tissues in this setting. Today, the standard of care is CEA, a blood test where you get your results a few days later. Importantly, Guardant Reveal fits into an oncologist workflow in the exact same way as CEA is used but gives them extraordinarily better performance. CEA has a sensitivity of 59% with 64% specificity in the surveillance setting versus 91% sensitivity with 100% specificity for Guardant Reveal. So, they are getting the better product market fit with the benefits of improved performance. It is still early but we are seeing strong uptake from both new users as well as customers that have been using other products on the market and benefiting from the deep relationships we have within the oncology community. From the onset, we have said that it takes more than just great technologies to drive durable, long-term adoption of new products. This type of sustained growth requires seamless integration into clinical workflows, demonstrated clinical utilities, regulatory approval and broad reimbursement. As for our work with Guardant360, we are committed to achieving excellence in each of these to ensure that our product drives superior value to the market and maximizes access for patients. We are making great progress in the reimbursement front and are confident we will have Medicare reimbursement in place for Guardant Reveal by end of 2021. At the beginning of April, the New York State Department of Health Clinical Laboratory Evaluation Program, or CLEP, approved Guardant Reveal for the detection and monitoring of MRD in patients with early-stage cancer. This approval is an important proof point for Reveal and builds on our commitment to improving care for all cancer patients by expanding access to our test through compliance with the appropriate clinical laboratory regulations. I'm so excited about what is ahead for Guardant and believe 2021 will be a pivotal year for us as we expand our product portfolio and invest across our business to build the foundation for complete cancer testing across the continuum of care. Looking ahead, in our therapy selection business, we will continue to expand the utility of Guardant360 with additional clinical data and broaden use of the test in the molecular response and monitoring settings. There have been more than 40 publications to date that highlight the utility of Guardant360 in this setting. We have generated data across multiple tumor sites; including lung, breast, gastric and bladder cancers, and multiple classes of therapies, including immuno-therapies that demonstrated detecting Guardant360 test a few weeks after treatment initiation can segment responders versus non-responders. To that end, a new study recently published in JCO Precision Oncology shows that Guardant360 provides an early indication of treatment response to pembrolizumab-based immunotherapy by detecting molecular response as measured by changes in circulating tumor DNA levels early on. This study adds to the growing body of evidence showing that our Guardant360 test can effectively measure molecular response, giving clinicians an earlier indication of whether to continue or stop treatment, to explore other therapeutic regimens, or to enroll the patient in the clinical trial. Monitoring molecular response is an important application of our technology platform that will soon usher in a new era of adaptive management of treatments and disease, all within the reach of any oncologist using a simple blood draw. We are also looking forward to the upcoming launch of our first tissue product, which we believe will address the unmet need that persists in the therapy selection market today due to the challenges with many of the existing tissue offerings. In recurrence monitoring, we will continue to drive the adoption of Guardant Reveal just as we did with Guardant360 several years ago, ushering in a new era of precision oncology for earlier stage patients. And finally in screening, we expect to complete enrollment of our ECLIPSE trial before the end of the year and to begin work in our expansion into other cancers types. To support our ambitious vision, we are continuing to grow our incredible team. I'm excited to welcome Dr. Craig Eagle who recently joined Guardant as our new Chief Medical Officer. Craig most recently served as Vice President of Medical Affairs Oncology for Genentech where he oversaw the medical programs across the oncology portfolio. Craig has a wealth of experience driving medical affairs, clinical development and clinical trial operations at leading pharmaceutical companies, and he will undoubtedly make a great impact as we continue to develop and commercialize best-in-class products and scale the company for the future. With that, I will now turn the call over to AmirAli for more details on our biopharma business and our pipeline activities.