Friday, May 12, 2023

AI Example: GPT4 Analyzes and Compares Two Moldx LBx Press Releases

One capability of GPT4 is to analyze and compare two different documents, such as press releases on related topics but from different companies.

Here, I asked GPT4 to read and compare two presses releases related to MolDx program coverage.  The first press release, 2023, explains Guardant coverage for MRD immunotherapy monitoring.  The second press release, 2022, explains Natera coverage for bladder cancer using MRD.   

I have not altered what GPT4 wrote, although I might have written different answers as a human expert.  This is just an exercise to see what GPT4 might do.   Note that GPT 4 has a random factor, so if the exact same questions were asked again, the results would vary.  My full prompt and press clippings are here.


Medicare “MOLDX” is a program that gives coverage for new molecular cancer tests.  One important area is minimal residual disease testing, which is looking for traces of cancer DNA in the patient’s blood.   MOLDX issues this coverage one test (and one cancer) at a time.  

Below, PART ONE is a press release from the company GUARDANT getting coverage for immunotherapy response.  The test is called “RESPONSE (TM)”.    PART TWO is a press release from the company NATERA getting coverage for its SIGNATERA (TM ) test in bladder cancer.

Please summarize each press release.  Please contrast and compare the two press releases for key similarities and differences.  

GPT4 Answers: (verbatim)


Guardant Health has received Medicare coverage for its Guardant360 Response test under the Molecular Diagnostics Services program (MolDX). This test is the first blood-only liquid biopsy that can monitor molecular response to immune checkpoint inhibitors in patients with metastatic or inoperable solid tumors. Following this decision, the test is now covered for Medicare patients in the U.S. who are on an immune checkpoint inhibitor therapy. The coverage includes a Guardant360 CDx or LDT test to establish a ctDNA baseline before therapy and a Guardant360 Response test 4 to 10 weeks after the start of the therapy to measure the change in ctDNA level. This adds to the existing Medicare coverage of Guardant Health tests for cancer patients.


Natera, a leader in cell-free DNA testing, has received coverage from the CMS Molecular Diagnostics Services Program (MolDX) for its Signatera molecular residual disease (MRD) test in patients with muscle invasive bladder cancer (MIBC). This decision is based on evidence from multiple validation studies showing that the Signatera test can provide early assessment of therapy effectiveness in both neoadjuvant and adjuvant settings. This represents the first coverage expansion under the foundational local coverage determination (LCD) for MRD testing in solid tumors (LCD L38779). This addition complements the existing Medicare coverage for Signatera in colorectal cancer and for pan-cancer immunotherapy monitoring.


Both press releases announce the expansion of Medicare coverage for their respective molecular diagnostic tests, Guardant360 Response by Guardant and Signatera by Natera. Both companies operate under the Molecular Diagnostics Services program (MolDX) and both tests offer non-invasive, blood-based solutions for monitoring cancer progression and response to therapy.

The primary difference between the two is the specific application and function of the tests. Guardant's Guardant360 Response test is specifically designed to monitor the response of metastatic or inoperable solid tumors to immune checkpoint inhibitor therapy. It includes a baseline ctDNA test before therapy and another one 4 to 10 weeks after the start of therapy.

Natera's Signatera test, on the other hand, is focused on detecting minimal residual disease (MRD) in patients with muscle invasive bladder cancer. Its coverage expansion is based on the demonstrated ability of the test to provide an early assessment of therapy effectiveness in both neoadjuvant and adjuvant settings. This is the first expansion of coverage for MRD testing in solid tumors under a foundational local coverage determination (LCD).

In summary, while both tests are designed to monitor cancer progression and response to therapy, they target different types of cancer and have different specific uses.


HUMAN:  Can you say anything or infer anything about how the MolDx program makes its decisions?

GPT4: (Verbatim)

The MolDx (Molecular Diagnostic Services) program is administered by Palmetto GBA, a Medicare Administrative Contractor. It was developed to identify and establish coverage and reimbursement for molecular diagnostic tests.

From the press releases you provided, we can infer several factors that MolDx considers when making decisions about coverage:

Clinical Validity: The MolDx program seems to require robust evidence of the test's clinical validity. Both Guardant and Natera presented data from multiple studies showing that their tests are reliable and effective for their intended uses.

Clinical Utility: In addition to proving a test's clinical validity, companies likely need to demonstrate its clinical utility. This means showing that the test can provide information that will help doctors make better decisions about patient care. For instance, the Guardant360 Response test can help doctors track a patient's response to immune checkpoint inhibitor therapy, and the Signatera test can provide an early assessment of therapy effectiveness in both neoadjuvant and adjuvant settings.

Unmet Medical Need: The MolDx program may also consider whether a test addresses an unmet medical need. The Guardant360 Response test is the first blood-only test that can monitor molecular response to immune checkpoint inhibitors, and the Signatera test addresses a high rate of recurrence in muscle invasive bladder cancer.

Quality and Quantity of Evidence: It appears that MolDx requires a substantial amount of high-quality evidence to grant coverage. Both Guardant and Natera cited multiple validation studies in their press releases.

Test's Relevance to Medicare Population: Given that MolDx is a Medicare program, the tests likely need to be relevant to diseases and conditions common in the Medicare population. Both cancer monitoring tests would fall into this category.

It's worth noting that while these inferences seem consistent with the press releases, the exact decision-making process of MolDx isn't specified in these documents. The actual process could be more complex and involve other factors not mentioned here.

Repeat - responses are GPT4 responses verbatim, with no human edits. A human expert might respond differently.