Tracking Your Progress
While patients are being treated with immunotherapy, doctors can monitor their progress with blood tests or imaging. A range of tests have been developed or are being explored to inform patients and their doctors about whether their cancer is responding to the treatment. Early and frequent testing can make sure each patient is treated with the right therapy at the right dose.
Imaging may include computed tomography (CT) scans, x-rays, positron emission tomography (PET) scans, and magnetic resonance imaging (MRI). With these tests, doctors hope to visualize the effect of the treatment on the size of the tumor. Patients enrolled in immunotherapy clinical trials might undergo imaging tests designed to provide information on more than just the size and shape of the tumor (Juergens 2016). For instance, a variation of PET can be used to monitor immune status, and an iron oxide nanoparticle probe can be used with MRI to monitor macrophages in tumors (Iv 2015; Radu 2008).
In addition to imaging, blood-based assays can provide information on response to immunotherapy. Several blood-based biomarkers are used to indicate the current tumor burden. As tumors grow, whole cells or cellular components like DNA or proteins are released into the bloodstream. The tumor-derived material can be detected by laboratory tests. Biomarker technology is advancing just as fast as immunotherapy, and new biomarkers in development use multi-color laser imaging, protein microarrays, and high-throughput DNA sequencing to give extensive information to doctors and patients on how a drug is affecting the body (Yuan 2016).
Some common blood-based biomarkers include:
Prostate-specific antigen (PSA) is a reliable protein marker in blood for monitoring the response of prostate tumors to treatments (Kiper 2005; Fong 2009). Successful treatment will reduce PSA, and the levels may become undetectable. A rise in PSA can indicate that the therapy is not working (Wilkinson 2008; NCBI 2017).
Carcinoembryonic antigen (CEA) is a tumor marker in blood that can be used to monitor some patients, most commonly those with colorectal cancer (Das 2017). As with PSA, successful treatment will reduce CEA levels (Lech 2016; Patel 2010).
Levels of another protein, called cancer antigen-125 (CA-125), are often monitored in blood after treatment of patients with ovarian cancer (Kobayashi 2012). If CA-125 levels drop, the treatment is effectively fighting the cancer (Gupta 2009).
Response to breast cancer therapy can be monitored in blood with a tumor marker called cancer antigen 15-3 (CA 15-3) (Henry 2014).
Circulating Tumor Cells
Whole cancer cells also circulate in the blood of cancer patients and can be used to monitor response to treatment. Circulating cancer cells are rare, often fewer than 10 per milliliter of blood, but scientists have developed extremely sensitive isolation and analysis methods (Miller 2010). Circulating cancer cell analysis is not standard clinical practice but is increasingly used in laboratory and clinical studies, including studies of immunotherapies. For example, in a phase III trial of a whole-cell vaccine for melanoma patients, those without circulating cancer cells were significantly more likely to survive at least three years (Hoshimoto 2012). More information about circulating tumor cell testing is available in the Cancer Treatment: The Critical Factors protocol.
T cell counts
For patients being treated with immunotherapy, a detailed analysis of the immune cells is helpful. The total number of T cells is important, but cytotoxic T cells, which are critical to many immunotherapies, should also be monitored (Nonomura 2016; Klinger 2012).
Circulating Tumor DNA
In addition to proteins and whole cells, small amounts of tumor DNA can also be found in blood. If the tumor-specific DNA modifications are known, the amount of circulating tumor DNA can be used to monitor response to treatment (Xi 2016; Gremel 2016). One study suggests breast cancer recurrence can be detected earlier with circulating tumor DNA than with other clinical techniques (Olsson 2015). Circulating DNA biomarkers are not standard clinical practice, but are part of some ongoing clinical trials (Krishnamurthy 2017).
NK cell counts
A number of the supplements described in the Integrative Interventions section may boost the number of NK cells in blood. NK cells can destroy cancer cells directly and also facilitate the effects of many immunotherapies. For some patients, monitoring NK cell numbers can be informative (Sun 2011). Studies of antibody-dependent cellular cytotoxicity antibodies often quantify the number of NK cells in the blood and determine whether they are activated (Chow 2016).
Disclaimer and Safety Information
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