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Cancer 101 FAQ: My oncologist told me my counts are low, so I need to delay my next chemo treatment? Is this going to be harmful?
It’s not unusual to need to delay treatment and adjust the chemotherapy dosing based on low blood counts or other side effects. That approach is built into our standard treatment algorithms to account for the variability in individual people and a need to keep people as safe as possible during aggressive treatment. Standard dosing is conventionally based on a typical maximal tolerated dose for a given drug or regimen, meaning that you often run on the high side and therefore may well need to gradually adjust the treatment dose based on real-time feedback of a person’s low blood counts or other treatment-related prohibitive side effects. It’s therefore a common occurrence and not a terrible complication to need to delay the next treatment and/or lower the treatment dose over the course of therapy.
In terms of the interval of treatment delays, there’s no clear best answer, but delays are often arbitrarily given in week intervals. This is often in the ballpark of the amount of time it takes for blood counts to recover from prohibitively low levels to a threshold for safe administration of further chemotherapy. If we assume that three weeks between treatments is the standard for a particular regimen (such as a single day every three weeks or days 1 and 8 of a 21 day schedule), and some people need an extra week or two for their blood counts to recover to a safe level, that’s delay isn’t a meaningful break in terms of a gap in treatment (for better or for worse — it isn’t much “time off” to either feel better or not be actively treating the cancer, depending on your greater concern), but instead is just the required time to recover from the ongoing effects of the most recently administered treatment. We consider the chemo to be working during that time. It’s also important to know that if counts are low, the risks of delaying a week or two for counts to recover to a safer level, and/or the risks of lowering the dose of treatment, are very likely less than than the risks of infection, bleeding, etc. that may occur from treating too early.
Cancer 101 FAQ: How Do You Assess Response to Cancer Treatment?
For most cancers, there is visible evidence of a cancer on scans such as CT scans that are done periodically during the course of a patient’s treatment. A baseline scan is done, ideally just shortly before the start of treatment, and new scans done after some fixed duration of treatment are then compared with the new scans. The general concept is to see whether the repeat scans demonstrate tumor shrinkage, an increase in the size of measurable disease or new lesions (indicating progression), or stable findings. For clinical trials, there is a formal definition of complete response, partial response, stable disease, or progression that are incorporated into the RECIST criteria (Response Evaluation Criteria in Solid Tumors), but clinical practice doesn’t tend to be as precise. Obviously, we are happy to see tumor shrinkage even if it falls shy of the formal definition of a partial response, and stable disease is often very welcome compared to an alternative of disease progression.
Cancer 101 FAQ: I was told I have lung cancer, but it went to my spine, so do I also have bone cancer?
No, but this is a very common misinterpretation.
Cancer is categorized by the cell type from which a cancer developed. The place where cancer begins is called the primary cancer. Cancer can spread via the bloodstream (metastasize) to other parts of the body and grow in these other areas. Typical areas for a cancer to metastasize to include the liver, the lungs, the bones, the brain, and the adrenal glands (on top of the kidneys) — but different types of primary cancers have a greater or lesser tendency to spread to particular parts of the body. Colon cancer tends to spread to the liver, while prostate cancer classically spreads to the skeleton. Lung cancer can spread to all of these places.
Cancer 101 FAQ: Primer on PET Scans
The following content is offered by the moderators and is adapted from text that appears in several different posts and discussion threads on this topic.
PET stands for “positron emission tomography”, and a PET scan is a procedure designed to identify abnormal cellular activity that might indicate cancer. A prominent use for the PET scan (or combination PET/CT) is in achieving accurate staging of cancer.
In a PET scan, the patient is injected with a glucose-based tracer substance: think of it as a “hot sugar” . The PET scan picks up where this sugar localizes in the body. The idea in use for oncology is that the cancer cells, because they’re very active, eat up more sugar than non-cancerous cells and so the cancer cells will collect this tracer and will appear brighter on the scan than normal tissue.
PET scan results are reported in “SUV” units, in which SUV stands for “standardized uptake value”. The SUV is just a measure that indicates how bright the tissue is on the scan; that is, how much cellular activity is occurring in that area. This activity can represent various things, from inflammation to infection to cancer. There is no threshold SUV number that distinguishes cancer from inflammation or infection, but higher numbers (especially in the high single digits or more) are most suggestive of cancer.
PET scans are very sensitive (finding abnormality when one exists), but not perfectly specific, meaning that they can be positive for things other than cancer. In reviewing the PET scan, medical personnel look for the shape and location of the abnormal activity as well as the SUV number.
Most cancer types (e.g., lung, breast, colon) show up well on PET scans. Certain cancers (e.g., renal cell) are not seen as well with the PET scan. Some areas of the body (e.g., heart, brain, sometimes the bowels) normally have a significant glucose uptake/metabolic activity anyway, soincreased SUV numbers in those areas are of less concern than high activity in other areas. Given this activity, other types of scans (e.g., MRIs) might be more useful than PET scans for imaging certain tumors (e.g., brain tumors).
Some studies have supported a correlation of cancers with higher uptake (maximum SUV) being associated with a more aggressive clinical behavior, or conversely, low PET uptake with a more indolent clinical behavior of the cancer. In addition, though PET scans are not a standard imaging test for assessing response to therapy (compared with the far more established CT scan), some research suggests that PET scans may provide early feedback about the clinical benefit of lack of benefit from a systemic therapy. However, PET scans also tend to pick up inflammation in the area of recent prior surgery or radiation and are therefore well known to be very difficult to interpret in that setting. Continue reading
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