Chemotherapy just in case?
In regards to what "theoretical" microscopic disease may be left behind, spontaneous remissions in cancer suggests that the body can heal itself. It seems like most apparently occur in just a few types of malignancies: malignant melanoma, renal cell cancer, low-grade non-Hodgkin's lymphoma, chronic lymphocytic leukaemia and neuroblastoma in children. However, spontaneous remissions do occur in vastly different other types of cancers.
The very existence of spontaneous remissions represents a threat to some in the cancer industry. But such anomalies can pave the way to a better understanding of the causes of cancer which can then lead to rational therapies. Historical observations of spontaneous remissions of breast cancer after the onset of menopause lead to approaches of hormonal treatment which is a mainstay of adjuvant and palliative therapy in breast cancer.
Regardless, spontaneous remissions represent an important clue as to how the body can defend itself against cancer. Researchers should think "outside the box" at this important phenomenon rather than see it as a threat to their conventional thinking and appreciate the insight it may provide to rational approaches to cancer treatment.
For some common cancers, it is not clear that early detection and treatment actually prolong patients' lives. Early detection may just mean patients spend a longer time knowing they have cancer, and yet die at the same time they would have died anyway if the tumor had been diagnosed later. A decision to forgo cancer screening can be a reasonable option.
And the mutagenic (changes in form) effects of the wrong chemo can start the chain of metastatic events. A chemo-induced gene mutation can happen when the original chemo received does not work. The cancer can either continue to grow or comes back. When it does this, the tumor acts more aggressively. The mutagenic effects of chemotherapy on a genetically-unstable tumor, drives the tumor into a state of more aggressive behavior. You may even might kill off a whole lot of cancer, only to cause a mutation in the remaining cancer, such that the remaining cancer behaves in a more aggressive fashion.
When your first-line treatment does not work, there are several downsides:
It can take months for tests to confirm whether chemotherapy has been effective. If it has not, the cancer may have progressed. And then the patient, if strong enough, has to go back to square one and try again with something new.
Ineffective chemotherapy can cause the patient to become sicker or suffer serious side effects with no treatment benefit.
Many chemotherapies can cause mutations leading to drug-resistant tumors. Exposure to drugs may actually diminish subsequent benefit from treatment.
With patients absorbing a larger percentage of their own costs of care, the expenses associated with ineffective treatments become a personal financial burden.
Ineffective chemotherapy can diminish not just the quality of life but also the quantity of life through organ toxicity, immunosuppression, and/or by inducing mutations in genetically unstable tumor cells to more aggressive phenotypes.
The tumor microenvironment is characterized by regions of fluctuating hypoxia, low pH, and nutrient deprivation. Each of these microenvironment factors has been shown to cause severe disturbance in cell metabolism and physiology.
Both in vivo and in vitro data demonstrate that exposure of tumor cells to adverse conditions can directly cause mutations, contributing to genetic instability (Mutat Res;1998 May 25;400[1-2]:439-46).
Mutagenesis induced by the tumor microenvironment
Genetic Instability Induced by the Tumor Microenvironment
Genetic instability and the tumor microenvironment
Gregory D. Pawelski