Why Does Cancer Come Back Even After Best Treatment? Concept Of Micrometastases

Cure rates for cancer are better now than ever before.  In spite of this, cancer can recur.  This article discusses why and how cancer sometimes comes back even after potentially curative treatment.

In the year 2007, 51-year-old Geetanjali(name changed), a single mother of two college-going daughters, was referred to me with a recently diagnosed cancer of the thyroid gland.  She underwent surgery and was recommended post-operative radio-iodine treatment and endocrine therapy, which she took.  Three and a half years later, she developed a recurrence of the cancer in the lymph nodes of her neck.  She underwent a second surgery to remove the recurrent cancer – this surgery was a longer one than her first one.  Eleven years after her second surgery, the proud grandmother of three children is completely free of cancer and is living a normal life.

Her questions eleven years ago were:

  1. Why did the cancer come back?
  2. Was the initial treatment not adequate?
  3. Could anything else have been done to prevent it?
  4. Can anything else be done to prevent it from coming back again?

This article addresses the first question – why does cancer come back?

The principle of curative cancer treatment is to eradicate all cancer without leaving even a single cancer cell behind.  Extensive spread to distant organs (called metastatic disease) can preclude cure.  Thus, pre-treatment evaluation is aimed at ruling out extensive metastases where cancer cannot be removed completely.

Sometimes, however, very tiny amounts of disease could have spread from the original cancer, lurking in different parts of the body.  The best available medical tests and scans may not be able to pick up this spread.   This disease which is too small to be detected by currently available diagnostics is called micrometastasic disease.  The more aggressive the cancer, and higher the stage at diagnosis, the higher is the chance of micrometastatic disease.

Curative treatment is aimed at removing all cancer completely.  A patient is offered curative treatment when all detectable cancer can be eradicated by treatment like surgery, radiotherapy, or chemotherapy (or a combination of these). In addition, for every patient (based on various factors), the possibility of undetected micrometastatic disease can be estimated.  Potential micrometastatic spread is the reason why many cancer patients are given adjuvant (additional) therapy even after the complete removal of all detectable cancer.  And early detection of recurrence is one of the reasons why cancer patients are advised regular follow-up.

Consequently, a cancer recurrence is not actually cancer that has “come back”.  It is cancer that was always present but has only now grown to a size that is detectable.

A corollary to this is – the longer a cancer survivor remains recurrence-free, the lesser the chances of recurrence in the future.

Many recurrent cancers can be treated again and cured, provided they are detected in time.  For some cancers, the chances of recurrence become so low after a certain period of time, that follow-up is no longer required.

To summarize, recurrence is a recognized characteristic of cancer.  The chances of recurrence vary and can be reasonably estimated for an individual patient.  Optimal treatment and follow-up are important to achieve the best possible outcomes.

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