Throughout my practice as a radiation oncologist, I have noticed a recurring question that patients ask; “If the surgeon sticks a needle into the tumor or if they expose the tumor to air, will the tumor spread?”  The answer to the question is that realistically, the possibility is very low. In 2015, the Mayo Clinic analyzed 250 patients that had biopsies and found no risk of tumors spreading associated with the procedure. They went further and analyzed 2,000 Medicare patients with pancreatic cancer and found no significant difference in cancer spread between those that had a biopsy versus those that did not.

I was not able to find any scientific surgical data that indicates exposing a tumor to air will cause it to spread.  Unfortunately, there are old case reports where tumors were ruptured, directly transected, and contamination of surgical instruments increased the risk of spread or contamination. However, today’s modern surgical techniques minimize these risks. Imaging studies such as CT scans, ultrasounds, PET scans, and MRI imaging allow better visualization of the tumor size, shape, blood supply, etc.  These technologies have allowed surgeons to plan ahead on their surgery. Common examples include giving preoperative chemotherapy and radiation for locally advanced rectal cancers. Studies show this results in improved sphincter-sparing (not having a permanent colostomy) as well as improving the chances cancer doesn’t come back locally after surgery. In breast cancers, imaging studies such as MRI have allowed some patients to be treated with chemotherapy before surgery, to shrink a tumor’s size to improve surgical outcomes and increase the possibility that breast conservation therapy can be done.

Related reading: 12 Common Myths About Cancer

The importance of a biopsy or surgery is critical for a patient’s cancer treatment. A biopsy documents the presence of cancer. For most cancer treatments, more than one type of treatment is used; this includes surgery, chemotherapy, and radiation. Thus, it is important to ensure the risks involved with treatment is applied to cancer and not a benign tumor.

Biopsies are also necessary not only to justify risks of therapy but to also establish proper treatments. For most malignancies, surgery plays a primary role by removing the tumor and allowing chemotherapy and radiation to target what may have escaped or microscopic cells that may have been left behind after surgery.

A good example where surgery is not required for a cure would be anal cancer.  These tumors can be cured entirely with chemotherapy and radiation. However, these tumors can sometimes be hard to distinguish between a deficient lying rectal cancer.  For rectal cancer, treatment would require not only chemotherapy and radiation but also a radical surgery that sometimes leads to a permanent colostomy. The only way to distinguish these vastly different tumors and treatments is with a biopsy.

Unfortunately, many cancers are invasive or infiltrating. This means at the microscopic level; the cancer cells are breaking through protective membranes and entering lymphatic and vascular spaces. This allows cancer to spread towards lymph nodes or into the blood system. Many times cancer may have already spread before surgery. Current medical imaging may not have been able to pick up small lesions, and by the time the patient has surgery or shortly after, these lesions may have grown larger.  Therefore, leading to the belief that surgery or the exposure to air caused the tumors to spread.

Since I began practicing radiation oncology over 20 years ago, there has been an explosion in cancer biology as well as drug therapy.  We are now able to determine the molecular profile of a tumor. By knowing its genetic makeup, we can determine if a cancer has a high likelihood to spread and thereby benefit from chemotherapy. Additionally, the presence of specific genes also allows oncologists to be able to select particular drug therapies. When certain types of genes are found, they can increase the aggressiveness, as well as evasiveness of a tumor from the immune system. There are now specific drugs that are designed to shut this gene down causing the tumor to die or be more recognizable to the body’s immune system.

In conclusion, there is no definitive evidence that a biopsy or surgery has led to a spread of cancer. A biopsy or surgery is necessary for a cancer diagnosis, proper treatment, and in some cases, a cure.

Robert Gin, MD is a radiation oncologist at Arizona Oncology’s Green Valley and St. Mary’s offices. He earned his medical degree at the University of Arizona Medical School. Dr. Gin is board certified in radiation oncology and is a member of the American Society for Radiation Oncology.

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