Although surgery to remove a tumor can improve the prognosis for some cancer patients, for others it might actually cause dormant cancers to grow and shorten survival, according to a review of research published in the June 10 Annals of Oncology. This is a subject that has been discussed throughout the decades.
“Surgery is a major tool in cancer treatment. A lot of randomized clinical trials have demonstrated that in most clinical situations, primary tumor removal may cure patients, although not all patients,” says Romano Demicheli, MD, PhD, a researcher in the Department of Medical Oncology at the Istituto Nazionale Tumori in Milan, Italy. “Surgery, however, may have detrimental traits for some patients, in addition to its undeniable benefits.”
Dr. Demicheli and his colleagues looked at the history of research into the possibility of surgery triggering tumor growth. Over the past century, several doctors have theorized that an initial tumor creates a sort of balance that prevents other tumors from taking hold and spreading—an idea referred to as “concomitant resistance.” Once that main tumor is surgically removed, isolated cancer cells or small abnormal groups of cells that would have otherwise remained dormant can begin to proliferate and grow.
How might the first tumor suppress additional cancer growth? For one thing, the primary tumor may release substances that inhibit the growth of new blood vessels (angiogenesis) that feed tumors. If that is the case, levels of these substances fall dramatically once the tumor is removed, and small groups of cancer cells that have spread from the primary tumor start recruiting new blood vessels. The healing process after surgery also stimulates angiogenesis. In addition, trauma that occurs to normal tissue during surgery can promote the ability of circulating tumor cells (CTCs) to grow. Other triggering methods, which are not well understood at the current time, may act on individual dormant tumor cells.
Even though there has been a great deal of evidence from studies that surgery can fuel cancer growth, many doctors remain uncomfortable with the idea that surgery may not always be beneficial to their cancer patients. The authors say the problem is one of perception—doctors tend to view tumors as they do bacterial infections, as independent collections of abnormal cells. “In this case, the disease results from invading ‘alien enemies’ that need to be completely destroyed in order to achieve the cure,” they write in the report.
In the future, doctors can improve their understanding of cancer by instead starting to view tumors as organ-like structures, the authors say. This change in perspective could have a real impact on the way cancer is treated. “The new way to view the tumor suggests new research lines that will result in improvements of the current treatments (maybe in new therapies in the place of surgery),” explains Dr. Demicheli.
However, he is quick to point out that surgery still has an important place in cancer treatment. “We do not advocate the elimination of surgery from the therapeutic approach,” he says. “We say, on the contrary, that we should study how to add to the surgical phase other treatments aimed to control detrimental effects.” For example, researchers could study the effectiveness of giving patients angiogenesis inhibitors to suppress new blood vessel growth after surgery.
Also, it is possible that less extensive surgery may be preferable to more destructive surgery because it reduces trauma to the tissue. For instance, research on laparoscopic colectomy (surgery to remove the colon) and open colectomy for the treatment of colon cancer that has not spread suggests laparoscopic surgery may lower the chance that the cancer will recur after surgery.
Demicheli R, Retsky MW, Grushesky JM, Baum M, Gukas ID. The effects of surgery on tumor growth: a century of investigations. Annals of Oncology. Published online June 10, 2008.