As the result of the rarity of appendix cancer (appendix cancer accounts for less than 1 percent of tumors that originate in the gastrointestinal tract), there is a lack of scientific data to guide treatment decisions. As a result, current treatment guidelines are the same as for colon cancer.
Like many other cancers, some people respond to treatment while others do not. To understand why there is a treatment disparity, researchers at the University of California San Diego School of Medicine and Moores Cancer Center along with Foundation Medicine, performed genetic profiling on 703 appendiceal tumors. This study was the largest study of appendiceal cancer to date.
Their findings were published online August 8 in JCO Precision Oncology. The results of their study confirmed that genetic mutations in appendix cancer are distinct from those found in colon cancer and that mutations in the genes TP53 and GNAS are good predictors of survival among people with appendix cancer.
“For tumors that are rare like appendix cancer, obtaining molecular profiles will help identify potential treatment options since we don’t have the clinical trial data to help guide treatments as we do in common tumors,” said lead author John Paul Shen, MD. “Equally important, the mutation profile can be used as a biomarker to separate high-risk patients, who need intensive treatment, from low-risk patients who may not need such intensive treatment.”
The retrospective study found that appendix cancer is comprised of five distinct subtypes: mucinous adenocarcinomas (46 percent), adenocarcinomas (30 percent), goblet cell carcinoids (12 percent), pseudomyxoma peritonei (7.7 percent) and signet ring cell carcinomas (5.2 percent).
The researchers also found that a mutation in the gene GNAS, which is rare in colon cancer but is often present in appendix cancer, especially in mucinous adenocarcinomas (52 percent) and pseudomyxoma peritonei (72 percent). They also found that people with tumors harboring a GNAS mutation had a median survival of almost ten (10) years, while those whose tumors had a TP53 mutation had a median survival of only three years. People who had neither gene mutation had a six-year median survival rate.
Shen concluded that “This striking finding raises the question of whether patients with early stage, GNAS-mutant tumors need to be treated with chemotherapy, as it is possible they could be cured with surgery alone; a question we will focus on in our next study.”
Understanding the molecular differences between the subtypes of appendiceal tumors is an important stepping stone for future clinical trials to develop and test different therapeutic approaches that are specific to this disease,” said senior author Olivier Harismendy, Ph.D., assistant professor of medicine at UC San Diego Moores Cancer Center.
This study reinforces the need to have a better understanding of the underlying genetic makeup of cancer tumors, especially rare cancer tumors. Expanding our knowledge of cancer’s genetics will help us to both prognosticate the disease’s progression as well as improve our ability to treat cancer properly.
Joel T. Nowak, MA, MSW wrote this Post. Joel is the CEO/Executive Director of Cancer ABCs. He is a Cancer Thriver diagnosed with five primary cancers - Thyroid, Metastatic Prostate, Renal, Melanoma, and the rare cancer Appendiceal cancer.