A multi-institutional, retrospective review of the medical records of survivors of cancer occurring in childhood, adolescence, or young adulthood revealed a high number of cases of therapy-associated polyposis (TAP). The findings from this study were reported in Cancer Prevention Research.
Previous reports of “a phenomenon of striking gastrointestinal polyposis” have been described in a limited number of cancer survivors previously treated with chemotherapy and/or radiation therapy. This condition has been called TAP and defined as an “apparently acquired phenotype” since a defining criteria is the absence of an association with a hereditary predisposition, such as familial adenomatous polyposis. Nevertheless, the number of cases of TAP reported in the medical literature is low, and the condition remains poorly understood.
In this study, clinicopathologic data were obtained through a review of the medical records of patients who were evaluated at 8 cancer genetic programs and had received chemotherapy and/or radiation therapy for the treatment of cancer occurring in children or adolescents/young adults (AYA). Polyposis was defined as a cumulative lifetime incidence of 10 or more polyps occurring anywhere in the gastrointestinal tract. Those patients with a personal or family history of a germline genetic alteration associated with an increased susceptibility to colorectal cancer were excluded from the study.
Baseline characteristics of the 34 patients with TAP included a median age of 18 years at their original cancer diagnosis which was Hodgkin lymphoma (n=27), neuroblastoma (n=3), acute myeloid leukemia (n=1), medulloblastoma (n=1), nephroblastoma (n=1), and non-Hodgkin lymphoma (n=1). Cancer treatment included alkylating chemotherapy (n=20), abdominopelvic radiation therapy (n=21), and the combination of these therapies (n=12).
Included in this patient cohort were patients with cancer diagnosed at age 30 or younger, as well as those who received a cancer diagnosis between the ages of 31 and 45 years if the first identified gastrointestinal polyp was found at least 10 years following cancer therapy. The median age at TAP diagnosis was 49 years, which was a median of 27 years following initiation of treatment for the index cancer.
As part of surveillance, data were available for a median of 4 colonoscopies over 6 years, and 23 patients underwent esophagogastroduodenectomy (EGD).
This patient cohort had a median lifetime aggregate of 32 colorectal polyps, and 10 patients developed colorectal cancer. Five of the patients with a history of abdominopelvic radiotherapy and 3 of those without a history abdominopelvic radiotherapy were found to have developed polyps prior to age 45 years, which is currently included as the year to initiate screening colonoscopy in those treated with abdominopelvic radiation therapy, according to guidelines from the Children’s Oncology Group (COG). Furthermore, 3 of the 9 patients with colon cancer who were previously exposed to abdominopelvic radiation were younger than the recommended age for screening colonoscopy.
With respect to these findings, the study authors proposed “that COG guidelines be expanded to include individuals who received chemotherapy (without abdominopelvic radiation), and that initiation of screening begin at age 35 or 10 years after age of chemotherapy, whichever occurs first.”
Notably, TAP was characterized by heterogeneous phenotypes in this patient cohort. For example, of the 23 patients who underwent EGD, gastroduodenal polyps, excluding fundic polyps, were observed in 7 patients.