Israel Medical Association Journal

Germline pathogenic variants (PVs) in the RET proto-oncogene (OMIM 164761) are associated with a diverse phenotype based on the type of PV. Gain-of-function (GOF) PVs are associated with the highly penetrant multiple endocrine neoplasia type 2 (MEN2-OMIM 171400), which are hallmarked by an increased risk for developing medullary thyroid cancer (MTC), pheochromocytoma, and parathyroid adenomas. Loss-of-function (LOF) RET PVs are associated with incompletely penetrant Hirschsprung's disease (HSCR OMIM 142623), which are pathologically characterized by the absence of enteric ganglia affecting the distal colon and clinically manifest as neonatal intestinal obstruction. Despite anecdotal reports of familial clustering of neoplasms in HSCR families, mostly MEN2-associated tumors [1,2], HSCR is not considered to be associated with an increased risk for developing cancer [3]. We report on a family with an unusual multigenerational solid tumor phenotype and severe HSCR phenotype with a LOF RET PV.

Background: Dedicated, organ-specific screening clinics have been shown to significantly reduce cancer morbidity and mortality.

Objectives: To establish a dedicated clinic for Clalit Health Service patients at high risk for hereditary gastrointestinal cancer and to provide them with clinical and genetic counseling, diagnostic screening and follow–up.

Results: During the 3 years of the clinic's activity, 634 high risk families, including 3804 at-risk relatives, were evaluated. The most common conditions were hereditary colorectal syndromes, Lynch syndrome (n=259), undefined young-onset or familial colorectal cancer (n=214), familial adenomatous polyposis (n=55), and others (n=106). They entered follow-up protocols and 52 underwent surgical procedures.

Conclusions: Consistent public and professional education is needed to increase awareness of hereditary colorectal cancer and the possibility of family screening, early diagnosis and therapy. The public health services – i.e., the four health management organizations – should provide genetic testing for these patients who, at present, are required to pay for almost all of these available but costly tests. Dedicated colorectal surgical units are needed to provide the specialized therapeutic procedures needed by patients with familial colorectal cancer. Our future plans include adding psychosocial support for these at-risk patients and their families as well as preventive lifestyle and dietary intervention.