Background: Signet-ring cell carcinoma (SRCC) is an uncommon tumor entity in rectal cancer, often considered to be resistant to non-surgical therapy. In locally advanced primary or recurrent rectal cancer, diagnostic information from magnetic resonance imaging (MRI) is considered superior in planning the optimal treatment strategy, which usually includes preoperative radiotherapy. The recognition of MRI features that correlate with the radiation response might ultimately be used to select patients for tailored treatment and, in addition, avoid potentially toxic therapy in non-responding patients.
Material and methods: In a cohort of 120 rectal cancer patients who had received preoperative radiotherapy (50 Gy in 2 Gy fractions), six patients were noted to have SRCC tumor differentiation. Initial diagnostic MRI examination included assessment of local T- and N-stage and tumor morphology. Histological tumor response was subsequently assessed in the resected specimens, and postoperative follow-up data was compiled until disease recurrence.
Results: Following the preoperative radiotherapy, two distinctly different histological responses - complete response (ypT0N0) or no response - were observed. Extensive mesorectal lymph node metastasis (N2 disease) at the pretreatment MRI examination was unambiguously associated with lack of response and rapid development of disseminated disease. Importantly, patients with complete response have been observed for 23-52 months postoperatively without evidence of recurrent disease.
Discussion: Our review may suggest that patients with locally advanced growth of rectal SRCC, despite poorer outcome when compared to patients with conventional-type rectal adenocarcinoma, when presenting limited lymph node disease should be offered preoperative radiotherapy in a tentatively curative setting.