Neoplastic mesorectal microfoci (MMF) following neoadjuvant chemoradiotherapy: clinical and prognostic implications.

BACKGROUND

Neoplastic microfoci have frequently been found in the mesorectum, with poor outcome. In this study, incidence and clinical significance of mesorectal microfoci (MMF) were analyzed in patients operated upon for rectal cancer following neoadjuvant chemoradiation.

METHODS

A case series of 68 patients with extraperitoneal rectal cancer, treated with neoadjuvant chemoradiation and surgery (including total mesorectal excision), was investigated for the presence of neoplastic MMF.

RESULTS

Mesorectal microfoci were found in 26 cases (38.2%). Increasing incidence of microfoci was statistically related to pathologic involvement of bowel wall (P = 0.0006), Mandard's tumor regression grading (P = 0.0006) and pathologic neoplastic mesorectal involvement (P < 0.00001). None of the nine patients with complete tumor disappearance displayed both microfoci and lymph node metastasis. Only one local recurrence developed in a patient with multiple MMF. Out of 9 pT0 or TRG1 patients, 1 (11.1%) had distant metastases, compared to 15 out of 59 pT1-4 or TRG2-5 (25.4%, P = 0.70).

CONCLUSIONS

A remarkable incidence of MMF was found following chemoradiation. However, when this therapy induces complete regression of primary tumor (pT0-TRG1), node metastases and neoplastic MMF could also disappear, as shown in our cases. These features should be confirmed because they could significantly impact the treatment decision-making of rectal cancers.