Objective: To characterize patterns of recurrence in locally advanced rectal cancer treated with combined modality therapy (CMT): neoadjuvant chemoradiation + total mesorectal excision + adjuvant chemotherapy.
Methods: A total of 593 consecutive rectal cancer patients (1998 to 2007) with locally advanced (stage II/III) disease (noted on endorectal ultrasound or magnetic resonance imaging) who received CMT were analyzed for patterns of recurrence.
Results: After median 44-month follow-up (interquartile range, 25 to 64 months), 119 patients (20%) recurred: 105 distant, 7 local, 7 local and distant, and 112 distant-only recurrence. Ninety-three (78%) had single-organ recurrence, and 26 (22%) had multiple-organ recurrence. The most common site of distant recurrence was lung (69% of all patients with distant relapse); 20% had liver recurrence. Fourteen patients (2.4%) recurred locally. Pulmonary metastases were most commonly identified by computed tomographic scan versus abnormal positron emission tomographic (PET) scan or carcinoembryonic antigen (CEA). Risk factors associated with pulmonary recurrence were the following: pathologic stage, tumor distance from anal verge, lymphovascular or perineural invasion. Five-year freedom from pulmonary recurrence for patients with 0, 1, 2, or 3 risk factors was 99%, 90%, 61%, and 42%, respectively. Thirty of 59 patents with pulmonary recurrence underwent lung metastasectomy; 3-year freedom from recurrence was 37%.
Conclusions: Unlike colon cancer, which most frequently recurs in the liver, locally advanced rectal cancer treated with CMT relapses most frequently in the lung. Pulmonary metastasis was associated with advanced pathologic stage, low-lying tumor, lymphovascular invasion, or perineural invasion. Confirmation of pulmonary metastasis usually requires serial imaging because metastases are often small when initially detected, well below the resolution of PET, and not necessarily associated with elevated CEA. Individualized risk-based surveillance strategies are recommended in this patient population.