Zhang Zhifei, Abdalla Ahmed, Mazzara Paul, Alame Amer, Hawasli Abdelkadr and Aref Amer*
Rectal Cancer Group, Van Elslander Cancer Center, Ascension St. John Hospital, USAFulltext PDF
Background: Preoperative chemoradiotherapy is the standard of care for locally advanced rectal
cancer. It results in significant macroscopic tumor response and pathological downstaging.
Understanding the relationship between the Residual Gross Abnormality (RGA), the only visible
mark of the disease that can be detected preoperatively or intraoperatively, and possible occult
microscopic cancer is important for planning the ensuing surgical resections.
Methods: We retrospectively reviewed the medical records and pathology slides of patients
undergoing rectal resection after neoadjuvant chemoradiotherapy in our center between 2011 and
2018. We observed the relationship between the RGA and residual microscopic cancer.
Results: Fifty-seven patients with locally advanced rectal cancer received neoadjuvant therapy
followed by surgical excision. Two, 48 and 5 tumors were clinically staged as T2, T3, and T4,
respectively. Two patients had missing clinical staging data. Sixteen patients (28%) had a complete
pathological response and were excluded from further analysis. Of the remaining 41 tumors, ypT1
stage was noticed in 5, while ypT2, ypT3, and ypT4 were noticed in 14, 21, and 1 case, respectively.
No microscopic disease was detected solely outside the Gross Mucosal Abnormality (GMA) or in
the perirectal fat without involving the rectal wall directly underneath GMA. Occult microscopic
disease extending outside GMA was seen only in 2/41 cases (5%) and extended by 1 cm.
Conclusion: When local excision is contemplated to confirm the residual tumor pathological
response status without therapeutic intent, the surgical excisions need not extend beyond the
borders of GMA and adjacent perirectal fat. The incidence of occult microscopic disease outside
GMA is very low; when present, it extends by only 1 cm. This information is useful in planning
surgical resection or the design of the radiation therapy boost.
Chemoradiotherapy; Resection; Residual tumor; Tumor response
Zhifei Z, Ahmed A, Paul M, Amer A, Abdelkadr H, Amer A. Pattern of Distribution of Residual Microscopic Disease Following Neoadjuvant Therapy for Rectal Cancer. World J Surg Surgical Res. 2021; 4: 1315..