Patterns of Locoregional Recurrence and Their Predictors in Rectal Cancer Patients Treated with Surgery and Chemoradiation
Presenter: T. Yu.
Presenter's Affiliation: MD Andersen Cancer Center
Type of Session: Scientific
- The current standard of care for treating locally advanced rectal cancer is combined modality chemotherapy and radiation with surgical resection.
- Little is known about the location of tumor recurrences following this therapy.
- Information about the likely location of tumor recurrences could help radiation oncologists adjust the size of their radiation treatment fields in an effort to minimize treatment related toxicities.
- A retrospective study of 600 patients with rectal adenocarcinoma treated at the MD Anderson Cancer Center between October 1987 and September 2001 was performed.
- 600 patients were identified with 517 receiving preoperative chemoradiation and 83 receiving postoperative chemoradiation.
- The majority of patients received 5-Fluorouracil chemotherapy for a median duration of 25 days.
- Median follow-up was 63.7 months.
- The location of recurrences was classified as in-field if it occurred within the radiation treatment field by at least 1 cm, as marginal if it occurred within 1 cm of the treatment field (either in or out) and out-of-field if it occurred greater than 1 cm outside the treatment field.
- Imaging studies were reviewed by 2 radiologists.
- A multivariate analysis was performed using the Cox regression analysis.
- 52 patients (7.5 %) experienced local tumor recurrences.
- 38 patients had images of recurrences available.
- 26 patients (61.9%) had in-field recurrences, 7 (16.7%) had marginal recurrences, and 9 (21.4%) had out of field recurrences.
- On multivariate analysis, the presence of a positive radial margin and the pathologic N stage were both significant predictive factors for an in-field recurrence.
- There were not any significant factors found which were related to an increased likelihood of an out-of-field recurrence.
- The overall rate of locoregional recurrences after tri-modality therapy was low.
- The majority of recurrences were in-field recurrences (62%).
- The majority of recurrences were in the low-pelvis (54%).
- A significant number of failures were seen in the pre-sacral region (23%).
- With an appropriate field design, it is possible that the number of marginal recurrences could be reduced.
- The practice of delivering a radiation boost to the rectum and surrounding margins should be continued.
The authors performed a well designed retrospective study of 600 rectal cancer patients and were able to shed some new light on the patterns of recurrence after combined modality therapy. It would appear reasonable to continue boosting the areas at particular risk for local recurrence based on this research. However, this conclusion would be strengthened if improved local control rates were seen in those patients who actually received a boost. Because of the nature of retrospective research, these findings need to be considered as hypothesis generating, rather than hypothesis proving. It would not be prudent to consider changing the standard radiation fields for locally advanced rectal cancer based on the results of this analysis. It will be interesting to examine the local recurrence rates and patterns in patients receiving more intense systemic treatment during their radiation, with newer chemotherapeutics and biologic agents.