Flattened tumor requires a more careful attention for residual distal cancer spread in locally advanced lower rectal carcinoma after chemoradiotherapy

Impact of Microscopically Positive (≤1 mm) Distal Margins on Disease Recurrence in Rectal Cancer Treated by Neoadjuvant Chemoradiotherapy

BACKGROUND

The adequate distal resection margin is still controversial in rectal cancer treated by neoadjuvant chemoradiotherapy (nCRT). The aim of this study was to assess the impact of a distal margin of ≤1 mm on locoregional recurrence-free survival (LRRFS).

METHODS

Among 255 patients treated with nCRT and surgery at the National Cancer Institute of Milan, 83 (32.5%) had a distal margin of ≤1 mm and 172 (67.5%) had a distal margin of >1 mm. Survival analyses were performed to assess the impact of distal margin on 5-year LRRFS, as well as Cox survival analysis. The role of distal margin on survival was analyzed according to different tumor regression grades (TRGs).

RESULTS

The overall 5-year LRRFS rate was 77.6% with a distal margin of ≤1 mm vs. 88.3% with a distal margin of >1 mm (Log-rank p = 0.09). Only stage ypT4 was an independent predictor of worse LRRFS (HR 15.14, p = 0.026). The 5-year LRRFS was significantly lower in TRG3-5 patients with a distal margin of ≤1 mm compared to those with a distal margin of >1 mm (68.5% vs. 84.2%, p = 0.027), while no difference was observed in case of TRG1-2 (p = 0.77).

CONCLUSIONS

Low-responder rectal cancers after nCRT still require a distal margin of >1 mm to reduce the high likelihood of local relapse.

Microscopic intramural extension of rectal cancer after neoadjuvant chemoradiation: A meta-analysis based on individual patient data

OBJECTIVE

In selected rectal cancer patients with residual local disease following neoadjuvant chemoradiation (CRT) and the preference of an organ preservation pathway, additional treatment with dose escalation by endoluminal radiotherapy (RT) may ultimately result in a clinical complete response. To date, the widespread introduction of selective endoluminal radiation techniques is hampered by a lack of evidence-based guidelines that describe the radiation treatment volume in relation to the residual tumor mass. In order to convert an incomplete response into a complete one with additional treatment such as dose-escalation with endoluminal RT from a theoretical perspective, it seems important to treat all remaining microscopic tumor cells after CRT. In this setting, residual tumor extension beneath normal appearing mucosa (microscopic intramural spread - MIS) becomes relevant for accurate tumor volume and margin estimation. With the goal of providing evidence-based guidelines that define an appropriate treatment volume and patient selection, we present results from a meta-analysis based on individual patient data of studies that have assessed the extent or range of MIS of rectal cancers after neoadjuvant CRT. This meta-analysis should provide an estimate of the residual tumor volume/extension that needs to be targeted by any additional radiation therapy boost in order to achieve complete tumor eradication after initial incomplete or near-complete response following standard CRT.

METHODS AND MATERIALS

A PubMed search was performed. Additional articles were selected based on identification from reference lists. Papers were eligible when reporting MIS in patients who were treated by total mesorectal excision or local excision/transanal endoscopic microsurgery (TEM) after neo-adjuvant long-course CRT. The mean MIS was calculated for the entire group along with the 70th until 95th percentiles. Additional exploratory subgroup analyses were performed.

RESULTS

Individual patient data from 349 patients with residual disease from five studies were analyzed. 80% of tumors showed no MIS. In order to appropriately treat MIS in 95% of rectal cancer patients after CRT, a margin of 5.5 mm around the macroscopic tumor would suffice. An exploratory subgroup analysis showed that T-stage after CRT (ypT) and time interval between neoadjuvant CRT and surgery are significant factors predicting the extent of MIS (p < 0.001.) The group of ypT1 had the smallest MIS, followed by the ypT3-4 group, while the ypT2 group had the largest MIS (p < 0.001). Regarding time interval between CRT and surgery, a statistically significant difference was seen when comparing the three time-interval groups (less than 8 weeks, 8-12 weeks, and more than 12 weeks), where waiting more than 12 weeks after CRT resulted in the largest MIS (p < 0.0001).

CONCLUSION

Based on this meta-analysis, in order to treat the MIS for 95% of rectal cancer patients after CRT, a Clinical Target Volume (CTV) margin of 5.5 mm from the lateral most edge of the macroscopic tumor would suffice. 80% of tumors showed no MIS and would not require an extra CTV margin for treatment. These findings support the feasibility of localized radiotherapy boosts for dose-escalation to improve response among patients with incomplete response after standard CRT and can also be applied in the surgical setting.

Preoperative chemoradiotherapy using S-1 combined with celecoxib for advanced lower rectal cancer: Phase I/II study

OBJECTIVES

To clarify the safety and efficacy of celecoxib combined with chemoradiotherapy using S-1 for lower rectal cancer.

METHODS

Twenty-one patients with pathologically proven lower rectal adenocarcinoma (cT3-T4, Tx N+, M0) were included in this study. A total dose of 45 Gy was administered in daily fractions of 1.8 Gy. Celecoxib was given orally twice daily with S-1 on the day of irradiation. The dose of celecoxib was set at 400 mg/day. In Phase I, the S-1 dose was started at 80 mg/m²/day; in Phase II, S-1 was administered in the same dose as Phase I. Patients underwent surgery six to eight weeks after completing chemoradiotherapy, followed by six months of postoperative adjuvant chemotherapy.

RESULTS

The S-1 recommended dose was 80 mg/m²/day. The pathological complete remission rate was 15.8%, the rate of protocol completion was 14.3%, and the rate of adverse events exceeding Grade 3 was 19.0%. Surgery was performed in 19 cases, with a sphincter-sparing rate of 31.6%. Postoperative complications exceeding Grade 3 occurred in 52.4% of cases. The three year overall survival and relapse-free survival rates were 89.3% and 67.0%, respectively.

CONCLUSIONS

We failed to show a synergistic or additive therapeutic effect of preoperative CRT using S-1, combined with celecoxib, for lower advanced rectal cancer beyond CRT using 5 FU or capecitabine alone. The incidence of complications, evidently involving intestinal ischemia, was relatively high. This treatment strategy is not recommended at present.