No date

Session Item

Sunday

November 29

10:30 - 11:30

Clinical Stream 2

Proffered papers 17: GI

Session Code: 2200

Session Type: Proffered Papers

Track: Clinical

10:50 - 11:00

pCR versus 2 years DFS:an update analysis of a pooled dataset of 5492 locally advanced rectal cancer

Presentation Number: OC-0334

Abstract

Abstract Title:

pCR versus 2 years DFS:an update analysis of a pooled dataset of 5492 locally advanced rectal cancer

(1)Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Radiation Oncology, Rome, Italy;(2)GROW School for Oncology and Developmental Biology- Maastricht University, Radiation Oncology, Maastricht, The Netherlands;(3)Maria Skłodowska-Curie Memorial Cancer Centre, Radiotherapy, Warsaw, Poland;(4)EORTC Headquarters, Statistics, Brussels, Belgium;(5)Centre Antoine Lacassagne- Nice Côte-d'Azur University, Radiation Oncology, Nice, France;(6)Mount Vernon Centre for Cancer Treatment-, Radiation Oncology, Northwood, United Kingdom;(7)Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia;(8)University Hospital Frankfurt- Goethe University, Radiotherapy and Oncology, Frankfurt-, Germany;(9)Pisa University Hospital, Radiation Oncology, Pisa, Italy;

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Purpose or Objective

Patients (pts) with locally advanced rectal cancer (LARC) exhibit heterogeneous responses to treatment. Patients who achieved a pathological complete response (pCR) are considered to be a more favorable subpopulation with less local recurrence (LR) and distance metastases (DM) as well as better overall survival (OS). As reported in a previous large database analysis, comparing with pCR, 2 years disease free survival (2yDFS) can be considered a stronger predictor of OS. The aim of this study was to update the previous analysis on a more copious pooled set of LARC pts.

Material and Methods

Pooled and treatment subgroup analysis were performed on 11 large international rectal cancer trials: Accord 12/0405, EORTC 22921, FFCD 9203, CAO/ARO/AIO-94, CAO-ARO-AIO-04, INTERACT, I-CNR-RT, XELOX , two Polish trials and TROG 01.04. All the selected LARC pts received long-course radiotherapy (LC-RT) with or without concomitant and/or adjuvant chemotherapy (CT) and surgical procedure. Pts with no information regarding pCR were excluded.

We calculated 2yDFS as no distance metastasis or local recurrence within 2 years. Furthermore we divided pts, depending of treatment, in 4 subgroup: only LC-RT, LC-RT+ concomitant CT, LC-RT + adjuvant CT and adjuvant LC-RT.

Pearson’s Chi-squared, Kaplan-Meier curve and Logrank test were used for data analysis. A p-value less than 0.01 was considered as a statistical significant value.

Results

Overall 5492 pts out of 7936 LARC pts satisfied the inclusion criteria in this pooled dataset and were analyzed in this study.

According to the patterns of recurrences, 3 pts groups were identified: 11% had pCR and 2yDFS (excellent prognosis), 66% had no pCR but 2yDFS (good prognosis) and 20% had neither pCR and 2yDFS (poor prognosis).

Pathological CR was confirmed as an early good predictor of OS, independently of clinical tumor stage (cT3 p< 0.01, cT4 p= 0.02) while pCRs obtained after the only LC-RT seem to not predict OS (p= 0.21).

Furthermore, the results confirmed that 2yDFS was a strong predictor of OS compared to pCR for LARC pts (Figure 1) independently of clinical tumor stage (p<0.01) and treatment type (p<0.01) (Figure 2).

The landmark analysis shows that achieving a pCR is significantly beneficial when there is 2yDFS. In the case of early recurrence or metastasis, pCR status appears to be statistically irrelevant for OS.

Conclusion

This update analysis confirmed that 2yDFS is a stronger predictor of OS compared with pCR in more than 5000 LARC pts. These results support that accurate prediction models should be developed for 2yDFS to select LARC pts for more intensified treatment strategies.