ESTRO 2024 - Abstract Book

S1570

Clinical - Lower GI

ESTRO 2024

Table 1 shows the survival endpoints and acute and chronic toxicity rates ≥ G3 for this population and the PROSPECT study arms.

Survival rates in the 3 arms are quite similar. Regarding 5-year DFS, PROSPECT fCRT arm showed the lowest rates. In the context of our patient sample, which is based on RWD, it is evident that 37 (15%) of the patients were directed towards conservative treatment approaches. Of these, 10 (27%) developed re-growth. The reported toxicity rates are very encouraging when compared to both arms of the PROSPECT study (10,1% versus 41% of Folfox arm). Furthermore, pCR rates are higher at 33.7% compared to 21.9% in the Folfox arm and especially 24.3% in the nCRT arm.

When interpreting the data, it is important to consider the different RT dose received by patients in RWD cohort (55/45 in 25 fractions) compared to the lower dose received in the PROSPECT fCRT arm (50.4 Gy in 28 fractions).

Table 1. Patient characteristics and endpoints. RWD: Real-World Data; OS: overall survival; DFS: disease free survival: LR: local recurrence; pCR: pathological complete response; fCRT: fluoropyrimidine-based chemotherapy; G3: grade 3.

Conclusion:

In summary, our RWD suggests that our institution's nCRT regimen offers competitive survival results with potential benefits, including improved pCR rates, better compliance, and fewer toxicities. 15% of our patients received conservative treatments, reflecting a trend towards organ-preserving surgery in suitable cases. Our patients experienced lower toxicity and higher pCR rates compared to the PROSPECT trial, with similar survival rates. Both the PROSPECT Folfox arm and our RWD arm showed the best 5-year DFS rates, indicating the potential to reduce distant metastases risk through intensified chemotherapy and higher radiation therapy doses. These findings emphasize the importance of personalized treatment in managing LARC.

Keywords: rectal cancer, radiotherapy intensification

References:

1. Schrag D, Shi Q, Weiser MR, Gollub MJ, Saltz LB, Musher BL, et al. Preoperative Treatment of Locally Advanced Rectal Cancer. New England Journal of Medicine. 2023;389:322–34

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