Acute toxicity of radiochemotherapy in rectal cancer patients: a risk particularly for carriers of the TGFB1 Pro25 variant.

Purpose: Transforming growth factor-beta1 is related to adverse events in radiochemotherapy. We investigated TGFB1 genetic variability in relation to quality of life-impairing acute organ toxicity (QAOT) of neoadjuvant radiochemotherapy under clinical trial conditions.

Methods And Materials: Two independent patient cohorts (n = 88 and n = 75) diagnosed with International Union Against Cancer stage II/III rectal cancer received neoadjuvant radiation doses of 50.4 Gy combined with 5-fluorouracil-based chemotherapy. Toxicity was monitored according to Common Terminology Criteria for Adverse Events. QAOT was defined as a CTCAE grade ≥2 for at least one case of enteritis, proctitis, cystitis, or dermatitis. Nine germline polymorphisms covering the common genetic diversity in the TGFB1 gene were genotyped.

Results: In both cohorts, all patients carrying the TGFB1 Pro25 variant experienced QAOT (positive predictive value of 100%, adjusted p = 0.0006). In a multivariate logistic regression model, gender, age, body mass index, type of chemotherapy, or disease state had no significant impact on QAOT.

Conclusion: The TGFB1 Pro25 variant could be a relevant marker for individual treatment stratification and carriers may benefit from adaptive clinical care or specific radiation techniques.