The effect of fluoropyrimidines with or without thymidine phosphorylase inhibitor on the expression of thymidine phosphorylase

Implementation of pharmacogenomic testing in oncology care (PhOCus): study protocol of a pragmatic, randomized clinical trial

BACKGROUND

Many cancer patients who receive chemotherapy experience adverse drug effects. Pharmacogenomics (PGx) has promise to personalize chemotherapy drug dosing to maximize efficacy and safety. Fluoropyrimidines and irinotecan have well-known germline PGx associations. At our institution, we have delivered PGx clinical decision support (CDS) based on preemptively obtained genotyping results for a large number of non-oncology medications since 2012, but have not previously evaluated the utility of this strategy for patients initiating anti-cancer regimens. We hypothesize that providing oncologists with preemptive germline PGx information along with CDS will enable individualized dosing decisions and result in improved patient outcomes.

METHODS

Patients with oncologic malignancies for whom fluoropyrimidine and/or irinotecan-inclusive therapy is being planned will be enrolled and randomly assigned to PGx and control arms. Patients will be genotyped in a clinical laboratory across panels that include actionable variants in UGT1A1 and DPYD. For PGx arm patients, treating providers will be given access to the patient-specific PGx results with CDS prior to treatment initiation. In the control arm, genotyping will be deferred, and dosing will occur as per usual care. Co-primary endpoints are dose intensity deviation rate (the proportion of patients receiving dose modifications during the first treatment cycle), and grade ⩾3 treatment-related toxicities throughout the treatment course. Additional study endpoints will include cumulative drug dose intensity, progression-free survival, dosing of additional PGx supportive medications, and patient-reported quality of life and understanding of PGx.

DISCUSSION

Providing a platform of integrated germline PGx information may promote personalized chemotherapy dosing decisions and establish a new model of care to optimize oncology treatment planning.

Phase I clinical study of three times a day oral administration of TAS-102 in patients with solid tumors

TAS-102 is a novel formulation of the fluorinated pyrimidine analogue trifluorothymidine (FTD) with an inhibitor of thymidine phosphorylase. The purpose of this study was to determine the MTD and DLT for TAS-102 administered three times a day on days 1-5 and 8-12 every 4 weeks. Fifteen patients were enrolled with two patients experiencing dose-limiting fatigue and granulocytopenia at the first dose level (80 mg/m2/day). Granulocytopenia was the primary toxicity: 7 patients experienced grade 3 or 4 granulocytopenia with the first course. No responses were noted, but nine patients demonstrated prolonged stable disease in this heavily pretreated 5-FU refractory population.

Immunohistochemical analysis of thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase in rectal cancer (cUICC II/III): correlation with histopathologic tumor regression after 5-fluorouracil-based long-term neoadjuvant chemoradiotherapy

In locally advanced rectal cancer, neoadjuvant 5-fluorouracil (5-FU)-based long-term chemoradiotherapy leads to marked tumor reduction and decrease of local recurrence rate. Thymidylate synthase (TS), thymidine phosphorylase (TP), and dihydropyrimidine dehydrogenase (DPD) are known to be important biomarkers to predict tumor response to 5-FU-based therapy. The aim of this study was to examine the correlation between TS, TP, and DPD protein expression and histopathologic tumor regression after neoadjuvant chemoradiotherapy. The results were compared with the recently published mRNA data. Preoperative biopsies (n = 25) and resection specimens (n = 40) from patients with rectal carcinoma (clinical UICC stage II/III) receiving neoadjuvant 5-FU-based chemoradiotherapy were studied for TS, TP, and DPD protein expression by immunohistochemistry using three different scoring systems (intensity, pattern, intensity + pattern). Results were compared with histopathologic tumor regression. A significant correlation between protein expression and tumor response was only seen when both staining intensity and staining pattern were considered. With this method, a significant association was seen between high TS expression in tumor biopsies as well as resection specimens and nonresponse of the tumor to therapy (P = 0.04). Furthermore, low TP expression in the resection specimens was significantly associated with lack of response (P = 0.02). For DPD no significant correlations were found at all. In conclusion, these results suggest that immunohistochemistry like RT-PCR is a suitable method to determine the correlation between TS, TP, and DPD expression and histopathologic tumor regression. However, precise results can only be achieved if staining intensity as well as staining pattern within the tumors are evaluated.