Search

Background: Cancer patients' attitudes toward progression-free survival (PFS) gains offered by treatment are not well understood, particularly in the absence of overall survival (OS) gains. The objectives were to describe patients' willingness to accept treatment that offers PFS gains without OS gains, to compare these findings with treatments offering OS gains, and to qualitatively summarize patients' reasons for their preferences., Methods: A multicenter, cross-sectional, convergent mixed-methods study design recruited patients who had received at least 3 months of systemic therapy for incurable solid tumors. A treatment trade-off exercise determined the gains in imaging PFS that patients require to prefer additional systemic treatment for a scenario of a newly diagnosed, asymptomatic, incurable abdominal tumor. A qualitative, descriptive, thematic analysis explored factors influencing patients' decisions, and a narrative method integrated the quantitative and qualitative findings., Results: In total, 100 patients participated (63% were older than 60 years of age). If additional treatment with added toxicity offered no OS advantage, 17% would prefer it for no PFS benefit; 26% for some PFS benefit (range, 3-9 months), whereas 51% would decline it regardless of PFS benefit. Similarly, 71% preferred additional treatment offering a 6-month OS advantage dependent on described toxicity levels (P = .03). A spectrum of reasons for these preferences reflected the complexity of participants' attitudes and values., Conclusions: Prolongation of time to progression was not universally valued. Most patients did not prefer treatments that negatively affect quality of life for PFS gains alone. Implications for individual decision making, policy, and trials research are discussed., (© The Author(s) 2023. Published by Oxford University Press.)

Background: The expression of P-glycoprotein (Pgp) is intimately associated with cancer development. In order to explore the therapeutic value of Pgp as a target for chemotherapy, we studied the effect of PSC 833 (PSC), a potent inhibitor of Pgp, on 1,2-dimethylhydrazine (1,2-DMH)-initiated colorectal carcinogenesis in rats., Materials and Methods: Male Fischer 344 rats, initiated with 1,2-DMH coupled with partial hepatectomy, were exposed to dietary 1% orotic acid for 22 weeks. They were then fed either the AIN93G basal diet (BD) or BD containing PSC (a daily dose of 15 mg/kg body weight) for 35 weeks., Results: PSC significantly inhibited colorectal tumor multiplicity by 53% and tumor burden by 74%. PSC-mediated inhibition was evident in tumors as small as 2 mm in diameter and remained effective throughout the course of tumor growth. Histological assessment showed that PSC significantly inhibited tumor progression to colorectal adenocarcinoma by 63%., Conclusion: Collectively, this study indicates that PSC inhibited experimental colorectal carcinogenesis initiated with 1,2-DMH in rats.

Studies in our laboratory on the role of P-glycoprotein (Pgp, coded by mdr1 gene) have led to the hypothesis that over-expression of Pgp is closely associated with the development of cancer. It was conceived therefore that inhibitors of Pgp should inhibit the development of cancer. We have reported that PSC833 (PSC), a potent inhibitor of Pgp, inhibits the development of liver cancer in rats. Similarly, based on the intrinsic over-expression of Pgp in experimental mammary carcinogenesis, we studied the effect of PSC on N-methyl-N-nitrosourea induced mammary cancer in female Sprague-Dawley rats. The study indicates that PSC at daily dietary doses of 15 (PSC15) and 30 mg/kg (PSC30) body wt resulted in dose-dependent inhibition of the incidence as well as the growth of mammary tumors. Compared with controls, PSC15 and PSC30 inhibited: (i) mean tumor multiplicity by 32 and 67%, (ii) median tumor burden by 46 and 93% and (iii) incidence of ulcerated tumors by 40 and 82%, respectively. Most remarkably, PSC delayed median tumor incidence by 8 weeks, and exerted a 100% inhibitory effect on the incidence of large tumors, 4 cm(3) and greater. In all the cases, although the inhibitory effect of PSC was evident at both doses, only PSC30 exhibited statistical significance. A possible compounding effect that was also observed in PSC30-treated rats was a decrease in body weight gain not attributed to diminished food consumption. All in all, consistent with recent reports, which have demonstrated inhibition of cancer development by compromising Pgp function, this study introduces a novel role for Pgp in breast cancer and potentially an unexplored therapeutic approach in treating the disease.

We report a serendipitous finding of urinary calculi in rats fed a semi-synthetic basal diet. This observation was made during ongoing studies to evaluate the inhibitory effect of PSC 833, a potent inhibitor of P-glycoprotein, on development of tumors in rodent tumor model systems. A large number of specific-pathogen-free (SPF) female Sprague-Dawley and SPF male Fischer 344 rats being fed the diet were euthanized when it became evident clinically that they were uremic. At necropsy, the renal pelvis, ureters, and urinary bladder contained numerous calculi. The presence of urinary calculi was determined to be related to the source of a Food Chemical Codex grade of choline bitartrate. Rats being fed the same basal diet containing the United States Pharmacopia grade of choline bitartrate failed to develop urinary calculi. Interestingly, rats treated with the P-glycoprotein inhibitor were at significantly reduced risk of developing urinary calculi. This finding highlights how something seemingly innocuous as a minor dietary constituent can have a profound impact and, thereby, affect experimental outcome.