Leucovorin rescue from raltitrexed (tomudex)-induced antiproliferative effects: in vitro cell line and in vivo mouse studies.

Raltitrexed (RTX) is an antifolate thymidylate synthase (TS) inhibitor that is effective for the treatment of advanced colorectal cancer and other solid tumors. However, a small minority of patients receiving RTX monotherapy will experience grade III/IV gastrointestinal toxicity that can be life-threatening, particularly if copresenting with neutropenia. Lack of vigilance in recognition and treatment of symptoms of toxicity or violations of protocol have led to treatment-related deaths in some hospitals. The safety of RTX could be improved if an effective rescue agent was available. Leucovorin (LV) is a reduced folate cofactor that competes with RTX for transport and polyglutamation in both tumor and normal tissues and thus has potential as a rescue agent. In vitro cell studies are presented suggesting that the growth-inhibitory, and potentially cytotoxic, effects of RTX on populations of viable cells can be reversed by the delayed administration of LV. The mechanisms involved are inhibition of further drug uptake and polyglutamation and a redistribution and/or reduction in the concentration of preformed raltitrexed polyglutamates. A more clinically relevant in vivo mouse model was used to test the hypothesis further. BALB/c mice treated with 100 mg/kg/day x 4 days of RTX were used as a model for gastrointestinal and bone marrow toxicity. LV (200 mg/kg), which was given after the onset of severe weight loss and diarrhea (twice daily, days 5-7), prevented further weight loss and induced earlier recovery. This was accompanied by improvement in the histological appearance of the intestine (day 7) and the concentration of neutrophils and platelets in the blood (day 9). BALB/c mice could not tolerate 100 mg/kg daily x 5 days unless LV (200 mg/kg twice daily) was given on days 6-8. Measurement of RTX (polyglutamates) by RIA after 100 mg/kg RTX daily (days 1-4) showed less drug in plasma (3-4-fold), liver (8-11-fold), kidney (3-4-fold), and small intestinal epithelium (3-4-fold) on day 7 in LV-treated mice (100 or 200 mg/kg twice daily) compared with controls. A single injection of 100 mg/kg RTX (day 1) gave plasma levels of 3-4 pmol/ml on day 4 that are more clinically relevant. Administration of LV (100 or 200 mg/kg; twice daily on days 4-6) reduced the RTX concentration in the liver 2-4-fold on days 7, 9, and 11 compared with controls. A model is proposed where LV and/or its anabolic products can compete with RTX uptake into tissues and interfere with the homeostatic regulation of RTX polyglutamates. These data support the use of LV rescue in the small minority of patients treated with RTX who present with a severe pattern of antiproliferative toxicities. The use of LV is not recommended routinely because the antitumor activity of RTX may similarly be reversed.

Balb/c mice as a preclinical model for raltitrexed-induced gastrointestinal toxicity.

Raltitrexed (RTX) is an antifolate thymidylate synthase (TS) inhibitor used for the treatment of advanced colorectal cancer. RTX induces proliferating tissue toxicities that are largely confined to the intestine, with diarrhea being a severe side effect in a small but significant minority of patients. Similarly, weight loss and diarrhea were observed in BALB/c mice, and a maximum tolerated dose (MTD) was determined as approximately 5-10 mg/kg/day x 5 days. At an equivalent dose of 10 mg/kg/day x 5 days (dl-5), DBA2 mice lost considerably less weight, leading to a higher MTD (>500 mg/kg/day x 5 days), and there was no evidence of diarrhea. Histopathological consequences of damage, such as changes in small intestinal crypt architecture and villus atrophy induced by the 10-mg/kg/day dose, were greater and of longer duration in BALB/c mice. A higher dose of RTX (100 mg/kg/day x 5) induced weight loss and histopathological damage similar to that seen in BALB/c mice (10 mg/kg/ day x 5) but was of later onset, nadir, and recovery. Small changes to the colon were only observed in BALB/c mice. Pretreatment levels of plasma thymidine, deoxyuridine (approximately 1 microM), and folate (approximately40 ng/ml) were similar in both mouse strains. A single injection of radiolabeled RTX (5 mg/kg/ day) did not lead to any marked difference 24 h later in the total drug concentration and distribution of polyglutamates (comprising 70-80% of drug extracted) in the liver, kidney, and intestinal epithelium (large and small intestine) between the two mouse strains. Further studies used a RIA to measure RTX polyglutamate formation in tissues at various times and drug doses. This led to the conclusion that, although there was a higher accumulation of RTX in BALB/c small intestinal epithelium (days 4-6), it may be an effect secondary to another undetermined cause of increased drug sensitivity. This model represents a vehicle by which the etiology and treatment of severe clinical toxicity induced by RTX may be evaluated.

Single agent infusional 5-fluorouracil is not effective second-line therapy after raltitrexed (Tomudex) in advanced colorectal cancer.

Raltitrexed (Tomudex) is currently licensed for first-line treatment of advanced colorectal cancer. We evaluated 101 patients treated with raltitrexed whose data were collected prospectively, in order to study the outcome of second-line treatments used after this drug. Of 98 evaluable patients, 50 received second-line treatments, the commonest being 5-fluorouracil (5-FU)-based therapy (22 patients with 20 evaluable) and mitomycin-c (MMC) (22 patients with 18 evaluable). Only 1 response was seen in a patient treated with 5-FU and MMC and none following other treatments. This patient was not evaluable for outcome of raltitrexed treatment, having stopped after two courses. Patients who had responded to raltitrexed and later progressed off treatment were more likely to be offered second-line 5-FU, but despite the earlier sensitivity to thymidylate synthase inhibition, response rates were minimal. Underlying mechanisms for this lack of activity and proposals for future studies are discussed.

Unknown primary carcinoma: randomised studies are needed to identify optimal treatments and their benefits.

This is a retrospective review of 101 patients with unknown primary carcinoma (UPC) treated between 1989 and 1994, on whom data were collected prospectively. 92 patients received platinum-based chemotherapy and 9 had single agent 5-fluorouracil (5-FU). In the platinum group, an objective response rate of 37.2% was seen, with a median duration of 4.5 months (range 1.9-17.5). There were no responses with 5-FU alone, while median survival was 6.4 months and was not different from the platinum group (P = 0.09). Considerable symptomatic resolution was noted, although the contribution of chemotherapy alone to this is difficult to define. The impact of tumour response on quality of life and survival in UPC requires further elucidation in prospective studies with a "best supportive care' arm. The superiority of platinum-based treatments reported in selected subgroups cannot be applied to the whole spectrum of UPC.

Primary osteosarcoma of the breast.

Osteosarcoma is a rare primary breast tumour. We report on a 55-year-old woman who presented with a left breast lump and a mammogram suggestive of carcinoma. At lumpectomy, a 3 cm mass was removed. Histology was consistent with primary osteosarcoma. There was satisfactory surgical clearance and no evidence of metastasis. She received four courses of adjuvant post-operative chemotherapy and remains free of disease at 14 months from diagnosis.

ZD1694 (Tomudex): a new thymidylate synthase inhibitor with activity in colorectal cancer.

ZD1694 (Tomudex) is a new antifolate which is a specific inhibitor of thymidylate synthase (TS). Evidence suggests that ZD1694 has a spectrum of activity that only partially overlaps with 5-fluorouracil (modulated with leucovorin) against colon tumours in vitro. Potent cytotoxic activity is dependent upon active uptake into cells via the reduced folate/methotrexate cell membrane carrier (RFC) and subsequent metabolism to polyglutamated forms (tri, tetra and pentaglutamates). These polyglutamates are approximately 60-fold more active as TS inhibitors and are not effluxed readily from cells. Extensive polyglutamation also occurs in various mouse tissues (e.g. small intestinal epithelium, liver and kidney), resulting in high tissue/plasma drug ratios which persist for a prolonged period. ZD1694 has antitumour activity in mice, although the high plasma thymidine in this species complicates: (1) the interpretation of therapeutic index; (2) tumour types in which activity is likely to be observed; and (3) translation of doses and schedules for clinical evaluation. ZD1694 entered clinical study and has completed Phase I and II evaluation, with activity observed in several tumour types. Appreciable activity in the Phase II colorectal study (29% objective response rate on interim analysis) led to the current Phase III study, randomised against 5-fluorouracil/leucovorin.

Campylobacter fetus endocarditis: two case reports and review.

We report two cases of Campylobacter fetus endocarditis. The first case involved a bicuspid native aortic valve in a 60-year-old woman, and the second involved a prosthetic aortic valve in a 76-year-old woman. No source of infection was identified in either case. Despite antibiotic therapy, hemodynamic deterioration necessitated valve replacement; both patients recovered completely. C. fetus is an uncommon cause of human infection but may be responsible for severe illnesses such as endocarditis and thrombophlebitis because of its tendency to attack the vascular endothelium. Review of the literature revealed 21 cases of endocarditis caused by this organism, usually involving the aortic valve. To our knowledge, there are only two reported cases of prosthetic valve endocarditis. Our second patient is the oldest one encountered so far with this condition.