High-dose cytosine arabinoside in previously treated patients with poor-prognosis non-Hodgkin's lymphoma

The Impact of Immunological Checkpoint Inhibitors and Targeted Therapy on Chronic Pruritus in Cancer Patients

Although pruritus may sometimes be a consequential situation to neoplasms, it more frequently emerges after commencing chemotherapy. In this review, we present our analysis of the chemotherapy treatments that most often induce skin changes and itching. After discussing conventional chemotherapies capable of inducing pruritus, we present our evaluation of new drugs such as immunological checkpoint inhibitors (ICIs), tyrosine kinase inhibitors, and monoclonal antibodies. Although ICIs and targeted therapy are thought to damage tumor cells, these therapies can modify homeostatic events of the epidermis and dermis, causing the occurrence of cutaneous toxicities in treated subjects. In the face of greater efficacy, greater skin toxicity has been reported for most of these drugs. A remarkable aspect of some reports is the presence of a probable correlation between cutaneous toxicity and treatment effectiveness in tumor patients who were treated with novel drugs such as nivolumab or pembrolizumab. Findings from these experiments demonstrate that the occurrence of any grade of skin side effects can be considered as a predictor of a better outcome. In the near future, studies on the relationship between the onset of skin alterations and outcomes could open new perspectives on the treatment of neoplasms through specific target therapy.

Pilot phase I/II study of new salvage therapy (CHASE) for refractory or relapsed malignant lymphoma

A pilot phase I/II study was conducted as a single-institute trial for evaluation of the feasibility and efficacy of a new salvage chemotherapy, CHASE, for patients with refractory or relapsed lymphoma . The CHASE regimen, consisting of cyclophosphamide, cytosine arabinoside, etoposide, and dexamethasone, was administered every 3 weeks in a maximum of 5 courses. A total of 16 patients were eligible and registered for this study. Myelosuppression was the major toxicity. Although grade 4 leukopenia and grade 3 thrombocytopenia were identified in 15 and 16 patients, respectively, duration of the nadir was brief (median, 3 days). Nonhematological grade 4 toxicity was not observed, and transient elevations of bilirubin and grade 3 aspartate aminotransferase/alanine aminotransferase (AST/ALT) were observed in 2 and 3 courses, respectively, in a total of 57 courses. Complete and partial response rates were 71.4% (10/14) and 7.1% (1/14), respectively. The median percentage of maximal CD34+ cells was 6.1% on day 15, and a median number of 1.88 x 10(6) CD34+ cells/kg per apheresis were obtained. Thirteen patients received high-dose chemoradiotherapy followed by autologous peripheral blood stem cell transplantation. With a median follow-up time of 36 months from the start of CHASE, the overall survival rate for the 16 patients was 66.6%. These results indicated that CHASE is a safe and effective salvage regimen for malignant lymphoma, has sufficient mobilizing effect on peripheral blood stem cells, and warrants further phase II study.

Cisplatin, fludarabine, and cytarabine: a novel, pharmacologically designed salvage therapy for patients with refractory, histologically aggressive or mantle cell non-Hodgkin's lymphoma

BACKGROUND

Based on in vitro synergism, the combination of cytarabine (ara-C) and cisplatin is the basis of many salvage regimens for patients with aggressive non-Hodgkin lymphoma (NHL). However, patients with previously refractory disease are significantly less likely to respond, stimulating the search for novel salvage regimens. In vitro, fludarabine enhances the cytotoxicity of both ara-C and cisplatin, increasing ara-C incorporation into DNA and inhibiting repair of platinum/DNA adducts, suggesting that the combination of cisplatin, fludarabine, and ara-C (PFA) may have clinical utility.

METHODS

A Phase-II study of a 96 hour continuous infusion of cisplatin with two timed-sequential couplets of fludarabine and ara-C together with granulocyte colony stimulating factor was performed in 45 patients with previously refractory, histologically aggressive or mantle cell NHL.

RESULTS

Patients had predominantly diffuse large cell and/or immunoblastic NHL or its variants (80%), or they had mantle cell lymphoma (18%). Overall, 93% of patients had previously refractory disease, with a median International Prognostic Index score of 3. A median of 2 cycles per patient were delivered (range, 1-4 cycles) with significant myelosuppression; there were medians of 2 days of neutropenia < 0.5 x 10(9)/L (range, 0-12 days) and 3 days of thrombocytopenia < 20 x 10(9)/L (range, 0-24 days). This was more severe in older patients and was cumulative with successive cycles. Thirty-five percent of cycles were complicated by infections, nausea and emesis were prominent, but other nonhematologic toxicity was mild. Peripheral blood progenitor cells were mobilized adequately after the first cycle, but collections were impaired after more prolonged therapy. The overall response rate was 48% (7% of patients had complete responses, and 41% of patients had partial responses), with one toxic death due to tumor-lysis syndrome. Patients with mantle cell lymphoma were more likely to respond than patients with other histologies (88% vs. 39%, respectively; P = 0.019), although three of eight patients had relapsed rather than refractory disease. The median remission duration was 4 months, with 28% of potentially eligible patients able to proceed to subsequent high dose therapy. The actuarial 2 year survival rates were 20% +/- 6% overall and 50 +/- 18% for patients with mantle cell lymphoma.

CONCLUSIONS

Given the adverse outlook for these patients, the results are promising, particularly for patients with mantle cell lymphoma, and suggest that the addition of fludarabine as a potential biochemical modulator may enhance the activity of cisplatin and ara-C. This is associated with significant cumulative (but manageable) myelosuppression. This paradigm, in which a nucleoside analogue is used to inhibit the repair of platinum/DNA adducts, also may be applicable for the treatment of patients with other types of platinum-sensitive tumors.

Impact of high-dose cytosine arabinoside in poor-prognosis acute lymphoblastic leukemia: Cancer Institute experience, Chennai, India

High-dose cytosine arabinoside (HD-AraC) has been used in relapsed and refractory cases of acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). Sixty-two poor-prognosis ALL patients were treated with HD-AraC between 1983 and 1995 at the Cancer Institute, Chennai, India. Of them, 37 had experienced a relapse, 16 were partial responders (refractory) to the induction regimen, and 9 were high risk due to central nervous system or testicular involvement or total counts above 200,000/mm3 at presentation. Of the 37 patients with relapses, 22 (59.5%) achieved complete remission (CR) and 10 had no evidence of disease (NED); of the 16 refractory group patients, 10 achieved CR and 2 had NED; and of the 9 high-risk patients, 5 had NED at the end of the study. The 5-year event-free survival (EFS) values of relapsed, refractory and high-risk group categories were 21.7%, 12.5%, and 55.6%, with a mean duration of 41 months, 18 months, and 85 months, respectively. Total alopecia and grade IV myelosuppression were the predominant toxicities. HD-AraC is an effective drug in the treatment of relapsed and refractory acute leukemias and can overcome relative drug resistance in high concentrations.

Long-term follow-up of platinum-based lymphoma salvage regimens. The M.D. Anderson Cancer Center experience

Platinum-based regimens have been the most commonly used salvage therapy for non-Hodgkin's lymphoma (NHL). In this update of two of these regimens with long-term follow-up data, we provide evidence that the etoposide-containing regimen (ESHAP) is superior to a cisplatin-cytosine arabinoside-based regimen (DHAP) in response rate, survival, and time to treatment failure. In spite of this superiority, the long-term outcome for most patients with relapsed or refractory NHL remains unfavorable. Newer salvage regimens such as MINE-ESHAP, or, when feasible, high-dose chemotherapy with transplant, are probably better choices than either DHAP or ESHAP alone.

Intracellular pharmacodynamic studies of the synergistic combination of 6-mercaptopurine and cytosine arabinoside in human leukemia cell lines

Selective combinations of purine and pyrimidine analogs increase remission rates in pediatric patients with relapsed leukemias. The combination of 6-mercaptopurine (6-MP) and cytosine arabinoside (ara-C) may exhibit synergism similar to that observed for fludarabine and ara-C and may diminish the potential for development of resistance since the two drugs are activated by separate enzymatic pathways. To determine the efficacy of the combination against human leukemia cells, we investigated the time-concentration relationships of the drugs given alone or in combination to the resultant cytotoxicity. To determine whether the combination leads to enhanced activity of deoxycytidine kinase (dCk), the rate-limiting enzyme in ara-C activation, we characterized the cellular dCk in CCRF/CEM/0, CCRF/CEM/ara-C/7A, and CCRF/CEM/ara-C/3A monoclonal cells before and after treatment with 6-MP. CCRF/CEM/0 (wild type), CCRF/CEM/ara-C/7A (approximately 50% ara-C-resistant as determined by ara-C sensitivity assay and dCk characterization), and CCRF/CEM/ara-C/3A (approximately 90% resistant to ara-C) human leukemia cells were incubated with various concentrations of 6-MP and ara-C given alone or in combination. Cell survival, inhibition of DNA synthetic capacity (DSC), ara-CTP anabolism, and dCk enzymatic characteristics were studied. Incubation of CEM/0 cells with 6-MP for 24 h, followed by ara-C for 48 h, increased cell-growth inhibition by approximately 0.5-1 log10, corresponding to 5- to 10-fold synergism, as compared with ara-C alone after identical drug incubation in all cell lines. Simultaneous administration showed no synergism, whereas reversal of the sequence produced an antagonistic effect. The ara-CTP levels were 2- to 3.5-fold and 3- to 5-fold higher in CEM/0 and CEM/ara-C/7A cells, respectively, in cells exposed to 6-MP followed by ara-C than in those exposed to ara-C alone at the same concentrations. Furthermore, a progressive increase in ara-CTP levels was noted in CEM/0 cells exposed to increasing concentrations of 6-MP followed by 10 or 20 microM ara-C. A significant decrease in DSC was observed upon treatment of wild-type and ara-C-resistant cells with 6-MP and ara-C. The combination of 6-MP and ara-C exhibits significant sequence-specific synergism in both wild-type and partially ara-C-resistant leukemia cell lines. The combination also exerts collateral sensitivity in the ara-C-resistant cell lines. 6-MP pretreatment may play a role in enhancing ara-C activation, thus producing drug synergism in sensitive and resistant leukemia cell lines.

Toxicity of high-dose cytosine arabinoside in the treatment of advanced childhood tumors resistant to conventional therapy. A Pediatric Oncology Group study

Experience with high-dose cytosine arabinoside (HDAC) in pediatric solid tumors is limited. Sixteen children with solid tumors resistant to conventional therapies were registered in a pilot Pediatric Oncology Group (POG) study that required the administration of HDAC at 3 g/m2 every 12 hours for four doses. There were four cases of rhabdomyosarcoma, two cases of fibrosarcoma, four cases of neuroblastoma, and one case each of germ cell tumor, Wilm's tumor, retinoblastoma, hepatocellular carcinoma, Ewing's sarcoma, and Burkitt's lymphoma. All eligible patients had advanced diseases and had previously received extensive chemotherapy. Thirteen patients received one course of HDAC and three patients received two courses of HDAC. Due to prior treatments, patients had less than normal marrow reserves. Short-term toxicity included nausea, vomiting, suppression of hemopoiesis, drug fever, and increased blood urea nitrogen (BUN), creatinine, and liver enzymes. All evaluable patients recovered from their toxicities. There were no drug-related deaths. None of the patients had neurologic problems, including the only patient with prior irradiation to the skull. With the above schedule, HDAC appears to have manageable toxicity.

Treatment of refractory Hodgkin's disease with high-dose cytosine arabinoside and mitoxantrone in combination. Results of a clinical phase II study of the German Hodgkin Study Group

In the present study, the activity and side effects of high-dose cytosine arabinoside (HD-Ara-C) in combination with mitoxantrone (mitox) (HAM) was evaluated in 32 heavily pretreated patients with refractory Hodgkin's disease. Therapy consisted of HD-Ara-C 3 g/m2 every 12 hours days 1 and 2 and mitox 10 mg/m2/d days 3 to 5. In subsequent steps, HD-Ara-C was escalated to six and eight doses for 3 and 4 days, respectively, and mitox to four doses on days 2 to 5. Thirty-two patients 17 to 55 years of age entered the study. Twenty-five cases presented with extranodal disease and disseminated organ involvement and 21 revealed systemic (B) symptoms. Eighteen patients (56%) responded with five complete and 13 partial remissions, ten patients (31%) had refractory disease, and four patients died from infections during treatment-induced cytopenia. The predominant toxicity was severe myelosuppression in all patients with major infections occurring during 55% of treatment courses. Ten of the responding 18 patients underwent subsequent autologous (n = 9) or allogeneic bone marrow transplant (BMT). Seven of these cases are currently alive at 5+ to 22+ months, six of them without evidence of disease. Among the remaining eight patients not receiving BMT, three are alive at 6+ to 19+ months from the initiation of HAM, two of them in ongoing remissions of 2+ and 5+ months' duration. Two patients died from transplant-related complications and six patients succumbed to progressive disease following relapse. The median survival for all treated patients is 6.2 months. These data indicate that HAM has a significant activity in refractory Hodgkin's disease. However, the substantial side effects and the lack of an obvious superiority to alternative, less intensive regimens limits the further application of the two-drug combination in its present form. Modifications in timing and dosage and the addition of hematopoietic growth factors will be evaluated in subsequent trials.

Acute tumor lysis syndrome and treatment response in patients treated for refractory chronic lymphocytic leukemia with short-course, high-dose cytosine arabinoside, cisplatin, and etoposide

Acute tumor lysis syndrome resulting from rapid neoplastic cell lysis after chemotherapy is an unusual event, generally seen in histological aggressive lymphatic tumors. The authors saw four patients who developed acute tumor lysis syndrome when treated for advanced-stage, refractory chronic lymphocytic leukemia (CLL) with an initial cycle of cytosine arabinoside (Ara-C) 2 g/m2 every 12 hours x 4, cisplatin 35 mg/m2 every 24 hours x 2, and etoposide 100 mg/m2 every 24 hours x 2 (ACE). With aggressive hydration, urine alkalinization, forced diuresis, and high-dose allopurinol, acute tumor lysis syndrome was not seen in three subsequent cases of CLL treated with ACE. Of a total of eight patients treated, seven patients had marked reductions in lymphocyte counts after the first course of ACE. Of the eight patients, three are alive: one in a complete remission greater than 2 years, one in partial remission after three cycles of ACE, and one in Richter's transformation to large cell lymphoma. The remaining patients died after one cycle of ACE chemotherapy, one as a direct complication of acute tumor lysis and pancytopenia, and four others from complications of severe pancytopenia and general debilitation. Therefore, ACE appears to cause a rapid dissolution of tumor cells in CLL, and with appropriate aggressive management of the tumor lysis and infectious complications may have a favorable impact on survival in advanced CLL.

Long-term follow-up of patients receiving salvage chemotherapy for intermediate and high grade non-Hodgkin's lymphomas

This is an analysis of the long-term follow-up data of 99 patients receiving HOAP-Bleo, IMVP-16 and PAC as salvage chemotherapy for refractory or relapsed intermediate or high grade non-Hodgkin's lymphomas. Most of the patients received HOAP-Bleo or PAC following failure of initial chemotherapy and IMVP-16 was used mainly for HOAP-Bleo failures. The longest follow-up time of the surviving patients was 108 months. Twenty-two and 29 per cent of the patients survived beyond 2 years following HOAP-Bleo and PAC respectively. The treatment outcome following IMVP-16 was worst with a 2-year survival of only 5 per cent, as it was used mainly following HOAP-Bleo failures. Although the prognosis of these refractory or relapsed cases are poor, salvage treatment is still worthwhile as a small proportion of these patients may have long-lasting remissions and occasional patients may be cured. Newer approaches such as autologous bone marrow transplantation should be compared with current salvage chemotherapy regimens.

Phase II cooperative study with a new alkylating drug, PTT-119, in the treatment of non-Hodgkin's lymphomas

In a phase II cooperative study involving eleven Italian haematological units, the efficacy and toxicity of a new alkylating compound, PTT-119, was evaluated in 53 patients with non-Hodgkin's lymphoma (NHL). Forty-five of the patients had been previously treated with various regimens of chemotherapy, the remaining eight were at the onset of the disease. PTT-119 was scheduled at 3.0 mg/kg every three weeks for a minimum of three administrations. Seven patients achieved a complete remission (CR), 19 a partial remission (PR); the overall response rate was 49%. The median duration of response was 6 months. Most frequent adverse effects were alopecia, nausea and vomiting and phlebitis due to the drug infusion. Myelosuppression was severe only in patients with bone marrow involvement or who were heavily pretreated. No liver, cardiac or renal toxicity was recorded. These data indicate that PTT-119 is an effective drug in the treatment of NHL; the matter of its non-cross-resistance with other alkylating compounds warrants further studies.

The toxicity of cytarabine

The principal toxicity of standard induction regimens for acute non-lymphocytic leukemia (ANLL) [including cytarabine (ARA-C) 100 mg/m2 for 7 days plus an anthracycline] is myelotoxicity, leading to death in at least 25% of cases during induction in non-selected patients. The complete remission rate is less than 35% in patients over 65 years of age, due in part to an age-related increase of myelotoxicity. The other important adverse effect of standard-dose cytarabine is gastrointestinal toxicity, especially oral mucositis, diarrhoea, intestinal ulceration, ileus and subsequent Gram-negative septicaemia. Idiosyncratic reactions like exanthema, fever and elevation of hepatic enzymes are relatively frequent, but do not represent therapeutic problems. Intermittent high-dose cytarabine (3 g/m2 in 8 to 12 doses) is extremely myelosuppressive. Similarly, the gastrointestinal toxicity is formidable and dose-limiting. Severe, and sometimes irreversible, cerebellar/cerebral toxicity in 5 to 15% of courses of treatment limits the peak dose of cytarabine. The pathogenesis, prophylactic and therapeutic measures are unknown. These major toxicities are age-related and prohibitive to the use of high-dose cytarabine therapy in patients older than 55 to 60 years. Subacute noncardiogenic pulmonary oedema occurs in some patients, with an incidence of about 20%, and seems to have an intriguing coincidence with precedent streptococcal septicaemia; high-dose systemic steroids may be beneficial. Corneal toxicity is very frequent in high-dose cytarabine therapy but is always reversible. It is largely preventable with prophylactic steroid or 2-deoxycytidine eyedrops. Fever, exanthema and hepatic toxicity have an incidence similar to that in standard dosage. The maximum tolerable cumulated dose of cytarabine is significantly lower when the agent is administered as a continuous infusion, due to myelosuppression and gastrointestinal toxicity. Conversely, continuous infusion may be less neurotoxic. The antileukaemic effect of continuous infusion high-dose cytarabine is less well established. The only significant toxicity of low-dose cytarabine is myelosuppression. Given the generally poor condition of leukaemia patients, low-dose cytarabine therapy is well tolerated, although occasional cases of diarrhoea, reversible cerebellar symptoms, peritoneal and pericardial reactions, and ocular toxicity have been reported. Continuous infusion may be more toxic than the usual intermittent dosage. It is concluded that the toxicity of the standard induction regimen for ANLL is acceptable in patients younger than 60 to 65 years with no concurrent disease. Low dose cytarabine is tolerable for virtually all ANLL patients, but the overall therapeutic efficacy still needs to be defined and compared to standard therapy in the relevant age groups.(ABSTRACT TRUNCATED AT 400 WORDS)

High-dose cytosine arabinoside in relapsed and refractory non-Hodgkin's lymphoma. Limited role as a single agent

Cytosine arabinoside (ara-C) is an S-phase active antineoplastic agent used in the treatment of several hematologic malignancies. We did a retrospective analysis on 48 patients with relapsed or refractory non-Hodgkin's lymphoma (NHL) who were treated with high-dose ara-C between 1982 and 1987. All patients received between 9 and 24 g/m2/course of treatment with 90% receiving 12g/m2/treatment. Fifteen patients (25%) achieved a complete or partial remission. Of these, five (10%) were complete responders. Long-term disease-free survival was maintained only in those responders who were consolidated with autologous bone marrow transplantation. Toxicity was primarily myelosuppression. Seventy-five percent of patients developed fever and neutropenia with an equivalent percent having severe thrombocytopenia sufficient to require platelet transfusion. Five patients (10%) had significant neurotoxicity. There were seven treatment-related deaths (15%). Patients in whom tumors contained a small cell component responded better than patients with purely large cell or undifferentiated lymphomas (50% versus 15%, P = 0.024). We conclude that high-dose ara-C given as 3g/m2 every 12 hours for four doses has a limited role when used as a single agent in the treatment of relapsed or refractory non-Hodgkin's lymphoma. However, there are subsets of patients who may respond favorably to this therapy.

Mitoxantrone and high-dose cytarabine as salvage therapy for refractory non-Hodgkin's lymphoma

Mitoxantrone (Novantrone, NO) and high-dose cytarabine (Ara-C, AC) have each been shown in monotherapy trials to be active in non-Hodgkin's lymphoma (NHL). In the current study, a combination of the two drugs (NOAC) was administered to 31 patients with advanced NHL refractory to modern sequential chemotherapy regimens. Ara-C was administered at 3 g/m2 as a 3 hour infusion every 12 hours on day 1 (2 doses) and mitoxantrone at 10 mg/m2/day on days 2 and 3. Of the 18 patients with high-grade malignant NHL, six have attained a complete remission (CR) and two, a partial remission (PR). One CR and 5 PRs were achieved among the other 13 patients with intermediate or low-grade NHL. The median time to relapse (TTR) of patients achieving CR was 7 months with a range from 4 to 17 months. Myelosuppression with subsequent infections was the major toxicity of this regimen. The median duration of severe neutropenia (less than 0.5/nl) was 9 days with a range of 0 to 27 days and the median duration of severe thrombocytopenia (less than 20/nl), 5 days with a range of 0 to 35 days. Infectious complications during cytopenia was seen in 45.3% of the courses administered and fever of unidentified origin was seen in 42.3%. About 63% of the patients were hospitalized for intravenous antibiotic or antimycotic treatment. Other side effects were mild and included nausea, stomatitis, and transient tachycardia of greater than 100/min. Thus, this regimen was active in refractory NHL with poor prognosis, and the toxic side effects were not excessive. Evaluation of the activity of this regimen at higher dose levels of Ara-C is warranted.

Effect of cytosine arabinoside on the human immunosystem: metabolism and cytotoxicity studied with mitogen-stimulated normal blood lymphocytes in vitro

The toxicity, metabolic effects and metabolism of cytosine arabinoside (Ara-C) were studied with normal human peripheral blood PHA-stimulated mononuclear cells in vitro. Clinically relevant Ara-C concentrations were toxic against mitogen-stimulated blood lymphocytes. Dose-dependent effects included: (i) increased cell loss, (ii) decreased DNA synthesis assessed by 3H-thymidine incorporation, (iii) decreased blastic transformation, (iv) decreased protein synthesis assessed by 14C-leucine incorporation, (v) an inhibition of the production of new cells, (vi) a delay in the proceeding of the PHA-stimulated cells to the cell cycle, (vii) an arresting of the cells in the S-phase, and (viii), a dose-dependent decrease of the number of mitoses in Ara-C-treated cultures. The mode of cell death was of the delayed type. The toxicity of Ara-C was effectively reversed by an excess of deoxycytidine, but not by cytidine or other conventional nucleosides, which is highly suggestive that the molecular mechanism of Ara-C toxicity is based on its anti-metabolic role in the salvage pathway of biosynthesis of DNA deoxycytidine. In fact, we demonstrated that Ara-C is metabolized to Ara-CTP and to a lesser extent also incorporated into DNA in human PHA-stimulated lymphocytes. Ara-C significantly decreased its own uptake and DNA incorporation. On the other hand, uracil arabinoside, which was the major catabolic product of Ara-C, was not toxic to human PHA-stimulated T-cells. The antiproliferative effect of Ara-C against human T-cells resembled that previously demonstrated with various cancer cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic progress--review XXVII. High dose chemotherapy in haematological malignancy

Having reviewed conventional chemotherapy of acute leukaemia in the preceding article, a discussion of high dose chemotherapy in haematological malignancy is presented. The indications and side-effects of high dose methotrexate, ifosfamide and etoposide (VP-16) are summarized in tabular form. The toxicity and effectiveness of high dose cytosine arabinoside in the treatment of refractory acute leukaemia is discussed. The use of high dose melphalan to treat patients with multiple myeloma or other tumours is reviewed. The most widely used cytoreductive regimes in bone marrow transplantation, high dose busulphan, high dose cyclophosphamide and total body irradiation are described.

Toxicity of high dose Ara-C in children and adolescents

The toxicity of high dose cytosine arabinoside (Ara-C) in 23 leukemic children aged 1.5 years to 16 years 11 months was evaluated. The group included 11 children with acute lymphoblastic leukemia (ALL), nine with acute nonlymphoblastic leukemia (ANLL), two with chronic myelocytic leukemia (CML) in blastic crisis, and one with Burkitt's lymphoma. Toxicity consisted of bone marrow suppression in all patients, with a mean nadir time of 11 days for platelets and granulocytes. All patients experienced nausea and vomiting; 12 of 23 had drug induced fever; seven of 23 conjunctivitis; five of 23 mucositis; four of 23 diarrhea, and one of 23 elevated transaminase with hyperbilirubinemia. Adverse reactions were mild and reversible in all patients. No serious neurologic toxicity was seen. The toxicity observed in four patients with prior cranial irradiation was not any different from nonirradiated patients. The only life-threatening effect was neutropenia, the consequences of which were generally well controlled with antibiotic therapy. While this agent was effective in induction of remission in AML patients resistant to standard doses of Ara-C, it had no significant effect in a very small number of patients with relapsed ALL and CML in blast crisis. Side effects of high dose Ara-C though relatively substantial are manageable enough to warrant wider scale efficacy trials of this agent in childhood leukemias and solid tumors.

Effect of cytosine arabinoside on the human immunosystem: toxicity against quiescent human peripheral blood mononuclear cells in vitro

The toxic and metabolic effects of cytosine arabinoside (Ara-C) were studied in vitro with normal human peripheral blood mononuclear cells. The majority of target cells were T-lymphocytes. Dose-dependent toxicity of clinically relevant Ara-C concentrations was manifested by increased cell loss, inhibition of spontaneous blastic transformation, inhibition of DNA synthesis assessed by 3H-thymidine incorporation, inhibition of protein synthesis assessed by 14C-leucine incorporation, and inhibition of the mitogenic response of T-lymphocytes when challenged with phytohemagglutinin after Ara-C treatment. Cell death among the resting cells was delayed and it was mainly, if not entirely, cell-cycle-independent, since most of the cells stayed in the G0- or G1-phase. The toxicity of Ara-C was effectively reversed by an excess of deoxycytidine. This suggests that the molecular mechanism of Ara-C toxicity against quiescent peripheral blood mononuclear cells is based on its anti-metabolic role in the salvage pathway of biosynthesis of DNA deoxycytidine.