Metronomic therapy for refractory/relapsed lymphoma: the PEP-C low-dose oral combination chemotherapy regimen

Abstract

Background: Metronomic therapy is the application of continuous, low dose chemotherapy. The doses of chemotherapy are usually not sufficient to destroy neoplastic cells, but impact the milieu, particularly angiogenesis.

Objective: To determine if the oral PEP-C regimen, consisting of prednisone 20 mgm, etoposide 50 mgm, procarbazine 50 mgm, and cyclophosphamide 50 mgm given in either a daily, alternate day, or fractionated basis, is effective in a variety of lymphomas.

Methods: One hundred twenty two patients were studied although the majority had low grade or mantle cell lymphoma. All had received at least two or more prior therapies.

Results: Overall, 75% achieved an objective response (OR) with 38% complete responses (CRs) or CRs unconfirmed, and 37% partial responses. ORs were achieved in mantle cell (85%), follicular (88%), marginal zone (71%), and small lymphocytic (67%) lymphomas. Chemosensitive disease was more responsive. Toxicity was minimal.

Conclusion: The PEP-C regimen is an easily administered highly effective treatment for heavily pretreated mantle cell and low grade lymphomas.

Keywords:

• Lymphoma
• Metronomic therapy
• Angiogenesis
• Low dose chemotherapy
• Mantle cell lymphoma
• Follicular lymphoma
• Marginal zone lymphoma
• Small cell lymphoma
• Refractory lymphoma

Background

Metronomic therapy offers a novel, less toxic approach for refractory or relapsed lymphoma patients who, because of prior therapy or ‘frailty’, are unable to tolerate intensive chemotherapy, usually given in an intermittent, bolus fashion. Metronomic application of chemotherapy entails a constant, usually daily, low dose of therapy not designed necessarily to attack the neoplastic cell, but to target the cancer’s milieu, its angiogenesis and/or microenviroment, elements vital for the survival and growth of the tumor.1^–5

The metronomic prednisone, etoposide, procarbazine, and cyclophosphamide (PEP-C) regimen, developed at Cornell over the past 20 years, has been successful in treating many patients with lymphoma, all of whom had refractory or relapsed disease from multiple prior chemotherapies, often in high dose.1^–3 While tumor microvascularity is putatively sensitive to low doses of chemotherapy not effective against tumor per se, continuous therapy may have additional effects, including overriding forms of drug resistance, such as those of the P-glycoprotein pump product expressed by the mdr-1 gene.⁶ Continuous intravenous infusion of chemotherapy throughout the day is probably the fullest expression of constant dosing. Nevertheless, oral chemotherapy given throughout the day may, to a large degree, mimic this action. In contrast to some oral maintenance regimens which employ only a single agent, the PEP-C regimen uses a combination of drugs given throughout the day with different mechanisms of action. This constant application of treatment continues over days, weeks, or months, in contrast to intravenous infusions which are applied for no more than a few days or a maximum of 1 week.⁶

Methods

The PEP-C regimen consists of oral prednisone 20 mg after breakfast, cyclophosphamide 50 mg after lunch, etoposide 50 mg after dinner, and procarbazine 50 mg at bedtime with an anti-emetic. All medications are administered daily, until the white blood count falls to less than 3000, whereupon treatment is withheld until recovery from the nadir. Therapy is then reinstituted on a daily, alternate day, or fractionated weekly basis (e.g. 5 of 7 days) depending on the patients’ tolerance. Doses given per day are held constant. Three reports have been published on the PEP-C regimen. The first report detailed the combination regimen in a broad array of lymphomas, while the latter two reports detailed results on its use in mantle cell lymphoma (MCL). The last of the reports, concerned with MCL, recounted results obtained with a combination of PEP-C with rituximab and thalidomide. All of the patients in these reports had received prior therapy, usually two or more chemotherapeutic regimens.1^–3

Results

Responses

In aggregate, 122 patients have been treated. Overall 75% achieved an objective response [complete response/complete responses unconfirmed, 38%; partial response, 37%]. Objective responses in mantle cell and low-grade lymphoma were the highest (mantle cell, 85%; follicular, 88%; marginal zone, 71%; and small lymphocytic, 67%). More complete or near complete remissions occurred with mantle cell (40%), follicular (54%), and marginal zone (36%) than with small lymphocytic (17%) lymphoma. Overall responses in more aggressive histologies, such as Hodgkin lymphoma (44%), large cell lymphoma (33%), and T-cell lymphoma (60%), were less, particularly in rapidly growing or ‘explosive’ disease. Chemosensitive relapsed patients were more responsive (overall response, 93%) than those chemoresistant (60%) with chemosensitive patients achieving double the number of complete responses.

Duration of response

Because some patients were arbitrarily removed from treatment for various reasons not related to PEP-C failure or toxicity, time on therapy was chosen as a measure. The median time on treatment was 9 months with patients in complete remission and/or with non-aggressive histologies faring best. Some patients have remained on therapy up to and beyond 4 years. Alternate reasons for removal from therapy included observation, patient non-compliance, transplantation, and experimental treatments.

Toxicity

Because a reduction in the white blood count by design was considered a target ‘end point’ of induction, it was not considered as an adverse reaction.</emph> Myelosuppression did occur, sometimes for weeks, usually in heavily pretreated patients. Nevertheless, infections requiring hospitalization occurred in only 5% of patients. There were some episodes of fever and infection not requiring hospitalization, gastrointestinal upset (in a few instances requiring withdrawal from therapy), hematuria, and anemia, but almost all were of Grade 1 or 2 toxicity and were easily managed with supportive measures. The percentage of patients experiencing Grade 3 or 4 toxicities was usually in low, single digits except for thrombocytopenia (11%).

Laboratory investigations

Angiogenesis biomarkers were analyzed on the available pre-treatment tissue specimens in those patients treated on the third (mantle cell) protocol (which included the employment of thalidomide and rituximab).6 In addition, dynamic levels of plasma vascular endothelial growth factor (VEGF) and circulating endothelial cells at baseline and during therapy were measured and correlated to response in a subset of patients with available specimens.

VEGF receptor (VEGFR) expression

VEGFR-1 expression was detected consistently by immunohistochemistry on the surface of the neoplastic B cells. In addition to neovasculature, VEGFR-1 expression in primary MCL B cells was higher than that of MCL cell line Jeko-1 and normal donor B cells by real time PCR. VEGFR-2 and VEGFR-3 expression on MCL B cells could not be demonstrated.

Vascular stroma profiling

Stromal angiogenesis was assessed using blood vascular and perivascular markers, including VEGFR-1, VEGFR-2, CD-34, alpha-smooth muscle actin, as well as lymphatic vascular markers of VEGFR-3, podoplanin, and LYVE-1. In addition to VEGFR-1, tumor neovessels were marked by VEGFR-2 and CD34. A majority of CD34⁺ tumor endothelial cells coexpressed VEGFR-2. Tumor B cells expressed VEGF-A in a paracrine fashion, in relation to VEGFR-2⁺ tumor endothelia. Most CD34⁺ tumor microvessels were ensheathed by alpha-smooth muscle actin-positive pericytes. Evident in the tumor-infiltrating sinus zone was significant lymphangiogenesis activity marked by VEGFR-3⁺, podoplanin⁺, and LYVE -1 lymphactic vessels, some of which coexpressed CD34. The heightened angiogenesis and lymphagiogenesis in MCL implicate their role in promoting lymphoma growth and spread.

Plasma VEGF

Baseline median plasma VEGF (N = 20) was 109·5pg/ml (range 7–319, n = 20) compared to 68·2 pg/ml (range 8–98, n = 5) in normal controls. There were no statiscally significant differences between responders and non-responders (100·5 pg/ml versus 155·9 pg/ml, P = 0·44), although the median VEGF trended higher in non-responders. Thirteen patients (11 responders and two non-responders with stable disease) had consecutive samples on therapy, and were analyzed in an exploratory fashion to correlate levels to clinical responses. Although not statistically significant, the median VEGF levels trended down with time during treatment in both responders and non-responders. At 3 months, 62% of the 13 patients had a reduction in plasma VEGF, while 38% had an increase.

Circulating endothelial cells (CECs)

Total CECs, defined as CD45⁻, CD146⁺,CD31⁺, CD34⁺ cells, were quantified in 10 consecutive patients (seven responders) during treatment. Median baseline CECs were 47·9 cells/ml (range 4·7–254·3 cells/ml). At month 1, eight out of 10 patients had an increase in CECs, while two had a decrease. Compared to baseline CECs, median CECs at month 1 trended up, although not statistically significant, and then trended down after month 2. No significant differences in median values were detected between responders and non-responders.

Discussion

While the exact mechanisms of metronomic therapy are not thoroughly understood, the principal targets of metronomic therapy are thought to be the endothelial cells of the growing tumor vasculature.4,5 In addition, metronomic therapy has been shown to suppress the surge of bone marrow derived endothelial progenitor cells mobilization following conventional ‘maximally tolerated dose therapy’.4,5 While the precise role of tumor angiogenesis in MCL pathogenesis remains under active investigation, our exploratory correlative data indicate that MCL has increased angiogenesis in the tumor microenvironment. Thus, our laboratory data, though limited, support the concept of anti-angiogenesis therapy in MCL. It is difficult to determine whether any putative beneficial effect in study 3 is due to anti-angiogenic properties of PEP-C or thalildomide since immunomodulatory drugs are reputed to have such properties and also impact the microenvironment. Immunomodulatory drugs, lenalidomide, as well as thalidomide, do have efficacy in MCL. The combination of thalidomide with rituximab was added to PEP-C, because of the reported efficacy of the two drugs in MCL.^7,8 Rapidly growing lymphomas responded less well to the metronomic therapy, since changes produced by anti-angiogenesis may not have been sufficiently rapid to control the disease.

Almost all patients had reductions in the blood counts on continuous therapy, although the doses of the individual drugs were kept to a minimum. It is possible that, although the individual doses were low, the overall additive impact was sufficient to create marrow suppression. Alternatively, it may have resulted from the constant presence of chemotherapy which may have overridden the protective effect of the P-glycoprotein pump highly expressed on stem cell, as well as on certain resistant tumors.⁶ While relapsing patients responded more readily to the PEP-C, resistant patients did respond, including patients who were resistant to alternative conventional chemotherapy regimens. Indeed, several patients were rendered eligible for transplant by PEP-C after conventional chemotherapy had failed to control the disease.

The PEP-C regimens offer significant and durable clinical activity in refractory and relapsing lymphoma. The data for the regimen compare favorably to the new or novel agents, such as bortezomib or temsirolimus. PEP-C is easy to administer and offers a different approach to therapy than that usually offered to lymphoma patients. This novel low-intensity anti-angiogenic approach warrants further study, including its use as initial therapy or as a maintenance strategy in both robust, as well as ‘fragile’ lymphoma patients.