Interactions Between Antiretrovirals and Antineoplastic Drug Therapy

Detrimental clinical interaction between ritonavir-boosted protease inhibitors and vinblastine in HIV-infected patients with Hodgkin's lymphoma

In order to analyze the clinical relevance of the pharmacokinetic interactions between vinblastine and antiretrovirals described in literature, we evaluated all HIV-infected patients with Hodgkin's lymphoma treated with vinblastine-containing regimens and combination antiretroviral therapy, in a single clinical center. The use of protease inhibitors was independently associated with WHO grade III-IV neutropenia. Moreover, an inverse correlation between dosage of ritonavir and mean nadir neutrophil count was found. The concomitant administration of vinblastine-containing chemotherapy regimens with protease inhibitors can lead to higher levels of neutropenia than those of different classes of drugs such as nonnucleoside reverse transcriptase inhibitors or integrase inhibitors.

No evidence for induction of ABC transporters in peripheral blood mononuclear cells in humans after 14 days of efavirenz treatment

Intracellular concentrations of antiretroviral drugs in peripheral blood mononuclear cells (PBMCs) are an important determinant of therapeutic success. In vitro data indicate that efavirenz induces several ATP-binding cassette (ABC) transporters, and pharmacogenetic studies found an association between ABCB1(C3435T) and efavirenz exposure and between this polymorphism and improved virological outcomes. We therefore aimed to clarify whether efavirenz also induces ABC transporters in vivo in PBMCs and whether intracellular concentrations might be altered after induction. Twelve healthy individuals received multiple oral doses of efavirenz over 14 days (400 mg once daily). Blood samples were drawn on study days 1 (single dose) and 14 (multiple dose), and efavirenz concentrations were analyzed by liquid chromatography-tandem mass spectrometry. Expression of P glycoprotein (P-gp) and of the multidrug resistance-associated proteins 1 and 2 as well as P-gp activity was analyzed in PBMCs on day 1 and day 14 using real-time reverse transcription-PCR (RT-PCR) and rhodamine 123 efflux. Although a clear autoinduction could be confirmed by a significant decrease of efavirenz exposure from day 1 to day 14, efavirenz did not change expression of the ABC transporters or P-gp activity in PBMCs. Moreover, intracellular concentrations of efavirenz were 1.3- to 1.8-fold higher than the corresponding plasma concentrations, and the intracellular/plasma concentration ratio remained constant during the treatment and did not correlate with ABC transporter expression or function. In conclusion, our study confirmed that intracellular concentrations of efavirenz are independent from these efflux transporters and demonstrated for the first time that the transporters are not induced in PBMCs in vivo after 2 weeks of treatment with efavirenz.

Potential role of UGT pharmacogenetics in cancer treatment and prevention: focus on tamoxifen and aromatase inhibitors

Tamoxifen (TAM) is a selective estrogen-receptor modulator that is widely used in the prevention and treatment of estrogen-receptor-positive breast cancer. Its use has significantly contributed to a decline in breast cancer mortality, since breast cancer patients treated with TAM for 5 years exhibit a 30-50% reduction in both the rate of disease recurrence after 10 years of patient follow-up and in the occurrence of contralateral breast cancer. However, in patients treated with TAM, there is substantial interindividual variability in the development of resistance to TAM therapy and in the incidence of TAM-induced adverse events, including deep-vein thrombosis, hot flashes, and the development of endometrial cancer. Aromatase inhibitors (AIs) have emerged as a viable alternative to TAM, working by inhibiting aromatase activity and blocking estrone/estrodiol biosynthesis in postmenopausal women. The current third-generation AIs, anastrozole, exemestane, and letrozole, were used initially for the treatment of metastatic breast cancer, demonstrating similar or greater benefit but less toxicity, compared with TAM, and are now being employed as adjuvant treatment for early breast cancer in postmenopausal women. This article will focus on the UDP-glucuronosyltransferases, a family of metabolizing enzymes that play an important role in the deactivation and clearance of TAM, anastrazole, and exemestane, and how interindividual differences in these enzymes may play a role in patient response to these agents.

Targeted therapies to treat non-AIDS-defining cancers in patients with HIV on HAART therapy: treatment considerations and research outlook

PURPOSE OF REVIEW

Highly active antiretroviral therapy has led to a dramatic improvement in the prognosis of patients diagnosed with HIV and AIDS. This includes a significant decline in the rates of AIDS-related cancers, including Kaposi's sarcoma and non-Hodgkin's lymphoma. Unfortunately, rates of non-AIDS-defining cancers are on the rise, and now exceed the rates of AIDS-related cancers in patients with HIV. Treating non-AIDS-defining cancers in patients who are on highly active antiretroviral therapy is an open and complicated clinical question.

RECENT FINDINGS

Newer targeted therapies are now available to treat cancers which were historically refractory to traditional cytotoxic chemotherapy. Highly active antiretroviral therapy agents are notorious for causing drug-drug interactions. The co-administration of targeted chemotherapies with highly active antiretroviral therapy could well impede the efficacy or increase the toxicity of these targeted therapies. Unfortunately little is known about possible drug-drug interactions because HIV patients are typically excluded from clinical trials.

SUMMARY

We highlight what is known about how and why highly active antiretroviral therapy agents can affect drug metabolism. We then present the clinical and pharmacological data for nine recently approved targeted therapies - imatinib, dasatinib, nilotinib, erlotinib, sunitinib, lapatinib, bortezomib, sorafenib, and temsirolimus. We conclude with considerations on how to use these new agents to treat non-AIDS-defining cancers, and discuss a future research agenda to better understand and predict potential highly active antiretroviral therapy-targeted therapy interactions.

Raltegravir-based HAART regimen in a patient with large B-cell lymphoma

OBJECTIVE

To describe the antiretroviral management of a patient diagnosed simultaneously with HIV/AIDS and diffuse large B-cell lymphoma, focusing on the drug-drug interactions between highly active antiretroviral therapy (HAART) and concomitant cancer chemotherapy.

CASE SUMMARY

A 55-year-old white man was recently diagnosed with HIV/AIDS and presented 1 month later with complaints of nausea, vomiting, abdominal pain, double vision, right eye discomfort/swelling, and a 3.6-kg weight loss. An excisional biopsy of a right inguinal lymph node confirmed a new diagnosis of diffuse large B-cell lymphoma. HAART and a chemotherapeutic regimen, including cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP) with intrathecal methotrexate, was to be initiated. As the potential for multiple drug-drug interactions existed, raltegravir, abacavir, and lamivudine were chosen for the initial HAART regimen. The patient achieved and maintained an undetectable viral load throughout 6 CHOP cycles.

DISCUSSION

HAART improves the chemotherapeutic response in patients with HIV and lymphoma. Multiple drug-drug interactions are possible in patients who are to receive CHOP and HAART. Cyclophosphamide and vincristine are metabolized via the CYP3A4 isoenzyme. Protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors both inhibit and induce CYP3A4, with the potential for altered chemotherapeutic and cytotoxic effects. When PIs are combined with CHOP, mortality is reduced, but increased adverse effects are demonstrated. Raltegravir, an integrase inhibitor, is eliminated via glucuronidation and results in minimal drug-drug interactions. Raltegravir improves virologic and immunologic responses in HAART-naïve patients and thus would be a suitable alternative for preventing chemotherapeutic-HAART interactions.

CONCLUSIONS

There is limited information published regarding the potential for interactions between HAART and cancer chemotherapy. While further research is necessary, it is important for clinicians to consider the potential for drug-drug interactions when designing a HAART regimen concurrently with chemotherapy.

Vincristine: Can its therapeutic index be enhanced?

Vincristine is one of the most widely used and more effective drugs in paediatric oncology. The dose-limiting toxicity of neuropathy, lack of proven neuroprotective measures and an incomplete understanding of the pharmacokinetics and pharmacogenetics of vincristine have limited its therapeutic potential. Recent advances in the understanding of vincristine pharmacokinetics and pharmacogenetics, and potential methods of preventing neurotoxicity are reviewed which could enable dose escalation and dose individualisation in order to enhance the therapeutic index.

Concurrent chemoradiotherapy with 5-fluorouracil and mitomycin C for invasive anal carcinoma in human immunodeficiency virus-positive patients receiving highly active antiretroviral therapy

PURPOSE

To report the clinical outcomes of chemoradiotherapy (CRT) for anal carcinoma in human immunodeficiency virus (HIV)-infected patients receiving highly active antiretroviral therapy.

PATIENTS AND METHODS

Between 1997 and 2008, 21 HIV-positive patients who were receiving highly active antiretroviral therapy were treated with CRT (50.4 Gy at 1.8 Gy/fraction plus a 5.4-10.8-Gy external boost; 5-fluorouracil, 1,000 mg/m(2), Days 1-4 and 29-32; and mitomycin C, 10 mg/m(2), Days 1 and 29). A retrospective analysis was performed with respect to the tumor response, local control, cancer-specific and overall survival, and toxicity. The immunologic parameters, including pre- and post-treatment CD4 count, viral load, and acquired immunodeficiency syndrome-specific morbidity was recorded during follow-up (median, 53 months; range, 10-99).

RESULTS

CRT could be completed in all 21 patients with a reduction in the chemotherapy dose and/or interruption of radiotherapy in 5 and 5 cases, respectively. Acute Grade 3 toxicity occurred in 8 (38%) of the 21 patients. A complete response was achieved in 17 patients (81%), and tumor persistence or early progression was noted in 4 (19%). Six patients (29%) died, 5 of cancer progression and 1 of treatment-related toxicity. The 5-year local control, cancer-specific, and overall survival rate was 59%, 75%, and 67%, respectively. The median CD4 count significantly decreased from 347.5 cells/microL before CRT to 125 cells/microL 3-7 weeks after CRT completion (p <.001). In 6 (32%) of 19 patients, an increase of the HIV viral load was noted. Both parameters returned to the pretreatment values with additional follow-up.

CONCLUSION

Our data have confirmed that in the highly active antiretroviral therapy era, HIV-related anal cancer can be treated with standard CRT without dose reductions. Close surveillance of the immunologic parameters is necessary.

Effect of highly active antiretroviral therapy on survival of HIV infected patients with non-small-cell lung cancer

OBJECTIVE

To evaluate the impact of highly active antiretroviral therapy (HAART) on survival in HIV infected patients with non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

All consecutive HIV infected patients with NSCLC diagnosed between 06/1996 and 03/2007 at two University hospitals in Paris (France) were prospectively followed until death. The association between survival and clinical and biological factors was analyzed by univariate and multivariate models. Survival analysis was performed by Kaplan-Meier estimates and the Cox proportional hazards regression model.

RESULTS

During the study period, NSCLC was diagnosed in 49 consecutive HIV infected patients (median age 46 years); 84% had advanced disease. Median survival was 8.1 months (range 5-10 months). In multivariate analysis, baseline parameters with significant positive impact on survival included performance status (PS) < or =1 (HR=0.2, 95%CI [0.09, 0.46], p=0.0001), stage I-II disease (HR=0.15, 95%CI [0.04, 0.53], p=0.003), and use of HAART (HR=0.4, 95%CI [0.2, 0.9], p=0.027).

CONCLUSION

HAART is a good prognostic factor for survival in HIV infected patients with NSCLC. Stage of disease and PS are two other valid survival prognostic factors.

Inhibition and induction of human cytochrome P450 enzymes: current status

Variability of drug metabolism, especially that of the most important phase I enzymes or cytochrome P450 (CYP) enzymes, is an important complicating factor in many areas of pharmacology and toxicology, in drug development, preclinical toxicity studies, clinical trials, drug therapy, environmental exposures and risk assessment. These frequently enormous consequences in mind, predictive and pre-emptying measures have been a top priority in both pharmacology and toxicology. This means the development of predictive in vitro approaches. The sound prediction is always based on the firm background of basic research on the phenomena of inhibition and induction and their underlying mechanisms; consequently the description of these aspects is the purpose of this review. We cover both inhibition and induction of CYP enzymes, always keeping in mind the basic mechanisms on which to build predictive and preventive in vitro approaches. Just because validation is an essential part of any in vitro-in vivo extrapolation scenario, we cover also necessary in vivo research and findings in order to provide a proper view to justify in vitro approaches and observations.

AIDS-related malignancies: state of the art and therapeutic challenges

Despite the impact of combination antiretroviral therapy (cART) on HIV-related mortality, malignancy remains an important cause of death in the current era. Although the advent of cART has resulted in reductions in the incidence of Kaposi's sarcoma and non-Hodgkin's lymphoma, non-AIDS-defining malignancies present an increased risk for HIV-infected patients, characterized by some common clinical features, generally with a more aggressive behavior and a more advanced disease at diagnosis, which is responsible for poorer patient outcomes. Specific therapeutic recommendations are lacking for these new nonopportunistic malignancies, such as Hodgkin's lymphoma, anal cancer, lung cancer, hepatocarcinoma, and many others. Antiretroviral agents have a propensity for causing drug interactions as a result of their ability to either inhibit or induce the cytochrome P450 (CYP) enzyme system. Because many antineoplastic drugs are also metabolized by the CYP system, coadministration with cART could result in either drug accumulation with increased toxicity, or decreased efficacy of one or both classes of drugs. Further research delineating the combined safety and pharmacokinetics of antiretrovirals and antineoplastic therapy is necessary. Special considerations of these AIDS-related and non-AIDS-related malignancies and their clinical and therapeutic aspects constitute the subject of this review.

Induction effects of ritonavir: implications for drug interactions

OBJECTIVE

To review the literature on the induction effects of ritonavir on the cytochrome P450 enzyme system and glucuronyl transferase and identify resultant established and potential drug interactions.

DATA SOURCES

Primary literature was identified from MEDLINE (1950-April 2008), EMBASE (1988-April 2008) and International Pharmaceutical Abstracts (1970-April 2008) using the search terms ritonavir, cytochrome P450 enzyme system, enzyme induction, glucuronyl transferase, and drug interactions. Additionally, relevant conference abstracts and references of relevant articles were reviewed.

STUDY SELECTION AND DATA ABSTRACTION

All English-language articles and abstracts identified were reviewed.

DATA SYNTHESIS

Ritonavir is a well-known inhibitor of the metabolism of numerous medications that are substrates of the CYP3A and CYP2D6 pathways. It also exhibits a biphasic, time-dependent effect on P-glycoprotein of inhibition followed by induction. Numerous pharmacokinetic studies suggested that ritonavir induces cytochrome P450 enzymes 3A, 1A2, 2B6, 2C9, and 2C19, as well as glucuronyl transferase. Additionally, several case reports described clinically significant subtherapeutic effects of drugs metabolized by these isoenzymes when coadministered with ritonavir. Both therapeutic and boosting doses of ritonavir appear to induce these enzymes; however, most of the studies of low-dose ritonavir involved a second protease inhibitor such as lopinavir, darunavir, or tipranavir. It is, therefore, difficult to distinguish the relative effects of additional medications unless well-designed, 3-way studies are conducted.

CONCLUSIONS

At both therapeutic and boosting doses, ritonavir exhibits a clinically relevant induction effect on numerous drug-metabolizing enzymes. A decrease or loss of therapeutic effect may be observed when ritonavir is coadministered with medications that are substrates for these enzymes. It is important for clinicians to be aware of drugs potentially impacted by ritonavir therapy to identify and manage these interactions.

HIV-specific differences in outcome of squamous cell carcinoma of the anal canal: a multicentric cohort study of HIV-positive patients receiving highly active antiretroviral therapy

PURPOSE

To define clinical outcome after definitive chemoradiotherapy (CRT) of anal carcinoma in HIV-infected patients treated with highly active antiretroviral therapy (HAART).

PATIENTS AND METHODS

A multicentric cohort comparison of 40 HIV-positive patients with HAART and 81 HIV-negative patients treated with radiotherapy (RT) or CRT was retrospectively performed. Local disease control (LC), relapse-free survival (RFS), overall survival (OS), cancer-specific survival (CSS), toxicity, and prognostic factors were investigated.

RESULTS

HIV-positive patients were younger (mean age, 48 v 62 years; P < .0005), predominantly male (93% v 25%; P < .0005), and with early-stage (P = .06) and large-cell histology (90% v 67%; P = .005) disease. RT or CRT resulted in complete response in 92% (HIV positive) and 96% (HIV negative) of cases. Five-year OS was 61% (95% CI, 44% to 78%) in HIV-positive and 65% (95% CI, 53% to 77%) in HIV-negative patients (median follow-up, 36 months). Five-year LC was 38% (95% CI, 5% to 71%) in HIV-positive and 87% (95% CI, 79% to 95%) in HIV-negative patients (P = .008) compromising CSS and sphincter preservation. Grade 3/4 acute skin (35% v 17% [HIV negative]; P = .04) and hematologic (33% v 12% [HIV negative]; P = .08) toxicity together approximated 50% in HIV-positive patients. RFS in HIV-positive patients was associated with RT dose (P = .08) and severe acute skin toxicity (P = .04).

CONCLUSION

Long-term LC and acute toxicity represent major clinical challenges in HIV-positive patients with anal carcinoma. Even if fluoropyrimidine-based CRT is feasible and may result in similar response rates and OS as in HIV-negative patients, improved treatment strategies with better long-term outcome are warranted.

Comparison of the induction of P-glycoprotein activity by nucleotide, nucleoside, and non-nucleoside reverse transcriptase inhibitors

Combination therapy against human immunodeficiency virus (HIV)-infection is complicated by drug-drug interactions between antiretrovirals and also between anti-HIV drugs and drugs used to treat co-morbidity. P-glycoprotein represents one important site for drug interactions and induction of its function could reduce the effectiveness of drugs that are P-glycoprotein substrates. We therefore investigated induction of P-glycoprotein function in LS180 cells by non-nucleoside and nucleoside reverse transcriptase inhibitors (NNRTIs and NRTIs) and tenofovir as essential components of antiretroviral combination therapy. P-glycoprotein activity was increased by all NNRTIs and some NRTIs with delavirdine (5.3-fold at 100 muM) having the largest effect.

Lopinavir–Ritonavir Dramatically Affects the Pharmacokinetics of Irinotecan in HIV Patients With Kaposi’s Sarcoma

The coadministration of protease inhibitors with anticancer drugs in the management of human immunodeficiency virus-related malignancies can cause potential drug-drug interactions. The effect of lopinavir/ritonavir (LPV/RTV) on the pharmacokinetics of irinotecan (CPT11) has been investigated in seven patients with Kaposi's sarcoma. Coadministration of LPV/RTV reduces the clearance of CPT11 by 47% (11.3+/-3.5 vs 21.3+/-6.3 l/h/m(2), P=0.0008). This effect was associated with an 81% reduction (P=0.02) of the AUC (area under the curve) of the oxidized metabolite APC (7-ethyl-10-[4-N-(5-aminopentanoic-acid)-1-piperidino]-carbonyloxycamptothecin). The LPV/RTV treatment also inhibited the formation of SN38 glucuronide (SN38G), as shown by the 36% decrease in the SN38G/SN38 AUCs ratio (5.9+/-1.6 vs 9.2+/-2.6, P=0.002) consistent with UGT1A1 inhibition by LPV/RTV. This dual effect resulted in increased availability of CPT11 for SN38 conversion and reduced inactivation on SN38, leading to a 204% increase (P=0.0001) in SN38 AUC in the presence of LPV/RTV. The clinical consequences of these substantial pharmacokinetic changes should be investigated.

Effect of axial coordination on the electronic structure and biological activity of dirhodium(II,II) complexes

The reactivities toward biomolecules of a series of three dirhodium(II,II) complexes that possess an increasing number of accessible axial coordination sites are compared. In cis-[Rh2(OAc)2(np)2]2+ (1; np=1,8-naphthyridine) both axial sites are available for coordination, whereas for cis-[Rh2(OAc)2(np)(pynp)]2+ (2; pynp=2-(2-pyridyl)1,8-naphthyridine) and cis-[Rh2(OAc)2(pynp)2]2+ (3) the bridging pynp ligand blocks one and two of the axial coordination sites in the complexes, respectively. The electronic absorption spectra of the complexes are consistent with strong metal-to-ligand charge transfer transitions at low energy and ligand-centered peaks localized on the np and/or pynp ligands in the UV and near-UV regions. Time-dependent density functional theory calculations were used to aid in the assignments. The three complexes exhibit metal-centered oxidations and reductions, localized on the aromatic ligands. The ability of the complexes to stabilize duplex DNA and to inhibit transcription in vitro is greatly affected by the availability of an open axial coordination site. The present work shows that open axial coordination sites on the dirhodium complexes are necessary for biological activity.

Comparison of the inhibitory activity of anti-HIV drugs on P-glycoprotein

Human immunodeficiency virus 1 (HIV-1) infections are treated with HIV-protease inhibitors (PIs), nucleoside (NRTIs), non-nucleoside (NNRTIs), and nucleotide reverse transcriptase inhibitors (NtRTIs). The combined administration of antiretrovirals improves patient outcomes while increasing the likelihood of drug interactions. Indeed, as substrates, inhibitors, and occasionally also inducers of P-glycoprotein (P-gp) PIs may substantially alter the pharmacokinetics of co-administered drugs. However, the P-gp inhibitory potencies specified in the numerous publications are not comparable, because they were determined with different assays and cell lines. Moreover, data on the interaction of other anti-HIV drugs with P-gp are sparse and conflicting. We therefore aimed to clarify, which anti-HIV drugs inhibit P-gp and to compare the inhibitory potencies using two independent standard methods (calcein uptake assay, flow cytometric rhodamine123 efflux assay). In the calcein assay, all PIs, all NNRTIs, abacavir, and tenofovir disoproxil fumarate acted as P-gp inhibitors with largely differing potencies between compounds. In P388/dx cells the ranking order of inhibition was: nelfinavir>ritonavir>tipranavir>lopinavir>quinidine (positive control)>delavirdine>saquinavir>amprenavir>atazanavir>efavirenz>nevirapine>abacavir>tenofovir disoproxil fumarate. In conclusion this is the first study to provide comprehensive information on the P-gp interaction profile of anti-HIV drugs under identical assay conditions. Our study reveals that many compounds may indeed inhibit P-gp substantially and further indicates that of the various systems tested, the calcein assay in P388/dx/P388 cells is the most suitable and reliable in vitro model for the quantification of P-gp inhibition.

Physician perceptions and preferences in the treatment of acquired immunodeficiency syndrome (AIDS)-related lymphoma

The optimal management of acquired immunodeficiency syndrome-related lymphoma (ARL) in the era of combination antiretroviral therapy (cART) is unclear. We administered a survey to determine physician preferences and perceptions in the management of ARL and to assess the variability in treatment in Canada. Of 196 lymphoma-treating physicians, 117 (63%) responded. The majority of respondents (98%) had a positive attitude towards the treatment of ARL. Most physicians (66%) recommended the concomitant use of cART in the care of their patients with ARL, and a majority (86%) recommended CHOP-like regimens (cyclophosphamide, doxorubicin, vincristine, and prednisone) to form the backbone of chemotherapy. The addition of rituximab was preferred by 43% of physicians, while 39% and 18% would either not use rituximab or were unsure of the agent's role, respectively. In logistic regression analysis, use of rituximab was predicted only by location of practice (province); physicians from the province of British Colombia were much more likely to administer rituximab than practitioners from Ontario (odds ratio 41.8; 95% confidence interval 7.44-235.1, p < 0.001). In the current cART era, physicians have a positive attitude towards the treatment of ARL. The majority prefer to use cART in combination with CHOP for ARL. The use and perceived benefit of rituximab may be influenced by interprovincial formulary differences and regional variation in guideline recommendations.

First Use of Tamoxifen in an HIV??Patient with Encapsulating Peritoneal Sclerosis

Encapsulating peritoneal sclerosis (EPS) is a rare but serious life-threatening complication in peritoneal dialysis patients. At present, there is no evidence-based standard therapy for EPS. Tamoxifen has been used and shown good results in non-HIV peritoneal dialysis patients with EPS. We report a case of a patient with HIV treated with antiretroviral therapy (zidovudine, lamivudine and saquinavir) for several years. He had end-stage renal disease and was treated with continuous ambulatory peritoneal dialysis (CAPD). After 11 years on CAPD, he developed EPS and was treated successfully with tamoxifen in combination with corticosteroids. No adverse effects were observed and no changes were noted in CD4 counts or HIV viral load during this therapy. These findings suggest that tamoxifen can be safely given to HIV patients with peritoneal dialysis-related EPS. Nevertheless, caution is required as tamoxifen could interact with certain antiretroviral agents.

Local tumor control and toxicity in HIV-associated anal carcinoma treated with radiotherapy in the era of antiretroviral therapy

PURPOSE

To investigate the outcome of HIV-seropositive patients under highly active antiretroviral treatment (HAART) with anal cancer treated with radiotherapy (RT) alone or in combination with standard chemotherapy (CT).

PATIENTS AND METHODS

Clinical outcome of 81 HIV-seronegative patients (1988-2003) and 10 consecutive HIV-seropositive patients under HAART (1997-2003) that were treated with 3-D conformal RT of 59.4 Gy and standard 5-fluorouracil and mitomycin-C were retrospectively analysed. 10 TNM-stage and age matched HIV-seronegative patients (1992-2003) were compared with the 10 HIV-seropositive patients. Pattern of care, local disease control (LC), overall survival (OS), cancer-specific survival (CSS), and toxicity were assessed.

RESULTS

RT with or without CT resulted in complete response in 100% of HIV-seropositive patients. LC was impaired compared to matched HIV-seronegative patients after a median follow-up of 44 months (p = 0.03). OS at 5 years was 70% in HIV-seropositive patients receiving HAART and 69% in the matched controls. Colostomy-free survival was 70% (HIV+) and 100% (matched HIV-) and 78% (all HIV-). No HIV-seropositive patient received an interstitial brachytherapy boost compared to 42% of all HIV-seronegative patients and adherence to chemotherapy seemed to be difficult in HIV-seropositive patients. Acute hematological toxicity reaching 50% was high in HIV-seropositive patients receiving MMC compared with 0% in matched HIV-seronegative patients (p = 0.05) or 12% in all HIV-seronegative patients. The rate of long-term side effects was low in HIV-seropositive patients.

CONCLUSION

Despite high response rates to organ preserving treatment with RT with or without CT, local tumor failure seems to be high in HIV-positive patients receiving HAART. HIV-seropositive patients are subject to treatment bias, being less likely treated with interstitial brachytherapy boost probably due to HIV-infection, and they are at risk to receive less chemotherapy.

Systemic treatment of AIDS-related Kaposi sarcoma: current status and perspectives

Kaposi's sarcoma (KS) is the most frequent type of cancer in patients with Acquired Immune Deficiency Syndrome (AIDS). In the western world, its incidence decreased dramatically in the era of highly active anti-retroviral therapy (HAART). In contrast, the incidence of KS has been steadily climbing in parallel with the AIDS epidemic in Africa over the past 10-15 years, being the most common cancer in adult men in countries like Uganda and Zimbabwe. AIDS-KS can be diagnosed at any stage of HIV infection, although it more commonly occurs in the setting of severe immune suppression, especially with an elevated viral load. Up to now, AIDS-KS is still an incurable disease. Its clinical course is variable, ranging from very indolent cases, requiring no or minimal therapy, to a rapidly progressive disease. Various local therapies are available to control small and asymptomatic lesions, while cytotoxic, immunological and biological therapies can be considered for more aggressive disease. The primary goal of therapy in most of the cases is to provide safe and effective palliation, in order to quality of life. Optimal anti-retroviral therapy is a key component of AIDS-KS management. There are still many questions to be answered in the management of patients with AIDS-KS, such as (1) What are the therapeutic agents that should be used in this disease, and in which sequence? and (2) What are the benefits and risks expected with each treatment option? The aim of this review is to discuss the systemic management of AIDS-KS, with special focus on the above mentioned questions.

Drug interactions in cancer therapy

Drug interactions in oncology are of particular importance owing to the narrow therapeutic index and the inherent toxicity of anticancer agents. Interactions with other medications can cause small changes in the pharmacokinetics or pharmacodynamics of a chemotherapy agent that could significantly alter its efficacy or toxicity. Improvements in in vitro methods and early clinical testing have made the prediction of potentially clinically significant drug interactions possible. We outline the types of drug interaction that occur in oncology, the mechanisms that underlie these interactions and describe select examples.

Life-threatening interaction between antiretroviral therapy and vinblastine in HIV-associated multicentric Castleman's disease

BACKGROUND

HIV-infected patients still present a high risk of developing lymphoproliferative malignancies, despite the fact that their prognosis has been considerably improved by highly active antiretroviral therapy (HAART). Potential interactions exist between antiretroviral drugs, in particular protease inhibitors, and anti-neoplastic ones, but their impact in terms of clinical and haematological adverse events remains unclear.

METHODS

We report a case of potentially life-threatening interaction between vinblastine and antiretroviral therapy in a patient presenting with HIV-associated multicentric Castleman's disease (MCD).

RESULTS

A 55-year-old HIV-1 infected patient was diagnosed with MCD while being treated with a salvage HAART regimen consisting of zidovudine, lamivudine, abacavir, nevirapine and ritonavir-boosted lopinavir. Vinblastine was prescribed as a monotherapy at the usual dose of 6 mg/m2 (i.e. 10 mg) every 3 weeks. The first vinblastine course was performed without HAART with no adverse event. Antiretroviral therapy was resumed for the two following courses which were associated with unexpected severe digestive and haematological toxicities, and moderate renal failure. Vinblastine was then administered alone at increasing doses without toxicity. HAART was finally resumed and we assessed that a decreased vinblastine dose of 2 mg/m2 was well tolerated, with a complete response of MCD.

CONCLUSIONS

HAART regimen comprising protease inhibitors, which are potent inhibitors of cytochrome P450 and P-gp, could interfere with anti-neoplastic drugs, as demonstrated with vinblastine in our case report.

Impact of transgene expression on drug metabolism following systemic adenoviral vector administration

BACKGROUND

Systemic administration of a first-generation adenovirus expressing E. coli beta-galactosidase (AdlacZ) alters expression and function of two hepatic drug-metabolizing enzymes, cytochrome P450 (CYP) 3A2 and 2C11, for 14 days. The objective of these studies was to determine how the transgene cassette influences CYP expression and function.

METHODS

Sprague-Dawley rats were given 5.7 x 10(12) viral particles (vp)/kg of either: AdlacZ, Ad expressing murine erythropoietin (Epo), Ad without a transgene (Null), or phosphate-buffered saline (Vehicle). Hepatic CYP protein expression, activity, mRNA and alanine aminotransferase (ALT) levels were analyzed 0.25, 1, 4, and 14 days following a single intravenous injection.

RESULTS

Administration of Epo did not alter CYP3A2 activity, but induced RNA levels by a factor of 2 at 4 and 14 days (P< or =0.01). This vector suppressed CYP2C11 activity levels by 45% at 1 day (P< or =0.05) and RNA levels throughout the study period (P< or =0.05). The Null vector suppressed CYP3A2 activity by 36, 63, 34, and 45% at 0.25, 1, 4 and 14 days, respectively (P< or =0.05). CYP2C11 activity was suppressed 1 day after administration (41%) and RNA levels were suppressed at 6 h (53%) and 1 day (36%, P< or =0.05). In contrast, AdlacZ suppressed both CYP3A2 and 2C11 at all time points.

CONCLUSIONS

The immunogenic and biological nature of the transgene cassette can influence changes in CYP3A2, but not the 2C11 isoform. The shift in transcription and translation of protein for maintenance of physiologic homeostasis to production of viral proteins and transgene product and their associated toxicity during viral infection may explain our observations.