Jr Kroep

Basis for effective combination cancer chemotherapy with antimetabolites.

Most current chemotherapy regimens for cancer consist of empirically designed combinations, based on efficacy and lack of overlapping toxicity. In the development of combinations, several aspects are often overlooked: (1) possible metabolic and biological interactions between drugs, (2) scheduling, and (3) different pharmacokinetic profiles. Antimetabolites are used widely in chemotherapy combinations for treatment of various leukemias and solid tumors. Ideally, the combination of two or more agents should be more effective than each agent separately (synergism), although additive and even antagonistic combinations may result in a higher therapeutic efficacy in the clinic. The median-drug effect analysis method is one of the most widely used methods for in vitro evaluation of combinations. Several examples of classical effective antimetabolite-(anti)metabolite combinations are discussed, such as that of methotrexate with 6-mercaptopurine or leucovorin in (childhood) leukemia and 5-fluorouracil (5FU) with leucovorin in colon cancer. More recent combinations include treatment of acute-myeloid leukemia with fludarabine and arabinosylcytosine. Other combinations, currently frequently used in the treatment of solid malignancies, include an antimetabolite with a DNA-damaging agent, such as gemcitabine with cisplatin and 5FU with the cisplatin analog oxaliplatin. The combination of 5FU and the topoisomerase inhibitor irinotecan is based on decreased repair of irinotecan-induced DNA damage. These combinations may increase induction of apoptosis. The latter combinations have dramatically changed the treatment of incurable cancers, such as lung and colon cancer, and have demonstrated that rationally designed drug combinations offer new possibilities to treat solid malignancies.

Sequence dependent effect of paclitaxel on gemcitabine metabolism in relation to cell cycle and cytotoxicity in non-small-cell lung cancer cell lines

Gemcitabine and paclitaxel are active agents in the treatment of non-small-cell lung cancer (NSCLC). To optimize treatment drug combinations, simultaneously and 4 and 24 h intervals, were studied using DNA flow cytometry and multiple drug effect analysis in the NSCLC cell lines H460, H322 and Lewis Lung. All combinations resulted in comparable cytotoxicity, varying from additivity to antagonism (combination index: 1.0–2.6). Gemcitabine caused a S (48%) and G1 (64%) arrest at IC-50 and 10 × IC-50 concentrations, respectively. Paclitaxel induced G2/M arrest (70%) which was maximal within 24 h at 10 × IC-50. Simultaneous treatment increased S-phase arrest, while at the 24 h interval after 72 h the first drug seemed to dominate the effect. Apoptosis was more pronounced when paclitaxel preceded gemcitabine (20% for both intervals) as compared to the reverse sequence (8%, P = 0.173 for the 4 h and 12%, P = 0.051 for the 24 h time interval). In H460 cells, paclitaxel increased 2-fold the accumulation of dFdCTP, the active metabolite of gemcitabine, in contrast to H322 cells. Paclitaxel did not affect deoxycytidine kinase levels, but ribonucleotide levels increased possibly explaining the increase in dFdCTP. Paclitaxel did not affect gemcitabine incorporation into DNA, but seemed to increase incorporation into RNA. Gemcitabine almost completely inhibited DNA synthesis in both cell lines (70–89%), while paclitaxel had a minor effect and did not increase that of gemcitabine. In conclusion, various gemcitabine–paclitaxel combinations did not show sequence dependent cytotoxic effects; all combinations were not more than additive. However, since paclitaxel increased dFdCTP accumulation, gemcitabine incorporation into RNA and the apoptotic index, the administration of paclitaxel prior to gemcitabine might be favourable as compared to reversed sequences.

Gemcitabine–cisplatin: A schedule finding study

PURPOSE To evaluate the tolerability of four alternating cisplatin-gemcitabine schedules. A secondary aim was to evaluate the clinical efficacy of this combination. PATIENTS AND METHODS Forty-one patients with advanced solid tumors received alternating sequences with a 4- and 24-hour interval of cisplatin and gemcitabine. Gemcitabine 800 mg/m2 was administered as a 30-min infusion on day 1, 8 and 15, and cisplatin 50 mg/m2 over 1 hour on day 1 and 8; in case of the 24-hour time interval the second drug was administered one day later. Four cisplatin-gemcitabine schedules were studied: gemcitabine four hour before cisplatin (10 patients), or vice versa (14 patients) and gemcitabine twenty-four hours before cisplatin (9 patients) or vice versa (8 patients). The sequence of drug administration was reversed in the second cycle of therapy in each individual patient, enabling the evaluation of sequence-dependent side effects. Twenty-six patients had received prior chemotherapy, of which twenty-one platinum-based. RESULTS The main toxicity was myelosuppression. Overall, grade 3 and 4 thrombocytopenia was observed in 27 out of 41 patients (66%) and was not schedule dependent. No serious bleeding occurred. Leukopenia was significantly different between the 4 alternating schedules (P = 0.01); gemcitabine 24 hours before cisplatin was significantly less toxic compared to both cisplatin 4 hours and 24 hours before gemcitabine (P = 0.01 and P = 0.003, respectively). Furthermore, paired analysis of the 4-hour and 24-hour data sets showed that leukopenia was significantly more serious when cisplatin preceded gemcitabine (P = 0.005). Although most patients received prior treatment, both prior chemotherapy and radiotherapy were not related to toxicity. Overall, grade 3 and 4 leukopenia occurred in 19 out of 41 patients (46%). Anemia (Hb < or = 6.0 mmol/l) was not sequence dependent and was observed in 63% of patients. Myelotoxicity was cumulative between cycles and caused frequent omission of gemcitabine on day 15. Overall, in 51% of administered cycles there was no omission of gemcitabine. A mean of 3.5 therapy cycles was administered. Non-hematological toxicity was moderate, consisting mainly of grade 1 and 2 nausea/vomiting and fatigue, and was not schedule dependent. Recently, we described that the schedule in which cisplatin was administered 24 hours before gemcitabine produced the best pharmacological profile. Based on this and because toxicity was manageable, the schedule cisplatin 24 hours prior to gemcitabine was chosen for phase II evaluation. Nine out of thirty-six evaluable patients had an objective response. These responses were observed in head and neck squamous-cell carcinoma (HNSCC), non-small-cell lung cancer (NSCLC), melanoma, adenocarcinoma of unknown origin, ovarian and esophageal carcinoma. CONCLUSIONS Myelosuppression was the most important toxicity. Leukopenia was schedule dependent: gemcitabine before cisplatin was less toxic than the reversed sequence, in this respect. Some encouraging responses were seen in patients with esophageal cancer. Currently, a phase II study with cisplatin 24 hours before gemcitabine is ongoing in patients with advanced upper gastro-intestinal tumors.

Role of deoxycytidine kinase (dCK), thymidine kinase 2 (TK2), and deoxycytidine deaminase (dCDA) in the antitumor activity of gemcitabine (dFdC).

Deoxycytidine kinase (dCK) and deaminase (dCDA) are as activating and inactivating enzymes, respectively, in the metabolism of several chemotherapeutically important deoxynucleoside analogues [1]. 2′2′-Difluorodeoxycytidine (dFdC; gemcitabine) has considerable antitumor activity against solid tumors, such as against the chemoresistant non-small cell lung cancer (NSCLC) and pancreatic cancer [2]. dCK catalyses the rate-limiting phosphorylation of CdR and its analogues to their corresponding monophos-phates [1,3]. To avoid an overestimation of the dCK activity by thymidine kinase 2 (TK2), which can also efficiently phosphorylate CdR [3], dCK activity was measured in the presence of thymidine (TdR) to inhibit TK2 [4]. dCDA inactivates cytidine (CR), CdR and its analogues to their deaminated products [5,6]. Previously we could not establish a relationship between antitumor activity and the dCK and dCDA activities [6], while in a cell line study more precise measurements of dCK showed a relation between sensitivity to dFdC and efficiency of dCK [7]. We now reevaluated the role of dCK, TK2 and dCDA in the antitumor effect of dFdC against different solid tumors.

Mechanisms of synergism between gemcitabine and cisplatin.

2′,2′-difluorodeoxycytidine (Gemcitabine, dFdC) is an antineoplastic agent with clinical activity against several cancer types.1 cis-Diamminedichloroplatinum (cisplatin, CDDP) is a drug with long established anticancer activity, which acts by Platinum (Pt)-DNA adduct formation.2,3 Because of the low toxicity profile of dFdC and the differences in mechanism of cytotoxicity, preclinical studies were performed that demonstrated synergism between dFdC and CDDP in several cancer cell lines and in vivo,4–8 which is likely to be related to increased formation of Pt-DNA adducts.8 Pre-treatment with dFdC gave the best results both in vitro and in vivo.6,7,8 Several potential mechanisms underlying the synergism were studied in vitro, based on these results several schedules were studied in patients.

Abstract S1-04: Optimal duration of extended letrozole treatment after 5 years of adjuvant endocrine therapy; results of the randomized phase III IDEAL trial (BOOG 2006-05)

Despite the success of adjuvant endocrine therapy in early breast cancer, approximately 50% of all recurrences still occur after the initial 5 years of follow-up. Earlier studies confirmed that endocrine therapy extension after 5 years of adjuvant tamoxifen with either tamoxifen or aromatase inhibitors up to 10 years leads to an improvement in survival. However, aromatase inhibitors are currently standard of care in the initial 5 years of adjuvant therapy, and the benefit of extended use beyond 5 years of AI based therapy is still debated. The randomized phase III IDEAL trial was designed to study the optimal duration of extended adjuvant endocrine therapy after the initial 5 years of any endocrine therapy. Between April 2007 and November 2011, 1824 postmenopausal, HR-positive early breast cancer patients were included by 74 hospitals in the Netherlands. Enrolled patients earlier received 5 years of any endocrine therapy (87.9% AI based),completed this treatment no longer than 2 years before randomization, and did not have any recurrence at the moment of inclusion. The included patients were randomly allocated to either 2.5 or 5 years of extended letrozole (daily 2.5mg). Primary outcome was disease free survival (DFS), secondary endpoints were overall survival (OS), distant disease free survival (DDFS), contralateral breast cancer and safety. Results & Discussion: Results will become available soon. Citation Format: Blok EJ, van de Velde CJH, Meershoek-Klein Kranenbarg EM, Putter H, van den Bosch J, Maartense E, van Leeuwen-Stok AE, Liefers G-J, Nortier JWR, Rutgers EJT, Kroep JR. Optimal duration of extended letrozole treatment after 5 years of adjuvant endocrine therapy; results of the randomized phase III IDEAL trial (BOOG 2006-05) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S1-04.

Abstract P2-09-08: Safety assessment of extended adjuvant endocrine therapy with letrozole; results of the randomized phase III IDEAL trial (BOOG 2006-05)

The implementation of adjuvant aromatase inhibitors (AI) has contributed significantly to an ongoing improvement in survival of early breast cancer patients, but the impact of extended AI on toxicity after use in the initial 5 years has not yet been studied. Earlier, it was established that even after 5 years of adjuvant tamoxifen, extended letrozole for 5 years was comparable to the earlier reported toxicities, without an effect on overall quality of life. The aim of the current study is to assess the reported toxicity in the IDEAL trial, investigating extended letrozole after 5 years of endocrine therapy. The Dutch phase III IDEAL trial was designed to study the optimal duration of extended adjuvant letrozole, by randomizing to either 2.5 or 5 years of letrozole after the completion of 5 years of any endocrine therapy. All patients were disease-free at the time of randomization. The primary outcome of this study, disease free survival after extended endocrine therapy, will be reported separately. Toxicity data were collected every 6 months in the first year, and annually thereafter until study completion. 1824 patients were included in the trial, of which 26 patients never started with therapy (n=1798). In total, 3434 adverse events were reported by 1283 patients, causing 360 (20%) patients to stop therapy due to these events. In total, 643 patients randomized to 5 years of therapy reported 1834 AEs (71.2%), whereas 640 patients on 2.5 years of therapy reported 1587 events (71.5%). In the 5 year AI group, 1456 (80%) of the AEs were reported within the initial 2.5 years causing 177 patients to stop therapy in this period, versus 29 patients who stopped due to toxicity after the therapy extension beyond 2.5 years. There was no significant difference in the proportion of grade 3/4 events between both groups (2.5yr: 9.8%, 5yr: 9.7%, X 2 p=0.52). Most reported AEs were arthralgia (n=248, 13.8% of all patients , 8.9% grade 3/4), hot flushes (n=215, 12%, 6.5% grade 3/4), osteoporosis (n=181, 10%, 2.2% grade 3/4), fatigue (n=156, 8.7%, 5.1% grade 3/4) and a decrease in joint function (n=114, 6.3%, 3.5% grade 3/4). In total, only one grade 5 AE was reported, which was unrelated to the treatment (bleeding and sepsis after cholecystectomy). Although the toxicity pattern is comparable to regular AI based adjuvant therapy, the percentage of specific adverse events like arthralgia and hot flushes is lower than expected. This observation is possibly a selection bias, since patients who encountered side effects during regular adjuvant therapy could have been less willing to participate in this trial. Remarkably, low numbers of AEs and therapy refusal due to toxicity were reported after therapy extension beyond 2.5 years. In conclusion, extended adjuvant endocrine therapy shows an acceptable toxicity pattern, and therapy extension beyond 2.5 years up to 5 years is well tolerated and safe. Citation Format: Blok EJ, Kroep JR, Meershoek-Klein Kranenbarg EM, Duym-de Carpentier M, Putter H, van den Bosch J, Maartense E, van Leeuwen-Stok AE, Liefers G-J, Nortier JWR, Rutgers EJT, van de Velde CJH. Safety assessment of extended adjuvant endocrine therapy with letrozole; results of the randomized phase III IDEAL trial (BOOG 2006-05) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-09-08.

Abstract PD2-07: 10-year follow-up and biomarker discovery for adjuvant endocrine therapy; results of the TEAM trial

Optimal endocrine therapy for postmenopausal, hormone-receptor positive (HR+) early breast cancer remains a point of discussion. The Tamoxifen Exemestane Adjuvant Multinational (TEAM) phase III trial showed no significant differences for disease free survival (DFS) and overall survival (OS) at 5 years between exemestane monotherapy and sequential treatment (tamoxifen followed by exemestane). We now report disease related outcomes at 10 years of follow-up (FU), and an explorative analysis to assess the predictive value of clinicopathological and immune-related biomarkers. In the TEAM trial, postmenopausal women with HR+ positive early breast cancer were randomly assigned to exemestane alone or sequential therapy. For this analysis, TEAM patients from countries that completed 10 years of FU were included. The primary endpoint was DFS at ten years, analyzed by intention to treat. Secondary outcomes were OS and cumulative incidence of relapse. An explorative per protocol analysis for relapse free survival (RFS) was performed to identify predictive pathological and immunological biomarkers, including centrally determined ER (ER-poor 0-6 vs ER-rich 7-8) and PR (0-4 vs 5-8) Allred scores, and the immunological markers CD8, FoxP3, classical HLA class 1 and HLA-G which were described earlier (Engels et al, Breast Cancer Treat Res, 2015). In total, 6120 patients were eligible for the current analysis, 3075 patients with exemestane monotherapy and 3045 patients randomized to sequential treatment. Median follow up was 9.83 years. DFS was 66.8% in the exemestane group and 66.8% in the sequential group (hazard ratio (HR) 0.96, 95% CI 0.88-1.05, p=0.389). OS was 74% in the exemestane, and 73% in the sequential group, respectively (HR 0.98, 95% CI 0.89-1.09, p=0.737). The cumulative incidence of relapse was 20% and 22% in the exemestane and sequential groups, respectively (HR 0.88, 95% CI 0.79-0.99, p=0.031). In the explorative per protocol analysis (n=4041), Allred score were available for 2996 patients; immunological markers for 1754 patients. Patients with above median numbers of FoxP3-positive T-cells showed a benefit of exemestane monotherapy for RFS (HR 0.56, 95% CI 0.42-0.75, p After ten years of follow up, both exemestane monotherapy and sequential therapy remain appropriate options for postmenopausal HR+ early breast cancer patients. Interestingly, the number of regulatory T-cells was a predictive factor for the benefit of exemestane monotherapy, which implies a role of the local immune system in endocrine therapy. Furthermore, data suggested that patients with a higher differentiation grade or ER-rich tumor derive more benefit from exemestane monotherapy. Citation Format: Blok EJ, Derks MGM, Kuppen PJK, Meershoek-Klein Kranenbarg EM, Engels CC, Liefers G-J, Putter H, Seynaeve CM, Kroep JR, Nortier JWR, Rea DW, Hasenburg A, Markopoulos CJ, Paridaens R, Bartlett JMS, van de Velde CJH. 10-year follow-up and biomarker discovery for adjuvant endocrine therapy; results of the TEAM trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD2-07.

Abstract S6-02: The efficacy and safety of the addition of ibandronate to adjuvant hormonal therapy in postmenopausal women with hormone-receptor positive early breast cancer. First results of the TEAM IIB trial (BOOG 2006-04)

Background: Results of clinical trials concerning adjuvant bisphosphonates for the prevention of (bone) metastases in patients with early breast cancer are conflicting. A recent large meta-analysis, however, suggests that bisphosphonates reduce the incidence of (bone) metastases and improve skeletal-related events in early breast cancer patients. Subgroup analyses show that postmenopausal women seem to benefit the most. In this subgroup a modest overall survival benefit was observed with the addition of adjuvant bisphosphonates to standard adjuvant systemic therapy (EBCTCG, Lancet, 2015). TEAM IIB, a randomized phase III study (ISRCTN17633610), prospectively investigates the value of the addition of ibandronate to adjuvant hormonal therapy in postmenopausal women with hormone receptor-positive breast cancer. Methods: Postmenopausal women with stage I-III breast cancer and an indication for adjuvant hormonal treatment were randomized to receive at least 5 years of hormonal therapy (tamoxifen followed by at least 2-3 years exemestane, or in case of high risk at least 5 years of exemestane) with or without ibandronate 50mg orally, once daily for three years. Primary endpoint was disease-free survival (DFS). Secondary endpoints included time to and rate of bone metastases, other sites of recurrence, overall survival and safety. The study was amended because of slower than anticipated accrual and the sample size calculations were amended accordingly in June 2009. To detect a hazard ratio (HR) of 0.615 with a 2-sided alpha of 0.05 and a power of 0.8, 139 DFS-events were required in the intention-to-treat population. Results: Between February 2007 and May 2014, 1116 patients were enrolled in 37 hospitals in the Netherlands of whom 40% had positive axillary lymph nodes and 56% of all patients received (neo)adjuvant chemotherapy (>95% anthracyclines, 69% taxanes). Baseline characteristics were well balanced. At September 9, 2016, 143 DFS events had been reported. Median follow-up was 4.6 years and 80 patients were still on ibandronate treatment. Adherence to 3 years ibandronate was 67%, 21 patients randomized to receive ibandronate never started. 19 patients, of whom 9 in the control group were excluded because of major ineligibility. In the ibandronate treated group 3-year DFS was 94.4% versus 90.8% in the control group (HR 0.84; 95% confidence interval [CI] 0.60-1.17). In total, 48 patients in the ibandronate versus 45 in the control group died, of whom 18 (37,5%) versus 28 (62,2%) of breast cancer. 3 years after randomization 1.6% of ibandronate treated patients developed bone metastases versus 4.6% in patients who were treated with adjuvant hormonal therapy only (HR 0.76; [CI] 0.43-1.32). 14 (29,2%) versus 9 (20%) of patients died because of secondary malignancies respectively. There was no significant difference in creatinine clearance during the first three years after randomization. 36 Serious adverse events (SAEs) were reported in the ibandronate group versus 51 in the control group. Of patients randomized to ibandronate 4 developed osteonecrosis, but without residual complaints. Conclusion: So far, at a median follow-up of 4.6 years there is no statistically significant benefit from adding ibandronate to adjuvant hormonal treatment in postmenopausal women with hormone-receptor positive early breast cancer. However, since hazard rates are in favor of ibandronate longer follow-up is warranted before final conclusions can be drawn. Citation Format: Vliek SB, Meershoek-Klein Kranenbarg E, van Rossum AGJ, Tanis BC, Putter H, van der Velden AWG, Hendriks MP, van Bochove A, van Riet Y, van Leeuwen-Stok AE, Tjan-Heijnen VCG, Kroep JR, Nortier JWR, van de Velde CJH, Linn SC. The efficacy and safety of the addition of ibandronate to adjuvant hormonal therapy in postmenopausal women with hormone-receptor positive early breast cancer. First results of the TEAM IIB trial (BOOG 2006-04) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S6-02.