Mathematical models of drug resistance and chemotherapy effects

Neoadjuvant hormonal therapy before radical prostatectomy in high-risk prostate cancer

Patients with high-risk prostate cancer treated with curative intent are at an increased risk of biochemical recurrence, metastatic progression and cancer-related death compared with patients treated for low-risk or intermediate-risk disease. Thus, these patients often need multimodal therapy to achieve complete disease control. Over the past two decades, multiple studies on the use of neoadjuvant treatment have been performed using conventional androgen deprivation therapy, which comprises luteinizing hormone-releasing hormone agonists or antagonists and/or first-line anti-androgens. However, despite results from these studies demonstrating a reduction in positive surgical margins and tumour volume, no benefit has been observed in hard oncological end points, such as cancer-related death. The introduction of potent androgen receptor signalling inhibitors (ARSIs), such as abiraterone, apalutamide, enzalutamide and darolutamide, has led to a renewed interest in using neoadjuvant hormonal treatment in high-risk prostate cancer. The addition of ARSIs to androgen deprivation therapy has demonstrated substantial survival benefits in the metastatic castration-resistant, non-metastatic castration-resistant and metastatic hormone-sensitive settings. Intuitively, a similar survival effect can be expected when applying ARSIs as a neoadjuvant strategy in high-risk prostate cancer. Most studies on neoadjuvant ARSIs use a pathological end point as a surrogate for long-term oncological outcome. However, no consensus yet exists regarding the ideal definition of pathological response following neoadjuvant hormonal therapy and pathologists might encounter difficulties in determining pathological response in hormonally treated prostate specimens. The neoadjuvant setting also provides opportunities to gain insight into resistance mechanisms against neoadjuvant hormonal therapy and, consequently, to guide personalized therapy.

Resistance to cytotoxic and anti-angiogenic anticancer agents: similarities and differences

Intrinsic resistance to anticancer drugs, or resistance developed during chemotherapy, remains a major obstacle to successful treatment. This is the case both for resistance to cytotoxic agents, directed at malignant cells, and for resistance to anti-angiogenic agents, directed at non-malignant endothelial cells. In this review, we will discuss mechanisms of resistance which have a bearing on both these conceptually different classes of drugs. The complexity of drug resistance, involving drug transporters, such as P-glycoprotein, as well as resistance related to the tissue structure of solid tumors and its consequences for drug delivery is discussed. Possible mechanisms of resistance to endothelial cell-targeted drugs, including inhibitors of the VEGF receptor and EGF receptor family, are reviewed. The resistance of cancer cells as well as endothelial cells related to anti-apoptotic signaling events initiated by cell integrin-matrix interactions is discussed. Current strategies to overcome resistance mechanisms are summarized; they include high-dose chemotherapy, tumor targeting of cytotoxics to improve tumor uptake, low-dose protracted (metronomic) chemotherapy and combinations of classical agents with anti-angiogenic agents. This review discusses primarily literature published in 2001 and 2002.

Phase II study of a multi-course high-dose chemotherapy regimen incorporating cyclophosphamide, thiotepa, and carboplatin in stage IV breast cancer

The purpose of this study was to determine the feasibility and efficacy of multiple courses of high-dose cyclophosphamide, carboplatin and thiotepa with peripheral blood progenitor cell (PBPC) transplantation in women with advanced breast cancer. Forty-one patients with advanced hormone-refractory breast cancer were enrolled in the study. The treatment started with two courses of 5-fluorouracil 500 mg/m(2), epirubicin 120 mg/m(2) and cyclophosphamide 500 mg/m(2) (FE(120)C) followed by PBPC harvesting. The high-dose regimen consisted of three subsequent courses of 'tiny' CTC, cyclophosphamide 4000 mg/m(2), thiotepa 320 mg/m(2) and carboplatin 1060 mg/m(2) (target AUC 13.3 mg/ml/min) (tCTC) divided over 4 consecutive days. The second and third courses were scheduled to begin on day 28 after the previous transplantation. A total of 86 tCTC courses was given to 33 of the 41 enrolled patients. Major toxicities consisted of hemorrhagic cystitis (six patients), prolonged gastro-intestinal toxicity (three patients) and veno-occlusive disease (two patients). There was one therapy-related death (unknown cause). Twenty patients (49%) achieved a complete response, nine (22%) a partial response and three patients stable disease after treatment. The median follow-up of the surviving patients was 43 months (range 25-61). Six patients remain in complete remission beyond 3 years. At 4 years, the progression-free survival (PFS) and overall survival (OS) for the whole patient group were 23 and 30% with a median duration of 12 and 27 months, respectively and for FE(120)C-responsive patients 32 and 36%, respectively with a median duration of 15 and 33 months. In the patient group with a PFS > or = 18 months all patients had limited disease (metastatic disease in only one or two sites) and fewer patients had bone or liver metastases compared to the overall patient group (33% vs 51%). This report shows that three closely spaced courses of tCTC are feasible, with acceptable toxicity. Triple tCTC can achieve complete or partial remission in most patients and long-term PFS in a selected subgroup of patients who have limited metastatic disease and are responsive to conventional-dose chemotherapy.

Utility of C-erbB-2 in tissue and in serum in the early diagnosis of recurrence in breast cancer patients: comparison with carcinoembryonic antigen and CA 15.3

To evaluate the utility of c-erbB-2, carcinoembryonic antigen (CEA) and CA 15.3 in the early diagnosis of recurrence, serial serum determinations of these antigens were performed in 200 patients (follow-up 1-4 years, mean 2.2 years) with primary breast cancer and no evidence of residual disease (NED) after radical treatment (radical mastectomy or simple mastectomy and radiotherapy). Eighty-nine patients developed metastases during follow-up. C-erbB-2, CEA and CA 15.3 were elevated (> 20 U ml-1, > 10 ng ml-1 or > 60 U ml-1 respectively) before diagnosis in 28%, 30% and 47% of the 89 patients with recurrence, with a lead time of 4.5 +/- 2.4, 4.9 +/- 2.4 and 4.8 +/- 2.4 months respectively. Tumour marker sensitivity was clearly related to the site of recurrence, with the lowest sensitivity found in locoregional relapse and the highest in patients with liver metastases. When patients with locoregional recurrences were excluded, sensitivity improved: 31% (c-erbB-2), 33% (CEA) and 56% (CA 15.3), with 76% having at least one of the three tumour markers. C-erbB-2 sensitivity in early diagnosis was significantly higher in patients with c-erbB-2 overexpression in tissue (8/10, 80%) than in those without overexpression (1/30, 3.3%) (P = 0.0001). Likewise, higher levels of both, c-erbB-2 and CA 15.3 at diagnosis of recurrence, higher sensitivity in early diagnosis of relapse and a higher lead time were found in PR+ patients (CA 15.3, P < 0.0001) or in PR- patients (c-erbB-2, P = 0.009). Specificity of the tumour markers was 100% for all three markers (111 NED patients). In conclusion, c-erbB-2 is a useful tool for early diagnosis of metastases, mainly in those patients with c-erbB-2 overexpression in tissue. Using all three markers simultaneously it is possible to increase the sensitivity in the early diagnosis of recurrence by 11.2%.

Use of serial carcinoembryonic antigen and CA 15.3 assays in detecting relapses in breast cancer patients

To evaluate the utility of CEA and CA 15.3 for early diagnosis of recurrence, serial serum determinations of both antigens were performed in 1023 patients (follow-up: 1-10 years, mean 6.2 years) with primary breast cancer (CA 15.3 in 533 cases) and no evidence of residual disease (NED) after radical treatment (radical mastectomy or simple mastectomy and radiotherapy). 246 patients developed metastases during follow-up.

RESULTS

CEA and CA 15.3 were elevated ( > 10 ng/ml or > 60 U/ml, respectively) prior to diagnosis in 40% (98/246) and 41% (37/91) of the patients with recurrence, with a lead time of 4.9 +/- 2.2 and 4.2 +/- 2.3 months, respectively. When patients with locoregional recurrences were excluded, sensitivity improved to 46% (CEA) and 54% (CA 15.3), and to 64% with both tumor markers (CEA and/or CA 15.3). Higher levels of both CEA and CA 15.3 at diagnosis of recurrence, higher sensitivity in early diagnosis of relapse, and a higher lead time were found in ER+ (CEA) or PgR+ patients (CA 15.3) than in those that were negative for these receptors in the primary tumor (p < 0.001). Specificity of the tumor markers was 99% for both CEA (777 NED patients) and for CA 15.3 (444 NED patients), respectively. In conclusion, CEA and CA 15.3 are useful tools for early diagnosis of metastases, mainly in those patients with ER+ or PR+ tumors.

The role of cell death in the growth of preneoplastic lesions: a Monte Carlo simulation model

A variety of experimental and clinical examples of preneoplasia demonstrate that regression of early lesions is common. This paper examines the hypothesis that early lesions operate under the identical growth kinetics of 'late' lesions (neoplasms), but that kinetic features favouring continuous growth in established lesions tend to favour extinction of lesions composed of small numbers of cells. Growth simulations of early lesions were produced using the Monte Carlo method, a technique demanding intensive computations. With the advent of powerful personal computers, this technique is now widely available to biologists. Simulating growth under conditions of cell loss similar to those observed in established tumours, the model predicts that the great majority of initiated cell clusters are expected to reach extinction within a few cell doubling times, and most early (promoted) lesions would not likely progress to the size of a clinically detectable lesion within the life span of the host organism. These Monte Carlo simulations provide a model of initiated cell growth consistent with the recently demonstrated role of early lesion cell death in the development of human lymphomas and in transgenic mice expressing the bcl-2 oncogene. The model demonstrates that small increments in the intrinsic cell loss probability in even the earliest progenitors of malignancy can strongly influence the subsequent development of neoplasia from initiated foci.