The immune system is regulated by a delicate balance of factors that initiate antitumor immune responses and inhibit excessive inflammation and autoimmunity. Cells from both the innate and adaptive immune systems work to eradicate pathogens and other threats, including cancer. A number of investigations^1-3 over the past decade suggest that a proportion of breast cancers are immunogenically active and that some breast tumors have a substantial lymphocytic infiltrate. Lymphocyte-predominant breast cancers are characterized by tumor-infiltrating lymphocytes comprising 50% or more of the tumor bed. Primary breast tumors with a robust immune infiltrate are associated with a better response to neoadjuvant chemotherapy.

The genetic and clinical heterogeneity of breast cancer makes the identification of effective therapies challenging. We designed I-SPY 2, a phase 2, multicenter, adaptively randomized trial to screen multiple experimental regimens in combination with standard neoadjuvant chemotherapy for breast cancer. The goal is to match experimental regimens with responding cancer subtypes. We report results for veliparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, combined with carboplatin. In this ongoing trial, women are eligible for participation if they have stage II or III breast cancer with a tumor 2.5 cm or larger in diameter; cancers are categorized into eight biomarker subtypes on the basis of status with regard to human epidermal growth factor receptor 2 (HER2), hormone receptors, and a 70-gene assay. Patients undergo adaptive randomization within each biomarker subtype to receive regimens that have better performance than the standard therapy. Regimens are evaluated within 10 biomarker signatures (i.e., prospectively defined combinations of biomarker subtypes). Veliparib–carboplatin plus standard therapy was considered for HER2-negative tumors and was therefore evaluated in 3 signatures. The primary end point is pathological complete response. Tumor volume changes measured by magnetic resonance imaging during treatment are used to predict whether a patient will have a pathological complete response. Regimens move on from phase 2 if and when they have a high Bayesian predictive probability of success in a subsequent phase 3 neoadjuvant trial within the biomarker signature in which they performed well. With regard to triple-negative breast cancer, veliparib–carboplatin had an 88% predicted probability of success in a phase 3 trial. A total of 72 patients were randomly assigned to receive veliparib–carboplatin, and 44 patients were concurrently assigned to receive control therapy; at the completion of chemotherapy, the estimated rates of pathological complete response in the triple-negative population were 51% (95% Bayesian probability interval [PI], 36 to 66%) in the veliparib–carboplatin group versus 26% (95% PI, 9 to 43%) in the control group. The toxicity of veliparib–carboplatin was greater than that of the control. The process used in our trial showed that veliparib–carboplatin added to standard therapy resulted in higher rates of pathological complete response than standard therapy alone specifically in triple-negative breast cancer. (Funded by the QuantumLeap Healthcare Collaborative and others; I-SPY 2 TRIAL ClinicalTrials.gov number, NCT01042379.)

The heterogeneity of breast cancer makes identifying effective therapies challenging. The I-SPY 2 trial, a multicenter, adaptive phase 2 trial of neoadjuvant therapy for high-risk clinical stage II or III breast cancer, evaluated multiple new agents added to standard chemotherapy to assess the effects on rates of pathological complete response (i.e., absence of residual cancer in the breast or lymph nodes at the time of surgery). We used adaptive randomization to compare standard neoadjuvant chemotherapy plus the tyrosine kinase inhibitor neratinib with control. Eligible women were categorized according to eight biomarker subtypes on the basis of human epidermal growth factor receptor 2 (HER2) status, hormone-receptor status, and risk according to a 70-gene profile. Neratinib was evaluated against control with regard to 10 biomarker signatures (prospectively defined combinations of subtypes). The primary end point was pathological complete response. Volume changes on serial magnetic resonance imaging were used to assess the likelihood of such a response in each patient. Adaptive assignment to experimental groups within each disease subtype was based on Bayesian probabilities of the superiority of the treatment over control. Enrollment in the experimental group was stopped when the 85% Bayesian predictive probability of success in a confirmatory phase 3 trial of neoadjuvant therapy reached a prespecified threshold for any biomarker signature (“graduation”). Enrollment was stopped for futility if the probability fell to below 10% for every biomarker signature. Neratinib reached the prespecified efficacy threshold with regard to the HER2-positive, hormone-receptor–negative signature. Among patients with HER2-positive, hormone-receptor–negative cancer, the mean estimated rate of pathological complete response was 56% (95% Bayesian probability interval [PI], 37 to 73%) among 115 patients in the neratinib group, as compared with 33% among 78 controls (95% PI, 11 to 54%). The final predictive probability of success in phase 3 testing was 79%. Neratinib added to standard therapy was highly likely to result in higher rates of pathological complete response than standard chemotherapy with trastuzumab among patients with HER2-positive, hormone-receptor–negative breast cancer. (Funded by QuantumLeap Healthcare Collaborative and others; I-SPY 2 TRIAL ClinicalTrials.gov number, NCT01042379.)

Neoadjuvant therapy and adjuvant systemic therapy are equally effective in improving breast cancer survival. However, neoadjuvant therapy improves rates of breast-conserving surgery owing to tumor downstaging^1,2 and allows assessment of response. The Collaborative Trials in Neoadjuvant Breast Cancer (CTNeoBC) working group evaluated the latter by conducting a pooled patient-level meta-analysis of nearly 12 000 patients from 12 randomized trials, largely with various regimens of standard chemotherapy, to assess the relationship between pathologic complete response (pCR) rates, event-free survival (EFS), and overall survival.³ Overall, pCR was found to have long-term benefit for patients (EFS hazard ratio, 0.48), with the strongest association observed for more aggressive breast cancer subtypes, such as triple-negative breast cancer (hormone receptor [HR]–negative, ERBB2 [formerly HER2]–negative disease) (EFS hazard ratio, 0.24), and ERBB2-positive disease (EFS hazard ratio, 0.39). Based on these data, the US Food and Drug Administration and the European Medicines Agency issued guidance for the use of pCR as a primary end point in support of accelerated drug approval.^4,5 Given the number of promising new agents, this provided the opportunity for new trial designs to rapidly identify drugs with the greatest activity.

Loss of expression of the hMLH1 and hPMS2 subunits of the MutLα-mismatch repair complex is a frequent event (9/10) in independent cisplatin resistant derivatives of a human ovarian carcinoma cell line. However, only hMLH1 mRNA is decreased in these MutLα-deficient lines. No alterations in the levels of the hMSH2 and hMSH6 (GTBP) subunits of the MutSα-complex are observed. An increase in the proportion of ovarian tumours negative for the hMLH1 subunit is observed in samples taken at second look laporotomy after chemotherapy (36%: 4/11), compared to untreated tumours (10%: 4/39). No significant difference is observed for hMSH2, hMSH6 or hPMS2. Furthermore, cisplatin and doxorubicin-resistant ovarian lines deficient in hMLH1 expression are cross-resistant to 6-thioguanine and the methylating agent N-methyl-N-nitrosourea (MNU). Depletion of O⁶-alkylguanine-DNA-alkyltransferase (ATase) activity confers only limited increased sensitivity to MNU. Thus the mismatch repair deficient lines retain DNA damage tolerance even after ATase depletion. The hMLH1 deficient lines also lose ability to engage G1 and G2 cell cycle arrest after cisplatin damage. Together these data suggest that loss of hMLH1 expression may be a high frequency event following exposure of ovarian tumour cells to cisplatin and may be critically involved in the development of drug resistance. Thus, the hMLH1 status of these cells appears to be highly correlated with the ability to engage cell death and cell cycle arrest after DNA damage induced by cisplatin.