Comparative clinical benefits of systemic adjuvant therapy for paradigm solid tumors

Adjuvant therapy employing cytotoxic chemotherapy, molecularly targeted agents, immunologic, and hormonal agents has shown a significant impact upon a variety of solid tumors. The principles that guide adjuvant therapy differ among various tumor types and specific modalities, but generally indicate a greater impact of therapy in the postsurgical setting of micrometastatic disease, for which adjuvant therapy is commonly pursued, vs. the setting of gross unresectable disease. This review of adjuvant therapies in current use for five major solid tumors highlights the rationale for current effective adjuvant therapy, and draws comparisons between the adjuvant regimens that have found application in solid tumors.

Phase II study of the MEK1/MEK2 inhibitor Trametinib in patients with metastatic BRAF-mutant cutaneous melanoma previously treated with or without a BRAF inhibitor

PURPOSE

BRAF mutations promote melanoma cell proliferation and survival primarily through activation of MEK. The purpose of this study was to determine the response rate (RR) for the selective, allosteric MEK1/MEK2 inhibitor trametinib (GSK1120212), in patients with metastatic BRAF-mutant melanoma.

PATIENTS AND METHODS

This was an open-label, two-stage, phase II study with two cohorts. Patients with metastatic BRAF-mutant melanoma previously treated with a BRAF inhibitor (cohort A) or treated with chemotherapy and/or immunotherapy (BRAF-inhibitor naive; cohort B) were enrolled. Patients received 2 mg of trametinib orally once daily.

RESULTS

In cohort A (n = 40), there were no confirmed objective responses and 11 patients (28%) with stable disease (SD); the median progression-free survival (PFS) was 1.8 months. In cohort B (n = 57), there was one (2%) complete response, 13 (23%) partial responses (PRs), and 29 patients (51%) with SD (confirmed RR, 25%); the median PFS was 4.0 months. One patient each with BRAF K601E and BRAF V600R had prolonged PR. The most frequent treatment-related adverse events for all patients were skin-related toxicity, nausea, peripheral edema, diarrhea, pruritis, and fatigue. No cutaneous squamous cell carcinoma was observed.

CONCLUSION

Trametinib was well tolerated. Significant clinical activity was observed in BRAF-inhibitor-naive patients previously treated with chemotherapy and/or immunotherapy. Minimal clinical activity was observed as sequential therapy in patients previously treated with a BRAF inhibitor. Together, these data suggest that BRAF-inhibitor resistance mechanisms likely confer resistance to MEK-inhibitor monotherapy. These data support further evaluation of trametinib in BRAF-inhibitor-naive BRAF-mutant melanoma, including rarer forms of BRAF-mutant melanoma.

The potential for BRAF V600 inhibitors in advanced cutaneous melanoma: rationale and latest evidence

Historically, patients with advanced cutaneous melanoma have a poor prognosis and limited treatment options. The discovery of selective v-raf murine sarcoma viral oncogene homolog B1 (BRAF) V600 mutation as an oncogenic mutation in cutaneous melanoma and the importance of the mitogen-activated protein kinase (MAPK) pathway in its tumourigenesis have changed the treatment paradigm for melanoma. Selective BRAF inhibitors and now MEK inhibitors have demonstrated response rates far higher than standard chemotherapeutic options and we review the phase I-III results for these agents in this article. The understanding of mechanisms of resistance that may occur upstream, downstream, at the BRAF level or bypassing the MAPK pathway provides a platform for rational drug development and combination therapies.

Selective BRAF inhibitors induce marked T-cell infiltration into human metastatic melanoma

PURPOSE

To evaluate the effects of treatment with the potent mutant BRAF inhibitors GSK2118436 or vemurafenib (PLX4720) on immune responses to metastatic melanoma in tissues taken before and after treatment.

EXPERIMENTAL DESIGN

Thirty-seven tumor biopsies were collected from 15 patients with unresectable American Joint Committee on Cancer stage III or IV melanoma immediately before and approximately 7 days after the commencement of BRAF inhibitor treatment and at the time of tumor progression. Immunohistochemical staining was carried out on the biopsies using specific antibodies for CD8, CD4, CD20, CD1a, and Granzyme B.

RESULTS

Tumor infiltration by CD4(+) and CD8(+) lymphocytes increased markedly following BRAF inhibitor treatment (both ρ = 0.015). There was a correlation between the degree of tumor infiltration by CD8(+) and Granzyme B-expressing lymphocytes in post-BRAF inhibitor-treated biopsies (r = 0.690 and ρ = 0.013). Increased intratumoral CD8(+) lymphocyte expression was correlated with a reduction in tumor size and an increase in necrosis in posttreatment biopsies (r = -0.793, ρ = 0.011; and r = 0.761, ρ = 0.004, respectively).

CONCLUSIONS

The increase in tumor-infiltrating lymphocytes induced by treatment with BRAF inhibitors provides strong support for conducting trials that combine BRAF inhibitors with immunotherapy in the hope of prolonging clinical responses.

Novel treatments for metastatic cutaneous melanoma and the management of emergent toxicities

The last 12 months have seen the beginning of a new era in the treatment options available for patients with metastatic cutaneous melanoma, a disease previously characterised by its poor prognosis and limited treatment options. Two mechanistically diverse agents have now demonstrated an overall survival benefit in different patient subgroups and further clinical trials are ongoing with emerging single agents and novel combinations. The first agent to demonstrate an overall survival benefit was the CTLA-4 antibody, ipilimumab, illustrating the importance of the immune system and immunomodulation in melanoma tumorigenesis. The second group of agents to show a survival benefit were the selective BRAF inhibitors, vemurafenib and GSK2118436, in patients who are BRAF V600 mutation positive. In addition, in the same BRAF mutant patient population, MEK inhibitors also show promising results and are currently under investigation in later stage trials. Although ipilimumab, BRAF and MEK inhibitors are just passing through the clinical trials arena, their use will rapidly become more widespread. Along with their significant clinical benefits, there are also unique adverse events related to these agents. Although the majority are mild and can be managed with supportive treatment, some toxicities require special management strategies. We outline up-to-date clinical development and management guidelines for ipilimumab, as well as the BRAF and MEK inhibitors.