Erin Roesch, MD
Breast cancer diagnosis and treatment in young women can present unique challenges based on their life stage, including potential impact on fertility and future pregnancy. The role of GnRH analogues for ovarian protection during chemotherapy has been shown in both the POEMS-SWOG S0230 and PROMISE-GIM6 studies. Zong and colleagues conducted a phase 3 trial in China among premenopausal women with stage I-III breast cancer receiving cyclophosphamide-containing chemotherapy, with randomization to GnRHa + chemotherapy vs chemotherapy alone. Among 301 patients eligible for primary endpoint analysis, the premature ovarian insufficiency rate at 12 months was 10.3% for the GnRHa group vs 44.5% for the control group (odds ratio 0.23; P < 0.001). The rate of ovarian function recovery was also 46.4% higher in the GnRHa group. Furthermore, although survival outcomes were similar between groups, in patients <35 years of age, the tumor-free survival was higher in the GnRHa group vs control (93% vs 62%, P = 0.004) ( Zong et al ). These data reinforce the role of GnRHa as a means to reduce POI risk and support ovarian function recovery in young women undergoing chemotherapy for breast cancer. Measures of fertility and timing of pregnancy after breast cancer diagnosis continue to be areas of active research.
The treatment landscape for early-stage HER2-positive breast cancer continues to rapidly evolve with efforts to enhance efficacy and minimize toxicity for patients. The phase 3 KAITLIN study included 1846 patients with early-stage HER2-positive breast cancer (node-positive or node-negative, hormone receptor-negative and ≥T2 primary tumor) with randomization after surgery to adjuvant AC followed by taxane + trastuzumab + pertuzumab (AC-THP) or AC followed by T-DM1 + pertuzumab (AC-KP). In both the overall and node-positive populations, there was no significant difference in IDFS between the arms (stratified HR 0.98 and 0.97, respectively). In the overall population, the 3-year IDFS was 93.1% for AC-KP and 94.2% for AC-THP. Treatment completion rates were lower for AC-KP vs AC-THP (65.0% vs 88.4%), with T-DM1 discontinuation driven mostly by lab abnormalities (elevated liver function tests and thrombocytopenia) ( Krop et al ). Many patients diagnosed with early HER2-positive breast cancer (specifically those with tumors >2cm or node-positive) are treated with neoadjuvant chemotherapy + HER2-targeted therapy with subsequent tailoring of adjuvant treatment pending response, including use of T-DM1 if residual disease present. Future escalation and de-escalation strategies are being explored to further optimize outcomes and decrease side effects.
The addition of CDK 4/6 inhibitors to endocrine therapy has led to improved survival outcomes for patients diagnosed with advanced HR-positive-HER2-negative breast cancer. Lu and colleagues presented exploratory updated OS results among 672 patients with extended follow-up (median 53.5 months) from MONALEESA-7, which was a phase 3 randomized trial of ribociclib + endocrine therapy vs endocrine therapy alone among peri/pre-menopausal patients with HR-positive/HER2-negative advanced breast cancer. Median OS was 58.7 months vs 48.0 months for the ribociclib and placebo arms, respectively (HR 0.76), and a more pronounced benefit was seen in patients <40 years of age (median OS 51.3 months vs 40.5 months for ribociclib vs placebo arm; HR 0.65) ( Lu et al ). Furthermore, there was a significant delay in time to chemotherapy with ribociclib vs placebo (50.9 months vs 36.8 months; HR 0.69) which can certainly impact quality of life. A prior pooled analysis of the various MONALEESA trials demonstrated consistent PFS benefit with ribociclib across all intrinsic breast cancer subtypes, with the exception of basal-like and a more pronounced favorable impact in HER2-enriched. Future research to elucidate differences among CDK 4/6 inhibitors, influence of breast cancer subtype on their effect and how this can be translated to routine clinical practice are warranted.