New evidence on the impact of dysregulation of the CDK4/6 pathway on breast cancer (BC) cell proliferation has led to the development of selective CDK4/6 inhibitors, which have radically changed the management of advanced BC. Despite the improved outcomes obtained by CDK4/6 inhibitors, approximately 10% of tumors show primary resistance, whereas acquired resistance appears to be an almost ubiquitous occurrence, leading to treatment failure. The identification of differentially expressed genes or genomic mutational signatures able to predict sensitivity or resistance to CDK4/6 inhibitors is critical for medical decision making and for avoiding or counteracting primary or acquired resistance against CDK4/6 inhibitors. In this review, we summarize the main mechanisms of resistance to CDK4/6 inhibitors, focusing on those associated with potentially relevant biomarkers that could predict patients’ response/resistance to treatment. Recent advances in biomarker identification are discussed, including the potential use of liquid biopsy for BC management and the role of multiple microRNAs as molecular predictors of cancer cell sensitivity and resistance to CDK4/6 inhibitors.

Transgender individuals exhibit a higher prevalence of cancer-related risk factors, such as substance abuse and sexually transmitted infections. These factors, coupled with suboptimal adherence to cancer screening recommendations, may lead to a higher incidence of cancers, such as breast and cervical cancer, and contribute to delayed diagnoses in transgender patients. Herein, we report a unique case of a transgender man with a history of alcohol and drug abuse, undergoing gender-affirming exogenous testosterone therapy, who developed synchronous locally advanced breast cancer and human papilloma virus (HPV)-related cervical cancer. He underwent concurrent chemoradiation for cervical cancer and surgery followed by endocrine therapy for breast cancer. The treatments were suboptimals due to patient’s comorbidities, among them liver cirrhosis leading to an early death. Additionally, we have conducted a review of existing literature, including case reports, clinical studies, and review articles investigating the role of potential risk factors specifically related to breast and cervical tumors in transgender men. Gender-affirming testosterone therapy is common among transgender men to induce gender affirmation, but its link to breast cancer risk remains ambiguous, with studies being limited and sometimes contradictory. Conversely, HPV is a well-established cause of up to 99% of cervical cancers. Despite persistent risk for cervical cancer in transgender men who retain their cervix, several studies indicate notable disparities in screening adherence, due to personal and structural barriers. Moreover, alcohol and drug use disorders, commonly encountered in transgender population, may negatively influence the adherence to screening programs. Current cancer screening guidelines for this population are somewhat unclear, and specific programs based on more robust data are urgently required along with further tailored studies.

Background/Objectives: HER2-positive breast cancer (HER2⁺BC) is an aggressive subtype, with neoadjuvant treatment (NAT) aiming to achieve a pathological complete response (pCR) to improve long-term outcomes. Trastuzumab emtansine (T-DM1) has been established as the standard of care in the adjuvant setting for HER2⁺BC patients who do not obtain pCR. The ATD study aimed to evaluate the real-world tolerability of T-DM1 in this setting. The secondary objective was to assess the effectiveness. Methods: This was a multicenter, retrospective study across 24 Italian oncology centers, including 410 patients with HER2⁺BC treated with adjuvant T-DM1 following a lack of pCR after NAT. Patient characteristics, NAT regimens, and surgical outcomes were recorded. Tolerability was assessed by documenting adverse events (AEs) according to the CTCAE (v5.0). Preliminary effectiveness was evaluated in terms of relapse-free survival (RFS) and overall survival (OS). Results: Overall, 228 patients (55.6%) experienced at least one AE related to T-DM1, with 4.9% experiencing grade 3 or higher AEs. The most common AEs were hepatotoxicity (18.5%) and thrombocytopenia (17.6%). T-DM1 was discontinued in 10.0% of patients due to toxicity. After a median follow-up of 25 months, 31 relapse events (7.6%) and 22 deaths (5.4%) were reported. The preliminary incidence of RFS and OS events was similar between patients who completed the T-DM1 course and those who discontinued it early. Conclusions: T-DM1 demonstrated a manageable safety profile, and the adverse events were consistent with those reported in randomized trials. The data are not yet sufficient to allow for a formal analysis of RFS and OS, and long-term follow-up is required.

We assessed the impact of DNA damage response and repair (DDR) biomarker expressions in 222 node-positive early breast cancer (BC) patients from a previous Phase III GOIM 9902 trial of adjuvant taxanes. At a median follow-up of 64 months, the original study showed no disease-free survival (DFS) or overall survival (OS) differences with the addition of docetaxel (D) to epirubicine-cyclophosphamide (EC). Immunohistochemistry was employed to assess the expression of DDR phosphoproteins (pATM, pATR, pCHK1, γH2AX, pRPA32, and pWEE1) in tumor tissue, and their association with clinical outcomes was evaluated through the Cox elastic net model. Over an extended follow-up of 234 months, we confirmed no significant differences in DFS or OS between patients treated with EC and those receiving D → EC. A DDR risk score, inversely driven by ATM and ATR expression, emerged as an independent prognostic factor for both DFS (HR = 0.41, p < 0.0001) and OS (HR = 0.61, p = 0.046). Further validation in a public adjuvant BC cohort was possible only for ATM, confirming its protective role. Overall, our findings confirm the potential role of the DDR pathway in BC prognostication and in shaping treatment strategies advocating for an integrated approach, combining molecular markers with clinical–pathological factors.