Cancer is the second leading cause of mortality in EU countries, and the needs to tackle cancer are obvious. New scientific understanding, techniques and methodologies are opening up horizons for significant improvements in diagnosis and care. However, take-up is uneven, research needs and potential outstrip currently available resources, manifestly beneficial practices—such as population-level screening for lung cancer—are still not generalised, and the quality of life of patients and survivors is only beginning to be given attention it merits. This paper, mainly based on a series of multistakeholder expert workshops organised by the European Alliance for Personalised Medicine (EAPM), looks at some of those specifics in the interest of planning a way forward. Part of this exercise also involves taking account of the specific nature of Europe and its constituent countries, where the complexities of planning a way forward are redoubled by the wide variations in national and regional approaches to cancer, local epidemiology and the wide disparities in health systems. Despite all the differences between cancers and national and regional resources and approaches to cancer care, there is a common objective in pursuing broader and more equal access to the best available care for all European citizens.

Background: Anti-EGFR therapy, combined with chemotherapy, represents the standard therapeutic approach for triple wild-type (KRAS/NRAS and BRAF), left-sided, microsatellite stable (MSS) metastatic colorectal cancer (mCRC). However, acquired resistance develops in approximately 50% of patients. This study evaluated the efficacy of anti-EGFR therapy re-challenge and analyzed circulating tumor DNA (ctDNA) for potential resistance mechanisms. Methods: Eleven patients with triple wild-type, MSS, HER2-negative, left-sided mCRC were included. All patients received Cetuximab with chemotherapy as the first-line treatment, with three patients subsequently receiving Cetuximab re-challenge. Twenty-one plasma samples were collected at baseline and at each response assessment for retrospective ctDNA analysis using next-generation sequencing with a 16-gene panel. Results: Genetic alterations were detected in only 14.2% of ctDNA samples. In one re-challenge patient, the KRAS: c.35G>A mutation appeared during progression. No RAS mutations were identified in four patients who progressed on first-line Cetuximab treatment. Conclusions: This preliminary study suggests that clinically based anti-EGFR re-challenge may benefit selected mCRC patients. The low detection rate of resistance-conferring mutations indicates potential alternative resistance mechanisms beyond RAS pathway alterations. Our findings, while limited by sample size and the retrospective design of ctDNA testing, contribute to the growing evidence supporting anti-EGFR re-challenge strategies in mCRC management.

The therapeutic efficacy of anti-HER2 monoclonal antibodies in breast cancer has traditionally been attributed to direct inhibition of signaling and antibody-dependent cellular cytotoxicity (ADCC). Recent evidence, however, has established complement activation through the classical pathway as a possible adjunct mechanism underlying the synergistic activity of the trastuzumab and pertuzumab combination. This synergy is mediated by complement-dependent cytotoxicity (CDC) and complement-dependent cellular phagocytosis (CDCP), and is lost upon C1q deletion in preclinical models. Tumor cells evade complement-mediated killing through overexpression of membrane-bound complement regulatory proteins (mCRPs), particularly CD55 and CD59, which correlate with shorter disease-free survival in patients treated with trastuzumab. C1q itself plays a dual, context-dependent role: it acts as a complement-independent tumor suppressor in HER2-positive breast cancer while promoting tumor progression in most other malignancies. Emerging therapeutic strategies, including biparatopic antibodies such as zanidatamab, complement-redirecting immunoconjugates, and mCRP-targeting approaches, aim to overcome complement resistance and enhance antitumor immunity. On this basis, we propose that HER2-positive breast cancer represents a conditionally complement-protective tumor, in which the balance between antibody-directed complement activation and mCRP-mediated evasion determines treatment outcome. This review evaluates the current evidence linking complement to anti-HER2 therapy and highlights future directions for successful treatment.