Prof. Heikki Joensuu

Prof. Heikki Joensuu is a professor of oncology at the University of Helsinki and a senior consultant in radiation oncology and medical oncology at Helsinki University Hospital (HUCH) and the Helsinki University Comprehensive Cancer Centre. Over a career spanning more than 35 years, he has become one of Europe's most internationally recognised cancer specialists, with a unique track record of contributions that have directly and durably changed cancer treatment standards worldwide.

His most celebrated contribution to oncology is the development of the Joensuu risk classification system for gastrointestinal stromal tumour (GIST) — a sarcoma-type tumour arising from the wall of the gastrointestinal tract that was poorly understood and largely untreatable before the imatinib era. Prof. Joensuu was a pioneering investigator in the application of imatinib (Gleevec/Glivec) to GIST following its original development for chronic myeloid leukaemia, and he developed a comprehensive, clinically validated risk stratification system — now known worldwide as the 'Joensuu risk classification' — that categorises GIST patients by risk of recurrence after surgery based on tumour size, mitotic rate, location, and rupture status. This classification system, subsequently refined and validated in large international datasets, guides adjuvant imatinib treatment decisions for GIST patients in clinical practice around the globe.

Beyond his GIST contributions, Prof. Joensuu has maintained an active clinical and research programme in breast cancer and other solid tumours, contributing to the evidence base for novel therapeutic agents and treatment combinations. His dual expertise in both radiation oncology and medical oncology gives him a comprehensive perspective on multimodality cancer treatment that is increasingly valued as cancer care grows more complex and integrated.

The Helsinki University Comprehensive Cancer Centre, where Prof. Joensuu is a senior faculty member, is Finland's leading cancer centre and a major European oncology research institution. It provides the infrastructure for the clinical trials and translational research that continue to define Prof. Joensuu's scientific output.

Prof. Joensuu completed his medical degree at the University of Helsinki before undertaking postgraduate training in oncology. He was awarded his PhD for early research into the biology and treatment of breast cancer, reflecting his foundational interest in solid tumour oncology that would expand significantly over his career.

He developed dual expertise in radiation oncology and medical oncology — an unusual combination that distinguishes him from most of his peers and enables him to contribute both to the radiotherapy and systemic treatment aspects of tumour management. His training incorporated exposure to early clinical trials of novel therapeutic agents, developing skills in clinical trial design and execution that proved central to his subsequent research in GIST and other tumours.

Prof. Joensuu holds the Fellowship of the European Society for Medical Oncology (FESMO) and holds a full professorship at the University of Helsinki. He has supervised numerous doctoral students in clinical oncology and translational cancer research, and his research group continues to produce important work on GIST biology, adjuvant therapy optimisation, and predictive biomarkers of cancer treatment response.

Prof. Joensuu's primary clinical subspecialty is the management of gastrointestinal stromal tumours (GIST), encompassing diagnosis, risk stratification using the Joensuu classification, surgical planning (in collaboration with GI surgeons), adjuvant imatinib therapy, and the management of metastatic or recurrent GIST — including selection of second-line (sunitinib) and subsequent therapies.

He also manages patients with other soft tissue sarcomas and rare solid tumours where targeted therapy may be applicable. In breast cancer, he has expertise in the selection and administration of systemic therapies — including chemotherapy, targeted agents, and endocrine therapy — and contributes to multidisciplinary breast tumour board decisions on complex cases.

Stereotactic radiotherapy is within his clinical repertoire for appropriate patients with brain metastases, limited extracranial oligometastases, or early-stage tumours in patients who are not surgical candidates. His dual medical oncology and radiation oncology background enables a comprehensive, integrated approach to complex treatment planning. He is experienced in coordinating multidisciplinary tumour boards for sarcoma and GI malignancy cases, ensuring that patients benefit from collective expertise across surgical, radiological, pathological, and oncological specialties.

Prof. Joensuu has authored over 400 peer-reviewed publications in leading journals including the Lancet, Journal of Clinical Oncology (JCO), Annals of Oncology, the New England Journal of Medicine, and Gut. His research has been highly cited internationally and has had direct clinical impact across multiple tumour types.

His foundational papers on imatinib in GIST — including the original case series demonstrating dramatic responses to imatinib in metastatic GIST, the development and validation of the risk classification system for resected GIST, and the randomised SSGXVIII/AIO trial demonstrating that three years of adjuvant imatinib provides greater relapse-free survival benefit than one year — represent some of the most influential contributions to sarcoma oncology of the past 25 years. The risk classification he developed is now formally endorsed in ESMO, NCCN, and other international GIST treatment guidelines.

Additional major research contributions include studies of trastuzumab (Herceptin) in early HER2-positive breast cancer — including the pivotal FinHer trial (Finland Herceptin trial), which was among the first randomised studies to demonstrate the efficacy of trastuzumab in early breast cancer — and investigations into the biology of treatment resistance in GIST. His research on the EJC (European Journal of Cancer) Award-winning studies further reflects the breadth and quality of his scientific output.

Prof. Joensuu consults in Finnish and English and is one of the world's most recognised experts for patients with GIST seeking specialist diagnosis, risk stratification, or second opinion on adjuvant therapy decisions. HUCH and the Helsinki University Comprehensive Cancer Centre welcome international referrals for GIST and other rare solid tumours, with multidisciplinary expertise including dedicated GIST pathologists, radiologists, and GI surgeons.

EU/EEA patients may be eligible for cross-border healthcare funding when referred for specialist oncology care in Helsinki. Non-EU patients are seen on a private referral basis, and the international patient office at HUCH can assist with coordination, cost estimates, and logistical support. For international patients seeking a second opinion on GIST risk classification or adjuvant imatinib decisions specifically, telemedicine consultations with Prof. Joensuu are available, allowing detailed review of pathology reports, mitotic counts, tumour size, and location data.

Given the rarity of GIST and the global reach of the Joensuu classification system, oncologists from many countries regularly consult Prof. Joensuu directly regarding complex or atypical cases — and such professional consultations are welcomed and accommodated where scheduling permits.

Prof. Joensuu has been recognised with the Finnish Cancer Society's Research Prize — one of the most prestigious research awards in Finnish oncology — for his extraordinary contributions to GIST research and cancer treatment innovation. The European Society for Medical Oncology (ESMO) has awarded him its Distinguished Fellowship (FESMO) in recognition of his exceptional contributions to European oncology.

He has received the Helsinki University Research Award for sustained scientific excellence, and the EJC (European Journal of Cancer) Award for outstanding contributions to European cancer research. His development of the Joensuu risk classification and co-leadership of the SSGXVIII/AIO and FinHer trials represent some of the most practically impactful research achievements in European oncology of the past two decades. He is a sought-after invited speaker at ESMO, ASCO, and CTOS (Connective Tissue Oncology Society) congresses, where he is recognised as a global authority on GIST and adjuvant targeted therapy.