Response Adapted Incorporation of Tislelizumab Into the Front-line Treatment of Older Patients With Hodgkin lYmphoma

Trial patients who are deemed eligible for the trial will receive 3 cycles of tislelizumab which will be administered at a dose of 200 mg (IV) on day 1 of each 21-day cycle. Patients will then undergo a PET-CT scan (PET1). Subsequent treatment is determined by the patient's stage and response to tislelizumab (as determined by PET1). Patients with early stage lymphoma and no high-risk features who respond very well to the initial 3 doses of tislelizumab will receive a further 2 doses of tislelizumab, followed by radiotherapy, followed by tislelizumab once every 21 days for up to 2 years. All other patients will receive a combination of tislelizumab with chemotherapy for between 2 and 6 cycles. Each cycle will last 28 days. Tislelizumab will be given on day 1 and chemotherapy (doxorubicin (also known as Adriamycin), vinblastine and dacarbazine, or AVD) will be given on days 1 and 15, as injections or infusions into a vein. Following this some patients may require radiotherapy depending on their response to treatment. Patients who are in complete metabolic response (CMR) at PET1 will receive 2 fewer cycles of tislelizumab and AVD therapy than those not in CMR. A further 1 or 2 PET scans will be performed to assess how well the lymphoma has responded to the trial treatment, depending on the results of previous scans. After completing the treatment patients will then be followed-up for at least 2 years from the start of their participation in the trial. Note: Initial patients will be recruited to a safety run in. Once 6 evaluable patients have completed 2 cycles of tislelizumab and AVD after PET1 the independent data monitoring committee (IDMC) will review the data, and if considered tolerable, recruitment will continue to the full sample size (80 patients).