Adult medulloblastoma is a rare entity with a predilection for the development of radiation-induced malignant glioma (RIMG). Management of RIMG in the setting of prior craniospinal irradiation is a challenging scenario.

We report a case of a 51-year-old male with short-interval development of multicentric malignant glioma with MET mutation who previously underwent craniospinal radiation for adult medulloblastoma. Due to radiographic findings, linear accelerator (LINAC)-based fractionated stereotactic/IMRT was delivered to the right temporal lesion alongside systemic therapy. The patient had interval development of an IDH wildtype, high-grade left cerebellar glioma and underwent surgical resection and subsequent gamma knife stereotactic radiosurgery (GKRS) to the cavity.

GKRS targeting the surgical cavity was delivered with a fractionated regimen of 27 Gy in 3 fractions to the margin. One year after completion of GKRS, the patient had not developed any symptomatic radiation necrosis or neuroimaging changes reflective of treatment toxicity. In this patient, GKRS to minimise the integral dose exposure of normal tissues surrounding the target volume proved to be particularly advantageous in the setting of prior craniospinal irradiation.

RIMG poses significant challenges for radiation oncologists, particularly in the reirradiation setting. Decision-making involving multidisciplinary input balanced the necessity of dose escalation achieved by GKRS, while minimising the cumulative dose in the setting of prior craniospinal irradiation.

Treatment of metachronous second primary non-small cell lung cancer (NSCLC) in patients already treated with definitive radiotherapy is a matter of debate, since most patients are excluded from surgical treatment, which remains a therapeutic standard for patients with isolated lung masses. Salvage chemotherapy or immunotherapy alone offers a low probability of disease control. The option of re-irradiation often remains the only viable, but the risks of severe acute or late toxicities affecting the surrounding normal tissues make this a real clinical challenge.

From January 2015 to April 2018, five patients (male/female: 4/1; age 54–81 years, median 68) with previously irradiated NSCLC presented with a second primary lung tumour.

A partial response was seen in four patients, one complete responses in the fifth. The toxicity was low: two patients experienced a grade 2 asymptomatic radiation pneumonitis after 6 and 12 months from the end of stereotactic body radiation therapy, resolved with cortisone therapy. No acute or late oesophageal or cardiac toxicity was found.

In this work, we present our initial experience about the use of stereotactic radiotherapy technique in already irradiated patients. We reported a local disease control in all cases with an acceptable toxicity.