My Husband Has Been On Chemotherapy For Over A Year

My husband has been on chemotherapy for over a year for initially non-Hodgkins Lymphoma and then Lymphoma of the CNS. He is about to go for stem cell therapy at the Royal Marsden and yesterday had chemo for the day in order to generate the stem cells for collection in 10 days. He wants to have a sauna now and has the temp at about 70 degrees. Is it safe so soon after chemo?