Ashya King left hospital today after finishing his course of proton beam therapy in Prague, almost two months after his parents took him out of Britain in a desperate bid for the treatment.
Doctors at the specialist centre said the five-year-old boy had responded well but his recovery from brain cancer is far from over.
His parents took him out of Southampton General Hospital in August without medical consent, sparking a Europe-wide police search.
Doctors had alerted police, fearing Ashya’s life was in danger without proper medical care, but Brett and Naghmeh King said they were doing what they thought was best for their son.
The NHS had refused to fund treatment at the Proton Therapy Center (PTC) in the Czech Republic but later reversed the decision.
He has now completed a 30-session course of the treatment, which is an alternative to traditional radiotherapy targeting cancerous cells.
The director of the Proton Therapy Center (PTC), Iva Tatounova, told Sky News: "We always thought Ashya would benefit from the specialist treatment here at the PTC.
"And whilst he is still not fully recovered, he's responded very well to the proton beam therapy and there is no reason that he will not continue to get stronger once he leaves here."
Ashya, who suffers from medulloblastoma, celebrated the end of his treatment with a party at the clinic and was seen in a video with his family earlier this week playing in a park.
His parents fought a protracted legal battle to get him to the centre, with a High Court judge only approving the move after they had been released from police custody in Spain, where they were found and arrested three days after going missing.Mr and Mrs King called the chase “ridiculous”, and the case caused a storm of controversy in Britain as critics accused authorities for demonising parents who go against doctors’ advice.
Hampshire Constabulary said they would not apologise for “being proactive” and the hospital claimed doctors had offered the family all the options they could.
The family are planning to return to Spain, where they have a house, because they fear losing Ashya if they come back to Britain.
"At the moment we don't feel 100% safe, I suppose you would call it, contemplating being in England until perhaps they do this investigation into how everything was conducted for us," Mr King said.
"Once that has been established then we can think about going back to England."
The PTC claims their treatment is more effective than conventional radiotherapy as it limits the damage to other vital organs and causes less severe long-term side effects.
The NHS is building two proton beam centres, one in London and one in Manchester, which are expected to open in 2018, and funds the treatment abroad in some cases.
In pictures: Ashya King's case
In pictures: Ashya King's case
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Brett King, back left, and Naghemeh King, right, accompany their son Ashya King (5) center, as he arrives for pre-cancer treatment examinations at the Motol hospital in Prague, Czech Republic
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Ashya King (5) arrives for pre-cancer treatment examinations at the Motol hospital in Prague, Czech Republic
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Brett King, father of five year old Ashya King, talks to members of the press after holding a press conference at his lawyer's office in Seville, Spain
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Brett and Naghemeh King, parents of Ashya King, attend a press conference in Sevilla, Spain. The British parents are heading to see him at a hospital in southern Spain following release their from custody after United Kingdom authorities dropped accusations of child cruelty against them
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British couple Brett (L) and Naghemeh (2L) King leave Soto del Real Prision in Soto del Real, near Madrid, Spain
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Brett King leaving Soto del Real prison near Madrid, Spain after British authorities dropped the case against him and his wife for taking their son Ashya from Southampton General Hospital without the consent of doctors
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Naghemeh King leaves Soto del Real Prision in Soto del Real, near Madrid, Spain
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Ashya King in hospital with his mother
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Journalist work outside the Materno Infantil Hospital where Ashya King is hospitalized in Malaga, Spain
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Ethan Dallas and Sanjay Ganatra, friends of the family, deliver a petition of over 100,000 names calling for his parents' release from a Spanish jail
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Spanish judge Ismael Moreno arrives to the National Courts to take statement to the parents of Britain's five-year-old boy Ashya King, in Madrid, Spain
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Ashya King parents's lawyer, Juan Isidro Fernandez Diaz, arrives at the National court in Madrid
AP Photo/Andres Kudacki
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Spanish policemen stand guard as a police van carrying the parents of Ashya King arrives at the courthouse in Madrid
JAVIER SORIANO/AFP/Getty Images
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Ashya King’s parents after their court appearance
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Ashya King's father explained why he took his son to Spain in a video uploaded to YouTube
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This photo of Ashya King being examined by doctors in hospital was posted on Facebook by his brother, Naveed
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Ashya King and his brother Naveed
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Ashya King on a hospital bed
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A CCTV still issued by Hampshire Police of Ashya King with his father Brett King at around 4pm yesterday
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The exterior of Southampton General Hospital where Ashya King, who has a brain tumour was taken by his parents from the hospital without the blessing of doctors
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Hampshire Constabulary said there are 'serious concerns' for the life of Ashya King as he needs constant medical care. Officers said his parents - Brett, 51, and Naghemeh, 45, - boarded a cross-Channel ferry from Portsmouth to Cherbourg at 4pm yesterday with Ashya's six siblings
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Ashya King, who has a brain tumour and was taken by his parents from hospital without the blessing of doctors
“Proton beam therapy can be very costly and it is not clear whether all children treated privately abroad are treated appropriately,” a spokesperson said.
“It is important not to lose sight of the fact that conventional radiotherapy is, in most cases, both safe and effective with a low risk of complications.”
Additional reporting by PAReuse content