In a multi-institutional phase II trial, a team led by oncologist Dr. Monika Metzger of St. Jude Children's Research Hospital tracked two-year outcomes of 88 children. The participants had either received low-toxicity chemotherapy and achieved a complete response or had a partial response from chemotherapy and received additional low-dose, involved-field radiotherapy.
The 47 chemotherapy-only patients had an 89.4% two-year event-free survival rate, compared with 92.5% for those who received the combined treatment. Overall, two-year event-free free survival was 90.8%. For five-year event-free survival, the chemotherapy-only patients had an estimated rate of 89.4%, similar to the 87.5% rate for those who received radiation therapy (JAMA, June 27, 2012, Vol. 307:24, pp. 2610-2616).
The prospective study began enrolling patients in March 2000 and achieved its enrollment goal in December 2008. The primary objective of the trial was to report outcomes of patients treated with four cycles of low-toxicity chemotherapy (vinblastine, doxorubicin, methotrexate, and prednisone [VAMP]) with or without radiotherapy.
For those who did not show a complete response, 25.5 Gy involved-field radiotherapy was prescribed. The radiation therapy was administered in 17 fractions of 1.5 Gy two to four weeks after completing the four chemotherapy cycles, and it included treatment of initially involved nodes, as well as the surrounding nodal region.
Treatment was well-tolerated without major complications, according to the researchers. Nine patients (10%) required hospitalization to treat neutropenia and/or infection.
Long-term adverse events in those who received radiation therapy included subclinical pulmonary dysfunction (12 patients), asymptomatic hypothyroidism (nine patients), asymptomatic left ventricular dysfunction (four patients), osteonecrosis (two patients), and moderate osteopenia (two patients).
None of the 41 patients who underwent radiotherapy had developed a second cancer as of March 2012.
While the authors cautioned that the outcomes need to be replicated in a larger study, they recommended that radiation therapy be prescribed on an individualized basis to pediatric patients based on their early response to chemotherapy. Radiation therapy treatments simply may not be needed.