Change in radiotherapy treatment volumes with initial alkylating chemotherapy in anaplastic gliomas

Abstract

Objective

Although not a standard approach, adjuvant chemotherapy alone is sometimes used to avoid radiotherapy (RT) for anaplastic gliomas, with RT reserved for salvage. The impact of this approach on salvage RT volume size at progression is unknown. We assessed patterns/predictors of response in anaplastic glioma patients treated with adjuvant chemotherapy alone.

Methods

Anaplastic glioma patients treated with resection and adjuvant chemotherapy were identified from hospital records. Planning target volumes (PTV) for salvage RT were constructed per guidelines on every MRI while patients received chemotherapy, and percentage change and maximal response were recorded. Differences in outcomes by demographic and pathologic factors were analyzed with χ ² and independent samples t tests.

Results

We identified 23 patients, with anaplastic astrocytoma (AA), oligoastrocytoma (AOA), and oligodendroglioma (AOD) in 2, 14, and 6 patients, respectively (one unknown). Seventeen (74 %) had volumetric reduction of ≥10 %, five had enlargement of ≥10 %, and one had stable disease after chemotherapy. Among responders, maximal response occurred at 269 days (mean) and mean reduction in PTV was 35 %. AOA/AA were more likely than AOD to have enlargement (29.4 versus 16.7 %, respectively; p = 0.055). Ten of 23 received RT at progression, with mean PTV volume 4 % below baseline (range −39 to +140 %). Salvage RT volumes among patients without response by 90 days were significantly larger than baseline (+28.2 % without versus −13.9 % with response, p = 0.028).

Conclusion

Chemotherapy results in an initial volumetric response. However, RT volumes at salvage are not meaningfully different than baseline. Patients without response by 90 days are likely to require RT to significantly larger volumes at progression.