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The following is a summary of “Intra-prostatic recurrences after radiotherapy with focal boost: Location and dose mapping in the FLAME trial,” published in the September 2024 issue of Oncology by Guricová et al.

The FLAME trial established a significant association between the dose delivered to the gross tumor volume (GTV) and tumor control in patients with prostate cancer, prompting questions about the potential for dose de-escalation to the remaining prostate gland. This study aimed to investigate the localization of intraprostatic recurrences relative to the GTV and assess the doses administered at these sites. Researchers analyzed data from patients in the FLAME trial who experienced intraprostatic recurrences, including pre-treatment imaging, GTV delineations, dose distributions, and post-recurrence imaging using PSMA-PET CT. Pre-treatment images were aligned with post-recurrence images to determine if recurrences occurred at the GTV location, with overlap indicative of a recurrence at the primary tumor site.

Out of 535 patients in the FLAME trial, 28 had intraprostatic recurrences, with the location determined for 24 patients. Notably, one patient’s recurrence occurred outside the GTV within the prostate gland. The median dose delivered to 98% of the GTV (D98%) was 76.5 Gy, with a range of 73.3–86.5 Gy. Among these, only one patient who experienced a recurrence within the GTV received a substantial focal boost of 86.5 Gy. The D98% for the majority of patients was less than 81 Gy.

The findings indicate that intraprostatic recurrences in patients with intermediate- and high-risk prostate cancer primarily occurred at the location of the primary tumor. Notably, nearly all patients with recurrences did not receive a high dose of the GTV, suggesting that intraprostatic failure is more likely attributable to inadequate treatment of the primary tumor rather than insufficient dosing to the remaining prostate gland. This analysis underscores the importance of delivering an adequate dose to the GTV to minimize the risk of recurrence. It highlights the need for careful consideration before implementing dose de-escalation strategies.

Source: sciencedirect.com/science/article/pii/S0167814024035138