Can dedicated breast PET help to reduce overdiagnosis and overtreatment by differentiating between indolent and potentially aggressive ductal carcinoma in situ?

Objectives: To analyze the utility of metabolic imaging, and specifically of dedicated breast positron emission tomography (dbPET) to differentiate between indolent and potentially aggressive ductal carcinoma in situ (DCIS).

Methods: After institutional review board approval, we retrospectively reviewed the cases of pure DCIS who underwent dbPET before biopsy and surgery in Lucus Augusti Universitary Hospital (Lugo, Spain) and in Fudan Cancer Institute (Shanghai, China) between January 2016 and May 2018. Grade 1 and "non-comedo" grade 2 DCIS were considered low-risk disease, while intermediate-grade with necrosis or grade 3 cases were included in the high-risk group. DbPET sensitivity and specificity to differentiate between indolent and potentially aggressive DCIS were determined along with their respective 95% confidence intervals.

Results: We enrolled 139 surgery-confirmed pure DCIS cases. Fifty were high-risk neoplasms and 89 low-risk DCIS. Only seven low-risk lesions were positive at dbPET and five of potentially aggressive neoplasms did not show FDG uptake, all included into the field of view (FOV). Sensitivity and specificity of dbPET to differentiate between indolent and potentially aggressive DCIS were 90% (95% CI, 77-96%) and 92% (95% CI, 84-97%), respectively.

Conclusion: Metabolic imaging could help to identify the subgroup of indolent lesions from those potentially aggressive ones that may be managed by active surveillance.

Key Points: • Low- and high-grade DCIS likely arise from two distinct evolutionary paths and when low-grade lesions progress to invasive cancer, the tumor is frequently low grade and well differentiated. • Ongoing clinical trials evaluate whether patients with low-risk DCIS could be safely managed by an active surveillance approach, with avoidance of unnecessary treatments and without impact on ipsilateral invasive breast cancer free survival time. • Dedicated breast PET may differentiate harmless from potentially hazardous DCIS, supporting active surveillance for the management of those women with low-grade DCIS, decreasing the rate of the upgrade to invasive carcinoma at surgical excision.