Feasibility of [11C]Acetate-PET in LAM and TSC

Lymphangioleiomyomatosis (LAM) is a rare, multisystem disease of women, consisting of a diffuse proliferation of smooth muscle actin-positive cells (LAM cells), which harbor inactivating mutations in either the TSC1 or TSC2 tumor suppressor gene. These inactivating mutations result in constitutive activation of mammalian/mechanistic TOR (target of rapamycin) complex 1 (mTORC1), which integrates growth factor and nutrient signaling to stimulate cell growth and metabolism. Pulmonary LAM is characterized by associated progressive cystic destruction of the lung parenchyma, recurrent pneumothorax, and chylous pleural effusions. Extrapulmonary proliferative lesions of LAM include renal angiomyolipomas and lymphangiomyomas. LAM can occur as a sporadic disorder where LAM cells harbor somatic inactivating mutations of the TSC1 or TSC2 gene, or in women with Tuberous Sclerosis Complex (TSC).

Rapamycin is an FKBP12-dependent allosteric inhibitor of mTORC1 approved by the FDA for the treatment of LAM and TSC-associated renal angiomyolipomas. Clinical trials of TSC and LAM have shown that 12 month-treatment with rapamycin induces response of renal angiomyolipomas and stabilization of pulmonary function. However, lung function decline and tumor growth resume when treatment is interrupted.

Sensitive and specific biomarkers of response to therapy and/or disease progression, including biomarkers of tumor metabolic activity, would facilitate clinical trials of novel therapeutic agents for LAM and enable optimization of current rapamycin-based regimens.

Our preclinical studies showed that lipogenic pathways can be detected in preclinical animal models of TSC and LAM using PET-based metabolic imaging.

The proposed study aims to quantitatively and non-invasively assess metabolic activity and response to rapamycin in LAM patients using [11C]acetate positron emission tomography (PET) imaging.

Inclusion criteria

• diagnosis of LAM (or TSC-LAM)
• age 18 or over
• at least one renal angiomyolipoma (at least 1 cm in each diameter) confirmed by CT or MRI
• no prior treatment with rapamycin/rapalogs OR candidate for initiating treatment with rapamycin/rapalogs OR under treatment with rapamycin/rapalogs for minimum 3 months and maximum of 1 year

Exclusion criteria

• under treatment with rapamycin or rapalogs for < 3 months or > 1 year
• participated in research studies involving radiation exposure (> 50 mSv/year) in the past 12 months