Comparison of 18F-FDG PET/CT and DW-MRI in assessment of neoadjuvant radiochemotherapy response in locally advanced rectal cancer patients

OBJECTIVE

Our aim is to evaluate if different metabolic parameters obtained by ¹⁸F-FDG PET/CT and diffusion weighted magnetic resonance imaging (DW-MRI) can aid in neoadjuvant radiochemotherapy (RCT) response assessment in locally advanced rectal cancer (LARC) patients.

METHODS

Out of 20 LARC patients, who were planned to receive neoadjuvant RCT, 19 were included in this prospective study. Patients had ¹⁸F-FDG PET/CT and DW-MRI at initial staging, interim (2 weeks after onset of RCT) and after completion of RCT (post-therapy). Standardized uptake value (SUV) parameters (SUVmax, SUVmean, SUVpeak, SULpeak), metabolic tumor volume (MTV) and tumor lesion glycolysis (TLG) detected on PET images and apparent diffusion coefficient (ADC) values (for b=400 and b=1000s/mm²) obtained from DW-MRI were recorded. Postoperative tumor regression grade (TRG) was used as gold-standard, except for 2 patients who were under complete remission with non-operative management 19 months post-therapy and scored as responders.

RESULTS

On interim PET/CT, no significant difference was found among PET parameters between responders and non-responders, whereas post-therapy SUVmax, SUVpeak, MTV, SULpeak, TLG (P=0.02, P=0.014, P=0.025, P=0.007, P=0.02, respectively) and initial MTV (P=0.034) were significantly lower in responders. ADC response index (RI) was higher in responders (interim P=0.026; post-therapy: P=0.018) and ROC analysis revealed that a threshold of ADC RI>41.6% for interim MRI and >44.6% for post-therapy MRI had sensitivity and specificity of 75.0% and 90.9%, respectively.

CONCLUSIONS

While interim ¹⁸F-FDG PET/CT failed to predict therapy response during RCT, post-therapy PET could accurately differentiate responders. DW-MRI was found to be more promising in interim detection of RCT response.

Is it possible NET-redifferentiation after chemotherapy? 68Ga DOTA-peptide imaging as a game-changer in therapy management

A 64-year-old man with pancreatic grade III neuroendocrine carcinoma underwent ⁶⁸Ga DOTANOC PET/CT scan for staging. The pancreatic lesion, multiple peripancreatic lymph nodes and multiple gross metastases in both hepatic lobes were revealed with intense uptake. After 3 cycles of chemotherapy containing cisplatin and etoposide the primary and metastatic lesions were decreased in size, however showing higher uptake on follow-up ⁶⁸Ga DOTANOC PET/CT scan. Another biopsy from liver demonstrated a significant decrease in Ki-67 proliferation index from 35 to 1%. The patient received 2 cycles of peptide receptor-targeted radionuclide therapy with ¹⁷⁷Lu DOTANOC.

Diagnostic impact of 18F-FDG PET/CT on the management of rare breast carcinomas: Apocrine and neuroendocrine carcinomas

OBJECTIVE

We aimed to evaluate the diagnostic impact of ¹⁸F-FDG PET/CT in staging apocrine breast carcinoma (ABC) and primary breast neuroendocrine carcinoma (PBNEC) and to demonstrate possible alterations of the ¹⁸F-FDG uptake in these histopathologic subtypes. In addition, we aimed to compare ¹⁸F-FDG PET/CT findings between ABC, PBNEC and invasive ductal carcinoma.

MATERIAL AND METHODS

A total of 570 patients and 585 breast lesions were retrospectively included in this study. After patients were classified into molecular subtypes according to the histopathological analysis, ¹⁸F-FDG PET/CT imaging was performed. The SUVmax findings of primary tumors obtained from ¹⁸F-FDG PET/CT were compared between the groups.

RESULTS

Invasive ductal carcinoma was the most prevalent breast carcinoma (77.7%, n=446), with a low proportion of ABC (4.1%, n=24) and PBNEC (2.4%; n=14) diagnosed. The highest mean SUVmax was calculated in HER2 subtype of ABC and ¹⁸F-FDG uptake ratio in HER2 and TN subtypes were found statistically higher than Luminal B type of ABC (p=0.038 and p=0.019, respectively). Although ¹⁸F-FDG uptake in Luminal B subtype of PBNEC was higher than Luminal A subtype, difference was not statistically significant. Additionally, the axillary metastasis rate was significantly higher in the ABC group (p=0.015).

CONCLUSIONS

The histopathological ABC subtype group showed different ¹⁸F-FDG uptake than the invasive ductal carcinoma group. Even if ¹⁸F-FDG uptake was lower in the PBNEC group than in the other groups, PET/CT showed and adequate performance in detecting primary tumors and metastases. The ¹⁸F-FDG PET/CT scan results may contribute to the initial staging and management of ABC and PBNEC patients.