INTRODUCTION Bladder tumor is the second most common neoplasm in the genitourinary tract. Most cases of ex novo diagnosis of bladder cancers are present as non-invasive muscle tumors, which are treatable through endourological procedures. The current standard is based on conventional transurethral resection of bladder tumor, although high rates of recurrence have been reported following resection of the primary tumor. Given the importance of a correct initial diagnosis in these cases, en bloc transurethral resection has developed over the past 2 decades. This technique was born, according to the literature, with 3 main objectives: to improve the quality of the surgical piece for its anatomopathological reading, reduce the rate of postoperative complications and reduce the rate of relapses in the surgical bed. This technique is used as a common practice of tumor resection in other centers and has been shown in multiple publications that it does not increase surgical risk or negatively affect cancer results.

OBJECTIVE The objective of our study is to compare feasibility, perioperative complication rate, accuracy of staging and recurrence/progression rates when performing en bloc resection by means of different energies: monopolar, bipolar and laser energy.

MATERIAL AND METHODS Between April 2018 and June 2021, a prospective randomized study will be conducted including patients undergoing a transurethral resection of initial or recurrent bladder tumor, either unifocal or multifocal. Patients with tumors less than 3 cm and with less than 3 tumors shall be included if multiple. Patients with more than 3 tumors or tumors over 3cm, those with evidence of invasive muscle tumor(cT2) or those with evidence of remote metastasis, whether lymphatic or organic, will be excluded.

Patients will be randomized into two groups:

• Group 1 (test): en bloc resection (n-180). It will be divided into 3 subgroups according to the energy used (monopolar, bipolar, laser energy).
• Group 2 (control): Conventional transurethral resection (n-120). It will be divided into 2 subgroups depending on the energy used (monopolar or bipolar).

A fact sheet will be given to the patient about the study and the signature of the informed consent will be requested in order to be included. The patient will be free to leave the study at any time without having to provide any justification and without affecting the treatment, intervention and follow-up that must be carried out.

The processing and storage of samples will be carried out in the pathological anatomy laboratory, according to standard clinical practice.

Patients will be monitored according to the usual clinical practice protocol (minimum 5-year follow-up), included in the non-muscle invasive bladder tumor protocols of the Puigvert Foundation.

Inclusion Criteria:

• Unifocal primary or recurrent bladder cancer with size less or equal than 3 cm
• Multifocal primary or recurrent bladder cancer less or equal than 3 lesions and with size less or equal than 3 cm

Exclusion Criteria:

• Evidence of > 3 tumors or > 3 cm
• Computed tomography/cystoscopy suspect of muscle-invasive bladder cancer (cT2 or higher)
• Computed tomography/magnetic resonance evidence of distant metastases