T 0641/01 (Catheters for treating prostate disease/MMTC INC.) 10-02-2004

1. The appeal complies with the requirements of Articles 106 to 108 and Rule 64 EPC and is, therefore, admissible.

2. Amendments (Article 123(2) EPC)

Independent claim 1 is based on originally-filed claims 1, 5 and 9. The wording of these claims is amended by the additional definition of inflating means which are disclosed by Figures 1b and 1c and the corresponding description on page 5, lines 13-17, and page 7, line 33 to page 8, line 1, of the published application, as well as by an explicit definition of the relation of cross-sectional values of the inflatable balloon in the deflated and inflated state, as is supported by the description of Figures 2a and 2b. Although the added features and properties are mentioned, strictly speaking, in the context of the description of a urethra catheter, it is clear from the statement on page 8, lines 19 to 2, of the application: "In addition, the rectal catheter shown in Figure 3 also possesses the advantages of the urethral catheter, discussed above." that they are disclosed for the rectal catheter as well.

The catheter arrangement according to claim 6 is disclosed by original claim 15 and the description on page 10, lines 5 to 7, of the application with the features of the urethra catheter being disclosed by original claim 1 and the description of Figures 1, 1b, 1c, 2a and 2b.

The Board is thus satisfied that the claims on file comply with the requirement of Article 123(2) EPC.

3. Clarity (Article 84 EPC)

3.1. In its contested decision (cf item 1.1), the examining division held that in particular the features "said inflatable balloon is adapted to be inflated to a given tissue squeezing pressure ... from a first cross-section value ... to a second cross-section value substantially larger than the cross- section of said urethra ... said tissue squeezing pressure being sufficient to squeeze and compress (prostate) tissue of said patient ... so as to increase the minimum distance between heated tissue of said patient and said microwave antenna means and to reduce the difference between outer and inner radii of the prostate tissue with respect to the microwave antenna means" (emphasis added), included in claims 1 of the requests then on file, defined properties of the inflatable balloon by results to be achieved.

The division argued that these definitions were unclear since they did not meet established criteria for the allowability of functional definitions. According to the examining division, physical properties of diseased prostate tissue varied to a great extent among individual patients. Hence, the claimed result, namely the application of a sufficient tissue squeezing pressure by the inflated balloon, could not be directly and positively verified and was thus considered unclear, the more so as a verification device was neither specified in the description nor known in the art. In any case, a vast number of experiments would have to be carried out in order to determine the proper tissue squeezing pressure, which, apart from ethical problems that might arise with patients, constituted undue experimentation.

3.2. The Board notes that the present wording of the claims does no longer require that the balloon should be inflated to a "given tissue squeezing pressure". All that is required is that the balloon is inflatable from a first cross-section value small enough to fit into a patient's rectum or urethra to a second cross-section larger than that of the rectum or urethra so that, in consequence, the inflated balloon will exert a squeezing pressure on the tissue surrounding the catheter and thereby increase the distance between the tissue and the microwave antenna.

As regards the aspect of control over the degree of inflation, the application documents hint on page 8, first paragraph, at the possibility of monitoring not only the proper positioning of the catheter but also the amount of inflation by means of fluoroscopy for a balloon filled with a radio-opaque liquid.

The Board has no doubt that the skilled person, who, in the present case, possesses the qualification of a mechanical engineer developing catheters for medical treatment, under instruction by a physician, would understand the meaning and implications of the claim definitions and, moreover, would have the knowledge as well as the technical means necessary to design a rectal or urethra catheter with an inflatable balloon having the properties specified in the claims in suit.

4. Novelty and inventive step (Articles 52(1), 54 and 56 EPC)

4.1. Both of the earlier European applications according to documents D8 and D9, which are comprised in the state of the art within the meaning of Articles 54(3) and (4) EPC, concern urethra catheters. Such catheters differ from a rectal catheter inter alia in their outer diameter so that the content of these applications is not detrimental to the novelty of the subject-matter of independent claims 1 and 6 on file.

4.2. As regards the available prior art published before the international filing date of the present application, an example of a conventional rectal catheter is given by document D1 (see in particular Figure 1 with the corresponding description). The known catheter comprises an inflatable balloon and corresponding inflating means. The balloon is arranged at the tip of the catheter at one side thereof so as to press the opposite side of the catheter against the wall of the rectum and thus to fix the catheter in position. By means of a reflector, microwave energy is directed preferentially in the direction opposite to the balloon towards the prostate. No compression of prostate tissue is foreseen.

The subject-matter of claim 1 on file differs from the rectal catheter known from D1 in that the inflatable balloon surrounds the microwave antenna and is designed to be inflated so as to exert squeezing pressure on the prostate and intermediate non-prostate tissue.

4.3. From document D6 (see in particular Figure 1 with the corresponding description) a generic endotract catheter for hyperthermia treatment by microwave heating of lesions on organs inside the body is known, which comprises an inflatable balloon surrounding the microwave antenna. The balloon and the microwave antenna are both situated at the tip of the catheter. The catheter is not specifically adapted for a treatment of the prostate via the rectum, as the microwave antenna is designed to apply a substantially uniform angular distribution of microwave field intensity to the surrounding tissue. The balloon is formed so as to come in its inflated state in close contact with the wall of the organ tract where the lesion is located so that a chamber of variable volume is formed around the microwave antenna and no gases or fluids remain in the gap between the antenna and the surface of the organ (column 1, lines 24-28 and 65-68; column 2, lines 54- 57). In order to allow the balloon to be inflated into intimate contact with the wall of the tract or lumen organ, it is made from a thin, highly flexible polymeric film (column 2, lines 57-62; column 3, lines 26-29; column 4, lines 4-17). The inflated balloon should comply with an uneven inner profile of the wall of the organ, but no compression of the surrounding tissue is intended.

The catheter according to present claim 1 differs in essence from the known catheter in that it is specifically adapted to be inserted into a male patient's rectum, that the inflatable balloon and the microwave antenna are situated at a distance from the tip of the catheter, that the catheter comprises distribution means for providing a distribution of microwave field intensity preferentially in a direction towards the prostate, and that the inflating means are configured to inflate the balloon to a cross-section larger than the cross-section of the rectum so as to squeeze and compress the surrounding tissue including that of the prostate.

4.4. Thus neither D1 nor D6 shows a rectal catheter comprising all features specified in claim 1 under consideration.

Moreover, none of the further documents referred to in the contested decision or cited in examination or in the International and European Search Reports discloses a rectal catheter for treating prostate diseases which possesses in combination microwave antenna means for preferential irradiation of the prostate and an inflatable balloon designed for squeezing and compressing the heated tissue.

Consequently, the subject-matter of claim 1 has to be regarded as novel over the available state of the art. The same applies to independent claim 6 directed to an arrangement of a rectal catheter as specified in claim 1 and a urethra catheter.

4.5. According to additional remarks added to the contested decision, the examining division considered a rectal catheter as disclosed by the application to be rendered obvious by a combination of the teachings of documents D1 and D6.

Apart from the facts that, in these remarks, the division does not particularly pay attention to the different functions served by the respective inflatable balloons according to D1, D6 and the present application and that it leaves all functional features out of consideration which relate to a squeezing and compression of tissue by the inflated balloon and to an increase in distance between the microwave antenna and the heated tissue, the division's analysis is apparently based on the opinion that claimed features missing from one of the documents are known from the other document and so conventional that they are arbitrarily interchangeable.

The Board is aware of the fact that the features distinguishing the claimed subject-matter from a catheter as known from either D1 or D6 are at least in part known from the other document and, moreover, were known as such before the international filing date of the present application for one type of catheter or another, as is apparent from documents cited in the search reports for the present application. For instance, a catheter comprising an inflatable balloon surrounding an antenna for microwave heating of tissue was used for the treatment of stenoses in blood vessels. More specifically, as regards the treatment of an enlarged prostate by means of a urethra catheter, it was known to use a balloon catheter for mechanically widening the urethra so as to remove a stenosis or to use a catheter with a microwave antenna for a hyperthermia treatment.

However, regarding the issue of inventive step, the decisive question to be answered is whether the skilled person would have applied such measures to a rectal catheter and would have accordingly modified a catheter as known from D1 or D6.

Unlike the situations encountered for treating the prostate by means of a urethra catheter or for a dilation treatment of stenoses in blood vessels, a treatment of the prostate from the side of the rectum does not require the widening of a stenosis. Therefore, the Board sees no incentive for the skilled person to purposefully modify a catheter as known from D1 or D6 so as to arrive at a rectal catheter for hyperthermia treatment of the prostate as defined in claim 1 under consideration having inflatable means for increasing the distance between the microwave antenna and the heated tissue. As a matter of fact, none of the available prior art documents hints at the idea to improve hyperthermia treatment of the prostate by means of a rectal catheter by squeezing and compressing the heated tissue so as to render the heating more homogeneous and increase the efficiency of heating diseased tissue without exceeding safe temperature limits for healthy tissue.

For these reasons, the Board considers the subject- matter of claims 1 and 6 to involve an inventive step within the meaning of Article 56 EPC.

Claims 2 to 5 and 7 to 11 are dependent claims and, therefore, their subject-matters also comply with Article 56 EPC.

5. In the result, the Board finds that the appellant's request satisfies the requirements of the EPC.